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Sample records for high mn austenitic

  1. High Mn austenitic stainless steel

    Science.gov (United States)

    Yamamoto, Yukinori [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Brady, Michael P [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Liu, Chain-tsuan [Knoxville, TN

    2010-07-13

    An austenitic stainless steel alloy includes, in weight percent: >4 to 15 Mn; 8 to 15 Ni; 14 to 16 Cr; 2.4 to 3 Al; 0.4 to 1 total of at least one of Nb and Ta; 0.05 to 0.2 C; 0.01 to 0.02 B; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1W; up to 3 Cu; up to 1 Si; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale including alumina, nanometer scale sized particles distributed throughout the microstructure, the particles including at least one of NbC and TaC, and a stable essentially single phase FCC austenitic matrix microstructure that is essentially delta-ferrite-free and essentially BCC-phase-free.

  2. Advanced Thermomechanical Processing for a High-Mn Austenitic Steel

    Science.gov (United States)

    Kusakin, Pavel; Tsuzaki, Kaneaki; Molodov, Dmitri A.; Kaibyshev, Rustam; Belyakov, Andrey

    2016-12-01

    The microstructures and mechanical properties of a warm-forged and annealed Fe-18Mn-0.6C-1.5Al TWIP steel were studied. The high dislocation density was evolved by warm forging and the ultrafine grains were developed by subsequent annealing. The dislocation strengthening and the grain refinement result in increased yield strength ranging from 500 to 1000 MPa and the product of ultimate tensile strength by total elongation as high as 70,000 MPa pct.

  3. Replacement of Ni by Mn in High-Ni-Containing Austenitic Cast Steels used for Turbo-Charger Application

    Science.gov (United States)

    Jung, Seungmun; Jo, Yong Hee; Jeon, Changwoo; Choi, Won-Mi; Lee, Byeong-Joo; Oh, Yong-Jun; Kim, Gi-Yong; Jang, Seongsik; Lee, Sunghak

    2017-02-01

    High-temperature tensile properties of austenitic cast steels fabricated by replacing Ni by Mn in a 20 wt pct Ni-containing steel were investigated. In a steel where 8 wt pct Ni was replaced by 9.2 wt pct of Mn, 17.4 and 9.8 pct of ferrite existed in equilibrium phase diagrams and actual microstructures, respectively, because a role of Mn as an austenite stabilizer decreased, and led to deterioration of high-temperature properties. When 2 to 6 wt pct Ni was replaced by 2.3 to 6.9 wt pct Mn, high-temperature properties were comparable to those of the 20 wt pct Ni-containing steel because ferrites were absent, which indicated the successful replacement of 6 wt pct Ni by Mn, with cost reduction of 27 pct.

  4. Phase Equilibrium and Austenite Decomposition in Advanced High-Strength Medium-Mn Bainitic Steels

    Directory of Open Access Journals (Sweden)

    Adam Grajcar

    2016-10-01

    Full Text Available The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature were carried out. The study comprised the determination of the time-temperature-transformation (TTT diagrams and continuous cooling transformation (CCT diagrams of the investigated steels. The diagrams were used to determine continuous and isothermal cooling paths suitable for production of bainite-based steels. It was found that the various Mn content strongly influences the hardenability of the steels and hence the austenite decomposition during cooling. The knowledge of CCT diagrams and the analysis of experimental dilatometric curves enabled to produce bainite-austenite mixtures in the thermomechanical simulator. Light microscopy (LM, scanning electron microscopy (SEM, and transmission electron microscopy (TEM were used to assess the effect of heat treatment on morphological details of produced multiphase microstructures.

  5. Microstructural Changes in a High-Manganese Austenitic Fe-Mn-Al-C Steel

    Directory of Open Access Journals (Sweden)

    Witkowska M.

    2014-10-01

    Full Text Available Microstructural changes in the age-hardenable Fe-28wt.%Mn-9wt.%Al-1wt.%C steel during ageing at 550°C for various times have been investigated by transmission electron microscopy (TEM and X-ray diffraction (XRD. The steel was produced in an induction furnace and the ingot, after homogenization at 1150°C for 3 hours under a protective argon atmosphere, was hot-rolled and subsequently cold-rolled up to 23% reduction. The sheet was then aged at 550°C for various times in an argon atmosphere and cooled in air. XRD analysis and TEM observations revealed a modulated structure and superlattice reflections produced by spinodal decomposition, which occurred during ageing at 550°C. Theexistence of satellites suggests that either (Fe, Mn3AlCx carbides were formed within the austenite matrix by spinodal decomposition during cooling or chemical fluctuactions occurred between the (Fe, Mn3AlCx carbides and the austenitic matrix.

  6. Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/ε-martensite high-Mn steels.

    Science.gov (United States)

    Seol, Jae-Bok; Lee, B-H; Choi, P; Lee, S-G; Park, C-G

    2013-09-01

    We introduce a new experimental approach for the identification of the atomistic position of interstitial carbon in a high-Mn binary alloy consisting of austenite and ε-martensite. Using combined nano-beam secondary ion mass spectroscopy, atomic force microscopy and electron backscatter diffraction analyses, we clearly observe carbon partitioning to austenite. Nano-beam secondary ion mass spectroscopy and atom probe tomography studies also reveal carbon trapping at crystal imperfections as identified by transmission electron microscopy. Three main trapping sites can be distinguished: phase boundaries between austenite and ε-martensite, stacking faults in austenite, and prior austenite grain boundaries. Our findings suggest that segregation and/or partitioning of carbon can contribute to the austenite-to-martensite transformation of the investigated alloy.

  7. Microstructural change during isothermal aging in high manganese austenitic steels; Ko Mn osutenaito ko no koon hentai ni tomonau soshiki henka

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Y.; Tsuchiyama, T.; Takaki, S. [Kyushu Univ., Fukuoka (Japan). Graduate School

    1998-04-01

    Since high Mn austenitic ({gamma}) steels represented by the Hadfield steel (13mass%Mn-1.2mass%C steel) had a good toughness and showed a remarkable work hardening during cold working, they were used in special rails and components of stone crushers as wear-resistant materials. In this study, the microstructure change during isothermal aging was investigated in the 13mass%Mn-0.9mass%C steel and the 22mass%Mn-0.6mass%C steel. The microstructure change during isothermal aging in high Mn austenitic steels could be classified into three types: the grain boundary precipitation of carbide, the precipitation of platelet carbide within grains, and the formation of lamella structure through eutectic transformation. In the 13mass%Mn-0.9mass%C steel, all kinds of microstructure changes occurred. The carbide precipitation reaction in the high Mn austenitic steels was effectively suppressed in the 22mass%Mn-0.6mass%C steel, in which the increased amount of Mn content was the same as the decreased amount of carbon content, and the isothermal aging curve shifted to a longer duration. 10 refs., 11 figs.

  8. Deformation behavior of duplex austenite and ε-martensite high-Mn steel

    Directory of Open Access Journals (Sweden)

    Ki Hyuk Kwon, Byeong-Chan Suh, Sung-Il Baik, Young-Woon Kim, Jong-Kyo Choi and Nack J Kim

    2013-01-01

    Full Text Available Deformation and work hardening behavior of Fe–17Mn–0.02C steel containing ε-martensite within the austenite matrix have been investigated by means of in situ microstructural observations and x-ray diffraction analysis. During deformation, the steel shows the deformation-induced transformation of austenite → ε-martensite → α'-martensite as well as the direct transformation of austenite → α'-martensite. Based on the calculation of changes in the fraction of each constituent phase, we found that the phase transformation of austenite → ε-martensite is more effective in work hardening than that of ε-martensite → α'-martensite. Moreover, reverse transformation of ε-martensite → austenite has also been observed during deformation. It originates from the formation of stacking faults within the deformed ε-martensite, resulting in the formation of 6H-long periodic ordered structure.

  9. In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel

    Institute of Scientific and Technical Information of China (English)

    Feng Liu; Guang Xu; Yu-long Zhang; Hai-jiang Hu; Lin-xin Zhou; Zheng-liang Xue

    2013-01-01

    In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel were conducted on a high-temperature laser scanning confocal microscope during continuous heating and subsequent isothermal holding at 850, 1000, and 1100◦C for 30 min. A grain growth model was proposed based on experimental results. It is indicated that the austenite grain size increases with austenitizing temperature and holding time. When the austenitizing temperature is above 1100◦C, the austenite grains grow rapidly, and abnormal austenite grains occur. In addition, the eff ect of heating rate on austenite grain growth was investigated, and the relation between austenite grains and bainite morphology after bainitic transformations was also discussed.

  10. Austenite formation in C-Mn steel

    OpenAIRE

    Savran, V.I.

    2009-01-01

    The production process of almost all modern steels involves austenitization formation of the austenite phase upon continuous heating. Many of the microstructural features and properties that are obtained upon subsequent cooling are to a large extend determined by the evolution of the microstructure and chemical inhomogeneities during austenitization. In spite of its importance, austenitization so far has received much less attention than the transformations on cooling; however, the interest i...

  11. Austenite formation in C-Mn steel

    NARCIS (Netherlands)

    Savran, V.I.

    2009-01-01

    The production process of almost all modern steels involves austenitization formation of the austenite phase upon continuous heating. Many of the microstructural features and properties that are obtained upon subsequent cooling are to a large extend determined by the evolution of the microstructure

  12. Third Generation 0.3C-4.0Mn Advanced High Strength Steels Through a Dual Stabilization Heat Treatment: Austenite Stabilization Through Paraequilibrium Carbon Partitioning

    Science.gov (United States)

    Qu, Hao; Michal, Gary M.; Heuer, Arthur H.

    2014-06-01

    In excess of 30 vol. pct austenite can be retained in 0.3C-4.0Mn steels subjected to a dual stabilization heat treatment (DSHT) schedule—a five stage precisely controlled cooling schedule that is a variant of the quench and partition process. The temperature of the second quench (stage III) in the DSHT process plays an essential role in the retained austenite contents produced at carbon-partitioning temperatures of 723 K or 748 K (450° C or 475 °C) (stage IV). A thermodynamic model successfully predicted the retained austenite contents in heat-treated steels, particularly for a completely austenitized material. The microstructure and mechanical behavior of two heat-treated steels with similar levels of retained austenite (~30 vol. pct) were studied. Optimum properties—tensile strengths up to 1650 MPa and ~20 pct total elongation—were observed in a steel containing 0.3C-4.0Mn-2.1Si, 1.5 Al, and 0.5 Cr.

  13. Cyclic Deformation Behavior of Fe-18Cr-18Mn-0.63N Nickel-Free High-Nitrogen Austenitic Stainless Steel

    Science.gov (United States)

    Shao, C. W.; Shi, F.; Li, X. W.

    2015-04-01

    Cyclic deformation and damage behavior of a Ni-free high-nitrogen austenitic stainless steel with a composition of Fe-18Cr-18Mn-0.63N (weight pct) were studied, and the internal stress and effective stress were estimated by partitioning the hysteresis loop during cyclic straining at total strain amplitudes ranging from 3.0 × 10-3 to 1.0 × 10-2. It is found that immediate cyclic softening takes place at all strain amplitudes and subsequently a saturation or quasi-saturation state develops and occupies the main part of the whole fatigue life. The internal stress increases with increasing strain amplitude, while the variation of effective stress with strain amplitude is somewhat complicated. Such a phenomenon is discussed in terms of dislocation structures and the short-range ordering caused by the interaction between nitrogen atoms and substitutional atoms. The relationship of fatigue life vs plastic strain amplitude ( N f-Δ ɛ pl/2) follows a bilinear Coffin-Manson rule, resulting from the variation in slip deformation mode with the applied strain amplitude. At the low strain amplitude, cracks initiate along slip bands, and planar slip dislocation configurations dominate the major characteristic of internal microstructures. At high strain amplitudes, intergranular (mostly along grain boundaries and few along twin boundaries) cracks are generally found, and the deformation microstructures are mainly composed of dislocation cells, stacking faults and a small amount of deformation twins, in addition to planar slip dislocation structures.

  14. Phase instability of thermally aged CrMn austenitic steels

    Science.gov (United States)

    Ruedl, E.; Sasaki, T.

    1984-05-01

    The microstructural changes taking place in several commercial Cr-Mn austenitic steels during ageing at 873 and 1073 K were examined by analytical electron microscopy. Phase identification was obtained by electron diffraction, energy dispersive X-ray analysis and electron energy loss spectrometry. It was found that the phase changes depend on the carbon and nitrogen content of the materials as well as on the presence of Mo and delta ferrite.

  15. Prediction and Validation of the Austenite Phase Fraction upon Intercritical Annealing of Medium Mn Steels

    NARCIS (Netherlands)

    Farahani, H.; Xu, W.; Van der Zwaag, S.

    2015-01-01

    In this research, the effects of Mn and Si concentration and that of the isothermal intercritical holding temperature on the austenite-to-ferrite (γ → α) and the martensite-to-austenite (α′ → γ) phase transformations are studied for a series of Fe-C-Mn-Si steels with up to 7 wt pct Mn. The model is

  16. Thermodynamic stability of austenitic Ni-Mn-Cu cast iron

    Directory of Open Access Journals (Sweden)

    A. Janus

    2014-07-01

    Full Text Available The performed research was aimed at determining thermodynamic stability of structures of Ni-Mn-Cu cast iron castings. Examined were 35 alloys. The castings were tempered at 900 °C for 2 hours. Two cooling speeds were used: furnace-cooling and water-cooling. In the alloys with the nickel equivalent value less than 20,0 %, partial transition of austenite to martensite took place. The austenite decomposition ratio and the related growth of hardness was higher for smaller nickel equivalent value and was clearly larger in annealed castings than in hardened ones. Obtaining thermodynamically stable structure of castings requires larger than 20,0 % value of the nickel equivalent.

  17. Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

    Institute of Scientific and Technical Information of China (English)

    Hua-bing Li; Zhou-hua Jiang; Yang Cao; Zu-rui Zhang

    2009-01-01

    18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical duc-tile-brittle transition behavior and excellent pitting corrosion resistance properties.

  18. Fatigue behaviors and damage mechanism of a Cr-Mn-N austenitic steel

    DEFF Research Database (Denmark)

    Lv, Z.; Cai, P.; Yu, Tianbo;

    2017-01-01

    Four-point bending fatigue tests were conducted on a Cr-Mn-N austenitic steel at room temperature, at frequency of 20 Hz and the stress ratio of R = 0.1, in air. The fatigue strength of this Cr-Mn-N austenitic steel was measured to be 503 MPa in the maximum stress from the S-N curve obtained...

  19. Phase stability of high manganese austenitic steels for cryogenic applications

    CERN Document Server

    Couturier, K

    2000-01-01

    The aim of this work is to study the austenitic stability against a' martensitic transformation of three non-magnetic austenitic steels : a new stainless steel X2CrMnNiMoN 19-12-11-1 grade, a traditional X8CrMnNiN 19-11-6 grade and a high manganese X8MnCrNi 28-7-1 grade. Measurements of relative magnetic susceptibility at room temperature are performed on strained tensile specimens at 4.2 K. A special extensometer for high precision strain measurements at low temperature has been developed at CERN to test specimens up to various levels of plastic strain. Moreover, the high precision strain recording of the extensometer enables a detailed study of the serrated yield phenomena associated with 4.2 K tensile testing and their influence on the evolution of magnetic susceptibility. The results show that high Mn contents increase the stability of the austenitic structure against a' martensitic transformation, while keeping high strength at cryogenic temperature. Moreover, proper elaboration through primary and possi...

  20. Non-metallic inclusions in high manganese austenitic alloys

    OpenAIRE

    A. Grajcar; L. Bulkowski; U. Galisz

    2011-01-01

    Purpose: The aim of the paper is to identify the type, fraction and chemical composition of non-metallic inclusions modified by rare-earth elements in an advanced group of high-manganese austenitic C-Mn-Si-Al-type steels with Nb and Ti microadditions.Design/methodology/approach: The heats of 3 high-Mn steels of a various content of Si, Al and Ti were melted in a vacuum induction furnace and a modification of non-metallic inclusions was carried out by the mischmetal in the amount of 0.87 g or ...

  1. Austenite phase formation in rapidly solidified Fe-Cr-Mn-C steels

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S.R.; Davies, H.A.; Rainforth, W.M.

    1999-12-10

    Steels having compositions (wt%) 0.05--0.5C, 12.5--20Cr, 8--25Mn and 0--0.51N have been chill-block melt-spun to ribbons in order to investigate systematically, by X-ray diffractometry and electron microscopy, the effects of rapid solidification and of solute concentrations on the formation of the austenite phase. The austenite is most easily formed at (wt%) 16Cr--8Mn for 0.3C ribbons while {alpha}{prime}-martensite or {epsilon}-martensite was observed at lower concentrations of Cr or Mn and {alpha}-ferrite appeared for Cr {gt} 18 wt%. The volume fraction of austenite in the steel ribbons studied was found, by multiple regression analysis, to obey the equation {gamma}(%) = 94 + 26.8C + Mn x (8.4 {minus} 0.08Mn {minus} 0.44Cr) {minus} (Cr {minus} 17.7){sup 2}. Thus, the effect of Mn on {gamma} formation followed a non-linear function, containing an interaction term including the Cr and Mn contents, and first- and second-order terms involving the Mn concentration. This indicates the ranges over when Mn is a {gamma}-former or an {alpha}-former. Iso-austenitic lines, constructed on the basis of this new equation, are nearly orthogonal to those in the Schaeffler diagram for Cr-Mn steels so that use of the latter for prediction of the austenite content in the present case would be inappropriate.

  2. Effect of alloying elements on branching of primary austenite dendrites in Ni-Mn-Cu cast iron

    National Research Council Canada - National Science Library

    A. Janus

    2011-01-01

    Within the research, determined were direction and intensity of influence of individual alloying elements on branching degree of primary austenite dendrites in austenitic cast iron Ni-Mn-Cu. 30 cast shafts dia...

  3. Effect of Si and Nb on the solidification mode of a Cr-Ni-Mn-N austenitic hydrogen-resistant steels%Si和Nb对Cr-Ni-Mn-N奥氏体抗氢钢凝固方式的影响

    Institute of Scientific and Technical Information of China (English)

    谭军; 袁金才; 李守新; 万晔; 马禄铭; 李依依

    2002-01-01

    @@ Introduction Nitronic 50 is a Nitrogen-strengthened Cr-Ni-Mn austenitic stainless steel, with high strength and good corrosion resistance[1]. However, these properties are greatly influenced by the microstructure. When used in weld and cast condition, the microstructure with δ-ferrite as leading phase is responsible for larger resistantce to hot cracking than that with austenite as leading phase[2].

  4. Effect of Plastic Deformation on Magnetic Properties of Fe-40%Ni-2%Mn Austenitic Alloy

    Institute of Scientific and Technical Information of China (English)

    Selva Büyükakkas; H Aktas; S Akturk

    2007-01-01

    The effects of plastic deformation on the magnetic properties of austenite structure in an Fe-40%Ni-2%Mn alloy is investigated by using Mssbauer spectroscopy and Differential Scanning Calorimetry (DSC) techniques The morphology of the alloy has been obtained by using Scanning Electron Microscopy (SEM). The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnetic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mssbauer spectroscopy. The Curie point (TC) and the Neel temperature (TN) have been investigated by means of DSC system for non-deformed and deformed Fe-Ni-Mn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic Fe-Ni-Mn alloy.

  5. Mechanical characteristics and swelling of austenitic Fe-Cr-Mn steels irradiated in the SM-2 and BOR-60 reactors

    Science.gov (United States)

    Shamardin, V. K.; Bulanova, T. M.; Neustroev, V. S.; Ivanov, L. I.; Djomina, E. V.; Platov, Yu. M.

    1991-03-01

    Three types of austenitic Fe-Cr-Mn stainless steels were irradiated simultaneously with Fe-Cr-Ni austenitic steel at temperatures from 400 to 800°C in the mixed spectrum of the high flux SM-2 reactor to 10 dpa and 700 appm of He and in the BOR-60 reactor to 60 dpa without He generation. The paper presents the swelling and mechanical properties of steels irradiated in the BOR-60 and SM-2 as a function of the concentration of transmuted He and the value of atomic displacement.

  6. Abrasive Wear Behaviors of Light-weight Austenitic Fe-24Mn-7Al-1C Steel and Mn13Cr2 Steel

    Institute of Scientific and Technical Information of China (English)

    Shi-guang PENG; Ren-bo SONG; Zhi-dong TAN; Chang-hong CAI; Ke GUO; Zhong-hong WANG

    2016-01-01

    The impact abrasive wear behaviors of light-weight austenitic Fe-24Mn-7Al-1C steel with increasing impact wear conditions were studied by comparing with the modified Hadfield (Mn13Cr2)steel.Wear tests were performed with the MLD-10 abrasive wear testing machine.Main parameters such as impact energy,impacting frequency and wear time were evaluated.To explore the abrasive wear behaviors under different impact energies,the parameters in-cluding mass loss,wear resistance and hardness were evaluated in detail.The microstructures of the steels were fur-ther analyzed using optical microscopy (OM),scanning electron microscopy (SEM),transmission electron micros-copy (TEM)and X-ray diffraction (XRD).Results showed that the light-weight austenitic Fe-24Mn-7Al-1C steel had a better wear resistance than Mn13Cr2 steel under the impact energy tested.The wear resistance of light-weight austenitic Fe-24Mn-7Al-1C steel was about 1.09-1.17 times as high as that of Mn13Cr2 steel under low and medi-um impact energy (0.5-2.0 J)conditions,and 1.41 times under high impact energy (4.0 J)condition.In Mn13Cr2 steel,the evolution of dislocation substructure with increasing impact energy showed typical stacking fault,interac-tion of twins and dislocations,as well as mechanical twins.The high work-hardening rate in Fe-24Mn-7Al-1C steel was caused by Taylor lattice and high density of dislocation tangles.

  7. Austenite formation during intercritical annealing in C-Mn cold-rolled dual phase steel

    Institute of Scientific and Technical Information of China (English)

    李声慈; 康永林; 朱国明; 邝霜

    2015-01-01

    Two different kinds of experimental techniques were used to in-situ study the austenite formation during intercritical annealing in C-Mn dual phase steel. The microstructure evolution was observed by confocal laser scanning microscope, and the austenite isothermal and non-isothermal transformation kinetics were studied by dilatometry. The results indicate that banded structure is produced for the reason of composition segregation and the competition between recrystallization and phase transformation. Austenite prefers to nucleate not only at ferrite/ferrite grain boundaries, but also inside the grains of ferrite. Furthermore, the austenitizing process is accomplished mainly via migration of the existing austenite/ferrite interface rather than nucleation of new grains. The incubation process can be divided into two stages which are controlled by carbon and manganese diffusion, respectively. During the incubation process, the nucleation rate of austenite decreases, and austenite growth changes from two-dimensional to one-dimensional. The partitioning coefficient, defined as the ratio of manganese content in the austenite to that in the adjacent ferrite, increases with increasing soaking time.

  8. Magnetic analysis of martensitic and austenitic phases in metamagnetic NiMn(In, Sn) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lázpita, P., E-mail: patricia.lazpita@ehu.es [University of Basque Country (UPV/EHU), Leioa (Spain); Escolar, J. [University of Basque Country (UPV/EHU), Leioa (Spain); Chernenko, V.A. [University of Basque Country (UPV/EHU), Leioa (Spain); BCMaterials, Parque Tecnológico de Bizkaia, Ed. 500, Derio 48160 (Spain); Ikerbasque, Basque Foundation for Science, Bilbao 48013 (Spain); Barandiarán, J.M. [University of Basque Country (UPV/EHU), Leioa (Spain); BCMaterials, Parque Tecnológico de Bizkaia, Ed. 500, Derio 48160 (Spain)

    2015-09-25

    Highlights: • NiMnIn austenite and martensite have similar Ising-type critical exponents. • NiMnIn critical exponents rule out disordered states as spin-glass in martensite. • In NiMnIn alloys, magnetism arises mainly from moments localized at Mn atoms. • NiCoMnSn critical exponents are close to the ones from tricritical mean field model. • NiCoMnSn complex magnetic state results from three different magnetic atoms. - Abstract: Two different metamagnetic shape memory alloys of nominal composition Ni{sub 50}Mn{sub 36}In{sub 14} and Ni{sub 42}Co{sub 8}Mn{sub 39}Sn{sub 11} have been studied by means of modified Arrott plots to give insight into the magnetic states of both the austenitic and martensitic phases. For Ni{sub 50}Mn{sub 36}In{sub 14} alloy, the same critical exponents (β = 0.32 and γ = 2.0) are obtained in austenite and martensite. They suggest that localized moments at Mn atoms are responsible for the magnetism of both phases according to the Ising model. The martensite, however, displays a rather complex behavior because β continuously changes with temperature. In Ni{sub 43}Co{sub 6.5}Mn{sub 39}Sn{sub 11.5}, critical exponents in the austenite are β = 0.27 and γ = 1.0. They are close to the tricritical mean field model, but no reliable fits were obtained in the martensite. The results are discussed in terms of microscopically different magnetic states in two alloys reflecting a complex interplay between the ferromagnetic and antiferromagnetic contributions.

  9. Effect of alloying elements on solidification of primary austenite in Ni-Mn-Cu cast iron

    Directory of Open Access Journals (Sweden)

    A. Janus

    2011-04-01

    Full Text Available Within the research, determined were direction and intensity of alloying elements influence on solidification way (directional orvolumetric of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu. 50 cast shafts dia. 20 mm were analysed.Chemical composition of the alloy was as follows: 1.7 to 3.3 % C, 1.4 to 3.1 % Si, 2.8 to 9.9 % Ni, 0.4 to 7.7 % Mn, 0 to 4.6 % Cu, 0.14 to0.16 % P and 0.03 to 0.04 % S. The discriminant analysis revealed that carbon influences solidification of primary austenite dendrites most intensively. It clearly increases the tendency to volumetric solidification. Influence of the other elements is much weaker. This means that the solidification way of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu does not differ from that in an unalloyed cast iron.

  10. Numerical Simulation of Austenite Recrystallization in CSP Hot Rolled C-Mn Steel Strip

    Institute of Scientific and Technical Information of China (English)

    TANG Guang-bo; LIU Zheng-dong; DONG Han; GAN Yong; KANG Yong-lin; LI Lie-jun; MAO Xin-ping

    2007-01-01

    An integrated mathematical model is developed to predict the microstructure evolution of C-Mn steel during multipass hot rolling on the CSP production line, and the thermal evolution, the temperature distribution, the deformation, and the austenite recrystallization are simulated. The characteristics of austenite recrystallization of hot rolled C-Mn steel in the CSP process are also discussed. The simulation of the microstructure evolution of C-Mn steel ZJ510L during CSP multipass hot rolling indicates that dynamic recrystallization and metadynamic recrystallization may easily occur in the first few passes, where nonuniform recrystallization and inhomogeneous grain size microstructure may readily occur; during the last few passes, static recrystallization may occur dominantly, and the microstructure will become more homogeneous and partial recrystallization may occur at relatively low temperature.

  11. Modeling Recrystallization of Austenite for C-Mn Steels during Hot Deformation by Cellular Automaton

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using a cellular automaton method, microstructure evolution of recrystallization in austenite during hot deformation was simulated for C-Mn steels. A model takes into account the influence of deformation temperature, strain, and strain rate on the dynamic recrystallization fraction, and the effect of the keeping time on the static recrystallization fraction based on a hot deformation test on a Gleeble-1500 simulator. In addition, the size changing of γ grains during continuous hot deformation was simulated by applying the model.

  12. Change in the properties of Fe-Cr-Ni and Fe-Cr-Mn austenitic steels under mixed and fast neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shamardin, V.K. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors; Bulanova, T.M. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors; Golovanov, V.N. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors; Neustroyev, V.S. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors; Povstyanko, A.V. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors; Ostrovsky, Z.E. [State Sci. Centre of Russian Federation, Dimitrovgrad (Russian Federation). Res. Inst. of Atomic Reactors

    1996-10-01

    Detailed investigations are performed on mechanical properties, swelling and structure of different types of Fe-Cr-Ni and Fe-Cr-Mn austenitic stainless steels irradiated in the SM-2 high-flux research reactor and BOR-60 fast reactor. Steel irradiation temperatures are ranging from 100 up to 800 C and the maximum achieved level of damage doses is 60 dpa for Fe-Cr-Mn steel (with 4-5% of Ni) and 30 dpa for steels of the C-12Cr-20Mn-W-T type. Presented are dose dependencies of swelling and mechanical properties of Fe-Cr-Ni and Fe-Cr-Mn steels. It is shown that at temperatures below 530 C the investigated Fe-Cr-Mn steel systems are less susceptible to swelling as compared to Fe-Cr-Ni ones. Fe-Cr-Mn steels showed a lower value of irradiation embrittlement after irradiation in the mixed spectrum at temperatures from 100 up to 400 C and much higher embrittlement after irradiation from 350 up to 400 C in the fast spectrum in comparison with Fe-Cr-Ni steels. Higher hardening rate of Fe-Cr-Mn steels after their irradiation in BOR-60 is attributed to the presence of dislocation loops and defects of high density in the structure. The structural change features in Fe-Cr-Mn steels under irradiation are considered taking into account austenite stabilization in the initial state. (orig.).

  13. Research on Mediate Temperature Decomposition of High Nitrogen Austenite

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-ling; BEI Duo-hui; HU Ming-juan; ZHU Zu-chang

    2004-01-01

    The decomposed products from high nitrogen austenite aging at 225℃ were investigated by TEM. It is found that the shape of decomposition products inside the austenite grains is not regular and not strictly oriented. Preferential nucleation of γ-Fe4N at dislocations and grain boundaries has been observed. It also has been found that during the first stage of the high nitrogen austenite decomposition a large quantity of ultra-fine γ-Fe4N precipitate inside the parent austenite, which has been thought to be the undecomposed region before. The ultimate products are composed of highly dispersed α-Fe and γ-Fe4N, with both of them maintaining nanometer scale. The micro-hardness of them can be as high as900HV.

  14. Change in the properties of FeCrNi and FeCrMn austenitic steels under mixed and fast neutron irradiation

    Science.gov (United States)

    Shamardin, V. K.; Bulanova, T. M.; Golovanov, V. N.; Neustroyev, V. S.; Povstyanko, A. V.; Ostrovsky, Z. E.

    1996-10-01

    Detailed investigations are performed on mechanical properties, swelling and structure of different types of FeCrNi and FeCrMn austenitic stainless steels irradiated in the SM-2 high-flux research reactor and BOR-60 fast reactor. Steel irradiation temperatures are ranging from 100 up to 800°C and the maximum achieved level of damage doses is 60 dpa for FeCrMn steel (with 4-5% of Ni) and 30 dpa for steels of the C12Cr20MnWT type. Presented are dose dependencies of swelling and mechanical properties of FeCrNi and FeCrMn steels. It is shown that at temperatures below 530°C the investigated FeCrMn steel systems are less susceptible to swelling as compared to FeCrNi ones. FeCrMn steels showed a lower value of irradiation embrittlement after irradiation in the mixed spectrum at temperatures from 100 up to 400°C and much higher embrittlement after irradiation from 350 up to 400°C in the fast spectrum in comparison with FeCrNi steels. Higher hardening rate of FeCrMn steels after their irradiation in BOR-60 is attributed to the presence of dislocation loops and defects of high density in the structure. The structural change features in FeCrMn steels under irradiation are considered taking into account austenite stabilization in the initial state.

  15. The critical analysis of austenitic manganese steel T130Mn135 used for castings in the mining industry

    Science.gov (United States)

    Josan, A.; Pinca Bretotean, C.; Putan, V.

    2016-02-01

    This paper presents the critical analysis of making technology of austenitic manganese steel T130Mn135, used for castings of the type Mills hammer at a Romanian foundry. Are analyzed 11 charges of steel for castings and is determined the diagram of the heat treatment. After the applying of the heat treatment results a single-phase structure, consisting of homogeneous austenite. For all the 11 charges is presented the variation of chemical composition.

  16. Effect of Nickel Equivalent on Austenite Transition Ratio in Ni-Mn-Cu Cast Iron

    Directory of Open Access Journals (Sweden)

    Janus A.

    2013-06-01

    Full Text Available Determined was quantitative effect of nickel equivalent value on austenite decomposition degree during cooling-down castings of Ni-Mn- Cu cast iron. Chemical composition of the alloy was 1.8 to 5.0 % C, 1.3 to 3.0 % Si, 3.1 to 7.7 % Ni, 0.4 to 6.3 % Mn, 0.1 to 4.9 % Cu, 0.14 to 0.16 % P and 0.03 to 0.04 % S. Analysed were castings with representative wall thickness 10, 15 and 20 mm. Scope of the examination comprised chemical analysis (including WDS, microscopic observations (optical and scanning microscopy, image analyser, as well as Brinell hardness and HV microhardness measurements of structural components.

  17. Metallurgical Source of Cryogenic Intergranular Fracture of Fe-38Mn Austenitic Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    SEM and Field emitting TEM-EDAX were used to investigate the fracture surface of series impact specimens and the grain boundary chemistries of VIM (vacuum-induction-melted) Fe-38Mn austenitic alloy before and after ESR (electroslag remelting,). The quantity and the size of inclusions were also examined. The results show that the VIM Fe-38Mn aust enitinic alloy water-quenched from 1 100 ℃ undergoes an obvious ductile-to-brittle transition, and the impact work at ambient temperature is 242 J, the corresponding fracture surface exhibits adimple character. However, the impact work at 77 K of VIM alloy is only 25 J and the fracture mode is IGF (intergranular f racture). After ESR, the impact work at ambient temperature is 320 J and the fra cture surface exhibits a character of "volcano lava" (meaning excellent toughn ess); The impact work at 77 K is up to 300 J and the fracture mode is microvoid coalescence mixed with quasi-cleavage. The segregation of Mn is not found in all specimens, but the segregation of S is observed, and the S segregation is decreased after ESR. The examined results of inclusions show that ESR reduces the quantity and improves the morphology of inclusions. From the above results it can be seen that the cryogenic IGF of VIM Fe-38Mn austenitic alloy is related to the S segregation at grain boundary. After ESR the decrease in the quantity and size of inclusion results in the increase of the impact work at ambient temperature, while the restriction of IGF is related to the decrease in the total level, and hence in the grain boundary segregation of S.

  18. Characterization of Tensile Strain Hardening Behaviors for 32Mn-7Cr-1Mo-0.3N Cryogenic Austenitic Steel

    Institute of Scientific and Technical Information of China (English)

    Liang QIU; Ruidong FU; Cunyu WANG; Yangzeng ZHENG

    2006-01-01

    The strain hardening behaviors of 32Mn-7Cr-1Mo-0.3N austenitic steel were characterized by a simple and effective method. The results show that Hollomon relationship is not applicable during total uniform deformation stage. The flow equation was proposed, Inσ=aexp(lnε/b)+c. The variation rates of strain hardening exponents with true strain at 77 K are obviously higher than that at other temperatures and the value of d2σ/dε2 becomes positive during high strain stage. The characters of this variation are principal reasons for increasing elongation at 77 K. The forming of mechanical twin as well as ε-martensite leads to a high elongation at 77 K.

  19. Oxidation resistant high creep strength austenitic stainless steel

    Science.gov (United States)

    Brady, Michael P.; Pint, Bruce A.; Liu, Chain-Tsuan; Maziasz, Philip J.; Yamamoto, Yukinori; Lu, Zhao P.

    2010-06-29

    An austenitic stainless steel displaying high temperature oxidation and creep resistance has a composition that includes in weight percent 15 to 21 Ni, 10 to 15 Cr, 2 to 3.5 Al, 0.1 to 1 Nb, and 0.05 to 0.15 C, and that is free of or has very low levels of N, Ti and V. The alloy forms an external continuous alumina protective scale to provide a high oxidation resistance at temperatures of 700 to 800.degree. C. and forms NbC nanocarbides and a stable essentially single phase fcc austenitic matrix microstructure to give high strength and high creep resistance at these temperatures.

  20. Fracture behavior of neutron-irradiated high-manganese austenitic steels

    Science.gov (United States)

    Yoshida, H.; Miyata, K.; Narui, M.; Kayano, H.

    1991-03-01

    The instrumented Charpy impact test was applied to study the fracture behavior of high-manganese austenitic steels before and after neutron irradiations. Quarter-size specimens of a commercial high-manganese steel (18% Mn-5% Ni-16% Cr), three reference steels (21% Mn-1% Ni-9% Cr, 20% Mn-1% Ni-11% Cr, 15% Mn-1% Ni-13% Cr) and two model steels (17% Mn-4.5% Si-6.5% Cr, 22% Mn-4.5% Si-6.5% Cr-0.2% N) were used for the impact tests at temperatures between 77 and 523 K. The load-deflection curves showed typical features corresponding to characteristics of the fracture properties. The temperature dependences of fracture energy and failure deflection obtained from the curves clearly demonstrate only small effects up to 2 × 10 23 n/m 2 ( E > 0.1 MeV) and brittleness at room temperature in 17% Mn-Si-Cr steel at 1.6 × 10 25 n/m 2 ( E > 0.1 MeV), while ductility still remains in 22%Mn-Si-Cr steel.

  1. The effect of hydrogen on strain hardening and fracture mechanism of high-nitrogen austenitic steel

    Science.gov (United States)

    Maier, G. G.; Astafurova, E. G.; Melnikov, E. V.; Moskvina, V. A.; Vojtsik, V. F.; Galchenko, N. K.; Zakharov, G. N.

    2016-07-01

    High-nitrogen austenitic steels are perspective materials for an electron-beam welding and for producing of wear-resistant coatings, which can be used for application in aggressive atmospheres. The tensile behavior and fracture mechanism of high-nitrogen austenitic steel Fe-20Cr-22Mn-1.5V-0.2C-0.6N (in wt.%) after electrochemical hydrogen charging for 2, 10 and 40 hours have been investigated. Hydrogenation of steel provides a loss of yield strength, uniform elongation and tensile strength. The degradation of tensile properties becomes stronger with increase in charging duration - it occurs more intensive in specimens hydrogenated for 40 hours as compared to ones charged for 2-10 hours. Fracture analysis reveals a hydrogen-induced formation of brittle surface layers up to 6 μm thick after 40 hours of saturation. Hydrogenation changes fracture mode of steel from mixed intergranular-transgranular to mainly transgranular one.

  2. High Energy Rate Forming Induced Phase Transition in Austenitic Steel

    Science.gov (United States)

    Kovacs, T.; Kuzsella, L.

    2017-02-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea means indirect hardening setup. Austenitic stainless steels have high plasticity and can be cold formed easily. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness [1]. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  3. Effect of alloying elements on branching of primary austenite dendrites in Ni-Mn-Cu cast iron

    Directory of Open Access Journals (Sweden)

    A. Janus

    2011-04-01

    Full Text Available Within the research, determined were direction and intensity of influence of individual alloying elements on branching degree of primary austenite dendrites in austenitic cast iron Ni-Mn-Cu. 30 cast shafts dia. 20 mm were analysed. Chemical composition of the alloywas as follows: 2.0 to 3.3 % C, 1.4 to 3.1 % Si, 2.8 to 9.5 % Ni, 0.4 to 7.7 % Mn, 0 to 4.6 % Cu, 0.14 to 0.16 % P and 0.03 to 0.04 % S.Analysis was performed separately for the dendrites solidifying in directional and volumetric way. The average distance "x" between the2nd order arms was accepted as the criterion of branching degree. It was found that influence of C, Si, Ni, Mn and Cu on the parameter "x"is statistically significant. Intensity of carbon influence is decidedly higher than that of other elements, and the influence is more intensive in the directionally solidifying dendrites. However, in the case of the alloyed cast iron Ni-Mn-Cu, combined influence of the alloying elements on solidification course of primary austenite can be significant.

  4. High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

    Institute of Scientific and Technical Information of China (English)

    LI Hua-bing; JIANG Zhou-hua; SHEN Ming-hui; YOU Xiang-mi

    2007-01-01

    A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe-Cr-Mn-Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 0.69% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel-free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 0.81 %. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃× 1 h followed by water quenching, the microstructure consisted of homogeneous austenite.

  5. STRUCTURAL STABILITY OF HIGH NITROGEN AUSTENITIC STAINLESS STEELS

    Directory of Open Access Journals (Sweden)

    Jana Bakajová

    2011-05-01

    Full Text Available This paper deals with the structural stability of an austenitic stainless steel with high nitrogen content. The investigated steel was heat treated at 800°C using different annealing times. Investigation was carried out using light microscopy, transmission electron microscopy and thermodynamic calculations. Three phases were identified by electron diffraction: Cr2N, sigma – phase and M23C6. The thermodynamic prediction is in good agreement with the experimental result. The only is the M23C6 carbide phase which is not thermodynamically predicted. Cr2N is the majority secondary phase and occurs in the form of discrete particles or cells (lamellas of Cr2N and austenite.

  6. PRECIPITATION BEHAVIOR OF M2N IN A HIGH-NITROGEN AUSTENITIC STAINLESS STEEL DURING ISOTHERMAL AGING

    Institute of Scientific and Technical Information of China (English)

    F. Shi; L.J. Wang; W.F. Cui; C.M. Liu

    2007-01-01

    The precipitation behavior of M2N and the microstructural evolution in a Cr-Mn austenitic stainless steel with a high nitrogen content of 0.43mass% during isothermal aging has been investigated using optical microscopy (OM), scanning electron microscopy ( SEM), and transmission electron microscopy (TEM). The aging treatments have led to the decomposition of nitrogen supersaturated austenitic matrix through discontinuous cellular precipitation. The precipitated cells comprise alternate lamellae of M2N precipitate and austenitic matrix. This kind of precipitate morphology is similar to that of pearlite. However, owing to the non-eutectoidic mechanism of the reaction, the growth characteristic of the cellular precipitates is different from that of pearlite in Fe-C binary alloys. M2N precipitate in the cell possesses a hexagonal crystal structure with the parameters a=0.4752nm and c=0.4429nm, and the orientation relationship between the MN precipitates and austenite determined from the SADP is [01110]M2N// [101]γ,[2-1-10]M2N// [010]γ.

  7. The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite.

    Science.gov (United States)

    Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

    2013-10-23

    The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c' elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

  8. Impact Toughness Properties of Nickel- and Manganese-Free High Nitrogen Austenitic Stainless Steels

    Science.gov (United States)

    Mohammadzadeh, Roghayeh; Akbari, Alireza; Mohammadzadeh, Mina

    2016-12-01

    A large amount of manganese (>10 wt pct) in nickel-free high nitrogen austenitic stainless steels (Ni-free HNASSs) can induce toxicity. In order to develop Ni-free HNASSs with low or no manganese, it is necessary to investigate their mechanical properties for biomedical applications. This work aims to study the Charpy V-notch (CVN) impact toughness properties of a Ni- and Mn-free Fe-22.7Cr-2.4Mo-1.2N HNASS plate in the temperature range of 103 K to 423 K (-170 °C to 150 °C). The results show that unlike conventional AISI 316L austenitic stainless steel, the Ni- and Mn-free HNASS exhibits a sharp ductile-to-brittle transition (DBT). The intergranular brittle fracture associated with some plasticity and deformation bands is observed on the fracture surface at 298 K (25 °C). Electron backscattered diffraction (EBSD) analysis of the impact-tested sample in the longitudinal direction indicates that deformation bands are parallel to {111} slip planes. By decreasing the temperature to 273 K, 263 K, and 103 K (0 °C, -10 °C, and -70 °C), entirely intergranular brittle fracture occurs on the fracture surface. The fracture mode changes from brittle fracture to ductile as the temperature increases to 423 K (150 °C). The decrease in impact toughness is discussed on the basis of temperature sensitivity of plastic flow and planarity of deformation mechanism.

  9. Effect of initial microstructure on austenite formation kinetics in high-strength experimental microalloyed steels

    Institute of Scientific and Technical Information of China (English)

    Edgar Lpez-Martnez; Octavio Vzquez-Gmez; Hctor Javier Vergara-Hernndez; Bernardo Campillo

    2015-01-01

    Austenite formation kinetics in two high-strength experimental microalloyed steels with different initial microstructures compris-ing bainite–martensite and ferrite–martensite/austenite microconstituents was studied during continuous heating by dilatometric analysis. Austenite formation occurred in two steps:(1) carbide dissolution and precipitation and (2) transformation of residual ferrite to austenite. Di-latometric analysis was used to determine the critical temperatures of austenite formation and continuous heating transformation diagrams for heating rates ranging from 0.03°C×s−1 to 0.67°C×s−1. The austenite volume fraction was fitted using the Johnson–Mehl–Avrami–Kolmogorov equation to determine the kinetic parameters k and n as functions of the heating rate. Both n and k parameters increased with increasing heat-ing rate, which suggests an increase in the nucleation and growth rates of austenite. The activation energy of austenite formation was deter-mined by the Kissinger method. Two activation energies were associated with each of the two austenite formation steps. In the first step, the austenite growth rate was controlled by carbon diffusion from carbide dissolution and precipitation;in the second step, it was controlled by the dissolution of residual ferrite to austenite.

  10. Determination of the orientation relationship between austenite and incommensurate 7M modulated martensite in Ni-Mn-Ga alloys

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z.B. [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Zhang, Y.D. [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite Paul Verlaine - Metz, 57045 Metz (France); Esling, C., E-mail: claude.esling@univ-metz.fr [Laboratoire d' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite Paul Verlaine - Metz, 57045 Metz (France); Zhao, X. [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Zuo, L., E-mail: lzuo@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China)

    2011-04-15

    For Ni-Mn-Ga ferromagnetic shape memory alloys, a large magnetic-field-induced strain could be reached through the reorientation of martensitic variants in the martensite state. Owing to the collective and displacive nature of the austenite to martensite transformation, a certain orientation relationship (OR) between the parent and the product phase is required to minimize the transformation strain and the strain energy generated, which brings about self-accommodating groups of martensitic variants with specific orientation correlations. In this work, the microstructural and crystallographic characteristics of martensitic variants in a polycrystalline Ni{sub 50}Mn{sub 30}Ga{sub 20} alloy were investigated by electron backscatter diffraction analysis. With accurate orientation measurement on inherited martensitic variants, the local orientations of parent austenite grains were predicted using four classical OR for the martensitic transformation. Furthermore, a specific OR, namely the Pitsch relation with (1 0 1){sub A}//(1 2-bar 10-bar){sub 7M} and [1 0 1-bar]{sub A}//[10-bar 10-bar 1]{sub 7M}, was unambiguously determined by considering the magnitude of discontinuity between the lattices of the product and parent phases and the structural modulation of the incommensurate 7M modulated martensite. The present procedure to determine the OR, without recourse to the presence of retained austenite, is in general applicable to a variety of materials with modulated superstructure for insight into their martensitic transformation processes.

  11. Effect of Austenite Transformation on Abrasive Wear and Corrosion Resistance of Spheroidal Ni-Mn-Cu Cast Iron

    Directory of Open Access Journals (Sweden)

    Medyński D.

    2016-09-01

    Full Text Available Within the presented work, the effect of austenite transformation on abrasive wear as well as on rate and nature of corrosive destruction of spheroidal Ni-Mn-Cu cast iron was determined. Cast iron contained: 3.1÷3.4 %C, 2.1÷2.3 %Si, 2.3÷3.3 %Mn, 2.3÷2.5 %Cu and 4.8÷9.3 %Ni. At a higher degree of austenite transformation in the alloys with nickel equivalent below 16.0%, abrasive wear resistance was significantly higher. Examinations of the corrosion resistance were carried out with the use of gravimetric and potentiodynamic method. It was shown that higher degree of austenite transformation results in significantly higher abrasive wear resistance and slightly higher corrosion rate, as determined by the gravimetric method. However, results of potentiodynamic examinations showed creation of a smaller number of deep pinholes, which is a favourable phenomenon from the viewpoint of corrosion resistance.

  12. Effect of austenitization heat treatment on the magnetic properties of Fe-40wt% Ni-2wt% Mn alloy

    Institute of Scientific and Technical Information of China (English)

    S. Buyukakkas; H. Aktas; S. Akturk

    2007-01-01

    The effect of austenitization heat treatment on magnetic properties was examined by means of M(o)ssbauer spectroscopy on an Fe-40wt%Ni-2wt%Mn alloy. The morphology of the alloy was obtained by using scanning electron microscopy (SEM) under different heat treatment conditions. The magnetic behavior of the non heat-treated alloy is ferromagnetic. A mixed magnetic structure including both paramagnetic and ferromagnetic states was obtained at 800℃ after 6 and 12 h heat treatments. In addition, the magnetic structure of the heat-treated alloy at 1150℃ for 12 h was ferromagnetic. With the volume fraction changing, the effective hyperfine field of the ferromagnetic austenite phase and isomery shift values were also determined by M(o)ssbauer spectroscopy.

  13. Effects of Mo on the Precipitation Behaviors in High-Nitrogen Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    Feng Shi; Yang Qi; Chunming Liu

    2011-01-01

    Precipitation behaviors of Fe-18Cr-18Mn-0.63N and Fe-18Cr-18Mn-2Mo-0.69N high-nitrogen austenitic stainless steels during isothermally aging at 850℃ have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The experimental results show that precipitation displays a discontinuous cellular way and the precipitates are identified as Cr2N in Fe-18Cr-18Mn-0.63N steel. The addition of Mo makes precipitation occur not only at the grain boundary but also inside the grain and precipitation also displays discontinuous cellular way. The precipitates at the grain boundary and in the cell are both identified as G2N phase and χ phase and the precipitates inside the grain are identified as χ phase in Fe-18Cr-18Mn-2Mo-0.69N steel. The nucleations of χ phase and Cr2N phase at the grain boundary are both governed by the diffusion of Cr atoms. The formation and growth of χ phase inside the grain are induced by the impoverishment of N atoms with increasing aging time.

  14. High Nitrogen Austenitic Stainless Steel Precipitation During Isothermal Annealing

    Directory of Open Access Journals (Sweden)

    Maria Domankova

    2016-07-01

    Full Text Available The time-temperature-precipitation in high-nitrogen austenitic stainless steel was investigated using light optical microscopy, transmission electron microscopy, selected area diffraction and energy-dispersive X-ray spectroscopy. The isothermal precipitation kinetics curves and the corresponding precipitation activation energy were obtained. The diffusion activation energy of M2N precipitation is 129 kJ/mol. The results show that critical temperature for M2N precipitation is about 825°C with the corresponding incubation period 2.5 min.

  15. submitter Physical Properties of a High-Strength Austenitic Stainless Steel for the Precompression Structure of the ITER Central Solenoid

    CERN Document Server

    Sgobba, Stefano; Arauzo, Ana; Roussel, Pascal; Libeyre, Paul

    2016-01-01

    The ITER central solenoid (CS) consists of six independent coils kept together by a precompression support structure that must react vertical tensile loads and provide sufficient preload to maintain coil-to-coil contact when the solenoid is energized. The CS precompression system includes tie plates, lower and upper key blocks, load distribution and isolation plates and other attachment, support and insulating hardware. The tie plates operating at 4 K are manufactured starting from forgings in a high-strength austenitic stainless steel (FXM-19) with a stringent specification. Moreover, forged components for the lower and upper key blocks have to be provided in the same FXM-19 grade with comparably strict requirements. FXM-19 is a high-nitrogen austenitic stainless steel, featuring high strength and toughness, ready weldability, and forgeability. It features as well higher integral thermal contraction down to 4 K compared with the very high Mn steel grade selected for the CS coil jackets, hence providing an ad...

  16. Mechanical characteristics and swelling of austenitic Fe-Cr-Mn steels irradiated in the SM-2 and BOR-60 reactors. [0. 4C-12Cr-19Mn-2Ni-Mo-N; 0. 4C-12Cr-14Mn-5Ni-Mo-2Al-B; 0. 4C-17Cr-17Mn-Cu-Mo-Nb-N; Fe-Cr-Ni steel: 0. 8C-16Cr-15Ni-3Mo-Nb; 316; 304

    Energy Technology Data Exchange (ETDEWEB)

    Shamardin, V.K.; Bulanova, T.M.; Neustroev, V.S. (Lenin (V.I.) Research Inst. of Atomic Reactors, Dimitrovgrad (USSR)); Ivanov, L.I.; Djomina, E.V.; Platov, Yu.M. (AN SSSR, Moscow (USSR). A.A. Baikov Inst. of Metallurgy)

    Three types of austenitic Fe-Cr-Mn stainless steels were irradiated simultaneously with Fe-Cr-Ni austenitic steel at temperatures from 400 to 800deg C in the mixed spectrum of the high flux SM-2 reactor to 10 dpa and 700 appm of He and in the BOR-60 reactor to 60 dpa without He generation. The paper presents the swelling and mechanical properties of steels irradiated in the BOR-60 and SM-2 as a function of the concentration of transmuted He and the value of atomic displacement. (orig.).

  17. The effect of solid solution treatment on the hardness and microstructure of 0.6%wt C-10.8%wt Mn-1.44%wt Cr austenitic manganese steel

    Science.gov (United States)

    Nurjaman, F.; Bahfie, F.; Astuti, W.; Shofi, A.

    2017-04-01

    Austenitic manganese steel is steel alloy that has high manganese content (10-14%wt Mn). The characteristics of austenitic manganese steel are good in toughness, ductility, and wear resistance. Effect of solid solution treatment on the hardness and microstructure of austenitic manganese steel was studied in this experiment. The solid solution treatment process of austenitic manganese steel, 0.6%wt C-10.8%wt Mn-1.44%wt Cr, was conducted by heating the material at varied temperatures (950°C, 1000°C, 1050°C) for an hour and then quenching it in two different quenching media, i.e. oil and water. Further, the samples were tempered at three different temperatures (300°C, 400°C, and 500°C) for 2 hours. The treated materials were analyzed by Rockwell Hardness Tester to obtain the information of materials hardness and by an optical microscope and XRD to investigate the microstructure phase of the treated materials. Heating the austenitic manganese steel at 950°C for an hour followed by water quenching dissolved all carbide in as-cast condition and resulted the fully austenitic on its microstructure. Carbide precipitation occurred due to the prolongation of soaking time in solid solution treatment and tempering process. The optimum hardness of sample was 53.3 HRC, which was resulted by heating this material until 1000°C for an hour, followed by water quenching and tempering at 400°C for 2 hours.

  18. Effect of Carbon and Phosphorous on the Solidification Microstructure in a Cr-Ni-Mn-N Austenitic Hydrogen-resistant Steel

    Institute of Scientific and Technical Information of China (English)

    Jun TAN; Luming MA; Shouxin LI; Lijian RONG; Jincai YUAN; Yiyi LI

    2001-01-01

    The influence of carbon and phosphorus on the solidification microstructure of a Cr-Ni-Mn-N austenitic steel was studied. The button specimens were prepared by vacuum induction melting and magnetic convection. The experimental results show that the increase of C or P concentration in the steel can change the solidification modes of Cr-Ni-Mn-N austenitic steels and has a significant effect on the morphology of the dendrites. The content of δ-ferrite in the microstructure reduces with increasing the concentration of C or P in the steel, there is a gradient of the content of δ-ferrite formed from surface through the center of the specimens.

  19. Synergistic Computational and Microstructural Design of Next- Generation High-Temperature Austenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Karaman, Ibrahim [Texas A& M Engineering Experiment Station, College Station, TX (United States); Arroyave, Raymundo [Texas A& M Engineering Experiment Station, College Station, TX (United States)

    2015-07-31

    The purpose of this project was to: 1) study deformation twinning, its evolution, thermal stability, and the contribution on mechanical response of the new advanced stainless steels, especially at elevated temperatures; 2) study alumina-scale formation on the surface, as an alternative for conventional chromium oxide, that shows better oxidation resistance, through alloy design; and 3) design new generation of high temperature stainless steels that form alumina scale and have thermally stable nano-twins. The work involved few baseline alloys for investigating the twin formation under tensile loading, thermal stability of these twins, and the role of deformation twins on the mechanical response of the alloys. These baseline alloys included Hadfield Steel (Fe-13Mn-1C), 316, 316L and 316N stainless steels. Another baseline alloy was studied for alumina-scale formation investigations. Hadfield steel showed twinning but undesired second phases formed at higher temperatures. 316N stainless steel did not show signs of deformation twinning. Conventional 316 stainless steel demonstrated extensive deformation twinning at room temperature. Investigations on this alloy, both in single crystalline and polycrystalline forms, showed that deformation twins evolve in a hierarchical manner, consisting of micron–sized bundles of nano-twins. The width of nano-twins stays almost constant as the extent of strain increases, but the width and number of the bundles increase with increasing strain. A systematic thermomechanical cycling study showed that the twins were stable at temperatures as high as 900°C, after the dislocations are annealed out. Using such cycles, volume fraction of the thermally stable deformation twins were increased up to 40% in 316 stainless steel. Using computational thermodynamics and kinetics calculations, we designed two generations of advanced austenitic stainless steels. In the first generation, Alloy 1, which had been proposed as an alumina

  20. Study of Fe-12Cr-20Mn-W-C austenitic steels irradiated in the SM-2 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shamardin, V.K.; Bulanova, T.M.; Neustroyev, V.S.; Ostrovsky, Z.E.; Kosenkov, V.M. (V.I. Lenin Research Inst. of Atomic Reactors, Dimitrovgrad (Russia)); Ivanov, L.I.; Djomina, E.V. (A.A. Baikov Inst. of Metallurgy, Academy of Science, Moscow (Russia))

    1992-09-01

    A comparison has been made between the mechanical properties and swelling of austenitic stainless steels EP-838 (Fe-Cr-Mn) and 316SS (Fe-Cr-Ni) irradiated in the mixed-neutron spectrum of the SM-2 reactor in the temperture range 400-800deg C (every 100deg C) to 16 dpa dose with 1000 and 3000 appm helium generation, correspondingly, determined by nickel content. EP-838 exhibited less susceptibility to void swelling and radiation hardening. Fe-12Cr-20Mn-W-0.1C steel without nickel irradiated at 100deg C to 21 dpa exhibited significant radiation hardening accompanied by [alpha]-phase formation in the steel structure. (orig.).

  1. Study of Fe-12Cr-20Mn-W-C austenitic steels irradiated in the SM-2 reactor

    Science.gov (United States)

    Shamardin, V. K.; Bulanova, T. M.; Neustroyev, V. S.; Ostrovsky, Z. E.; Kosenkov, V. M.; Ivanov, L. I.; Djomina, E. V.

    1992-09-01

    A comparison has been made between the mechanical properties and swelling of austenitic stainless steels EP-838 (Fe-Cr-Mn) and 316SS (Fe-Cr-Ni) irradiated in the mixed-neutron spectrum of the SM-2 reactor in the temperature range 400-800°C (every 100°C) to 16 dpa dose with 1000 and 3000 appm helium generation correspondingly, determined by nickel content. EP-838 exhibited less susceptibility to void swelling and radiation hardening. Fe-12Cr-20Mn-W-0.1C steel without nickel irradiated at 100°C to 21 dpa exhibited significant radiation hardening accompanied by α-phase formation in the steel structure.

  2. Scale-bridging analysis on deformation behavior of high-nitrogen austenitic steels.

    Science.gov (United States)

    Lee, Tae-Ho; Ha, Heon-Young; Hwang, Byoungchul; Kim, Sung-Joon; Shin, Eunjoo; Lee, Jong Wook

    2013-08-01

    Scale-bridging analysis on deformation behavior of high-nitrogen austenitic Fe-18Cr-10Mn-(0.39 and 0.69)N steels was performed by neutron diffraction, electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). Two important modes of deformation were identified depending on the nitrogen content: deformation twinning in the 0.69 N alloy and strain-induced martensitic transformation in the 0.39 N alloy. The phase fraction and deformation faulting probabilities were evaluated based on analyses of peak shift and asymmetry of neutron diffraction profiles. Semi in situ EBSD measurement was performed to investigate the orientation dependence of deformation microstructure and it showed that the variants of ε martensite as well as twin showed strong orientation dependence with respect to tensile axis. TEM observation showed that deformation twin with a {111} mathematical left angle bracket 112 mathematical right angle bracket crystallographic component was predominant in the 0.69 N alloy whereas two types of strain-induced martensites (ε and α' martensites) were observed in the 0.39 N alloy. It can be concluded that scale-bridging analysis using neutron diffraction, EBSD, and TEM can yield a comprehensive understanding of the deformation mechanism of nitrogen-alloyed austenitic steels.

  3. Investigation of Deformation Mechanisms in Deep-Drawn and Tensile-Strained Austenitic Mn-Based Twinning Induced Plasticity (TWIP) Steel

    NARCIS (Netherlands)

    Van Tol, R.T.; Zhao, L.; Schut, H.; Sietsma, J.

    2012-01-01

    The effect of strain on the deformation mechanisms in an austenitic Mn-based twinning induced plasticity (TWIP) steel is investigated using magnetic measurements, XRD, positron beam Doppler spectroscopy, and finite element method simulations. The experimental observations reveal the formation of a0-

  4. Transmission electron microscopy study of high temperature bainitic transformation in 1 wt.% Mn ductile iron

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadabadi, M.N. [Tohoku Univ., Sendai (Japan); Niyama, E. [Tohoku Univ., Sendai (Japan); Echigoya, J. [Tohoku Univ., Sendai (Japan)

    1995-04-01

    A 1 wt.% Mn ductile iron austenitized at 900 C for 90 min and austempered at 375 C for different periods was used to study some aspects of bainitic reaction in high Mn austempered ductile iron with reference to carbide precipitation in bainitic ferrite. Transmission electron microscopy (TEM) energy-dispersive X-ray analysis (EDXA) study shows that precipitation of carbide in the ferritic component of bainite is a function of the local concentration of alloying elements. In other words, in the region near graphite where Si segregates and there is negative Mn segregation as well as carbon, the bainitic ferrite is carbide free. However, in the intercellular region where Mn segregates and Si is depleted, the ferritic component of bainite occurs together with very fine and almost uniformly distributed carbide. Furthermore, TEM-EDXA results show that the increase in Mn content not only delays stage I (the initial transformation of austenite to ferrite and retained austenite) of the bainitic reaction, but also delays stage II (decomposition of retained austenite to ferrite and carbide). ((orig.))

  5. High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S. [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P., E-mail: pentti.karjalainen@oulu.fi [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland)

    2010-08-20

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 10{sup 6} cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  6. Contribution of deformation mechanisms to strength and ductility in two Cr-Mn grade austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S., E-mail: atef_saleh@s-petrol.suez.edu.eg [Materials Engineering Laboratory, Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P. [Materials Engineering Laboratory, Box 4200, University of Oulu, 90014 Oulu (Finland); Misra, R.D.K. [Center for Structural and Functional Materials and Chemical Engineering Department, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA. (United States); Talonen, J. [Outokumpu Oyj, Box 140, FI-02201 Espoo (Finland)

    2013-01-01

    The role of different deformation mechanisms in controlling mechanical properties were studied in two low-Ni, Cr-Mn austenitic stainless steel grades (Types 201 and 201L) by tensile testing and microstructure examinations. Tensile tests were carried out at two different strain rates, 5 Multiplication-Sign 10{sup -4} and 10{sup -2} s{sup -1}, in the temperature range from -80 Degree-Sign C to 200 Degree-Sign C. It was observed that the flow properties and work hardening rate are affected significantly by temperature and strain rate for the concerned steels through variation of deformation mechanism. Deformation-induced austenite-to-martensite transformation (TRIP effect) is the dominant mechanism at temperatures below room temperature. From 50 Degree-Sign C up to 200 Degree-Sign C, plastic deformation is controlled by mechanical twinning (TWIP effect) and dislocation glide. The electron backscattered diffraction (EBSD) technique and transmission electron microscopy (TEM) were employed to study the plastic deformation accommodation and identify the primary deformation mechanisms operating in the deformed steels.

  7. In Situ Observation of Austenite Growth During Continuous Heating in Very-Low-Carbon Fe-Mn and Ni Alloys

    Science.gov (United States)

    Enomoto, M.; Wan, X. L.

    2017-02-01

    The growth of austenite during continuous heating was observed in situ under a confocal scanning laser microscope in Fe-Mn and Ni alloys containing less than 0.01 mass pct C. The advancements of the α/γ boundary were measured in the temperature range of ca. 40 K, which encompassed the Ae3 line of the alloys. Below Ae3, the growth rates were of the same order of magnitude as those predicted from the carbon diffusion-controlled negligible partition local equilibrium in the (α + γ) two-phase region, whereas those observed near and above the Ae3 were ca. two orders of magnitude greater. The α/γ boundary mobilities evaluated therefrom were somewhat smaller than those obtained previously in massive ferrite transformation during continuous cooling in the same alloys, albeit the experimental scatter was large and fell near the mobilities proposed in the literature. The α/γ boundary migrated probably with a carbon diffusion spike ahead of the boundary and the solute drag of the carbon or alloy element is unlikely to be operative during the growth of austenite.

  8. On Various Aspects of Decomposition of Austenite in a High-Silicon Steel During Quenching and Partitioning

    Science.gov (United States)

    Somani, Mahesh Chandra; Porter, D. A.; Karjalainen, L. P.; Misra, R. D. K.

    2013-10-01

    Using a Gleeble thermomechanical simulator, a high-silicon steel (Fe-0.2C-1.5Si-2.0Mn-0.6Cr) was laboratory hot-rolled, re-austenitized, quenched into the M s-M f range, retaining 15 to 40 pct austenite at the quench stop temperature (T Q), and annealed for 10 to 1000 seconds at or above T Q in order to better understand the mechanisms operating during partitioning. Dilatometer measurements, transmission electron microscopy, and calculations showed that besides carbon partitioning, isothermal martensite and bainite form at the partitioning temperature. While isothermal martensite formation starts almost immediately after quenching with the rate of volume expansion dropping all the time, the beginning of bainite formation is marked by a sudden increase in the rate of expansion. The extent of its formation depends on the partitioning temperature following TTT diagram predictions. At the highest partitioning temperatures martensite tempering competes with partitioning. Small fractions of bainite and high-carbon martensite formed on cooling from the partitioning temperature. The average carbon content of the austenite retained at room temperature as determined from XRD measurements was close to the carbon content estimated from the M s temperature of the martensite formed during the final cooling.

  9. Austenite-to-pearlite isothermal decomposition mechanisms in a 0.44C-0.73Mn steel; Estudio de los mecanismos de descomposicion isotermica de austenita en perlita en un acero 0,44C-0,73Mn

    Energy Technology Data Exchange (ETDEWEB)

    Aranda, M. M.; Pimentel, G.; Cornide, J.; Capdevila, C.

    2012-11-01

    The goal of this paper is to determine the austenite-to-pearlite isothermal decomposition mechanisms in a 0.44C-0.73 Mn steel. More precisely, the role of austenitizing temperature (Tg), and hence the austenitic grain size (AGS), in the kinetics of pearlite formation has been studied. Results allow us to conclude that the average size of pearlitic colonies is increased as the AGS is increased. On the other hand, it appears that the inter lamellar spacing of the pearlite does not depend on the Tg.. but is controlled by the isothermal decomposition temperature of austenite (T). Finally, it was found that formation of pearlite is triggered for small AGS values and isothermal decomposition temperature regimes where the predominant controlling mechanism is due to carbon volume diffusion. (Author) 22 refs.

  10. Effect of Grain Size on Mechanical Properties of Nickel-Free High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    LI Hua-bing; JIANG Zhou-hua; ZHANG Zu-rui; YANG Yan

    2009-01-01

    The fine grained structures of nickel-free high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing.The relationship between microstructure and mechanical properties and gain size of nickel-free high nitrogen austenitic stainless steels was examined.High strength and good ductility of the steel were found.In the grain size range,the Hall-Petch dependency for yield stress,tensile strength,and hardness was valid for grain size ranges for the nickel-free high nitrogen austenitic stainless steel.In the present study,the ductility of cold rolled nickel-free high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined.The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.

  11. Austenite layer and precipitation in high Co-Ni maraging steel.

    Science.gov (United States)

    Wang, Chenchong; Zhang, Chi; Yang, Zhigang

    2014-12-01

    In high Co-Ni maraging steel, austenite has a great effect on the fracture toughness of the steel and the precipitated carbides are the main strengthening phase. In this study, both austenite layers and precipitation were observed and their formation theory was analyzed by Thermo-Calc simulation and several reported results. TEM and HRTEM observation results showed that the thickness of the austenite layers was about 5-10 nm and the length of the needle-like precipitated carbides was less than 10nm. The carbides maintained coherent or semi-coherent relation with the matrix.

  12. Formation and Growth Kinetics of Reverted Austenite During Tempering of a High Co-Ni Steel

    Science.gov (United States)

    Gruber, Marina; Ressel, Gerald; Méndez Martín, Francisca; Ploberger, Sarah; Marsoner, Stefan; Ebner, Reinhold

    2016-12-01

    It is well known that high Co-Ni steels exhibit excellent toughness. Since the good toughness in these steels is supposed to be related to thin layers of austenite between martensite crystals, this work presents an experimental study corroborated with diffusional calculations to characterize the evolution of reverted austenite. Atom probe measurements were conducted for analyzing the element distribution in austenite and martensite during tempering. These results were correlated with crystallographic information, which was obtained by using transmission electron microscopy investigations. Additionally, the experimental findings were compared with kinetic calculations with DICTRA™. The investigations reveal that reverted austenite formation during tempering is connected with a redistribution of Ni, Co, Cr, and Mo atoms. The austenite undergoes a Ni and Cr enrichment and a Co depletion, while in the neighboring martensite, a zone of Ni and Cr depletion and Co enrichment is formed. The changes in the chemical composition of austenite during tempering affect the stability of the austenite against phase transformation to martensite during plastic deformation and have thus decisive influence on the toughness of the material.

  13. Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

    Science.gov (United States)

    Lu, Z.; Faulkner, R. G.; Morgan, T. S.

    2008-12-01

    High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 × 10 -6 dpa/s) at 400 °C and 28 dpa (1.7 × 10 -6 dpa/s) at 465 °C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided (˜15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

  14. Formation of austenite in high Cr ferritic/martensitic steels by high fluence neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z. [IPTME, Loughborough University, Loughborough LE11 3U (United Kingdom)], E-mail: zheng.lu@lboro.ac.uk; Faulkner, R.G.; Morgan, T.S. [IPTME, Loughborough University, Loughborough LE11 3U (United Kingdom)

    2008-12-01

    High Cr ferritic/martensitic steels are leading candidates for structural components of future fusion reactors and new generation fission reactors due to their excellent swelling resistance and thermal properties. A commercial grade 12%CrMoVNb ferritic/martensitic stainless steel in the form of parent plate and off-normal weld materials was fast neutron irradiated up to 33 dpa (1.1 x 10{sup -6} dpa/s) at 400 deg. C and 28 dpa (1.7 x 10{sup -6} dpa/s) at 465 deg. C, respectively. TEM investigation shows that the fully martensitic weld metal transformed to a duplex austenite/ferrite structure due to high fluence neutron irradiation, the austenite was heavily voided ({approx}15 vol.%) and the ferrite was relatively void-free; whilst no austenite phases were detected in plate steel. Thermodynamic and phase equilibria software MTDATA has been employed for the first time to investigate neutron irradiation-induced phase transformations. The neutron irradiation effect is introduced by adding additional Gibbs free energy into the system. This additional energy is produced by high energy neutron irradiation and can be estimated from the increased dislocation loop density caused by irradiation. Modelling results show that neutron irradiation reduces the ferrite/austenite transformation temperature, especially for high Ni weld metal. The calculated results exhibit good agreement with experimental observation.

  15. Delta-Ferrite Distribution in a Continuous Casting Slab of Fe-Cr-Mn Austenitic Stainless Steel

    Science.gov (United States)

    Chen, Chao; Cheng, Guoguang

    2017-10-01

    The delta-ferrite distribution in a continuous casting slab of Fe-Cr-Mn stainless steel grade (200 series J4) was analyzed. The results showed that the ferrite fraction was less than 3 pct. The "M" type distribution was observed in the thickness direction. For the distribution at the centerline, the maximum ferrite content was found in the triangular zone of the macrostructure. In addition, in this zone, the carbon and sulfur were severely segregated. Furthermore, an equilibrium solidification calculation by Thermo-Calc® software indicates that the solidification mode of the composition in this triangular zone is the same as the solidification mode of the averaged composition, i.e., the FA (ferrite-austenite) mode. None of the nickel-chromium equivalent formulas combined with the Schaeffler-type diagram could predict the ferrite fraction of the Cr-Mn stainless steel grade in a reasonable manner. The authors propose that more attention should be paid to the development of prediction models for the ferrite fraction of stainless steels under continuous casting conditions.

  16. Control of relaxation cracking in austenitic high temperature components

    NARCIS (Netherlands)

    Wortel, J.C. van

    2007-01-01

    The degradation mechanism "relaxation cracking" is acting in austenitic components operating between 550°C (1020°F) and 750°C (1380°F). The brittle failures are always located in cold formed areas or in welded joints and are mostly addressed within 1 year service. More than 10 different names can be

  17. Control of relaxation cracking in austenitic high temperature components

    NARCIS (Netherlands)

    Wortel, J.C. van

    2007-01-01

    The degradation mechanism "relaxation cracking" is acting in austenitic components operating between 550°C (1020°F) and 750°C (1380°F). The brittle failures are always located in cold formed areas or in welded joints and are mostly addressed within 1 year service. More than 10 different names can be

  18. Preparation of high nitrogen and nickel-free austenitic stainless steel by powder injection molding

    Institute of Scientific and Technical Information of China (English)

    Dawei Cui; Junsheng Jiang; Guangming Cao; Enzhong Xiao; Xuanhui Qu

    2008-01-01

    High nitrogen and nickel-free austenitic stainless steel has received much recognition worldwide because it can solve the problem of "nickel-allergy" and has outstanding mechanical and physical properties. In this article, 0Cr17Mn11Mo3N was prepared by powder injection molding (PIM) technique accompanied with solid-nitriding. The results show that the critical solid loading can achieve up to 64vo1% by use of gas-atomized powders with the average size of 17.4 μm. The optimized sintering conditions are de- termined to be 1300℃,2 h in flowing nitrogen atmosphere, at which the relative density reaches to 99% and the N content is as high as 0.78wt%. After solution annealing at 1150℃for 90 min and water quench, the 0.2% yield strength, ultimate tensile strength (UTS), elongation, reduction in area, and hardness can reach as high as 580 MPa, 885 MPa, 26.0%, 29.1%, and Hv 222, respectively. C 2008 University of Science and Technology Beijing. All rights reserved.

  19. Partial transformation of austenite in Al-Mn-Si TRIP steel upon tensile straining: an in situ EBSD study

    DEFF Research Database (Denmark)

    Lomholt, Trine Nybo; Adachi, Y.; da Silva Fanta, Alice Bastos;

    2013-01-01

    The transformation of austenite to martensite in an Al–Mn–Si transformation-induced plasticity steel was investigated with in situ electron backscatter diffraction (EBSD) measurements under tensile straining. The visualisation of the microstructure upon straining allows for an investigation...... of the stability of austenite grains against strain-induced transformation, with particular focus on the grain size and the location of the austenite grains. The findings confirm that size and location of austenite grains are significant parameters for their stability. Small austenite grains were observed...... to be more stable than large grains, while austenite grains located beside bainitic ferrite are the most stable. Moreover, it is demonstrated that austenite grains transform gradually...

  20. High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless steels

    Science.gov (United States)

    Ritter, Ann M.; Henry, Michael F.; Savage, Warren F.

    1984-07-01

    Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures, and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques. The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs. Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase (NbCrN), sigma phase, and stringered phases rich in Mn and Cr.

  1. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  2. Synergistic Computational and Microstructural Design of Next- Generation High-Temperature Austenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Karaman, Ibrahim [Texas A& M Engineering Experiment Station, College Station, TX (United States); Arroyave, Raymundo [Texas A& M Engineering Experiment Station, College Station, TX (United States)

    2015-07-31

    The purpose of this project was to: 1) study deformation twinning, its evolution, thermal stability, and the contribution on mechanical response of the new advanced stainless steels, especially at elevated temperatures; 2) study alumina-scale formation on the surface, as an alternative for conventional chromium oxide, that shows better oxidation resistance, through alloy design; and 3) design new generation of high temperature stainless steels that form alumina scale and have thermally stable nano-twins. The work involved few baseline alloys for investigating the twin formation under tensile loading, thermal stability of these twins, and the role of deformation twins on the mechanical response of the alloys. These baseline alloys included Hadfield Steel (Fe-13Mn-1C), 316, 316L and 316N stainless steels. Another baseline alloy was studied for alumina-scale formation investigations. Hadfield steel showed twinning but undesired second phases formed at higher temperatures. 316N stainless steel did not show signs of deformation twinning. Conventional 316 stainless steel demonstrated extensive deformation twinning at room temperature. Investigations on this alloy, both in single crystalline and polycrystalline forms, showed that deformation twins evolve in a hierarchical manner, consisting of micron–sized bundles of nano-twins. The width of nano-twins stays almost constant as the extent of strain increases, but the width and number of the bundles increase with increasing strain. A systematic thermomechanical cycling study showed that the twins were stable at temperatures as high as 900°C, after the dislocations are annealed out. Using such cycles, volume fraction of the thermally stable deformation twins were increased up to 40% in 316 stainless steel. Using computational thermodynamics and kinetics calculations, we designed two generations of advanced austenitic stainless steels. In the first generation, Alloy 1, which had been proposed as an alumina

  3. Precipitation Kinetics of Cr2N in High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    SHI Feng; WANG Li-jun; CUI Wen-fang; LIU Chun-ming

    2008-01-01

    The precipitation behavior of Cr2N during isothermal aging in the temperature range from 700℃to 950℃ in Fe-18Cr-12Mn-0.48N(in mass percent)high nitrogen austenitic stainless steel,including morphology and content of precipitate,was investigated using optical microscopy,scanning electron microscopy,and transmission electron microscopy.The isothermal precipitation kinetics curve of Cr2N and the corresponding precipitation activation energy were obtained.The results show that Cr2N phase precipitates in a cellular way and its morphology is transformed from initial granular precipitates to lamellar ones in the cell with increasing aging time.The nose temperature of Cr2N precipitation is about 800℃,with a corresponding incubation period of 30 min,and the ceiling temperature of Cr2N precipitation is 950℃.The diffusion activation energy of Cr2N precipitation is 296 kJ/mol.

  4. The study of high speed fine turning of austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    W.S. Lin

    2008-04-01

    Full Text Available Purpose: The purpose of this research paper is focused on the surface roughness variation in high speed fine turning of the austenitic stainless steel.Design/methodology/approach: A series of experimental tests have been done to evaluate the possibility of high speed fine turning of the austenitic stainless steel from the surface roughness variation and machining stability.Findings: It was found that, the smaller the feed rate, the smaller the surface roughness value. But when the feed rate smaller than the critical feed rate, the chatter will occurs and the surface roughness of the work piece would be deteriorated.The higher the cutting speed is, the higher the cutting temperature of cutting tool is. The cutting tool will be soften and the surface roughness of the workpiece will be deteriorated.Research limitations/implications: The tool chattering would caused poor surface roughness in high speed fine turning for feed rate smaller than 0.02 mm/rev. The chatter suppression method must be considered when high speed fine turning of austenitic stainless steel.Originality/value: Most of the stainless steel machining proceeds at low cutting speed because the austenitic stainless steel is a hard machining material. The research result of this paper indicated that high speed fine turning of austenitic stainless steel is possible.

  5. Study of biocompatibility of medical grade high nitrogen nickel-free austenitic stainless steel in vitro.

    Science.gov (United States)

    Li, Menghua; Yin, Tieying; Wang, Yazhou; Du, Feifei; Zou, Xingzheng; Gregersen, Hans; Wang, Guixue

    2014-10-01

    Adverse effects of nickel ions being released into the living organism have resulted in development of high nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also improves steel properties. The cell cytocompatibility, blood compatibility and cell response of high nitrogen nickel-free austenitic stainless steel were studied in vitro. The mechanical properties and microstructure of this stainless steel were compared to the currently used 316L stainless steel. It was shown that the new steel material had comparable basic mechanical properties to 316L stainless steel and preserved the single austenite organization. The cell toxicity test showed no significant toxic side effects for MC3T3-E1 cells compared to nitinol alloy. Cell adhesion testing showed that the number of MC3T3-E1 cells was more than that on nitinol alloy and the cells grew in good condition. The hemolysis rate was lower than the national standard of 5% without influence on platelets. The total intracellular protein content and ALP activity and quantification of mineralization showed good cell response. We conclude that the high nitrogen nickel-free austenitic stainless steel is a promising new biomedical material for coronary stent development.

  6. In vitro Study on a New High Nitrogen Nickel-free Austenitic Stainless Steel for Coronary Stents

    Institute of Scientific and Technical Information of China (English)

    Yibin Ren; Peng Wan; Feng Liu; Bingchun Zhang; Ke Yang

    2011-01-01

    Most commercialized coronary stents are made of 316L stainless steels due to its good combination of properties, and currently some new stents are made of cobalt-based alloy owing to its higher mechanical properties. However, the presence of high quantity of nickel and/or cobalt elements in these materials, which are known to trigger the toxic and allergic responses, has caused many concerns. Nickel-free austenitic stainless steels have been developed in order to solve these problems. In this paper, based on the development of a new FeCr-Mn-Mo-N type high nitrogen nickel-free austenitic stainless steel, properties such as mechanical property, corrosion resistance in Hank′s solution, and in vitro blood compatibility including the kinetic clotting time and the platelets adhesion, were investigated in comparison to the above two conventional materials, a 316L stainless steel and a Co-28Cr-6Mo alloy. The results showed that the new high nitrogen steel possessed better combination of mechanical properties, corrosion resistance and blood compatibility than those of 316L steel and the Co-28Cr-6Mo alloy, and can be a promising alternative material for manufacture of coronary stents.

  7. Effects Of The Combined Heat And Cryogenic Treatment On The Stability Of Austenite In A High Co-Ni Steel

    Directory of Open Access Journals (Sweden)

    Gruber M.

    2015-09-01

    Full Text Available The stability of austenite is one of the most dominant factors affecting the toughness properties of high Co-Ni steels such as Aermet 100 and AF1410. Thus, the aim of this work was to get a deeper understanding on the impact of combined heat and cryogenic treatment on the stability of retained and reverted austenite. In order to characterize the evolution of the phase fraction of austenite during tempering at different temperatures and times, X-ray diffraction analyses were carried out. The stability of austenite, which was formed during tempering, was analyzed with dilatometric investigations by studying the transformation behavior of the austenite during cooling from tempering temperature down to −100°C. Additionally, transmission electron microscopy investigations were performed to characterize the chemical composition and phase distribution of austenite and martensite before and after tempering.

  8. Decomposition kinetics of expanded austenite with high nitrogen contents

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    This paper addresses the decomposition kinetics of synthesized homogeneous expanded austenite formed by gaseous nitriding of stainless steel AISI 304L and AISI 316L with nitrogen contents up to 38 at.% nitrogen. Isochronal annealing experiments were carried out in both inert (N2) and reducing (H2......) atmospheres. Differential thermal analysis (DTA) and thermogravimetry were applied for identification of the decomposition reactions and X-ray diffraction analysis was applied for phase analysis. CrN precipitated upon annealing; the activation energies are 187 kJ/mol and 128 kJ/mol for AISI 316L and AISI 304L...

  9. Effects of Ca(Y)-Si modifier on interface morphology and solute segregation during directional solidification of an austenite medium Mn steel

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The austenite medium Mn steel modified with controlled additions of Ca, Y, Si were directionally solidified using the vertical Bridgman method to study the effects of Ca(Y)-Si modifier on the solid-liquid (S-L) interface morphology and solute segregation. The interface morphology and the C and Mn segregation of the steel directionally solidified at 6.9 μm/s were investigated with an image analysis and a scanning electron microscope equipped with energy dispersive X-ray analysis. The 0.5wt% Ca-Si modified steel is solidified with a planar S-L interface. The interface of the 1.0wt% Ca-Si modified steel is similar to that of the 0.5wt% Ca-Si modified steel, but with larger nodes. The 1.5wt% Ca-Si modified steel displays a cellular growth parttern. The S-L interface morphology of the 0.5wt% Ca-Si+1.0wt% Y-Si modified Mn steel appears as dendritic interface, and primary austenite dendrites reveal developed lateral branching at the quenched liquid. In the meantime, the independent austenite colonies are formed ahead of the S-L interface. A mechanism involving constitutional supercooling explains the S-L interface evolution. It depends mainly on the difference in the contents of Ca, Y, and Si ahead of the S-L interface. The segregation of C and Mn ahead of the S-L interface enhanced by the modifiers is observed.

  10. Effect of non-isothermal deformation of austenite on ferrite transformation behavior studied by in-situ neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zengmin, E-mail: shzm@ctgu.edu.cn [College of Materials and Chemical Engineering, China Three Gorges University, Yichang 443002 (China); Tomota, Yo [Graduate School of Science and Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki 316-8511 (Japan); Harjo, Stefanus; Su, Yuhua [J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai, Ibaraki 319-1195 (Japan); Chi, Bo; Pu, Jian [School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Jian, Li, E-mail: lijian@hust.edu.cn [School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-04-17

    The microstructure evolution and phase transformation of high strength 22SiMn2TiB steel during non-isothermal deformation were investigated by using in situ time-of-flight (TOF) neutron diffraction technique. The results indicate that the deformation of austenite promotes pearlite and ferrite transformation while suppresses bainite transformation. Deformation texture forms in austenite and then it influences the evolution of transformation texture. Deformation of austenite brings the changes in lattice parameters of austenite caused by carbon partitioning and elastic strains during the transformation. Volume fraction of the retained austenite decreases with a decreased carbon content as deformation amount increases.

  11. Annealing effect on the magnetic induced austenite transformation in polycrystalline freestanding Ni-Co-Mn-In films produced by co-sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Crouïgneau, G., E-mail: guillaume.crouigneau@neel.cnrs.fr [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, Cedex 9 (France); Univ. Grenoble Alpes, CRETA, F-38000 Grenoble (France); CNRS, Inst. NEEL, F-38000 Grenoble (France); CNRS, CRETA, F-38000 Grenoble (France); Porcar, L.; Pairis, S.; Mossang, E.; Eyraud, E.; Bourgault, D. [Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, Cedex 9 (France); CNRS, Inst. NEEL, F-38000 Grenoble (France); Courtois, P. [Institut Laue Langevin, 38000 Grenoble (France)

    2015-01-21

    Ni-Co-Mn-In freestanding films, with a magneto-structural transformation at room temperature were successfully produced by co-sputtering and post-annealing methods leading to film composition mastering. For a post-annealing temperature of 700 °C, the phase transformation occurs slightly above room temperature, with a twisted martensitic microstructure phase observed at 300 K by Field Emission Scanning Electron Microscopy. Magnetization measurements on a polycrystalline film showed a phase transformation from a weakly magnetic martensite to a magnetic austenite phase. Moreover, an inverse magnetocaloric effect with an entropy variation of 4 J/kg K under 5 T was also measured. A simple magneto-actuation experiment based on the magnetic induced austenite transformation was also successfully completed. The possibility to insert such films in microsystems is clearly demonstrated in this work.

  12. High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

    2010-07-13

    An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

  13. High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

    2010-07-13

    An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

  14. Thermodynamic Calculation Study on Effect of Manganese on Stability of Austenite in High Nitrogen Stainless Steels

    Science.gov (United States)

    Wang, Qingchuan; Zhang, Bingchun; Yang, Ke

    2016-07-01

    A series of high nitrogen steels were studied by using thermodynamic calculations to investigate the effect of manganese on the stability of austenite. Surprisingly, it was found that the austenite stabilizing ability of manganese was strongly weakened by chromium, but it was strengthened by molybdenum. In addition, with an increase of manganese content, the ferrite stabilizing ability of chromium significantly increased, but that of molybdenum decreased. Therefore, strong interactions exist between manganese and the other alloying elements, which should be the main reason for the difference among different constituent diagrams.

  15. Pearlite transformation in high carbon steels deformed in metastable austenite region; Jun`antei austenite iki de kakoshita kotansoko no pearlite hentai

    Energy Technology Data Exchange (ETDEWEB)

    Daito, Y.; Aihara, K.; Nishizawa, T. [Sumitomo Metal Industries, Ltd., Osaka (Japan)

    1997-09-01

    Pearlite structure was discussed noticing particularly on the state of nucleus composition, for the case when high carbon steels mainly structured by pearlite was processed in metastable austenite region below the point A1 which is thought a non-recrystallized region. When the processing amount is increased in the metastable austenite region, the size of pearlite colonies decreased. This is because of increase in nucleus producing site as a result of the processing. Even with a steel of eutectoid carbon concentration of an equilibrium diagram, proeuctoid ferrite is produced if the processing is given in the metastable austenite region. Furthermore, the production amount of the proeuctoid ferrite increased with increasing processing amount. If the processing is given in the metastable austenite region, the region that becomes a single pearlite structure shifted to hypereuctoid carbon concentration side as the transformation temperature has fallen. The result of an experiment performed in carbon concentration at which the single pearlite structure is obtained agreed well with drive force equilibrium line of ferrite and cementite as calculated based on the Gibbs energy. 18 refs., 11 figs., 1 tab.

  16. Microstructure and high-temperature shape-memory effect in Ni54Mn25Ga21 alloy

    Institute of Scientific and Technical Information of China (English)

    MA Yun-qing; JIANG Cheng-bao; LI Yan; XU Hui-bin; WANG Cui-ping; LIU Xing-jun

    2006-01-01

    Ni54Mn25Ga21 alloy was prepared to investigate the microstructure, martensitic transformation and high-temperature shape-memory effect. Ni54Mn25Ga21 alloy exhibits single phase of non-modulated martensite with tetragonal structure at room temperature. Its martensitic start temperature Ms, martensitic finish temperature Mf on cooling, and austenitic start temperature As,austenitic finish temperature Af on heating are 260.2, 237.8, 262.5 and 287.8 ℃, respectively. The compressive strength and strain of Ni54Mn25Ga21 single crystal were measured to be 845 MPa and 20.5%, respectively, with compressive axis along the growth direction of the rods. An excellent shape-memory strain of 6.1%, which is the best performance among high-temperature shape-memory alloys up to the present, is obtained when prestrained to 8%.

  17. Radiation-induced instability of MnS precipitates and its possible consequences on IASCC of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M. [Argonne National Lab., IL (United States); Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    Irradiation assisted stress corrosion cracking (IASCC) continues to be a significant materials issue for the light water reactor industry and may also pose a problem for fusion power devices that employ water cooling. Although a number of potential mechanisms have been proposed to participate in this phenomenon, at this time it is not clear that any of these candidate mechanisms are sufficient to rationalize the observed failures. A new mechanism is proposed in this paper that involves the radiation-induced release into solution of elements not usually thought to participate in IASCC. It is shown in this paper that MnS precipitates, which contain most of the sulphur in stainless steels, are probably unstable under irradiation. First, the Mn transmutes very strongly to Fe in highly thermalized neutron spectra. Second, the combination of cascade-induced disordering and the inverse-Kirkendall effect operating at the incoherent interfaces of MnS precipitates will probably act as a pump to export Mn from the precipitate surface into the alloy matrix. Both of these processes will most likely allow some of the sulphur to re-enter the alloy matrix. Sulphur is known to exert a deleterious influence on grain boundary cracking. MnS precipitates are also thought to be a reservoir of other deleterious impurities such as fluorine which could be also released due to radiation-induced instability of the precipitates. This possibility has been confirmed by Auger electron spectroscopy of Types 304, 316, and 348 stainless steel specimens sectioned from several BWR components irradiated up to 3.5x10{sup 21} n/cm{sup 2} (E > 1 MeV).

  18. Effect of VN precipitates on formation of grain boundary and intragranular ferrite in a high N-V bearing steel; V-N tenkako no ryukai oyobi ryunai ferrite hentai ni oyobosu austenite chu no VN sekishutsu no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Omori, A.; Oi, K.; Kawabata, F.; Amano, K. [Kawasaki Steel Corp., Tokyo (Japan)

    1998-11-01

    The enhancement of ferrite nucleation owing to vanadium nitride (VN) precipitated in the austenite phase was studied for a 0.14%C- 1.45%Mn-0.06%V-0.009%N steel and the isothermal ferrite transformation behavior associated with VN precipitation was also quantitatively discussed. Vanadium nitrides precipitate on the austenite grain boundary in preference to the grain interior and increase the density of grain boundary ferrites. On the other hand, VN precipitates in austenite grain interior are less effective to intragranular ferrite nucleation. The calculation based on the classical nucleation theory shows that the activation energy of VN precipitates for a critical ferrite nucleus formation is one-fifth lower than that in case of no precipitate. The ferrite nucleation potency of VN precipitates is kept high even in higher temperature range above 700degreeC. (author)

  19. A Short review on wrought austenitic stainless steels at high temperatures: processing, microstructure, properties and performance

    Directory of Open Access Journals (Sweden)

    Ronald Lesley Plaut

    2007-12-01

    Full Text Available Wrought austenitic stainless steels are widely used in high temperature applications. This short review discusses initially the processing of this class of steels, with emphasis on solidification and hot working behavior. Following, a brief summary is made on the precipitation behavior and the numerous phases that may appear in their microstructures. Creep and oxidation resistance are, then, briefly discussed, and finalizing their performance is compared with other high temperature metallic materials.

  20. High Ductility and Toughness of a Micro-duplex Medium-Mn Steel in a Large Temperature Range from -196 °C to 200 °C

    DEFF Research Database (Denmark)

    Chen, Si-lian; Hu, Jun; Zhang, Xiaodan;

    2015-01-01

    A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperatures (625 degrees C and 650 degrees C). An ultrafine-grained micro-duplex structure consisting of alternating austenite and ferrite laths was developed by austenite reverse transformation (ART) during...... intercritical annealing after forging and hot rolling. Ultrahigh ductility with a total elongation higher than 30% was achieved in the temperature range from - 196 degrees C to 200 degrees C and high impact toughness no less than 200 J at - 40 degrees C was obtained. Based on the analysis of microstructure...

  1. Improved Creep Behavior of a High Nitrogen Nb-Stabilized 15Cr-15Ni Austenitic Stainless Steel Strengthened by Multiple Nanoprecipitates

    Science.gov (United States)

    Ha, Vu The; Jung, Woo Sang; Suh, Jin Yoo

    2011-11-01

    Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical (USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels. This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40 to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent copper precipitates inside the austenitic matrix.

  2. Microstructure Evolution and Age-Hardening Behavior of Microalloyed Austenitic Fe-30Mn-9Al-0.9C Light-Weight Steels

    Science.gov (United States)

    Moon, Joonoh; Park, Seong-Jun; Lee, Changhee; Han, Heung Nam; Lee, Tae-Ho; Lee, Chang-Hoon

    2017-10-01

    The aging behavior and mechanical properties of microalloyed austenitic Fe-30Mn-9Al-0.9C light-weight steels were investigated through transmission electron microscopy analysis, electron backscatter diffraction analysis, tensile tests, and Vickers hardness tests. The base steels were aged at 823 K (550 °C) for up to 10,000 minutes. The true stress-strain responses of solution-treated samples before aging showed that the addition of Nb and/or V improved the strength by grain refinement and precipitation hardening. During the process of tensile deformation, the strain-hardening rate of Fe-30Mn-9Al-0.9C steel steadily increased due to the microband-induced plasticity (MBIP) from the onset of plastic deformation to ɛ = 25 pct, while such behavior was weakened and not observed in Nb- and/or V-added steels despite MBIP. In the early stage of aging, the Vickers hardness gradually increased with an increase in the aging time due to the precipitation of κ-carbide of (Fe,Mn)3AlC and remained stagnant between the aging times of 1000 and 3000 minutes. The hardness increased again after 3000 minutes due to the formation of ferrite and brittle β-Mn.

  3. Evaluation of High Temperature Corrosion Resistance of Finned Tubes Made of Austenitic Steel And Nickel Alloys

    Directory of Open Access Journals (Sweden)

    Turowska A.

    2016-06-01

    Full Text Available The purpose of the paper was to evaluate the resistance to high temperature corrosion of laser welded joints of finned tubes made of austenitic steel (304,304H and nickel alloys (Inconel 600, Inconel 625. The scope of the paper covered the performance of corrosion resistance tests in the atmosphere of simulated exhaust gases of the following chemical composition: 0.2% HCl, 0.08% SO2, 9.0% O2 and N2 in the temperature of 800°C for 1000 hours. One found out that both tubes made of austenitic steel and those made of nickel alloy displayed good resistance to corrosion and could be applied in the energy industry.

  4. The Effects of Austenitizing Conditions on the Microstructure and Wear Resistance of a Centrifugally Cast High-Speed Steel Roll

    Science.gov (United States)

    Kang, Minwoo; Lee, Young-Kook

    2016-07-01

    The influences of austenitizing conditions on the microstructure and wear resistance of a centrifugally cast high-speed steel roll were investigated through thermodynamic calculation, microstructural analysis, and high-temperature wear tests. When the austenitizing temperature was between 1323 K and 1423 K (1050 °C and 1150 °C), coarse eutectic M2C plates were decomposed into a mixture of MC and M6C particles. However, at 1473 K (1200 °C), the M2C plates were first replaced by both new austenite grains and MC particles without M6C particles, and then remaining M2C particles were dissolved during the growth of MC particles. The wear resistance of the HSS roll was improved with increasing austenitizing temperature up to 1473 K (1200 °C) because the coarse eutectic M2C plates, which are vulnerable to crack propagation, changed to disconnected hard M6C and MC particles.

  5. Microstructure characterization in the weld joint of a high nickel austenitic alloy and Cr18-Ni8 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Na; Li, Yajiang; Wang, Juan [Shandong Univ., Jinan (CN). Key Lab. for Liquid - Solid Structural Evolution and Processing of Materials (Ministry of Education)

    2012-06-15

    High nickel austenitic alloy, 6 mm thick, and Cr18-Ni8 stainless steel with a thickness of 0.6 mm were joined by pulsed current tungsten inert gas arc welding without filler metal in this work. Metallographic examination, microhardness measurement and electron microprobe analysis were used to reveal microstructural characteristics in the joint. The results indicated that the weld metal consisted of {gamma}-austenite, {delta}-ferrite and carbides without the appearance of martensite. There were dendrite crystals at the edge of the weld metal near the high nickel austenitic alloy and isometric crystals in the center of the weld metal. The microhardness of the weld metal was the highest due to the existence of carbides and its finer structure. Graphite flakes were still embedded in the austenite matrix of the heat-affected zone without the formation of martensite. (orig.)

  6. High-spin Mn wheels.

    Science.gov (United States)

    Manoli, Maria; Prescimone, Alessandro; Bagai, Rashmi; Mishra, Abhudaya; Murugesu, Muralee; Parsons, Simon; Wernsdorfer, Wolfgang; Christou, George; Brechin, Euan K

    2007-08-20

    The syntheses, structures, and magnetic properties of the complexes [MnIV4MnIII10MnII2O2(OCH3)12(tmp)8(O2CCH3)10].3Et2O (1.3Et2O), [MnIV2MnIII18MnII2O6(OCH3)14(O2CCH3)16(tmp)8(HIm)2].2CH3OH (2.2CH3OH), and [MnIV2MnIII18MnII2O6(OCH3)14(O2CCH3)16(Br-mp)8(HIm)2].2C6H14.5CH3OH (3.2C6H14.5CH3OH) are reported. The unusual wheel-like complexes were prepared by the treatment of [Mn3O(O2CCH3)6(HIm)3](O2CCH3) (HIm = imidazole) with 1,1,1-tris-(hydroxymethyl)propane (H3tmp) (1 and 2) or 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (Br-mpH3) (3) in the presence of sodium methoxide (NaOCH3, 2, and 3) in CH3OH. Complex 1.3Et2O crystallizes in the triclinic space group P, while complexes 2.2CH3OH and 3.2C6H14.5CH3OH crystallize in the orthorhombic space group Pbca. Direct current magnetic susceptibility data, collected for 1-3 in the respective 1.8-300 K and 0.1-7 T temperature and magnetic-field ranges, afford spin ground-state values of S = 14 +/- 1 for complex 1 and S = 9 +/- 1 for complexes 2 and 3. Alternating current susceptibility measurements performed on all three complexes in the 1.8-10 K temperature range in a 3.5 G oscillating field at frequencies between 50 and 1000 Hz reveal out-of-phase chi"M signals below approximately 3 K. Single-crystal hysteresis loop and relaxation measurements confirm single-molecule magnetism behavior.

  7. Effect of the Content of Retained Austenite and Grain Size on the Fatigue Bending Strength of Steels Carburized in a Low-Pressure Atmosphere

    Science.gov (United States)

    Kula, P.; Dybowski, K.; Lipa, S.; Januszewicz, B.; Pietrasik, R.; Atraszkiewicz, R.; Wołowiec, E.

    2014-11-01

    The effect of the content of retained austenite and of the initial austenite grain size on high-cycle fatigue of two low-alloy steels 16MnCr5 and 17CrNi6-6 after carburizing in a low-pressure atmosphere (acetylene, ethylene and hydrogen) and subsequent high-pressure gas quenching is investigated.

  8. Microstructure evolution and phase composition of high-manganese austenitic steels

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2008-12-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution and phase composition of new-developed high-manganese austenitic steels.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator. Evaluation of processes controlling work hardening and occurring after deformation at 900°C were identified by microstructure observations of the specimens solution heat-treated after plastic deformation to a true strain equal 0.23, 0.50 and 0.91. Phase composition of steels was confirmed by X-ray diffraction analysis.Findings: The steels have a fine-grained austenite microstructure with many annealing twins to a temperature of about 1000°C. The initiation of dynamic recrystallization occurs already after true deformation equal 0.29. Participation of fine grains arranged in a matrix of dynamically recovered grains essentially increases after increasing true strain to 0.5. Fully dynamically recrystallized microstructure of steel can be obtained after the true strain equal 0.9. The conditions of hot-working influence phase state of investigated steels. Steel no. 1 keeps stable austenite microstructure independently from conditions of plastic deformation. Steel with initial bi-phase microstructure keeps a certain portion of εmartensite, yet dependant on conditions of hot-working.Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of microstructure evolution in subsequent stages of multi-stage compression test should be investigated.Practical implications: The obtained microstructure – hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures.Originality/value: The hot-working behaviour and

  9. Microstructural and Texture Development in Two Austenitic Steels with High-Manganese Content

    DEFF Research Database (Denmark)

    Bhattacharya, Basudev; Ray, Ranjit Kumar; Leffers, Torben

    2015-01-01

    Two austenitic steels, Fe-21.3Mn-3.44Si-3.74Al-0.5C and Fe-29.8Mn-2.96Si-2.73Al-0.52C, were subjected to cold rolling with 30 to 80 pct reduction with an increment of 10 pct and subsequently the development of their microstructures and textures were studied. The overall texture after 80 pct cold...... reduction was Brass type. A weak Copper component {112}〈111〉 was present at the early stage of deformation, which disappeared completely after 60 pct cold reduction. Extensive shear banding took place in both the steels, right from rather low cold rolling levels, which became more prominent at higher...... amounts of cold rolling. Formation of twin bands, along with cellular dislocation network, was observed in Steel A after 30 pct cold rolling. In case of Steel B, denser twin bands and dislocation cellular network were observed in early stage of deformation. After 80 pct cold reduction, the development...

  10. Segregation Behaviour of Third Generation Advanced High-Strength Mn-Al Steels

    Directory of Open Access Journals (Sweden)

    A. Grajcar

    2012-04-01

    Full Text Available The paper addresses the macro- and microsegregation of alloying elements in the new-developed Mn-Al TRIP steels, which belong to the third generation of advanced high-strength steels (AHSS used in the automotive industry. The segregation behaviour both in the as-cast state and after hot forging was assessed in the macro scale by OES and by EDS measurements in different structural constituents. The structural investigations were carried out using light and scanning electron microscopy. A special attention was paid to the effect of Nb microaddition on the structure and the segregation of alloying elements. The tendency of Mn and Al to macrosegregation was found. It is difficult to remove in Nb-free steels. Microsegregation of Mn and Al between austenite and ferritic structural constituents can be removed.

  11. High Ductility and Toughness of a Micro-duplex Medium-Mn Steel in a Large Temperature Range from -196 °C to 200 °C

    DEFF Research Database (Denmark)

    Chen, Si-lian; Hu, Jun; Zhang, Xiaodan

    2015-01-01

    A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperatures (625 degrees C and 650 degrees C). An ultrafine-grained micro-duplex structure consisting of alternating austenite and ferrite laths was developed by austenite reverse transformation (ART) during...... and mechanical properties, it was found that the enhanced ductility was determined by the phase transformation effect 'of austenite (TRIP effect), while the delayed ductile to brittle transition was controlled by austenite stability....

  12. Flexural Strength and Toughness of Austenitic Stainless Steel Reinforced High-Cr White Cast Iron Composite

    Science.gov (United States)

    Sallam, H. E. M.; Abd El-Aziz, Kh.; Abd El-Raouf, H.; Elbanna, E. M.

    2013-12-01

    Flexural behavior of high-Cr white cast iron (WCI) reinforced with different shapes, i.e., I- and T-sections, and volume fractions of austenitic stainless steel (310 SS) were examined under three-point bending test. The dimensions of casted beams used for bending test were (50 × 100 × 500 mm3). Carbon and alloying elements diffusion enhanced the metallurgical bond across the interface of casted beams. Carbon diffusion from high-Cr WCI into 310 SS resulted in the formation of Cr-carbides in 310 SS near the interface and Ni diffusion from 310 SS into high-Cr WCI led to the formation of austenite within a network of M7C3 eutectic carbides in high-Cr WCI near the interface. Inserting 310 SS plates into high-Cr WCI beams resulted in a significant improvement in their toughness. All specimens of this metal matrix composite failed in a ductile mode with higher plastic deformation prior to failure. The high-Cr WCI specimen reinforced with I-section of 310 SS revealed higher toughness compared to that with T-section at the same volume fraction. The presence of the upper flange increased the reinforcement efficiency for delaying the crack growth.

  13. Mechanism of Austenite Evolution During Deformation of Ultra-High Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shu-lan; SUN Xin-jun; DONG Han

    2008-01-01

    The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultra-high carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformation be-tween Acm to Arcm. The transformation during deformation is still considered as a diffusion-controlled process. With the increase of time and reduction, the pearlite fraction increased. At the beginning of the transformation, the pearli- te was lamelliform. When the rate of reduction was increased to 70%, some of the induced lamellar pearlite was bro-ken up under deformation.

  14. Surface stability and conductivity of a high Cr and Ni austenitic stainless steel plates for PEMFC

    Institute of Scientific and Technical Information of China (English)

    TIAN Rujin; SUN Juncai; WANG Jianli

    2006-01-01

    In order to use stainless steel as bipolar plate for PEMFC, electrochemical behavior of a high Cr and Ni austenitic stainless steel was studied in the solutions containing different concentration of H2SO4 and 2 mg·L-1 F-, and interfacial contact resistance was measured after corrosion tests. The experimental results show that the passive current density lowers with decreasing the concentration of H2SO4. The interfacial contact resistance between carbon paper and passive film formed in the simulated PEMFC environment is higher than the goal of bipolar plate for PEMFC. Surface conductivity should be further reduced by surface modification.

  15. Analysis of Magnetism in High Nitrogen Austenitic Stainless Steel and Its Elimination by High Temperature Gas Nitriding

    Institute of Scientific and Technical Information of China (English)

    Peng Wan; Yibin Ren; Bingchun Zhang; Ke Yang

    2011-01-01

    Stable austenitic structure in medical stainless steels is basically required for surgical implantation. A weak magnetism was found in a high nitrogen nickel-free austenitic stainless steel for cardiovascular stent application. This magnetic behavior in high nitrogen stainless steel was investigated by optical microscopy, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and superconducting quantum interference device (SQUID). The results showed that the magnetism came from the composition segregation of ferrite formation elements such as Cr and Mo in the steel and some δ-ferrites were locally formed during the pressurized electroslag remelting process. The magnetism of high nitrogen stainless steel could be eliminated by a proper high temperature gas nitriding (HTGN).

  16. Orientation dependence of variant selection and intersection reactions of ɛ martensite in a high-manganese austenitic steel

    Science.gov (United States)

    Zhang, X.; Sawaguchi, T.; Ogawa, K.; Yin, F.; Zhao, X.

    2011-09-01

    The orientation dependence of ɛ martensite during loading of a polycrystalline austenitic Fe-30Mn-4Si-2Al steel has been investigated by electron backscatter diffraction, emphasising the variant selection rule and plate-plate intersection reactions. Two types of plate-plate intersection reactions, which are characterised by incident shear direction of either 30° or 90° with respect to the intersection axis, were found in the grains along the [001]-[111] directions and [001]-[101] directions, respectively. In the intersecting volume of the latter type reaction, a γ phase rotated 90° from the austenite matrix along the ⟨011⟩ zone axis of the intersecting ɛ plates, which was theoretically predicted by Sleeswyk [A.W. Sleeswyk, Philos. Mag. 7 (1962) p.1597], has been experimentally observed for the first time.

  17. Bainitic stabilization of austenite in low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, M.L.; Olson, G.B.

    1992-01-01

    Stabilization of retained austenite via bainitic transformation was studied in a triple-phase, ferrite/bainite/austenite steel 0.26C1.52Si-1.2Mn. Volume fraction and stability of retained austenite are varied by isothermal transformation time at 752F following intercritical annealing at 1418F. Austenite stability is measured using the Bolling-Richman technique. Austenite content is measured by and austenite carbon content is estimated from lattice parameters. Strength and ductility measured in both uniaxial and plane-strain tension are correlated with austenite amount and stability. While austenite content peaks at 3 minutes transformation time, stability continues to increase out to 5 minutes associated with a saturation of austenite carbon content and continued refinement of austenite particle size. Despite the reduced austenite content of 8 percent, the higher stability provided by the 5 minutes treatment gives superior mechanical properties.

  18. Bainitic stabilization of austenite in low alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, M.L.; Olson, G.B.

    1992-12-31

    Stabilization of retained austenite via bainitic transformation was studied in a triple-phase, ferrite/bainite/austenite steel 0.26C1.52Si-1.2Mn. Volume fraction and stability of retained austenite are varied by isothermal transformation time at 752F following intercritical annealing at 1418F. Austenite stability is measured using the Bolling-Richman technique. Austenite content is measured by and austenite carbon content is estimated from lattice parameters. Strength and ductility measured in both uniaxial and plane-strain tension are correlated with austenite amount and stability. While austenite content peaks at 3 minutes transformation time, stability continues to increase out to 5 minutes associated with a saturation of austenite carbon content and continued refinement of austenite particle size. Despite the reduced austenite content of 8 percent, the higher stability provided by the 5 minutes treatment gives superior mechanical properties.

  19. Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Stubbins, James [Univ. of Illinois, Urbana-Champaign, IL (United States); Heuser, Brent [Univ. of Illinois, Urbana-Champaign, IL (United States); Robertson, Ian [Kyushu Univ. (Japan); Sehitoglu, Huseyin [Univ. of Illinois, Urbana-Champaign, IL (United States); Sofronis, Petros [Kyushu Univ. (Japan); Gewirth, Andrew [Kyushu Univ. (Japan)

    2015-04-22

    This “Blue Sky” project was directed at exploring the opportunities that would be gained by developing Oxide Dispersion Strengthened (ODS) alloys based on the Fe-Cr-Ni austenitic alloy system. A great deal of research effort has been directed toward ferritic and ferritic/martensitic ODS alloys which has resulted in reasonable advances in alloy properties. Similar gains should be possible with austenitic alloy which would also take advantage of other superior properties of that alloy system. The research effort was aimed at the developing an in-depth understanding of the microstructural-level strengthening effects of ODS particles in austentic alloys. This was accomplished on a variety of alloy compositions with the main focus on 304SS and 316SS compositions. A further goal was to develop an understanding other the role of ODS particles on crack propagation and creep performance. Since these later two properties require bulk alloy material which was not available, this work was carried out on promising austentic alloy systems which could later be enhanced with ODS strengthening. The research relied on a large variety of micro-analytical techniques, many of which were available through various scientific user facilities. Access to these facilities throughout the course of this work was instrumental in gathering complimentary data from various analysis techniques to form a well-rounded picture of the processes which control austenitic ODS alloy performance. Micromechanical testing of the austenitic ODS alloys confirmed their highly superior mechanical properties at elevated temperature from the enhanced strengthening effects. The study analyzed the microstructural mechanisms that provide this enhanced high temperature performance. The findings confirm that the smallest size ODS particles provide the most potent strengthening component. Larger particles and other thermally- driven precipitate structures were less effective contributors and, in some cases, limited

  20. Research on High-Speed Drilling Performances of Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    J.W.Zhong; Y.P.Ma; F.H.Sun; M.Chen

    2004-01-01

    Due to specific properties arising from their structure (high ductility, high toughness,strong tenacious and low heat conductivity), the stainless steels have poor machinability. The drilling of the stainless steels becomes the machining difficulty for their serious work-hardening and abrasion of tools. In this paper, the austenitic stainless steel is used as the work-piece to perform the contrastive experiments with the TiN coated and TiAlN-coated high-speed steel drills. The cutting force, torque, cutting temperature, and the abrasion of drills and tool life are tested and analyzed in the process of high-speed drilling. Experiment results show the effect of drilling speed on cutting force, cutting temperature, and drill wear. TiAlN-coated drills demonstrate better performances in high speed drilling. The research results will be of great benefit in the selection of drills and in the control of tool wear in high speed drilling of stainless steels.

  1. Dynamic recrystallization and precipitation in high manganese austenitic stainless steel during hot compression

    Institute of Scientific and Technical Information of China (English)

    Amir Momeni; Shahab Kazemi; Golam Ebrahimi; Alireza Maldar

    2014-01-01

    Dynamic recrystallization and precipitation in a high manganese austenitic stainless steel were investigated by hot compression tests over temperatures of 950-1150°C at strain rates of 0.001 s-1-1 s-1. All the flow curves within the studied deformation regimes were typ-ical of dynamic recrystallization. A window was constructed to determine the value of apparent activation energy as a function of strain rate and deformation temperature. The kinetics of dynamic recrystallization was analyzed using the Avrami kinetics equation. A range of apparent activation energy for hot deformation from 303 kJ/mol to 477 kJ/mol is obtained at different deformation regimes. Microscopic characterization confirms that under a certain deformation condition (medium Zener-Hollomon parameter (Z) values), dynamic recrystalliza-tion appears at first, but large particles can not inhibit the recrystallization. At low or high Z values, dynamic recrystallization may occur be-fore dynamic precipitation and proceeds faster. In both cases, secondary phase precipitation is observed along prior austenite grain bounda-ries. Stress relaxation tests at the same deformation temperatures also confirm the possibility of dynamic precipitation. Unexpectedly, the Avrami's exponent value increases with the increase of Z value. It is associated with the priority of dynamic recrystallization to dynamic pre-cipitation at higher Z values.

  2. Corrosion Behavior of the Stressed Sensitized Austenitic Stainless Steels of High Nitrogen Content in Seawater

    Directory of Open Access Journals (Sweden)

    A. Almubarak

    2013-01-01

    Full Text Available The purpose of this paper is to study the effect of high nitrogen content on corrosion behavior of austenitic stainless steels in seawater under severe conditions such as tensile stresses and existence of sensitization in the structure. A constant tensile stress has been applied to sensitized specimens types 304, 316L, 304LN, 304NH, and 316NH stainless steels. Microstructure investigation revealed various degrees of stress corrosion cracking. SCC was severe in type 304, moderate in types 316L and 304LN, and very slight in types 304NH and 316NH. The electrochemical polarization curves showed an obvious second current peak for the sensitized alloys which indicated the existence of second phase in the structure and the presence of intergranular stress corrosion cracking. EPR test provided a rapid and efficient nondestructive testing method for showing passivity, degree of sensitization and determining IGSCC for stainless steels in seawater. A significant conclusion was obtained that austenitic stainless steels of high nitrogen content corrode at a much slower rate increase pitting resistance and offer an excellent resistance to stress corrosion cracking in seawater.

  3. High corrosion resistance of austenitic stainless steel alloyed with nitrogen in an acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Metikos-Hukovic, M., E-mail: mmetik@fkit.h [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Babic, R. [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Grubac, Z. [Department of General and Inorganic Chemistry, Faculty of Chemistry and Technology, University of Split, 21000 Split (Croatia); Petrovic, Z. [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Lajci, N. [Faculty of Mine and Metallurgy, University of Prishtina, 10000 Prishtina, Kosovo (Country Unknown)

    2011-06-15

    Highlights: {yields} ASS alloyed with nitrogen treated at 1150 {sup o}C exhibits microstructure homogeneity. {yields} Passivation peak of ASS corresponds to oxidation of metal and absorbed hydrogen. {yields} Transfer phenomena and conductivity depend on the film formation potential. {yields} Electronic structure of the passive film and its corrosion resistance correlate well. {yields} Passive film on ASS with nitrogen is low disordered and high corrosion resistant. - Abstract: Passivity of austenitic stainless steel containing nitrogen (ASS N25) was investigated in comparison with AISI 316L in deareated acid solution, pH 0.4. A peculiar nature of the passivation peak in a potentiodynamic curve and the kinetic parameters of formation and growth of the oxide film have been discussed. The electronic-semiconducting properties of the passive films have been correlated with their corrosion resistance. Alloying austenitic stainless steel with nitrogen increases its microstructure homogeneity and decreases the concentration of charge carriers, which beneficially affects the protecting and electronic properties of the passive oxide film.

  4. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Swaminathan, Srinivasan, E-mail: swaminathan@kist.re.kr [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of); Krishna, Nanda Gopala [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kim, Dong-Ik, E-mail: dongikkim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of)

    2015-10-30

    Highlights: • Initial oxidation characteristics of Cu-bearing austenitic stainless steel at 650 °C were studied. • Strong segregation and oxidation of Mn and Nb were found in the entire oxide scale. • Surface coverage by metallic Cu-rich precipitates increases with exposure time. • Chemical heterogeneity of oxide scale revealed initial oxidation to be non-selective. • Fe-Cr and Mn-Cr mixed oxides were realized along with binary oxides of Fe, Cr and Mn. - Abstract: Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr{sub 2}O{sub 4} and MnCr{sub 2}O{sub 4} along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  5. On the Plasma (ion) Carburized Layer of High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Y. Ueda; N. Kanayama; K. Ichii; T. Oishi; H. Miyake

    2004-01-01

    The manganese concentration of austenitic stainless steel decreases from the inner layer towards the surface of the plasma (ion) carburized layer due to the evaporation of manganese from the specimen surface. The carbon concentration in the carburized layer is influenced by alloyed elements such as Ct, Ni, Si, and Mo, as well as Nitrogen. This study examined the effects of nitrogen on the properties of the carburized layer of high nitrogen stainless steel. Plasma (ion)carburizing was carried out for 14.4 ks at 1303 K in an atmosphere of CH4+H2 gas mixtures under a pressure of 350 Pa. The plasma carburized layer of the high nitrogen stainless steel was thinner than that of an austentric stainless steel containing no nitrogen. This suggested that the nitrogen raised the activity of carbon in the plasma carburized layer, GDOES measurement indicated that the nitrogen level in the layer did not vary after plasma (ion) carburizing.

  6. High-resolution X-ray diffraction investigation on the evolution of the substructure of individual austenite grains in TRIP steels during tensile deformation

    NARCIS (Netherlands)

    Blondé, R.J.P.; Jimenez-Melero, E.; Huizenga, R.M.; Zhao, L.; Wright, J.; Brück, E.H.; Van der Zwaag, S.; Van Dijk, N.H.

    2014-01-01

    The martensitic transformation behaviour of the metastable austenite phase in low-alloyed transformation-induced plasticity (TRIP) steels has been studied in situ using high-energy X-ray diffraction during deformation. The austenite stability during tensile deformation has been evaluated at

  7. Effect of Grain Size on Void Formation during High-Energy Electron Irradiation of Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Singh, Bachu Narain

    1974-01-01

    Thin foils of an ‘ experimental ’ austenitic stainless steel, with and without dispersions of aluminium oxide particles, are irradiated with 1 MeV electrons in a High Voltage Electron Microscope at 600°C. Evidence of grain size dependent void nucleation, void concentration, and void volume swelling...

  8. Study of intergranular embrittlement in Fe-12Mn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.J.

    1982-06-01

    A high resolution scanning Auger microscopic study has been performed on the intergranular fracture surfaces of Fe-12Mn steels in the as-austenitized condition. Fracture mode below the ductile-brittle transition temperature was intergranular whenever the alloy was quenched from the austenite field. The intergranular fracture surface failed to reveal any consistent segregation of P, S, As, O, or N. The occasional appearance of S or O on the fracture surface was found to be due to a low density precipitation of MnS and MnO/sub 2/ along the prior austenite boundaries. An AES study with Ar/sup +/ ion-sputtering showed no evidence of manganese enrichment along the prior austenite boundaries, but a slight segregation of carbon which does not appear to be implicated in the tendency toward intergranular fracture. Addition of 0.002% B with a 1000/sup 0/C/1h/WQ treatment yielded a high Charpy impact energy at liquid nitrogen temperature, preventing the intergranular fracture. High resolution AES studies showed that 3 at. % B on the prior austenite grain boundaries is most effective in increasing the grain boundary cohesive strength in an Fe-12Mn alloy. Trace additions of Mg, Zr, or V had negligible effects on the intergranular embrittlement. A 450/sup 0/C temper of the boron-modified alloys was found to cause tempered martensite embrittlement, leading to intergranular fracture. The embrittling treatment of the Fe-12Mn alloys with and without boron additions raised the ductile-brittle transition by 150/sup 0/C. This tempered martensite embrittlement was found to be due to the Mn enrichment of the fracture surface to 32 at. % Mn in the boron-modified alloy and 38 at. % Mn in the unmodified alloy. The Mn-enriched region along the prior austenite grain boundaries upon further tempering is believed to cause nucleation of austenite and to change the chemistry of the intergranular fracture surfaces. 61 figures.

  9. Internal friction mechanism of Fe-19Mn alloy at low and high strain amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shuke, E-mail: huangshuke@163.com [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Huang, Wenrong; Liu, Jianhui [Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Teng, Jin; Li, Ning; Wen, Yuhua [School of Manufacturing Science and Engineering, Sichuan University, Chengdu, Sichuan 610065 (China)

    2013-01-10

    Fe-Mn damping alloy, which can decrease the vibrating and noise effectively, will be widely applied to household appliances, automobiles, industrial facilities, etc. In this paper, the internal friction mechanism of Fe-19Mn alloy at low strain amplitude (10{sup -5} range) and high strain amplitude (10{sup -4} range) was investigated. The internal friction was measured using multifunction internal friction equipment and reversal torsion pendulum. The microstructure was observed using scanning electron microscopy. The phase transformation temperatures were determined using differential scanning calorimetry. The results indicated that the internal friction of Fe-19Mn alloy after solution treating was related to strain amplitude. The internal friction mechanism was believed to the movements of four damping sources ({epsilon}-martensite variant boundaries, stacking fault boundaries in {epsilon}-martensite and {gamma}-austenite, {gamma}/{epsilon} interfaces), which could be explained using the interactive movements of Shockley partial dislocations and point defects. At low strain amplitude (10{sup -5} range), the bowing out movements of Shockley partial dislocations are the main moving mode of generating internal friction. At high strain amplitude (10{sup -4} range), however, the breaking away movements of Shockley partial dislocations are the high internal friction mechanism of Fe-19Mn alloy.

  10. Fe-C-Mn-Si钢中奥氏体共格孪晶界对贝氏体铁素体变体选择的影响%INFLUENCE OF COHERENT AUSTENITE TWIN BOUNDARIES ON THE VARIANT SELECTION OF BAINITIC FERRITE IN Fe-C-Mn-Si STEELS

    Institute of Scientific and Technical Information of China (English)

    王西霞; 郭晖; 王鼎; 白银; 杨善武; 贺信莱

    2012-01-01

    将C含量(质量分数)分别为0.05%和0.4%的Fe-C-Mn-Si钢进行等温处理得到贝氏体组织,采用EBSD技术对奥氏体共格孪晶界上形成的贝氏体铁素体变体进行分析.结果表明,2种钢中的贝氏体铁素体与母相奥氏体均成近似K-S取向关系.奥氏体孪晶界两侧形成取向相同的变体对.此变体对形成后,孪晶界基本不再显现.晶体学分析表明,共格孪晶界两侧可能出现的变体对最多不超过3组,且这3组变体对的惯习面均与孪晶界平行,因此,贝氏体铁素体变体都将沿孪晶界生长.含C量为0.05%的Fe-C-Mn-Si钢中奥氏体孪晶界上只观察到一组贝氏体铁素体变体对的形成,这是因为C含量较低,贝氏体铁素体生长速度较快,消除了其它变体对的形核机会,先形核的变体对一旦形核就迅速覆盖整个孪晶面.而在含C量为0.4%的Fe-C-Mn-Si钢中,由于C含量较高,贝氏体铁素体生长速度较慢,3组变体对均有机会形核,因此,在孪晶界上可以观察到这3组变体对同时出现.%To develop higher performance steels the requirements of the control of the microstruc-ture is increasingly enhanced. The crystallographic orientation characteristics in the microstructure attract more and more attention because the mechanical properties are usually determined by the grain boundary density, especially high angle grain boundary density. So far researchers have conducted comprehensive investigation of the variant selection during the phase transformation. To decrease the nucleation barrier, the new phase usually chooses a specific orientation (variant) to decrease the inter-facial energy between the parent and new phases. The variant selection occurs on the grain boundaries has been well studied. The nucleation and variant selection on austenite twin boundaries, however, are seldom reported, especially in the low carbon steels in which austenite can hardly be retained to the room temperature. In this work

  11. The effect of MC and MN stabilizer additions on the creep rupture properties of helium implanted Fe-25% Ni-15% Cr austenitic alloy

    Science.gov (United States)

    Yamamoto, Norikazu; Nagakawa, Johsei; Shiraishi, Haruki

    1995-10-01

    Helium embrittlement resistance of Fe-25% Ni-15% Cr austenitic alloys with various MX (M = V, Ti, Nb, Zr; X = C, N) stabilizers was compared through post helium implantation creep testing at 923 K. While significant deterioration by helium in terms of creep rupture time and elongation occurred for all materials investigated, the suppression of the deterioration, especially in rupture time, was discerned for the materials in which semi-coherent MC (M = Ti, Ti + Nb, V + Ti) particles were distributed at high density. The material which contains the incoherent M 23C 6 as predominant precipitates seems to be less degraded by helium than those containing the MXs (M = Zr, V; X = C, N), if compared at the same number density of precipitates. Therefore, it is suggested that the high density dispersion of incoherent M 23C 6 as well as semi-coherent Ti containing MC particles would be beneficial in reducing the detrimental helium influences on mechanical properties.

  12. Effect of Annealing Temperature on the Microstructure, Tensile Properties, and Fracture Behavior of Cold-Rolled High-Mn Light-Weight Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae-Hyun; Cho, Kyung Mox [Pusan National University, Busan (Korea, Republic of); Park, Seong-Jun; Moon, Joonoh; Kang, Jun-Yun; Park, Jun-Young; Lee, Tae-Ho [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2017-05-15

    The effects of the annealing temperature on the microstructure and tensile properties of cold-rolled light-weight steels are investigated using two Fe-30Mn-xAl-0.9C alloys that contain different Al content. The initial alloy microstructure is composed of a single austenite or a mixture of austenite and ferrite depending on the nominal aluminum content. For the alloy with 9 wt%Al content, the recrystallization and grain growth of austenite occurrs depending on the annealing temperature. However, for the alloy with 11 wt%Al content, the β-Mn phase is observed after annealing for 10 min at 550~800 ℃. The β-Mn transformation kinetics is the fastest at 700 ℃. The formation of the β-Mn phase has a detrimental effect on the ductility, and this leads to significant decreases in the total elongation. The same alloy also forms κ-carbide and DO3 ordering at 550~900 ℃. The investigated alloys exhibit a fully recrystallized microstructure after annealing at 900 ℃ for 10 min, which results in a high total elongation of 25~55%with a high tensile strength of 900~1170 MPa.

  13. Corrosion Resistance and Pitting Behaviour of Low-Carbon High-Mn Steels in Chloride Solution

    Directory of Open Access Journals (Sweden)

    Grajcar A.

    2016-06-01

    Full Text Available Corrosion resistance of the X4MnSiAlNbTi27-4-2 and X6MnSiAlNbTi26-3-3 type austenitic steels, after hot deformation as well as after cold rolling, were evaluated in 3.5% NaCl solution using potentiodynamic polarization tests. A type of nonmetallic inclusions and their pitting corrosion behaviour were investigated. Additionally, the effect of cold deformation on the corrosion resistance of high-Mn steels was studied. The SEM micrographs revealed that corrosion damage formed in both investigated steels is characterized by various shapes and an irregular distribution at the metallic matrix, independently on the steel state (thermomechanically treated or cold worked. Corrosion pits are generated both in grain interiors, grain boundaries and along the deformation bands. Moreover, corrosion damage is stronger in cold deformed steels in comparison to the thermomechanically treated specimens. EDS analysis revealed that corrosion pits preferentially nucleated on MnS and AlN inclusions or complex oxysulphides. The morphology of corrosion damage in 3.5% NaCl supports the data registered in potentiodynamic tests.

  14. Mn based olivine electrode material with high power and energy.

    Science.gov (United States)

    Kim, Jongsoon; Seo, Dong-Hwa; Kim, Sung-Wook; Park, Young-Uk; Kang, Kisuk

    2010-02-28

    We report the Mn based olivine electrode material with high power and energy. Easier and more frequent nucleation by Fe and Co in Mn-based olivines significantly enhanced the rate capability as evidenced by the electrochemical results.

  15. High Ductility and Toughness of a Micro-duplex Medium-Mn Steel in a Large Temperature Range from -196 °C to 200 °C

    DEFF Research Database (Denmark)

    Chen, Si-lian; Hu, Jun; Zhang, Xiaodan;

    2015-01-01

    A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperatures (625 degrees C and 650 degrees C). An ultrafine-grained micro-duplex structure consisting of alternating austenite and ferrite laths was developed by austenite reverse transformation (ART) during...

  16. Thermal Stability of Austenite and Properties of Quenching & Partitioning (Q&P) Treated AHSS

    Science.gov (United States)

    Wu, R. M.; Wang, L.; Jin, X. J.

    A Fe-0.2C-1.87Mn-1.42Si-0.0405Al steel subjected to an appropriate Quenching & Partitioning treatment (Q&P) exhibits the combination of high tensile strength (1311 MPa) and high elongation (13.6%). The thermal decomposition of retained austenite in the as-treated steel has been studied at an elevated temperature of 500oC by means of differential scanning calorimetry (DSC). Activation energy has been obtained by performing a Kissinger analysis method. The DSC results show that the activation energy of thermal decomposition of the retained austenite in this Q&P steel is 221.3KJ/mol, which is in a good agreement with the result of retained austenite in similar chemical composition steel subjected to a TRansformation Induced Plasticity (TRIP) treatment. This investigation helps to investigate the stability of retained austenite in Q&P steels upon cooling or under external stress.

  17. Effects of high-pressure hydrogen charging on the structure of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hoelzel, M. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany)]. E-mail: Markus.Hoelzel@frm2.tum.de; Danilkin, S.A. [Hahn-Meitner-Institut, SF2, Glienicker Str. 100, 14109 Berlin (Germany); Ehrenberg, H. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany); Toebbens, D.M. [Hahn-Meitner-Institut, SF2, Glienicker Str. 100, 14109 Berlin (Germany); Udovic, T.J. [NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 8562, Gaithersburg, MD 20899-8562 (United States); Fuess, H. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany); Wipf, H. [Darmstadt University of Technology, Institute for Solid State Physics, Hochschulstrasse 6, 64289 Darmstadt (Germany)

    2004-10-25

    The effects of high-pressure hydrogen and deuterium charging on the structure of AISI type 304 and AISI type 310 austenitic stainless steels have been investigated by neutron and X-ray diffraction. Rietveld analyses of the neutron diffraction data revealed that hydrogen atoms occupy exclusively the octahedral interstitial sites in both steels. No phase transformations have been observed in 310 stainless steel within the whole range of hydrogen-to-metal atomic ratios H/Me up to {approx} 1. In 304 stainless steel, the formation of {epsilon}-martensite was observed not only after hydrogenation at 3.0 GPa (H/Me = 0.56), but also after applying a pressure of 4.0 GPa without hydrogen. The results differ significantly from published studies on cathodically hydrogenated samples, where high amounts of {epsilon}-martensite were observed in both steels. High-pressure hydrogenation and cathodic hydrogen charging result in different phase transformation behaviour. The discrepancies can be explained by different hydrogen distributions resulting in quite different stress states.

  18. Carburization of austenitic and ferritic alloys in hydrocarbon environments at high temperature

    Directory of Open Access Journals (Sweden)

    Serna, A.

    2003-12-01

    Full Text Available The technical and industrial aspects of high temperature corrosion of materials exposed to a variety of aggressive environments have significant importance. These environments include combustion product gases and hydrocarbon gases with low oxygen potentials and high carbon potentials. In the refinery and petrochemical industries, austenitic and ferritic alloys are usually used for tubes in fired furnaces. The temperature range for exposure of austenitic alloys is 800-1100 °C, and for ferritic alloys 500-700 °C, with carbon activities ac > 1 in many cases. In both applications, the carburization process involves carbon (coke deposition on the inner diameter, carbon absorption at the metal surface, diffusion of carbon inside the alloy, and precipitation and transformation of carbides to a depth increasing with service. The overall kinetics of the internal carburization are approximately parabolic, controlled by carbon diffusion and carbide precipitation. Ferritic alloys exhibit gross but uniform carburization while non-uniform intragranular and grain-boundary carburization is observed in austenitic alloys.

    La corrosión a alta temperatura, tal como la carburación de materiales expuestos a una amplia variedad de ambientes agresivos, tiene especial importancia desde el punto de vista técnico e industrial. Estos ambientes incluyen productos de combustión, gases e hidrocarburos con bajo potencial de oxígeno y alto potencial de carbono. En las industrias de refinación y petroquímica, las aleaciones austeníticas y ferríticas se utilizan en tuberías de hornos. El rango de temperatura de exposición para aleaciones austeníticas está entre 800-1.100°C y para aleaciones ferríticas está entre 500-700°C, con actividades de carbono ac>1 en algunos casos. En tuberías con ambas aleaciones, el proceso de carburación incluye deposición de carbón (coque en el diámetro interno, absorción de carbono en la superficie

  19. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale

    Science.gov (United States)

    Hossain, R.; Pahlevani, F.; Quadir, M. Z.; Sahajwalla, V.

    2016-10-01

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  20. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale.

    Science.gov (United States)

    Hossain, R; Pahlevani, F; Quadir, M Z; Sahajwalla, V

    2016-10-11

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels' performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  1. Cytotoxicity study of plasma-sprayed hydroxyapatite coating on high nitrogen austenitic stainless steels.

    Science.gov (United States)

    Ossa, C P O; Rogero, S O; Tschiptschin, A P

    2006-11-01

    Stainless steel has been frequently used for temporary implants but its use as permanent implants is restricted due to its low pitting corrosion resistance. Nitrogen additions to these steels improve both mechanical properties and corrosion resistance, particularly the pitting and crevice corrosion resistance. Many reports concerning allergic reactions caused by nickel led to the development of nickel free stainless steel; it has excellent mechanical properties and very high corrosion resistance. On the other hand, stainless steels are biologically tolerated and no chemical bonds are formed between the steel and the bone tissue. Hydroxyapatite coatings deposited on stainless steels improve osseointegration, due their capacity to form chemical bonds (bioactive fixation) with the bone tissue. In this work hydroxyapatite coatings were plasma-sprayed on three austenitic stainless steels: ASTM-F138, ASTM-F1586 and the nickel-free Böhler-P558. The coatings were analyzed by SEM and XDR. The cytotoxicity of the coatings/steels was studied using the neutral red uptake method by quantitative evaluation of cell viability. The three uncoated stainless steels and the hydroxyapatite coated Böhler-P558 did not have any toxic effect on the cell culture. The hydroxyapatite coated ASTM-F138 and ASTM-F1586 stainless steels presented cytotoxicity indexes (IC50%) lower than 50% and high nickel contents in the extracts.

  2. Multi-scale modeling of the impact response of a strain-rate sensitive high-manganese austenitic steel

    OpenAIRE

    Canadinç, Demircan; Önal, Orkun; Özmenci, Cemre

    2014-01-01

    A multi-scale modeling approach was applied to predict the impact response of a strain rate sensitive high-manganese austenitic steel. The roles of texture, geometry, and strain rate sensitivity were successfully taken into account all at once by coupling crystal plasticity and finite element (FE) analysis. Specifically, crystal plasticity was utilized to obtain the multi-axial flow rule at different strain rates based on the experimental deformation response under uniaxial ten...

  3. Highly Sensitive AMS Measurement of 53Mn at CIAE

    Institute of Scientific and Technical Information of China (English)

    DONG; Ke-jun; HU; Hao; LIU; Guang-shan; HE; Ming; LI; Zhen-yu; DOU; Liang; XIE; Lin-bo; LIU; Jian-cheng; WANG; Xiang-gao; SHEN; Hong-tao; LIN; De-yu; ZHENG; Guo-wen; WANG; Xiao-bo; LI; Heng; LI; Chao-li; WU; Shao-yong; YOU; Qu-bo; JIN; Chun-sheng; CHEN; Zhi-gang; YUAN; Jian; JIANG; Shan

    2013-01-01

    Methods for highly sensitive AMS measurement of 53Mn were explored by extracting different Mn-containing molecular ions in ion source and using different chemical forms of sample materials.Preliminary results indicate that a method for AMS measurement of 53Mn has been established and a-155355

  4. On the crystal structure of Cr2N precipitates in high-nitrogen austenitic stainless steel.

    Science.gov (United States)

    Lee, Tae-Ho; Oh, Chang-Seok; Han, Heung Nam; Lee, Chang Gil; Kim, Sung-Joon; Takaki, Setsuo

    2005-04-01

    The crystal structure of Cr(2)N precipitates in high-nitrogen austenitic stainless steel was investigated by transmission electron microscopy (TEM). Based on the analyses of selected area diffraction (SAD) patterns, the crystal structure of Cr(2)N was confirmed to be trigonal (P31m) and was characterized by three sets of superlattice reflections: (001), ((11/33)0)and ((11/33)1). These could be explained in terms of the epsilon-type occupational ordering of nitrogen. The static concentration waves (SCWs) method was applied to describe the ordered superstructure of Cr(2)N. The occupation probability function (OPF) for describing the distribution of N atoms in the Cr(2)N superstructure was derived based on the superlattice reflections obtained in the SAD patterns and could be expressed as: n(r)=c-1/6eta1cos2piz+4/3eta3cos(2pi/3)(x+y+3z). The crystallographic models for epsilon-type ordering, mainly suggested in the Fe-N system, were discussed in comparison to the present model.

  5. Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels

    Institute of Scientific and Technical Information of China (English)

    Hua-bing Li; Zhou-hua Jiang; Yan Yang; Yang Cao; Zu-rui Zhang

    2009-01-01

    Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels (HNSS) were investigated by electrochemical and immersion testing methods in chloride solution, respectively. The chemical constitution and composition in the depth of passive films formed on HNSS were analyzed by X-ray photoelectron spectrum (XPS). HNSS has excellent pitting and crevice corrosion resistance compared to 316L stainless steel. With increasing the nitrogen content in steels, pitting potentials and critical pitting temperature (CPT) increase, and the maximum, average pit depths and average weight loss decrease. The CPT of HNSS is correlated with the alloying element content through the measure of alloying for resistance to corrosion (MARC). The MARC can be expressed as an equation of CPT=2.55MARC-29. XPS results show that HNSS exhibiting excellent corrosion resis-tance is attributed to the enrichment of nitrogen on the surface of passive films, which forms ammonium ions increasing the local pH value and facilitating repassivation, and the synergistic effects of molybdenum and nitrogen.

  6. Analysis Of The Austenite Grain Growth In Low-Alloy Boron Steel With High Resistance To Abrasive Wear

    Directory of Open Access Journals (Sweden)

    Białobrzeska B.

    2015-09-01

    Full Text Available Today low-alloy steels with boron achieve high resistance to abrasive wear and high strength. These features are obtained by using advanced technology of manufacturing. This makes boron steels increasingly popular and their application more diverse. Application of these steels can extend the lifetime of very expensive machine construction in many industries such as mining, the automotive, and agriculture industries. An interesting subgroup of these materials is steel with boron intended for heat treatment. These steels are supplied by the manufacturer after cold or hot rolling so that it is possible for them to be heat treated in a suitable manner by the purchaser for its specific application. Very important factor that determines the mechanical properties of final product is austenite grain growth occurring during hot working process such us quenching or hot rolling. Investigation of the effect of heating temperature and holding time on the austenite grain size is necessary to understand the growth behavior under different conditions. This article presents the result of investigation of austenite grain growth in selected low-allow boron steel with high resistance to abrasive wear and attempts to describe the influence of chemical composition on this process.

  7. Evaluation of Tensile Property of Austenitic Alloys Exposed to High-Temperature S-CO{sub 2} Environment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyunmyung; Lee, Ho Jung; Jang, Changheui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-12-15

    Super-critical CO{sub 2} (S-CO{sub 2}) Brayton cycle has been considered to replace the current steam Rankine cycle in Sodium-cooled Fast Reactor (SFR) in order to improve the inherent safety and thermal efficiency. Several austenitic alloys are considered as the structural materials for high temperature S-CO{sub 2} environment. Microstructural change after long-term exposure to high temperature S-CO{sub 2} environment could affect to the mechanical properties. In this study, candidate materials (austenitic stainless steels and Alloy 800HT) were exposed to S-CO{sub 2} to assess oxidation resistance and the change in tensile properties. Loss of ductility was observed for some austenitic stainless steels even after 250 h exposure. The contribution of S-CO{sub 2} environment on such changes was analyzed based on the characterization of the surface oxide and carburization of the materials in which 316H and 800H showed different oxidation behaviors.

  8. Fatigue behavior in austenitic stainless steels in high-temperature water

    Science.gov (United States)

    Smith, Jean Laverty

    The fatigue life of Type 304 and Type 316NG austenitic stainless steel has been shown to be significantly lower in light water reactor environments than in air at 288°C. The focus of this study was to determine the effect of dissolved oxygen (DO) on fatigue crack initiation and early crack growth at 288°C using fully-reversed, constant strain, axial fatigue tests. The fatigue tests were chosen to evaluate fracture surface appearance, fatigue crack lengths, and fatigue crack growth rates. Additional studies were conducted to evaluate the oxide film growth kinetics of Type 304 and Type 316NG stainless steel in high-temperature water. Corrosion coupons were exposed for intervals up to 50 days to high-temperature water at 288°C with two different levels of dissolved oxygen. The coupons were evaluated for weight change, oxide film thickness, and oxide film composition. The fatigue testing and oxide evaluations conducted in this study indicate that in low-DO water, the bulk environment does not allow a passive film to form, and newly created metal surfaces do not oxidize. Fatigue cracks propagate as Mode I tensile cracks normal to the stress axis from the onset. The apparent lack of Stage I crack growth in low-DO water accounts for the significant reduction in life in this environment as compared to air. In high-DO water, the bulk environment supports the formation of a passive film and prevents the evolution of hydrogen. Crack growth initially occurs only along primary slip planes at angles 45° to the applied stress. As the crack length increases, the crack tip environment becomes increasingly independent of the bulk environment, water at the crack tip becomes unstable, and the newly created surfaces no longer re-oxidize. Subsequently, the increasing stress intensity allows slip to occur on additional planes, and the fatigue crack propagates as a Mode I tensile crack.

  9. Mechanical and tribological properties of high-nitrogen austenitic steels; Mechanische und tribologische Eigenschaften von hochstickstoffhaltigen Austeniten

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, A.; Weiss, S. [Universitaet Duisburg Essen, Institut fuer Produkt Engineering, Werkstofftechnik, Lotharstr. 1, 47057 Duisburg (Germany); Tikhovskiy, I. [MPI fuer Eisenforschung, Duesseldorf (Germany); Buescher, R. [Stryker Osteosynthesis GmbH, Schoenkirche, Universtaet Duisburg-Essen (Germany)

    2006-09-15

    Austenitic stainless steels provide a fair combination of strength, toughness and corrosion resistance. Undergoing tribological stresses - in particular under self-mating contact situations - their performance is not sufficient. Thus the more wear resistant austenitic Co-base alloys with different carbon contents are applied under these circumstances, which may prevail in medical applications. Austenitic high-Nitrogen Steels might be an alternative under these circumstances. Strength, corrosion resistance and tribologcial properties are similar to those of CoCrMo-alloys, while their toughness is higher. This contribution presents the metallurgical mechanisms, which bring about this combination of properties. (Abstract Copyright [2006], Wiley Periodicals, Inc.) [German] Austenitische rostfreie Staehle zeichnen sich durch eine guenstige Kombination von Festigkeit, Zaehigkeit und Korrosionsbestaendigkeit aus. Dagegen sind sie unter tribologischen Belastungen insbesondere im artgleichen Kontakt nicht verschleissbestaendig. Unter diesen Randbedingungen, die vielfach in der Medizintechnik vorliegen, werden daher die verschleissbestaendigeren aber ebenfalls austenitischen Co-Basislegierungen mit unterschiedlichen Kohlenstoffgehalten eingesetzt. Hochstickstoffhaltige austenitische Staehle koennen hier als eine weitere Moeglichkeit angesehen werden. Ihre Festigkeit, Korrosions- und Verschleissbestaendigkeit sind denen der Co-Basislegierungen vergleichbar, wobei die Zaehigkeit aber deutlich hoeher ist. In dem Beitrag werden die metallkundlichen Mechanismen vorgestellt, die zu dieser Kombination von Eigenschaften fuehren. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  10. High temperature strength and ductility of the (C+N) strengthening Fe-Cr-Mn(W,V) steels

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materials in fusion reactor have been investigated. The resultsshow that the high temperature strength and the creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C+N) complex-strengthening, so can be the high temperature ductility. The strength and ductility of the steels are superior to that of SUS316 steels and JPCAS below 673K. The relationship between strength, ductility andthe formation temperature is related to the evolution of deformation microstructure. The fracture and microstructure observation above 673Kindicates that the main way to further improve ductility at high temperature is the control of carbide coarsening at the grain boundaries.

  11. τ-MnAl with high coercivity and saturation magnetization

    Directory of Open Access Journals (Sweden)

    J. Z. Wei

    2014-12-01

    Full Text Available In this paper, high purity τ-Mn54Al46 and Mn54−xAl46Cxalloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD, powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm-1, coercivity of 0.5 T, and a maximum energy product of (BHmax = 24.7 kJm-3 were achieved for the pure Mn54Al46 powders without carbon doping. The carbon substituted Mn54−xAl46Cx, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μB which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μB at a volume expansion rate of ΔV/V ≈ 20%.

  12. ON THE TENSILE MECHANICAL PROPERTY OF Si-Mn TRIP STEELS AT HIGH STRAIN RATE

    Institute of Scientific and Technical Information of China (English)

    X.C. Wei; L. Li; R.Y. Fu; W. Shi

    2002-01-01

    Tensile mechanical properties of 1.6Si-1.58Mn-0.195C TRIP (transformation-inducedplasticity) steels under high strain rate and effects of DP (dual-phase) treatments werestudied and compared to the quasi-static tensile behavior. The results show that theincreasing of strain rate leads to increasing in their strengths and decreasing in theuniform elongation remarkably. Because the stable retained austenite in TRIP steelcan transform to martensite during tensile testing and the material exhibits excellentcharacteristic of transformation induced plasticity, the plastic deformation behavior isevidently improved and the combination of strength and elongation is superior to thatof dual-phase steel, although its strength is smaller than that of DP steel. However,DP treated steel shown lower elongation under dynamic tension in spite of higherstrength. A model was proposed to explain the excellent elongation rate of TRIPsteel compared with DP steel on the basis of SEM analysis and the strength of thecomponents in microstructure.

  13. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Science.gov (United States)

    Swaminathan, Srinivasan; Krishna, Nanda Gopala; Kim, Dong-Ik

    2015-10-01

    Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr2O4 and MnCr2O4 along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  14. Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (λN) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These λN laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of λN lath. The first is a genuinely {111} twin, and λN and α keep the accurate K-S relationship, and each λN and α form a sharp and smooth λN/α interface of {335}λN//{341}a, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of λN due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the λN and the (-matrix deviate from the accurate K-S OR, and the OR between two λN twin components deviate from the genuine {111} twin relationship. In addition, the λN/α interface of the second type of λN is not as sharp or smooth as that of the first one.

  15. High-Field Magnetization of Some Mn Alloys(Magnetism)

    OpenAIRE

    Tomiei, Hori; Hiroshi, Shiraishi; Hiroshi, Niida; Hiroaki, Kato; Giyuu, Kido; Yasuo, Yamaguchi; Yasuaki, Nakagawa; Shibaura Institute of Technology; Institute for Materials Research, Tohoku University

    1993-01-01

    We have made high-field magnetization measurements for some Mn alloys : ε-Mn_Ga with δ= -0.30, ε-(Mn_Fe_x)_3Sn with x=0.1 and 0.3, Fe_3Mn_4Ge_ and γ-(Mn_Fe_x)_Ga_y with x=0.44 and y=0.27. The ε-Mn_Ga has the hexagonal D0_ type structure and a distorted triangular antiferromagnetic spin structure. The hexagonal lattice is slightly distorted to an orthorhombic lattice at T_d of about 290 K with large magnetization. Pseudo-binary ε-(Mn_Fe_x)_3Sn has also the D0_ type structure, and the alloys wi...

  16. Applications of Thermo-Calc in Research of High Nitrogen Austenitic Stainless Steels%热力学计算在高氮奥氏体不锈钢研究中的应用

    Institute of Scientific and Technical Information of China (English)

    郎宇平; 陈海涛; 翁宇庆; 屈华鹏

    2013-01-01

    采用Thermo-Calc软件,计算了碳、铬、锰、镍元素和压力因素对22Cr高氮奥氏体不锈钢氮溶解度、凝固过程中相转变以及析出相的影响,并对设计的新型高氮奥氏体不锈钢组织及析出相进行了研究.结果表明:铬元素主要增加液态钢的氮溶解度,增加0.1%(质量分数)的碳即能显著增大奥氏体不锈钢在高温凝固时的最小氮溶解度.锰元素既增加液态钢中的饱和氮溶解度,又增加凝固初期的最小氮溶解度.适当的锰含量能扩大并稳定奥氏体相区,避免“铁素体阱”的出现.少量的镍含量既增加奥氏体不锈钢高温凝固时的最小氮溶解度,缩小高温δ铁素体存在的温度区间,也能使钢在室温下有完全的奥氏体组织.加压冶炼能有效促进氮溶解度.新型高氮奥氏体不锈钢的析出相主要为Cr23C6,Cr2N.采用热力学计算工具可以对高氮奥氏体不锈钢的冶炼、组织控制、热处理和热加工提供科学的指导.%The Thermo-Calc software was used to calculate the influence of pressure factor and elements including C,Cr,Mn and Ni on the solubility of nitrogen,the phase transformation during solidification in high nitrogen austenitic stainless steel with 22% (mass fraction) Cr.The microstructures and precipitates of new designed high austenitic stainless steel were studied also.The results show that Cr increases mainly the solubility of nitrogen in liquid steel.With about 0.1%C the minimum solubility of nitrogen during higher solidification temperature is enhanced remarkably.Mn increases not only the solubility of nitrogen in liquid steel but also the minimum solubility of nitrogen during earlier solidification.With proper Mn the phase area of austenite is extended and more stably,also the "ferrite trap" can be avoided.With a little nickel less than 2 % the minimum solubility of nitrogen during higher solidification temperature is enhanced and the temperature extension of

  17. Crack growth behavior of warm-rolled 316L austenitic stainless steel in high-temperature hydrogenated water

    Science.gov (United States)

    Choi, Kyoung Joon; Yoo, Seung Chang; Jin, Hyung-Ha; Kwon, Junhyun; Choi, Min-Jae; Hwang, Seong Sik; Kim, Ji Hyun

    2016-08-01

    To investigate the effects of warm rolling on the crack growth of 316L austenitic stainless steel, the crack growth rate was measured and the oxide structure was characterized in high-temperature hydrogenated water. The warm-rolled specimens showed a higher crack growth rate compared to the as-received specimens because the slip bands and dislocations produced during warm rolling served as paths for corrosion and cracking. The crack growth rate increased with the dissolved hydrogen concentration. This may be attributed to the decrease in performance and stability of the protective oxide layer formed on the surface of stainless steel in high-temperature water.

  18. Subgrain and dislocation structure changes in hot-deformed high-temperature Fe-Ni austenitic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ducki, K.J.; Rodak, K.; Hetmanczyk, M.; Kuc, D

    2003-08-28

    The influence of plastic deformation on the substructure of a high-temperature austenitic Fe-Ni alloy has been presented. Hot-torsion tests were executed at constant strain rates of 0.1 and 1.0 s{sup -1}, at testing temperatures in the range 900-1150 deg. C. The examination of the microstructure was carried out, using transmission electron microscopy. Direct measurements on the micrographs allowed the calculation of structural parameters: the average subgrain area, and the mean dislocation density. A detailed investigation has shown that the microstructure is inhomogeneous, consisting of dense dislocation walls, subgrains and recrystallized regions.

  19. Austenite stabilization and high strength-elongation product of a low silicon aluminum-free hot-rolled directly quenched and dynamically partitioned steel

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Xiao-Dong [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Xu, Yun-Bo, E-mail: yunbo_xu@126.com [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Yang, Xiao-Long; Hu, Zhi-Ping; Peng, Fei [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Ju, Xiao-Wei [Ceri Long Product Co., Ltd., Beijing 100176 (China); Wu, Di [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China)

    2015-06-15

    Microstructures composed of lath martensite and retained austenite with volume fraction between 8.0 vol.% and 12.0 vol.% were obtained in a low-C low-Si Al-free steel through hot-rolling direct quenching and dynamical partitioning (HDQ&DP) processes. The austenite stabilization mechanism in the low-C low-Si Al-free steel under the special dynamical partitioning processes is investigated by analyzing the carbon partition behavior from martensite to austenite and the carbide precipitation-coarsening behavior in martensite laths combining with the possible hot rolling deformation inheritance. Results show that the satisfying retained austenite amount in currently studied low-Si Al-free HDQ&DP steel is caused by the high-efficiency carbon enrichment in the 30–80 nm thick regions of austenite near the interfaces in the hot-rolled ultra-fast cooled structure and the avoidance of serious carbides coarsening during the continuous cooling procedures. The excellent strength-elongation product reaching up to 26,000 MPa% shows that the involved HDQ&DP process is a promising method to develop a new generation of advanced high strength steel. - Highlights: • HDQ&DP processes were applied to a low-C low-Si Al-free steel. • Effective partitioning time during the continuous cooling processes is 1–220 s. • Retained austenite with volume fraction between 8.0 vol. % and 12.0 vol. % has been obtained. • The special austenite stabilization mechanism has been expounded.

  20. Effects of Q&P Processing Conditions on Austenite Carbon Enrichment Studied by In Situ High-Energy X-ray Diffraction Experiments

    Directory of Open Access Journals (Sweden)

    Sébastien Yves Pierre Allain

    2017-06-01

    Full Text Available We report the first ultra-fast time-resolved quantitative information on the quenching and partitioning process of conventional high-strength steel by an in situ high-energy X-ray diffraction (HEXRD experiment. The time and temperature evolutions of phase fractions, their carbon content, and internal stresses were determined and discussed for different process parameters. It is shown that the austenite-to-martensite transformation below the martensite start temperature Ms is followed by a stage of fast carbon enrichment in austenite during isothermal holding at both 400 and 450 °C. The analysis proposed supports the concurrent bainite transformation and carbon diffusion from martensite to austenite as the main mechanisms of this enrichment. Furthermore, we give evidence that high hydrostatic tensile stresses in austenite are produced during the final quenching, and must be taken into account for the estimation of the carbon content in austenite. Finally, a large amount of carbon is shown to be trapped in the microstructure.

  1. Development of pseudoelasticity in Fe–10Ni–7Mn (wt%) high strength martensitic steel by intercritical heat treatment and subsequent ageing

    Energy Technology Data Exchange (ETDEWEB)

    Koohdar, H.R. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Nili-Ahmadabadi, M., E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Habibi-Parsa, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Jafarian, H.R. [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran (Iran, Islamic Republic of)

    2015-01-05

    In this research, ternary Fe–10Ni–7Mn (wt%) high strength martensitic steel was subjected to study the reverse transformation of martensite to austenite by intercritical annealing at 600 °C in the ferritic–austenitic (α+γ) dual phase region for various holding times. Subsequent isothermal ageing was performed at 480 °C for 3.6 ks. The experimental results revealed that during intercritical annealing above the heating rate of 5 °C/s, reverse martensite transformation occurs by the diffusionless mechanism. Also, the X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) analyses represented that the volume fraction of the retained austenite at room temperature increases with increasing the holding time up to 7.2 ks and then it gradually decreases. Furthermore, the cyclic tensile test results revealed pseudoelastic behavior of the retained austenite after subsequent ageing. The maximum amount of pseudoelasticity was obtained about 40% at the sixth loading–unloading cycle for the specimen intercritically annealed at 600 °C for 7.2 ks after subsequent isothermal ageing at 480 °C for 3.6 ks.

  2. Austenite formation during intercritical annealing

    OpenAIRE

    A. Lis; J. Lis

    2008-01-01

    Purpose: of this paper is the effect of the soft annealing of initial microstructure of the 6Mn16 steel on the kinetics of the austenite formation during next intercritical annealing.Design/methodology/approach: Analytical TEM point analysis with EDAX system attached to Philips CM20 was used to evaluate the concentration of Mn, Ni and Cr in the microstructure constituents of the multiphase steel and mainly Bainite- Martensite islands.Findings: The increase in soft annealing time from 1-60 hou...

  3. Low-Temperature Nitriding of Deformed Austenitic Stainless Steels with Various Nitrogen Contents Obtained by Prior High-Temperature Solution Nitriding

    Science.gov (United States)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2016-08-01

    In the past decades, high nitrogen steels (HNS) have been regarded as substitutes for conventional austenitic stainless steels because of their superior mechanical and corrosion properties. However, the main limitation to their wider application is their expensive production process. As an alternative, high-temperature solution nitriding has been applied to produce HNS from three commercially available stainless steel grades (AISI 304L, AISI 316, and EN 1.4369). The nitrogen content in each steel alloy is varied and its influence on the mechanical properties and the stability of the austenite investigated. Both hardness and yield stress increase and the alloys remain ductile. In addition, strain-induced transformation of austenite to martensite is suppressed, which is beneficial for subsequent low-temperature nitriding of the surface of deformed alloys. The combination of high- and low-temperature nitriding results in improved properties of both bulk and surface.

  4. The Formation of Multipoles during the High-Temperature Creep of Austenitic Stainless Steels

    DEFF Research Database (Denmark)

    Howell, J.; Nielsson, O.; Horsewell, Andy

    1981-01-01

    It is shown that multipole dislocation configurations can arise during power-law creep of certain austenitic stainless steels. These multipoles have been analysed in some detail for two particular steels (Alloy 800 and a modified AISI 316L) and it is suggested that they arise either during...... instantaneous loading or during the primary creep stage. Trace analysis has shown that the multipoles are confined to {1 1 1} planes during primary creep but are not necessarily confined to these planes during steady-state creep unless they are pinned by interstitials....

  5. Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel

    DEFF Research Database (Denmark)

    Carstensen, J.V.; Mayer, H.; Brøndsted, P.

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained...... in conventional rotating bending at 160 and 200 Hz and in ultrasonic axial loading at 20 kHz. Above 5 × 106 cycles the fatigue lifetimes found with both methods were comparable. The results show that the slope of the S–N curve significantly decreases beyond 108 cycles. Fracture surfaces were examined using...

  6. High temperature oxidation behavior of austenitic stainless steel AISI 304 in steam of nanofluids contain nanoparticle ZrO2

    Energy Technology Data Exchange (ETDEWEB)

    Prajitno, Djoko Hadi, E-mail: djokohp@batan.go.id; Syarif, Dani Gustaman, E-mail: djokohp@batan.go.id [Research Center for Nuclear Materials and Radiometry, Jl. Tamansari 71, Bandung 40132 (Indonesia)

    2014-03-24

    The objective of this study is to evaluate high temperature oxidation behavior of austenitic stainless steel SS 304 in steam of nanofluids contain nanoparticle ZrO{sub 2}. The oxidation was performed at high temperatures ranging from 600 to 800°C. The oxidation time was 60 minutes. After oxidation the surface of the samples was analyzed by different methods including, optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray diffraction examination show that the oxide scale formed during oxidation of stainless steel AISI 304 alloys is dominated by iron oxide, Fe{sub 2}O{sub 3}. Minor element such as Cr{sub 2}O{sub 3} is also appeared in the diffraction pattern. Characterization by optical microscope showed that cross section microstructure of stainless steel changed after oxidized with the oxide scale on the surface stainless steels. SEM and x-ray diffraction examination show that the oxide of ZrO{sub 2} appeared on the surface of stainless steel. Kinetic rate of oxidation of austenite stainless steel AISI 304 showed that increasing oxidation temperature and time will increase oxidation rate.

  7. On the comparison of microstructural characteristics and mechanical properties of high-vanadium austenitic manganese steels with the Hadfield steel

    Energy Technology Data Exchange (ETDEWEB)

    Moghaddam, E.G., E-mail: emad.g.moghaddam@gmail.com [Department of Materials Science and Engineering, Sharif University of Technology, P.O Box 11365-9466, Azadi Avenue, Tehran (Iran, Islamic Republic of); Tabarestan Steel Foundry, P.O Box 14358, No. 46, Bahar Road, South Shiraz Ave., Tehran (Iran, Islamic Republic of); Varahram, N.; Davami, P. [Department of Materials Science and Engineering, Sharif University of Technology, P.O Box 11365-9466, Azadi Avenue, Tehran (Iran, Islamic Republic of)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Mechanical properties of HV-AMS are affected by the type and distribution of VCs. Black-Right-Pointing-Pointer Solution treatment of Hadfield steels has no significant effect on HV-AMS alloys. Black-Right-Pointing-Pointer HV-AMS alloys have superior wear resistance compared with Hadfield steels. - Abstract: In this study, high-vanadium austenitic manganese steel (HV-AMS) alloys and the standard Hadfield steel were investigated. The microstructure of these high-vanadium alloyed Hadfield steels was studied thoroughly using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and was compared to the Hadfield steel. The hardness and unnotched Charpy impact strength of HV-AMS alloys and Hadfield steel were examined at ambient temperature in the as-cast and heat-treated conditions. A pin-on-disk wear test at linear speed of 10 m/min and a 55 N normal load was employed to evaluate the wear behavior of both steel samples. Microstructural results showed that varying the carbon content in HV-AMS alloys can affect the vanadium carbide morphology and its distribution in the austenite matrix which leads to considerable changes of the mechanical properties. Abrasion test revealed that HV-AMS alloys have superior wear resistance, about 5 times of the standard Hadfield steel.

  8. Mechanical Properties and Microstructure Evolution of Cold-deformed High-nitrogen Nickel-free Austenitic Stainless Steel during Annealing

    Institute of Scientific and Technical Information of China (English)

    XU Mingzhou; WANG Jianjun; LIU Chunming

    2012-01-01

    The mechanical properties and microstructure evolution of cold-deformed CrMnN austenitic stainless steel annealed in a temperature ranging from 50 ℃ to 650 ℃ for 90 min and at 550 ℃ for different time were investigated by tensile test,micro hardness test,and Transmission Electron Microscope (TEM).The steel was strengthened when it got annealed at temperatures ranging from 100 ℃ to 550 ℃,while it was softened when it got annealed at temperatures ranging from 550 ℃ to 650 ℃.Annealing temperature had stronger effect on mechanical properties than annealing time.TEM observations showed that nano-sized precipitates formed when the steel was annealed at 150 ℃ for 90 min,but the size and density of precipitates had no noticeable change with annealing temperature and time.Recrystallization occurred when the steel was annealed at temperatures above 550 ℃ for 90 min,and its scale increased with annealing temperature.Nanosized annealing twins were observed.The mechanisms that controlled the mechanical behaviors of the steel were discussed.

  9. Microstructural evolution in deformed austenitic TWinning Induced Plasticity steels

    NARCIS (Netherlands)

    Van Tol, R.T.

    2014-01-01

    This thesis studies the effect of plastic deformation on the stability of the austenitic microstructure against martensitic transformation and diffusional decomposition and its role in the phenomenon of delayed fracture in austenitic manganese (Mn)-based TWinning Induced Plasticity (TWIP) steels. Th

  10. Effects of carbon, nitrogen, and phosphorus on creep rupture ductility of high purity Ni-Cr austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Nakazawa, Takanori; Abo, Hideo; Tanino, Mitsuru; Komatsu, Hazime.

    1989-05-01

    Creep rupture ductility becomes one of the important properties of austenitic stainless steels as structural materials for fast breeder reactors. Using high purity nickel-chromium austenitic steels, the effects of carbon, nitrogen, and phosphorus on creep rupture ductility were investigated. Creep rupture tests were conducted at 600deg C and extensive microstructural works were performed. The results were as follows. Rupture strength increases with carbon or nitrogen content. Although the rupture ductility decreases with carbon, change in ductility with nitrogen is small. The ductility loss with carbon is due to the grain boundary embrittlement by carbides. With nitrogen, there is no precipitation during creep. Addition of phosphorus to ultra low carbon and nitrogen steels increases their rupture strength and ductility. Fine precipitates of (Fe,Cr)/sub 2/P are uniformly dispersed in the grains and coarse (Fe,Cr)/sub 2/P also precipitates on the grain boundary during creep. Grain boundary migration occurs extensively and few wedge type cracks are observed in the P containing steels. It is concluded that, from the viewpoint of increasing creep rupture ductility, nitrogen is much more effective than carbon and phosphorus is also beneficial. (author).

  11. Experimental Study on Edge-cracking in Austenitic Stainless Steel Cr15Mn9Cu2NiN during Hot Rolling%奥氏体不锈钢热轧边裂实验研究

    Institute of Scientific and Technical Information of China (English)

    朱亮; 魏鹏; 侯国清; 苏婷婷

    2012-01-01

    Austenitic stainless steel Crl5Mn9Cu2NiN is prone to suffer from edge cracking during hot rolling. Hot rolling test is conducted on an experimental hot rolling device, which is designed cooperate with thermal simulator. Formation mechanism of edge cracks is researched through this test. The resuks show thai, when press quantity reaches to a certain amount, samples will crack on edge at all test temperatures. All the edge cracks propagate along austenitic grain boundaries. In the range of 1000~l 1 50℃ deformation, cracking tendency of samples are severe, which is related to the reduction of ductility in austenitic stainless steel. The characteristic of microstructures in hot rolled specimens is deformation substructures and twins boundaries in coarse grains in this temperature range. But at 1200℃ deformation, the grain size of specimens is smaller, and all substructures and twins boundaries disappear in the grains.%奥氏体不锈钢Cr15Mn9Cu2NiN在热轧过程中容易产生边裂.在热模拟试验机上开发出热轧实验装置,进行热轧实验,分析该不锈钢边部裂纹产生的原因.结果表明,压下量达到一定程度时,在所有变形温度下,试样边部均会产生裂纹,裂纹均沿奥氏体晶界扩展.在1000~1150℃变形时裂纹倾向较大,分析认为这与奥氏体不锈钢在此温度区间内的延性下降有关.在该温度区间内,轧后试样的微观组织具有晶粒租大和晶粒内部变形亚结构与孪晶共同存在的特征,而在1200℃变形时,晶粒尺寸较小,晶粒内部的变形亚结构和孪晶全部消失.

  12. High permeability-high frequency stable MnZn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Kalarus, J. [Ferroxcube Polska, 96-100 Skierniewice (Poland); Kogias, G., E-mail: kogias@cperi.certh.gr [Centre for Research and Technology-Hellas, Chemical Process Engineering Research Institute, Laboratory of Inorganic Materials, 57001 Thessaloniki (Greece); Aristotle University of Thessaloniki, Department of Chemical Engineering, Laboratory of Materials Technology, 54124 Thessaloniki (Greece); Holz, D. [Ferroxcube Polska, 96-100 Skierniewice (Poland); Zaspalis, V.T. [Centre for Research and Technology-Hellas, Chemical Process Engineering Research Institute, Laboratory of Inorganic Materials, 57001 Thessaloniki (Greece); Aristotle University of Thessaloniki, Department of Chemical Engineering, Laboratory of Materials Technology, 54124 Thessaloniki (Greece)

    2012-09-15

    Modern MnZn ferrite applications require high magnetic initial permeability and exceptional frequency stability; the former implies large grains, while the latter high grain boundary resistivity. In this article the optimization of the final firing process is described for achieving both. The optimization is based on the homogeneous dissolution of dopants under oxidative conditions and their subsequent precipitation along grain boundaries. This was accomplished by integrating isothermal plateaus at the upper stadia of the cooling stage of the final firing process. MnZn ferrites of the basic composition [Mn{sub 0.47}Zn{sub 0.47}Fe{sub 0.06}{sup 2+}]Fe{sub 2}{sup 3+}O{sub 4} were synthesized with initial permeability (measured at f=10 kHz, B<0.1 mT, T=25 Degree-Sign C) 12,600 and losses, expressed as tan({delta})/{mu}{sub i}, of 3.1 Multiplication-Sign 10{sup -6} at 10 kHz and 20.5 Multiplication-Sign 10{sup -6} at 100 kHz (B<0.1 mT, T=25 Degree-Sign C), that reflect good frequency stability. These results could be reproduced in pilot production scale. - Highlights: Black-Right-Pointing-Pointer Optimization of sintering is described for achieving high initial permeability. Black-Right-Pointing-Pointer Optimization of sintering is described for receiving frequency stability. Black-Right-Pointing-Pointer For high permeability, high densities and large grain sizes are required. Black-Right-Pointing-Pointer The achieved initial permeability is higher than 12,500. Black-Right-Pointing-Pointer The losses, tan({delta})/{mu}{sub i}, are 3.1 Multiplication-Sign 10{sup -6} at 10 kHz and 20.5 Multiplication-Sign 10{sup -6} at 100 kHz.

  13. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    OpenAIRE

    2016-01-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dis...

  14. Effects of a high magnetic field on fracture toughness at 4. 2 K for austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Murase, S.; Kobatake, S.; Tanaka, M.; Tashiro, I.; Horigami, O.; Ogiwara, H. (Toshiba R and D Center, Kawasaki (Japan)); Shibata, K. (Univ. Tokyo, Bunkyo (Japan)); Nagai, K.; Ishikawa, K. (National Research Inst. for Metals, Sengen, Tsukuba (Japan))

    1993-01-01

    Structural stainless steels for cryogenic use in superconducting magnets for fusion reactors are used under high magnetic field and stress. The authors have performed fracture thoughness tests, using the unloading compliance method at 4.2 K on SUS304, 316LN and 304L stainless steels precracked at 77 K, in a varying magnetic field (0 and 8 T). Fracture toughness values (J[sub IC]) for 304 and 316LN steels at 8 T decreased by 17 and 20%, respectively, as compared with the 0 T condition. On the other hand, J[sub IC] for 304L steel was 30% increased by applying a high magnetic field of 8 T. Details of martensite formation and austenite stability are considered in discussion. (orig.).

  15. Effect of tungsten addition on high-temperature properties and microstructure of alumina-forming austenitic heat-resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Min-Ho [Division of Materials Science and Engineering, Hanyang University, Seongdong-ku, Seoul 133-791 (Korea, Republic of); Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsangu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Moon, Joonoh; Kang, Jun-Yun; Ha, Heon-Young [Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsangu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Choi, Baig Gyu [High Temperature Materials Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsangu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Lee, Tae-Ho [Ferrous Alloy Department, Advanced Metallic Materials Division, Korea Institute of Materials Science, 797 Changwondaero, Seongsangu, Changwon, Gyeongnam 642-831 (Korea, Republic of); Lee, Changhee, E-mail: chlee@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, Seongdong-ku, Seoul 133-791 (Korea, Republic of)

    2015-10-28

    High-temperature tensile and creep properties of W-added Alumina-Forming austenitic (AFA{sub W}) heat-resistant steel were investigated as compared with AFA steel without W. High-temperature tensile properties of two steels were similar to each other, but creep lifetime of AFA{sub W} steel was increased. Microstructural examination using SEM and TEM revealed that creep rate rapidly decreased when Laves phase initially precipitated. This indicated that the precipitation of Laves phase played an important role in hardening of AFA steel. It is also found that AFA{sub W} steel exhibited finer and denser Laves phase compared with AFA steel, which is due to partial substitution of W for Mo. The finer and denser distribution of Laves phase contributed to improved creep properties of AFA{sub W} steel by enhancement in precipitation hardening.

  16. Study on comprehensive properties of duplex austenitic surfacing alloys for impacting abrasion

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, comprehensive property crack resistance, work hardening and abrasion resistance of a series of double-phases austenitic alloys(FAW) has been studied by means of SEM, TEM and type MD-10 impacting wear test machine. FAW alloys are of middle chromium and low manganese, including Fe-Cr-Mo-C alloy,Fe-Cr-Mn-C alloy and Fe-Cr-Mn-Ni-C alloy, that are designed for working in condition of impacting abrasion resistance hardfacing.Study results show that the work hardening mechanism of FAW alloys are mainly deformation high dislocation density and dynamic carbide aging, the form of wearing is plastic chisel cutting. Adjusting the amount of carbon, nickel, manganese and other elements in austenitic phase area, the FAW alloy could fit different engineering conditions of high impacting, high temperature and so on.

  17. Low-Temperature Nitriding of Deformed Austenitic Stainless Steels with Various Nitrogen Contents Obtained by Prior High-Temperature Solution Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin;

    2016-01-01

    investigated. Both hardness and yield stress increase and the alloys remain ductile. In addition, strain-induced transformation of austenite to martensite is suppressed, which is beneficial for subsequent low-temperature nitriding of the surface of deformed alloys. The combination of high- and low...

  18. High/low-moment phase transition in hexagonal Mn-Fe-P-Si compounds

    NARCIS (Netherlands)

    Dung, N.H.; Zhang, L.; Ou, Z.Q.; Zhao, L.; Van Eijck, L.; Mulders, A.M.; Avdeev, M.; Suard, E.; Van Dijk, N.H.; Brück, E.

    2012-01-01

    Using high-resolution neutron diffraction measurements for Mn-rich hexagonal Mn-Fe-P-Si compounds, we show that the substitution of Mn for Fe on the 3f sites results in a linear decrease of the Fe/Mn(3f) magnetic moments, while the Mn(3g) magnetic moments remain constant. With increasing

  19. Analysis on Shear Deformation for High Manganese Austenite Steel during Hot Asymmetrical Rolling Process Using Finite Element Method

    Institute of Scientific and Technical Information of China (English)

    Feng-li SUI; Xin WANG; Jun ZHAO; Biao MA; Chang-sheng LI

    2015-01-01

    Based on the rigid-plastic ifnite element method (FEM), the shear stress ifeld of deformation region for high manganese austenite steel during hot asymmetrical rolling process was analyzed. The inlfuences of rolling parameters, such as thevelocity ratio of upper to lower rolls, theinitial temperature of workpiece and the reduction rate, on the shear deformation of three nodes in the upper, center and lower layers were discussed. As the rolling parameters change, distinct shear deformation appears in the up-per and lower layers, but the shear deformation in the center layer appears only when the velocity ratio is more than 1.00, and the absolute value of the shear stress in this layer is changed with rolling parameters. A mathematical model which relfected the change of the maximal absolute shear stress for the center layer was established, by which the maximal absolute shear stress for the center layer can be easily calculated and the appropriate rolling technology can be designed.

  20. Hydrogen embrittlement and hydrogen induced stress corrosion cracking of high alloyed austenitic materials; Wasserstoffversproedung und wasserstoffinduzierte Spannungsrisskorrosion hochlegierter austenitischer Werkstoffe

    Energy Technology Data Exchange (ETDEWEB)

    Mummert, K.; Uhlemann, M.; Engelmann, H.J. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany)

    1998-11-01

    The susceptiblity of high alloyed austenitic steels and nickel base alloys to hydrogen-induced cracking is particularly determined by 1. the distribution of hydrogen in the material, and 2. the microstructural deformation behaviour, which last process is determined by the effects of hydrogen with respect to the formation of dislocations and the stacking fault energy. The hydrogen has an influence on the process of slip localization in slip bands, which in turn affects the microstructural deformation behaviour. Slip localization increases with growing Ni contents of the alloys and clearly reduces the ductility of the Ni-base alloy. Although there is a local hydrogen source involved in stress corrosion cracking, emanating from the corrosion process at the cathode, crack growth is observed only in those cases when the hydrogen concentration in a small zone ahead of the crack tip reaches a critical value with respect to the stress conditions. Probability of onset of this process gets lower with growing Ni content of the alloy, due to increasing diffusion velocity of the hydrogen in the austenitic lattice. This is why particularly austenitic steels with low Ni contents are susceptible to transcrystalline stress corrosion cracking. In this case, the microstructural deformation process at the crack tip is also influenced by analogous processes, as could be observed in hydrogen-loaded specimens. (orig./CB) [Deutsch] Die Empfindlichkeit von hochlegierten austentischen Staehlen und Nickelbasislegierungen gegen wasserstoffinduziertes Risswachstum wird im wesentlichen bestimmt durch 1. die Verteilung von Wasserstoff im Werkstoff und 2. das mikrostrukturelle Verformungsverhalten. Das mikrostrukturelle Deformationsverhalten ist wiederum durch den Einfluss von Wasserstoff auf die Versetzungsbildung und die Stapelfehlerenergie charakterisiert. Das mikrostrukturelle Verformungsverhalten wird durch wasserstoffbeeinflusste Gleitlokalisierung in Gleitbaendern bestimmt. Diese nimmt mit

  1. Surface properties of nitrided layer on AISI 316L austenitic stainless steel produced by high temperature plasma nitriding in short time

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang, E-mail: metalytu@163.com [Department of Materials Science and Engineering, Yantai University, Qingquan Road 32, Yantai 264005 (China); Wang, Zhuo [Department of Materials Science and Engineering, Yantai University, Qingquan Road 32, Yantai 264005 (China); Wang, Liang [Department of Materials Science and Engineering, Dalian Maritime University, Linghai Road 1, Dalian 116026 (China)

    2014-04-01

    Graphical abstract: - Highlights: • The 8 μm nitrided layer was produced on the surface of AISI 316L stainless steel by plasma nitrided at high temperatures (540 °C) within 1 h. • The nitrided layer consisted of nitrogen expanded austenite and possibly a small amount of free-CrN and iron nitrides. • It could critically reduce processing time compared with low temperature nitriding. • High temperature plasma nitriding could improve pitting corrosion resistance of the substrate in 3.5% NaCl solution. - Abstract: It has generally been believed that the formation of the S phase or expanded austenite γ{sub N} with enough thickness depends on the temperature (lower than 480 °C) and duration of the process. In this work, we attempt to produce nitrogen expanded austenite layer at high temperature in short time. Nitriding of AISI 316L austenitic stainless steel was carried out at high temperatures (>520 °C) for times ranging from 5 to 120 min. The microstructures, chemical composition, the thickness and the morphology of the nitrided layer, as well as its surface hardness, were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, optical microscopy, scanning electron microscopy, and microhardness tester. The corrosion properties of the untreated and nitrided samples were evaluated using anodic polarization tests in 3.5% NaCl solution. The results confirmed that nitrided layer was shown to consist of γ{sub N} and a small amount of free-CrN and iron nitrides. High temperature plasma nitriding not only increased the surface hardness but also improved the corrosion resistance of the austenitic stainless steel, and it can critically reduce processing time compared with low temperature nitriding.

  2. An experience with in-service fabrication and inspection of austenitic stainless steel piping in high temperature sodium system

    Energy Technology Data Exchange (ETDEWEB)

    Ravi, S., E-mail: sravi@igcar.gov.in; Laha, K.; Sakthy, S.; Mathew, M.D.; Bhaduri, A.K.

    2015-04-01

    Highlights: • Procedure for changing 304L SS pipe to 316L SS in sodium loop has been established. • Hot leg made of 304L SS was isolated from existing cold leg made of 316LN SS. • Innovative welding was used in joining the new 316L SS pipe with existing 316LN SS. • The old components of 304L SS piping have been integrated with the new piping. - Abstract: A creep testing facility along with dynamic sodium loop was installed at Indira Gandhi Centre for Atomic Research, Kalpakkam, India to assess the creep behavior of fast reactor structural materials in flowing sodium. Type 304L austenitic stainless steel was used in the low cross section piping of hot-leg whereas 316LN austenitic stainless steel in the high cross section cold-leg of the sodium loop. The intended service life of the sodium loop was 10 years. The loop has performed successfully in the stipulated time period. To enhance its life time, it has been decided to replace the 304L piping with 316L piping in the hot-leg. There were more than 300 welding joints involved in the integration of cold-leg with the new 316L hot-leg. Continuous argon gas flow was maintained in the loop during welding to avoid contamination of sodium residue with air. Several innovative welding procedures have been adopted for joining the new hot-leg with the existing cold-leg in the presence of sodium residue adopting TIG welding technique. The joints were inspected for 100% X-ray radiography and qualified by performing tensile tests. The components used in the discarded hot-leg were retrieved, cleaned and integrated in the renovated loop. A method of cleaning component of sodium residue has been established. This paper highlights the in-service fabrication and inspection of the renovation.

  3. High Temperature Tensile Properties of Unirradiated and Neutron Irradiated 20 Cr-35 Ni Austenitic Steel

    Energy Technology Data Exchange (ETDEWEB)

    Roy, R.B.; Solly, B.

    1966-12-15

    The tensile properties of an unirradiated and neutron irradiated (at 40 deg C) 20 % Cr, 35 % Ni austenitic steel have been studied at 650 deg C, 750 deg C and 820 deg C. The tensile elongation and mode of fracture (transgranular) of unirradiated specimens tested at room temperature and 650 deg C are almost identical. At 750 deg C and 820 deg C the elongation decreases considerably and a large part of the total elongation is non-uniform. Furthermore, the mode of fracture at these temperatures is intergranular and microscopic evidence suggests that fracture is caused by formation and linkup of grain boundary cavities. YS and UTS decrease monotonically with temperature. Irradiated specimens show a further decrease in ductility and an increase in the tendency to grain boundary cracking. Irradiation has no significant effect on the YS, but the UTS are reduced. The embrittlement of the irradiated specimens is attributed to the presence of He and Li atoms produced during irradiation and the possible mechanisms are discussed. Prolonged annealing of irradiated and unirradiated specimens at 650 deg C appears to have no significant effect on tensile properties.

  4. MODULATED STRUCTURES AND ORDERING STRUCTURES IN ALLOYING AUSTENITIC MANGANESE STEEL

    Institute of Scientific and Technical Information of China (English)

    L. He; Z.H. Jin; J.D. Lu

    2001-01-01

    The microstructure of Fe-10Mn-2Cr-1.5C alloy has been investigated with transmission electron microscopy and X-ray diffractometer. The superlattice diffraction spots and satellite reflection pattrens have been observed in the present alloy, which means the appearence of the ordering structure and modulated structure in the alloy. It is also proved by X-ray diffraction analysis that the austenite in the alloy is more stable than that in traditional austenitic manganese steel. On the basis of this investigation,it is suggested that the C-Mn ordering clusters exist in austenitic manganese steel and the chromium can strengthen this effect by linking the weaker C-Mn couples together,which may play an important role in work hardening of austenitic manganese steel.

  5. Transformation in Austenitic Stainless Steel Sheet under Different Loading Directions

    NARCIS (Netherlands)

    Boogaard, van den A.H.; Krauer, J.; Hora, P.

    2011-01-01

    The stress-strain relation for austenitic stainless steels is based on 2 main contributions: work hardening and a phase transformation from austenite to martensite. The transformation is highly temperature dependent. In most models for phase transformation from austenite to martensite, the stress tr

  6. Heat treatment effects on the microstructure and mechanical properties of a medium manganese steel (0.2C-5Mn)

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H.F., E-mail: xuhaifeng228@163.com [School of Materials Science and Engineering, State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China) and National Engineering Research Center of Advanced Steel Technology NERCAST, Central Iron and Steel Research Institute CISRI, Beijing 100081 (China); Zhao, J. [School of Materials Science and Engineering, State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); National Engineering Research Center of Advanced Steel Technology (NERCAST), Central Iron and Steel Research Institute (CISRI), Beijing 100081 (China); Cao, W.Q.; Shi, J.; Wang, C.Y.; Wang, C. [National Engineering Research Center of Advanced Steel Technology NERCAST, Central Iron and Steel Research Institute (CISRI), Beijing 100081 (China); Li, J. [School of Materials Science and Engineering, State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Dong, H. [National Engineering Research Center of Advanced Steel Technology NERCAST, Central Iron and Steel Research Institute (CISRI), Beijing 100081 (China)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Substantially improved mechanical properties of 0.2C-5Mn steels. Black-Right-Pointing-Pointer Intercritical austenization followed by short time annealing. Black-Right-Pointing-Pointer Phase transformation induced plasticity of the large volume fractioned austenite. Black-Right-Pointing-Pointer Dependence of yield stress on austenite grain size accords with Hall-Petch equation. - Abstract: Microstructures and mechanical properties of 0.2C-5Mn steel processed under different heat treatment conditions were examined by scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was found that high temperature austenization (above Ac3) resulted in a full martensite structure after quenching, which gradually transformed into the ferrite/austenite duplex structure during the following annealing process. However, austenization in the intercritical region (between Ac1 and Ac3) gave a duplex structure after quenching, which was nearly not affected by followed annealing process. The ultrahigh strength {approx}1000 MPa and total elongation {approx}40% were only obtained in the specimens with 6 h annealing at 650 Degree-Sign C under both heat treatment conditions. However, the excellent mechanical properties could be obtained in the intercritically austenitized samples with only 10 min annealing at 650 Degree-Sign C. Based on the analysis on the relationship between microstructure and mechanical properties, it was found that the total elongation was strongly dependent on the austenite fraction, which was ascribed to the phase transformation induced plasticity of the large volume fraction of austenite. Otherwise, the dependence of the yield stress on the austenite grain size accords with Hall-Petch equation, which implies that the austenite is soft phase. It was concluded that 10 min annealing at 650 Degree-Sign C was enough to obtain a large volume fraction of austenite ({approx}30%) in 0

  7. The influence of silicon and aluminum on austenite deformation behavior during fatigue and tensile loading

    Science.gov (United States)

    Lehnhoff, Gregory R.

    Advanced high strength steels (AHSS) for automobile light-weighting utilize Si and Al alloying to retain austenite in the microstructure during thermal partitioning treatments. This research project utilized fully austenitic steels with varied Si and Al compositions to understand the effect of these elements on austenite deformation response, including deformation induced martensite formation and deformation twinning. Specific focus was directed at understanding austenite deformation response during fatigue loading. Independent alloying additions of 2.5 wt pct Si and Al were made to a base steel composition of 15 Ni - 11 Cr - 1 Mn - 0.03 C (wt pct). Weak beam dark field transmission electron microscopy (TEM) imaging of dissociated dislocations was implemented to experimentally determine the influences of Si and Al on austenite stacking fault energy (SFE). The 2.5 wt pct Si alloying addition decreased the SFE by 6.4 mJ/m2, while the 2.5 wt pct Al alloying increased the SFE by 12 mJ/m2. Fully reversed, total strain controlled, low cycle fatigue (LCF) tests indicated that all four alloys underwent primary cyclic hardening and stabilization. Secondary cyclic strain hardening was correlated to BCC martensite formation using Feritscope magnetic fraction measurements of LCF specimens; the formation of 1 pct martensite led to 7 MPa of secondary hardening. TEM showed that martensite predominantly formed as parallel, irregular bands through strain induced nucleation on austenite shear bands. The austenite shear bands consisted of austenite {111} planes with concentrated dislocations, stacking faults, and/or HCP epsilon-martensite. Aluminum alloying promoted martensite formation during LCF, while Si suppressed martensite. Therefore, the strain induced nucleation process was not suppressed by the increased SFE associated with Al alloying. Tensile testing indicated that Si alloying promoted deformation twinning by lowering the SFE. Similarly to LCF loading, Al promoted

  8. Effect of austenization temperature on the microstructure evolution of the medium manganese steel (0.2C-5Mn) during ART-annealing

    Institute of Scientific and Technical Information of China (English)

    Jie SHI; Haifeng XU; Jie ZHAO; Wenquan CAO; Chang WANG; Cunyu WANG; Jian LI; Han DONG

    2012-01-01

    Microstructure evolution during ART-annealing (austenite reverted transformation annealing) of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM,TEM and XRD.It was demonstrated that the initial microstructures resulted from austenization at different temperatures strongly affect the microstructure evolution during followed ART-annealing,even the ultrafine grained ferrite/austenite duplex structure with about 30% austenite could be obtained after long time ART-annealing in all cases.Austenization in the intercritical region (between Ac1 and Ac3) gave a duplex structure after quenching,which was nearly not affected by followed annealing process.However,high temperature anstenization (above Ac3) resulted in a full martensite structure after quenching,which gradually transformed into a ferrite/austenite duplex structure during the following annealing process. Based on the analysis of austenite fraction and carbon concentrate,it was found that not only carbon partitioning but also manganese partitioning in the austenite affected the stability of austenite and even dominated the development of lamellar ferrite and austenite duplex structure during intercritical annealing with different times.At last an austenite lath nucleation and thickening model was proposed to describe the microstructure evolution of medium mangenese steel during ART-annealing.

  9. High-spin ribbons and antiferromagnetic ordering of a Mn(II)-biradical-Mn(II) complex.

    Science.gov (United States)

    Fatila, Elisabeth M; Clérac, Rodolphe; Rouzières, Mathieu; Soldatov, Dmitriy V; Jennings, Michael; Preuss, Kathryn E

    2013-09-11

    A binuclear metal coordination complex of the first thiazyl-based biradical ligand 1 is reported (1 = 4,6-bis(1,2,3,5-dithiadiazolyl)pyrimidine; hfac =1,1,1,5,5,5,-hexafluoroacetylacetonato-). The Mn(hfac)2-biradical-Mn(hfac)2 complex 2 is a rare example of a discrete, molecular species employing a neutral bridging biradical ligand. It is soluble in common organic solvents and can be easily sublimed as a crystalline solid. Complex 2 has a spin ground state of S(T) = 4 resulting from antiferromagnetic coupling between the S(birad) = 1 biradical bridging ligand and two S(Mn) = 5/2 Mn(II) ions. Electrostatic contacts between atoms with large spin density promote a ferromagnetic arrangement of the moments of neighboring complexes in ribbon-like arrays. Weak antiferromagnetic coupling between these high-spin ribbons stabilizes an ordered antiferromagnetic ground state below 4.5 K. This is an unusual example of magnetic ordering in a molecular metal-radical complex, wherein the electrostatic contacts that direct the crystal packing are also responsible for providing an efficient exchange coupling pathway between molecules.

  10. Relationship between Microstructure and Corrosion Behavior of Martensitic High Nitrogen Stainless Steel 30Cr15Mo1N at Different Austenitizing Temperatures.

    Science.gov (United States)

    Jiang, Zhouhua; Feng, Hao; Li, Huabing; Zhu, Hongchun; Zhang, Shucai; Zhang, Binbin; Han, Yu; Zhang, Tao; Xu, Dake

    2017-07-27

    The relationship between microstructure and corrosion behavior of martensitic high nitrogen stainless steel 30Cr15Mo1N at different austenitizing temperatures was investigated by microscopy observation, electrochemical measurement, X-ray photoelectron spectroscopy analysis and immersion testing. The results indicated that finer Cr-rich M₂N dispersed more homogeneously than coarse M23C₆, and the fractions of M23C₆ and M₂N both decreased with increasing austenitizing temperature. The Cr-depleted zone around M23C₆ was wider and its minimum Cr concentration was lower than M₂N. The metastable pits initiated preferentially around coarse M23C₆ which induced severer Cr-depletion, and the pit growth followed the power law. The increasing of austenitizing temperature induced fewer metastable pit initiation sites, more uniform element distribution and higher contents of Cr, Mo and N in the matrix. In addition, the passive film thickened and Cr₂O₃, Cr(3+) and CrN enriched with increasing austenitizing temperature, which enhanced the stability of the passive film and repassivation ability of pits. Therefore, as austenitizing temperature increased, the metastable and stable pitting potentials increased and pit growth rate decreased, revealing less susceptible metastable pit initiation, larger repassivation tendency and higher corrosion resistance. The determining factor of pitting potentials could be divided into three stages: dissolution of M23C₆ (below 1000 °C), dissolution of M₂N (from 1000 to 1050 °C) and existence of a few undissolved precipitates and non-metallic inclusions (above 1050 °C).

  11. Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel

    Science.gov (United States)

    Karthik, B.; Veerababu, R.; Satyanarayana, D. V. V.

    2016-05-01

    Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel has been investigated using room temperature tensile tests and TEM. The alloy in both oxidised and unoxidised conditions exhibits a transition in flow behaviour that can be described best by the Ludwigson flow relationship as evident from the lowest values of the sum of residual squares, χ 2, of the fit. The transition in macroscopic flow behaviour with strain has been correlated to change in deformation mechanism from planar slip in the low strain regime (LSR) to deformation twinning and slip in the high strain regime (HSR) in solution treated (ST) condition of the alloy. However, the LSR of the alloy aged for longer times (>100 h) is characterized by the formation of dislocation tangles, while the HSR is marked by the formation of well-defined finer dislocation cell structure. This difference in deformation sub-structures in low and high strain regimes between ST and long term aged samples has been correlated to the change in stacking fault energy due to the precipitation of Cr2N and σ-phases. Further, the alloy in ST condition exhibits the highest strain hardening rate, which then progressively decreases with aging time.

  12. Effect of relative humidity in high temperature oxidation of ceria nanoparticles coating on 316L austenitic stainless steel

    Science.gov (United States)

    Giraldez Pizarro, Luis Miguel

    A solution of 20 wt. % colloidal dispersion of Cerium Oxide (CeO2) in 2.5% of acetic acid, was used for depositing a coating film on an austenitic stainless steel 316L. Cerium compounds have been distinguished as potential corrosion inhibitors in coatings over several alloys. The oxidation behavior of the cerium oxide coating on 316L austenitic stainless steel alloy was evaluated in dry and humid environments, the weight changes (W/A) was monitored as a function of time using a custom built Thermogravimetrical Analysis (TGA) instrument at temperatures of 750°C, 800°C and 850°C, and different relative humidity levels (0%, 10% and 20%) respectively. The parabolic oxidation rate and activation energy is calculated experimentally for each relative humidity level. A measurement of the effective diameter size of the ceria nanoparticles was performed using a Light Scattering technique. A characterization of the film morphology and thickness before the oxidation was executed using Atomic Force Microscopy (AFM). Microstructure and chemical composition of the oxidized coated substrates were analyzed using Scanning Electronic Microscopy (SEM) with energy dispersive spectroscopy (EDS). X-Ray Diffractometer (XRD) was used to characterize oxides formed in the surface upon isothermal treatment. A comparison of activation energy values obtained to identify the influence of relative humidity in the oxidation process at high temperature was conducted. Cerium oxides coating may prevent crevice corrosion and increase pitting resistance of 316L relative to the uncoated substrate at high temperatures and different levels of relative humidity acting as a protective oxidation barrier. The calculated parabolic rate constants, kp, at the experimental temperatures tend to increase as a function of humidity levels. The activation energy tends to increase proportionally to higher level of humidity exposures. At 0% relative humidity a value of 319.29 KJ/mol of activation energy is being

  13. Resistência à erosão por cavitação de aços inoxidáveis austeníticos CrMnSiN depositados por PTA Cavitation erosion resistance of CrMnSiN austenitic stainless steels deposited by PTA

    Directory of Open Access Journals (Sweden)

    Hélio Ormeu Ribeiro

    2010-06-01

    Full Text Available A erosão por cavitação deteriora componentes em serviço, tais como partes metálicas de bombas de água, válvulas e, em especial, pás de turbinas hidráulicas, sendo nesse último caso responsável por elevados prejuízos ligados tanto aos custos da manutenção direta, como sobretudo às perdas por interrupção na geração de energia elétrica. Dentre os materiais aplicados no reparo por soldagem de danos por cavitação incluem-se aços inoxidáveis tradicionais tipo AISI 308 e 309, aços inoxidáveis ao Co e ligas à base de Co (stellites, caracterizando-se essas últimas pela maior sensibilidade a trincas, dificuldade de esmerilhamento e pelo mais alto custo. Nesse contexto este trabalho buscou formular, depositar e analisar o desempenho de aços inoxidáveis austeníticos CrMnSiN, soldados pelo processo PTA. A resistência à erosão por cavitação foi avaliada segundo a norma ASTM G 32-92. A microestrutura foi caracterizada por microscopia ótica e microscopia eletrônica de varredura e a formação de martensitas α' e ε, induzida pela cavitação, foi avaliada por difração de raios-X. A integridade da superfície dos depósitos foi controlada por END, além disso a dureza e a facilidade de acabamaneto por esmerilhamento serviram como critérios para avaliar os revestimentos soldados. Verificou-se que os revestimentos aplicados por PTA eram livres de trincas de solidificação, com baixa porosidade, boa molhabilidade e adequado acabamento superficial. A melhor liga inoxidável austenítica elaborada (0,03%C; 0,35% N; 13,2%Cr; 11,8% Mn; 2,8%Si; bal %Fe mostrou uma resistência à erosão por cavitação próxima aquela das principais ligas comerciais.Cavitation erosion deteriorates components like metallic parts of water pumps, valves and blades of hydraulic turbines, in this last case being responsible for high economical losses, associated to direct maintenance costs, but above all due to the interruption of the electric

  14. Cluster dynamics modeling of the effect of high dose irradiation and helium on the microstructure of austenitic stainless steels

    Science.gov (United States)

    Brimbal, Daniel; Fournier, Lionel; Barbu, Alain

    2016-01-01

    A mean field cluster dynamics model has been developed in order to study the effect of high dose irradiation and helium on the microstructural evolution of metals. In this model, self-interstitial clusters, stacking-fault tetrahedra and helium-vacancy clusters are taken into account, in a configuration well adapted to austenitic stainless steels. For small helium-vacancy cluster sizes, the densities of each small cluster are calculated. However, for large sizes, only the mean number of helium atoms per cluster size is calculated. This aspect allows us to calculate the evolution of the microstructural features up to high irradiation doses in a few minutes. It is shown that the presence of stacking-fault tetrahedra notably reduces cavity sizes below 400 °C, but they have little influence on the microstructure above this temperature. The binding energies of vacancies to cavities are calculated using a new method essentially based on ab initio data. It is shown that helium has little effect on the cavity microstructure at 300 °C. However, at higher temperatures, even small helium production rates such as those typical of sodium-fast-reactors induce a notable increase in cavity density compared to an irradiation without helium.

  15. Effect of alloy grain size on the high-temperature oxidation behavior of the austenitic steel TP 347

    Directory of Open Access Journals (Sweden)

    Vicente Braz Trindade

    2005-12-01

    Full Text Available Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenite steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050 °C was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10-5 g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS. Oxidation of TP347 with a grain size of 4 µm at 750 °C in air follows a parabolic rate law. For a larger grain size (65 µm, complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr2O3, with some FeCr2O4 at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr2O3 formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.

  16. Hot deformation mechanism and microstructure evolution of an ultra-high nitrogen austenitic steel containing Nb and V

    Institute of Scientific and Technical Information of China (English)

    Rong-hua Zhang; Ze-an Zhou; Ming-wei Guo; Jian-jun Qi; Shu-hua Sun; Wan-tang Fu

    2015-01-01

    The flow curves of an ultra-high nitrogen austenitic steel containing niobium (Nb) and vanadium (V) were obtained by hot com-pression deformation at temperatures ranging from 1000℃ to 1200℃ and strain rates ranging from 0.001 s?1 to 10 s?1. The mechanical be-havior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dy-namic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and in-creasing strain rate. The hot deformation activation energy is approximately 631 kJ/mol, and a hot deformation equation is proposed. (Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050℃ to 1150℃ and in the strain rate range of 0.01 to 1 s?1.

  17. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [ORNL; Yamamoto, Yukinori [ORNL; Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Pankiw, Roman [Duraloy Technologies Inc; Voke, Don [Duraloy Technologies Inc

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  18. Multi-scale Modeling of the Impact Response of a Strain Rate Sensitive High-Manganese Austenitic Steel

    Directory of Open Access Journals (Sweden)

    Orkun eÖnal

    2014-09-01

    Full Text Available A multi-scale modeling approach was applied to predict the impact response of a strain rate sensitive high-manganese austenitic steel. The roles of texture, geometry and strain rate sensitivity were successfully taken into account all at once by coupling crystal plasticity and finite element (FE analysis. Specifically, crystal plasticity was utilized to obtain the multi-axial flow rule at different strain rates based on the experimental deformation response under uniaxial tensile loading. The equivalent stress – equivalent strain response was then incorporated into the FE model for the sake of a more representative hardening rule under impact loading. The current results demonstrate that reliable predictions can be obtained by proper coupling of crystal plasticity and FE analysis even if the experimental flow rule of the material is acquired under uniaxial loading and at moderate strain rates that are significantly slower than those attained during impact loading. Furthermore, the current findings also demonstrate the need for an experiment-based multi-scale modeling approach for the sake of reliable predictions of the impact response.

  19. Effect of austenite grain size in Fe-Mn alloys on {epsilon} martensitic transformation and their mechanical properties; Fe-Mn gokin no {epsilon} marutensaito hentai oyobi kikaiteki seishitsu ni oyobosu kessho ryukei no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakatsu, H. [Kyushu Univ., Fukuoka (Japan). Graduate School; Takaki, S. [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering

    1996-02-20

    The Fe-Mn two-components alloy samples varied with Mn content of 12 to 31 mass% were prepared by charging {gamma}-crystalline grain size using its recrystallization, and were surveyed on effects of the {gamma}-crystalline grain size on athermal {epsilon}-martensitic ({epsilon})-transformation and machining- induced {epsilon}-transformation. As a result of examining the relationship between the {gamma}-crystalline grain size or the {epsilon}-transformation and their mechanical properties, conclusion shown as follows is obtained. The athermal {epsilon} was formed at the alloy containing more than 10 mass% of Mn, maximum {epsilon} was shown at the composition containing about 17 mass% of Mn and the {epsilon} was almost not formed at the steel containing more than 27 mass% of Mn. When crushing the {gamma}-crystalline grain to fine powder, the {epsilon} martensitic transformation beginning temperature tended to reduce somewhat and production amount of the {epsilon} decreased extremely. On the steel containing Mn ranged 15 to 31 mass%, the fine powdering affected scarcely its durability but improved its elongation and its tensile strength. 26 refs., 11 figs., 1 tab.

  20. Effect of heat treatment on the mechanical properties and the structure of a high-nitrogen austenitic 02Kh20AG10N4MFB steel

    Science.gov (United States)

    Bannykh, I. O.; Sevost'yanov, M. A.; Prutskov, M. E.

    2016-07-01

    The effect of heat treatment on the mechanical properties of a high-nitrogen austenitic 02Kh20AG10N4MFB steel has been studied in the temperature region 550—1200°C. The yield strength and the ultimate tensile strength are shown to change nonmonotonically as a function of the heat treatment temperature. They sharply decrease in the annealing temperature range 850—900°C, which can demonstrate a change in the character of the structure-phase state of this steel. After annealing at 850—900°C, aging occurs with the precipitation of embrittling phases; at higher annealing temperatures, these particles dissolve and austenite recrystallizes. The study of the stress-strain diagrams makes it possible to find the laws of strain hardening of the 02Kh20AG10N4MFB steel as a function of the heat treatment temperature.

  1. Contacts for high-resistivity (Cd,Mn)Te crystals

    Energy Technology Data Exchange (ETDEWEB)

    Witkowska-Baran, M.; James, R.; Mycielski, A.; Kochanowska, D.; Szadkowski, A.J.; Jakiela, R.; Witkowska, B.; Kaliszek, W.; Domagala, J.; Lusakowska, E.; Domukhovski, V.; Dybko, K.; Cui, Y.; and James, R.B.

    2010-09-09

    Semi-insulating (Cd,Mn)Te crystals offer a material that may compete well with the commonly used (Cd,Zn)Te crystals for manufacturing large-area X- and gamma-ray detectors. The Bridgman growth method yields good quality, high-resistivity (10{sup 9} - 10{sup 10} {Omega} {center_dot} cm) crystals of (Cd,Mn)Te:V. Doping the as-grown crystals with the compensating agent vanadium ({approx} 10{sup 16} cm{sup -3}) ensures their high resistivity; thereafter, annealing them in cadmium vapors reduces the number of cadmium vacancies. Applying the crystals as detectors necessitates having satisfactory electrical contacts. Accordingly, we explored various techniques of ensuring good electrical contacts to these semi-insulating (Cd,Mn)Te crystals, assessing metallic layers, monocrystalline semiconductor layers, and amorphous (or nanocrystalline) semiconductor layers. We found that ZnTe heavily doped ({approx} 10{sup 18} cm{sup -3}) with Sb, and CdTe heavily doped ({approx} 10{sup 17} cm{sup -3}) with In, proved satisfactory semiconductor contact layers. They subsequently enabled us to establish good contacts (with only narrow tunneling barriers) to the Au layer that usually constitutes the most external contact layer. We outline our technology of applying electrical contacts to semi-insulating (Cd,Mn)Te, and describe some important properties.

  2. Microstructure influence on fatigue behaviour of austenitic stainless steels with high molybdenum content; Influencia de la microestructura en el comportamiento a fatiga de aceros inoxidables austeniticos con alto contenido en molibdeno

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J.; Gamboa, R.; Ranninger, C.

    2006-07-01

    Austenitic stainless steels with molybdenum present high mechanical properties and corrosion resistance to aggressive environments. These steels have been used to tank and vessel components for high liquids as phosphoric, nitric and sulphuric acids. These materials with low carbon and nitrogen addition have been proposed candidates as structural materials for the international thermonuclear experimental reactor (ITER) in-vessel components. Molybdenum addition in austenitic stainless steel improves mechanical and corrosion properties, but with it can produce the presence of nitrogen microstructure modifications by presence or precipitation of second phases. This paper summarises the fatigue and corrosion fatigue behaviour of two 317LN stainless steels with different microstructure. Fully austenitic steel microstructure show better fatigue, corrosion fatigue resistance and better ductility than austenitic steel with delta ferrite microstructure, mainly at low stresses. (Author)

  3. Solidification structure of C{sub 2.08}Cr{sub 25.43}Si{sub 1.19}Mn{sub 0.43}Fe{sub 70.87} powders fabricated by high pressure gas atomization

    Energy Technology Data Exchange (ETDEWEB)

    Dai Yongxiang; Yang Min; Song Changjiang [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai (China); Han, Qingyou [Mechanical Engineering Technology Department, Purdue University (United States); Zhai Qijie, E-mail: qjzhai@shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai (China)

    2010-01-15

    Powders of hypoeutectic high chromium white cast iron (C{sub 2.08}Cr{sub 25.43}Si{sub 1.19}Mn{sub 0.43}Fe{sub 70.87}) were produced by high pressure gas atomization. The microstructure of the powders was characterized using light microscopy, scanning electron microscopy and X-ray diffraction. The results showed that the as-atomized powders were mainly composed of austenite and M{sub 7}C{sub 3} (M = Fe, Cr) type carbide, and became ferrite and carbide after annealing. With the decrease of the powder diameter, the number of austenite grains, primary dendrite length and second dendrite arm spacing were decreased. The relationship between cooling rate and microstructure was also determined.

  4. The significance of ultrafine film-like retained austenite in governing very high cycle fatigue behavior in an ultrahigh-strength MN–SI–Cr–C steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P., E-mail: zhaoping12@mails.tsinghua.edu.cn [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Zhang, B.; Cheng, C. [Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China); Misra, R.D K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical and Materials Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968-0520 (United States); Gao, G., E-mail: gaogh@bjtu.edu.cn [Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China); Bai, B.; Weng, Y. [Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Materials Science and Engineering Research Center, Beijing Jiaotong University, Beijing 100044 (China)

    2015-10-01

    We elucidate here the very high cycle fatigue (VHCF) behavior of an ultrahigh-strength medium carbon Mn–Si–Cr–C steel processed using the approach of bainite-based quenching and partitioning (BQ&P). The microstructure of BQ&P process comprised of bainite, carbon-depleted martensite, retained austenite (RA) and small amount of martensite/austenite island (M/A). The tensile strength (R{sub m}) and fatigue limit strength after 10{sup 9} cycles (σ{sub w9}) and in the non-failed condition were 1688 MPa and 875 MPa, respectively such that σ{sub w9}/R{sub m} exceeded conventional steels and was 0.52. Two types of failure modes were observed depending on the surface and microstructure, notably surface-induced failure and non-inclusion-induced failure, where the non-inclusion-induced failure was influenced by the microstructure. Inclusion-induced failure was absent. The study underscores that film-like retained austenite was the underlying reason for superior fatigue properties, hitherto not previously obtained.

  5. Influence of welding parameters on nitrogen content in welding metal of 32Mn-7Cr-1Mo-0.3N austenitic steel

    Institute of Scientific and Technical Information of China (English)

    FU Rui-dong; QIU Liang; WANG Cun-yu; WANG Qing-feng; ZHENG Yang-zeng

    2005-01-01

    The transfer behavior of nitrogen into the welding metal during gas tungsten arc welding process of 32Mn-7Cr-1Mo-0.3N steel was investigated. The effects of gas tungsten arc welding process variables, such as the volume fraction of nitrogen in shielding gas, arc holding time and arc current on the nitrogen content in the welding metal were also evaluated. The results show that the volume fraction of nitrogen in gas mixture plays a major role in controlling the nitrogen content in the welding metal. It seems that there exhibits a maximum nitrogen content depending on the arc current and arc holding time. The optimum volume fraction of nitrogen in shielding gas is 4% or so. The role of gas tungsten arc welding processing parameters in controlling the transfer of nitrogen is further confirmed by the experimental results of gas tungsten arc welding process with feeding metal.

  6. Effect of Mn, Si, and Sb on High-temperature Oxidation of Fe-Mn-Al-Si-Sb-C Steels

    Energy Technology Data Exchange (ETDEWEB)

    Park, Soon Yong; Lee, Dong Bok [Sungkyunkwan University, Suwon (Korea, Republic of)

    2017-05-15

    High Mn twinning-induced plasticity (TWIP) steels with compositions of Fe-(18.0-18.17) Mn-1.51Al-(0.48-0.52)Si-(0.61-0.62)C-(0.52-0.54)Cr-(0.22-0.23)Ni-0.03Nb -(0-0.04)Sb (wt%) are oxidized at 650 ℃ and 750 ℃ for < 24 h in air in order to determine the effect of the alloying elements on the oxidation. They are oxidized parabolically to MnO{sub 2},Mn{sub 2}O{sub 3},FeO,Fe{sub 2}O{sub 3}, and FeMn{sub 2}O{sub 4} oxides with relatively fast rates. The formed scales are prone to spallation and bi-layered. The outer scales that are formed by the outward diffusion of cations are rich in Fe and Mn, while the inner scales that are formed by the inward diffusion of oxygen are rich in Fe, Mn, Al, Cr, and Si. The isothermal and cyclic oxidation resistance progressively increases with increments in the amount of Mn, Si, and Sb.

  7. Unusual Mn coordination and redox chemistry in the high capacity borate cathode Li7Mn(BO3)3.

    Science.gov (United States)

    Roos, Julian; Eames, Christopher; Wood, Stephen M; Whiteside, Alexander; Islam, M Saiful

    2015-09-14

    The recently discovered lithium-rich cathode material Li7Mn(BO3)3 has a high theoretical capacity and an unusual tetrahedral Mn(2+) coordination. Atomistic simulation and density functional theory (DFT) techniques are employed to provide insights into the defect and redox chemistry, the structural changes upon lithium extraction and the mechanisms of lithium ion diffusion. The most favourable intrinsic defects are Li/Mn anti-site pairs, where Li and Mn ions occupy interchanged positions, and Li Frenkel defects. DFT calculations reproduce the experimental cell voltage and confirm the presence of the unusually high Mn(V) redox state, which corresponds to a theoretical capacity of nearly 288 mA h g(-1). The ability to reach the high manganese oxidation state is related to both the initial tetrahedral coordination of Mn and the observed distortion/tilting of the BO3 units to accommodate the contraction of the Mn-O bonds upon oxidation. Molecular dynamics (MD) simulations indicate fast three-dimensional lithium diffusion in line with the good rate performance observed.

  8. Austenite grain growth behavior of a 82B high carbon steel%82B高碳钢奥氏体晶粒长大行为

    Institute of Scientific and Technical Information of China (English)

    金桂香; 王福明; 李克非; 付军; 李长荣

    2013-01-01

    利用直线截点法计算各试样的奥氏体平均晶粒尺寸,得出82B高碳钢的奥氏体粗化温度为950℃,通过Thermo-calc热力学计算和能谱分析可知,晶粒粗化的主要原因是950℃时V、Ti、Nb碳氮化物数量的大大减少,即析出相粒子钉扎作用的减弱和消除.随着加热温度的升高和保温时间的延长,82B高碳钢奥氏体晶粒尺寸增大,其生长模型的公式为D=6.82×104t0079 exp(-8.04×104/RT).当加热温度为1000℃,保温时间为60~90 min时,82B原奥氏体晶粒尺寸小于67μm,晶粒细小均匀,且微合金元素V充分溶解在奥氏体中.%The austenite grain coarsening temperature of 82B high carbon steel is 950℃ by measuring average grain size with linear cut point method.The results of EDS analysis and thermodynamic calculation based on Thermo-calc show that the main reason of grain coarsening is that the quantity of carbonitrides of elements V,Ti and Nb is decreased heavily for the steel heating at 950 ℃,which means the pinning effect of the precipitated phase particles is weakened or eliminated.The average austenite grain size increases with the increasing of the heating temperature and the holding time,which can be described by the austenite grain growth model D =6.82 × 104t0079exp(-8.04 × 104/RT).When the heating temperature is 1000 ℃ and the holding time is between 60 min and 90 min,the austenite grain size of 82B steel is uniform and smaller than 67 μm,and the micro-alloying element V is dissolved into austenite adequately.

  9. Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic-Martensitic Stainless Steels

    Science.gov (United States)

    Huang, Qiuliang; De Cooman, Bruno C.; Biermann, Horst; Mola, Javad

    2016-05-01

    The influence of martensite fraction ( f α') on the stabilization of austenite was studied by quench interruption below M s temperature of an Fe-13Cr-0.31C (mass pct) stainless steel. The interval between the quench interruption temperature and the secondary martensite start temperature, denoted as θ, was used to quantify the extent of austenite stabilization. In experiments with and without a reheating step subsequent to quench interruption, the variation of θ with f α' showed a transition after transformation of almost half of the austenite. This trend was observed regardless of the solution annealing temperature which influenced the martensite start temperature. The transition in θ was ascribed to a change in the type of martensite nucleation sites from austenite grain and twin boundaries at low f α' to the faults near austenite-martensite (A-M) boundaries at high f α'. At low temperatures, the local carbon enrichment of such boundaries was responsible for the enhanced stabilization at high f α'. At high temperatures, relevant to the quenching and partitioning processing, on the other hand, the pronounced stabilization at high f α' was attributed to the uniform partitioning of the carbon stored at A-M boundaries into the austenite. Reduction in the fault density of austenite served as an auxiliary stabilization mechanism at high temperatures.

  10. In situ synchrotron X-ray diffraction studies of the effect of microstructure on tensile behavior and retained austenite stability of thermo-mechanically processed transformation induced plasticity steel

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Kun [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Liss, Klaus-Dieter [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia); Timokhina, Ilana B. [Institute for Frontier Materials, Deakin University, Geelong, VIC 3217 (Australia); Pereloma, Elena V., E-mail: elenap@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia)

    2016-04-26

    Transmission electron microscopy and in situ synchrotron high-energy X-ray diffraction were used to investigate the martensitic transformation and lattice strains under uniaxial tensile loading of Fe-Mn-Si-C-Nb-Mo-Al Transformation Induced Plasticity (TRIP) steel subjected to different thermo-mechanical processing schedules. In contrast with most of the diffraction analysis of TRIP steels reported previously, the diffraction peaks from the martensite phase were separated from the peaks of the ferrite-bainite α-matrix. The volume fraction of retained γ-austenite, as well as the lattice strain, were determined from the diffraction patterns recorded during tensile deformation. Although significant austenite to martensite transformation starts around the macroscopic yield stress, some austenite grains had already experienced martensitic transformation. Hooke’s Law was used to calculate the phase stress of each phase from their lattice strain. The ferrite-bainite α-matrix was observed to yield earlier than austenite and martensite. The discrepancy between integrated phase stresses and experimental macroscopic stress is about 300 MPa. A small increase in carbon concentration in retained austenite at the early stage of deformation was detected, but with further straining a continuous slight decrease in carbon content occurred, indicating that mechanical stability factors, such as grain size, morphology and orientation of the retained austenite, played an important role during the retained austenite to martensite transformation.

  11. Corrosion Behaviour of a Highly Alloyed Austenitic Alloy UB6 in Contaminated Phosphoric Acid

    Directory of Open Access Journals (Sweden)

    M. Boudalia

    2013-01-01

    Full Text Available The influence of temperature (20–80°C on the electrochemical behaviour of passive films anodically formed on UB6 stainless steel in phosphoric acid solution (5.5 M H3PO4 has been examined by using potentiodynamic curves, electrochemical impedance spectroscopy, and Mott-Schottky analysis. UB6 stainless steel in contaminated phosphoric acid is characterised by high interfacial impedance, thereby, illustrating its high corrosion resistance. The obtained results show that the films behave as n-type and p-type semiconductors in the potential range above and below the flat band potential, respectively. This behaviour is assumed to be the consequence of the semiconducting properties of the iron oxide and chromium oxide regions which compose the passive film.

  12. Effects of Grit Blasting and Annealing on the High-Temperature Oxidation Behavior of Austenitic and Ferritic Fe-Cr Alloys

    Science.gov (United States)

    Proy, M.; Utrilla, M. V.; Otero, E.; Bouchaud, B.; Pedraza, F.

    2014-08-01

    Grit blasting (corundum) of an austenitic AISI 304 stainless steel (18Cr-8Ni) and of a low-alloy SA213 T22 ferritic steel (2.25Cr-1Mo) followed by annealing in argon resulted in enhanced outward diffusion of Cr, Mn, and Fe. Whereas 3 bar of blasting pressure allowed to grow more Cr2O3 and Mn x Cr3- x O4 spinel-rich scales, higher pressures gave rise to Fe2O3-enriched layers and were therefore disregarded. The effect of annealing pre-oxidation treatment on the isothermal oxidation resistance was subsequently evaluated for 48 h for both steels and the results were compared with their polished counterparts. The change of oxidation kinetics of the pre-oxidized 18Cr-8Ni samples at 850 °C was ascribed to the growth of a duplex Cr2O3/Mn x Cr3- x O4 scale that remained adherent to the substrate. Such a positive effect was less marked when considering the oxidation kinetics of the 2.25Cr-1Mo steel but a more compact and thinner Fe x Cr3- x O4 subscale grew at 650 °C compared to that of the polished samples. It appeared that the beneficial effect is very sensitive to the experimental blasting conditions. The input of Raman micro-spectroscopy was shown to be of ground importance in the precise identification of multiple oxide phases grown under the different conditions investigated in this study.

  13. High-temperature degradation and protection of ferritic and austenitic steels in steam generators

    Science.gov (United States)

    Martínez-Villafañe, A.; Almeraya-Calderón, M. F.; Gaona-Tiburcio, C.; Gonzalez-Rodriguez, J. G.; Porcayo-Calderón, J.

    1998-02-01

    The useful life of superheaters and reheaters of power stations which use heavy fuel oil is shortened and their continuous service is inhibited by corrosion (fireside) and creep-type problems. The increase of corrosion attack on boilers is caused by the presence of fuel ash deposits containing mainly vanadium, sodium, and sulfur which form low-melting-point compounds. The tubes are exposed to the action of high stresses and high temperatures, producing the so-called “creep damage.” In this work, two kinds of results are reported: lab and field studies using a 2.25Cr-1Mo steel. The laboratory work was in turn divided into two parts. In the first, the steel was exposed to the action of natural ash deposits in oxidant atmospheres at 600 ° for 24 h. In the second part, tensile specimens were creep tested in Na2SO4, V2O5, and their mixture over a temperature range of 580 to 620 °. In the field work, components of a power station were coated with different types of nickel-and iron-base coatings containing chromium, Fe-Cr, and Fe-Si using the powder flame spraying technique. After testing, the coated tubes were analyzed using electron microscopy. The results showed that all the coating systems had good corrosion resistance, especially those containing silicon or chromium.

  14. EFFECTS OF HIGH-DENSITY CURRENT PULSES ON WORKHARDENING BEHAVIORS OF AUSTENITE STAINLESS STEELIN WIRE-DRAWING DEFORMATION

    Institute of Scientific and Technical Information of China (English)

    K.F. Yao; P. Yu; J. Wang; W. Fang; M.X. Zheng

    2001-01-01

    The influence of high-density palsing current on the work-hardening behavior of H0Cr17Ni6Mn3 and 1Cr18Ni9 stainless steels in wire-drawing deformation processes has been studied. It was found that the drawing stress and the work-hardening rate of wires were significantly reduced by applying current pulses in drawing process. The work-hardening behavior of the multi-courses drawing deformation can be well described by Hollomon formula σ = kεn. With the application of current pulses in drawing deformation, the work-hardening exponents of H0Cr17Ni6Mn3 steel wires and 1Cr18Ni9 stainless steel wires were reduced by 33% and 45%, respectively, and their work-hardening coefficients were reduced by 41% and 47%, respectively. It was also found that the work-hardening coefficient of wires was reduced with the increment of the frequency of current pulses, while the work-hardening exponents of both steels were insensitive to the pulsing frequency.``

  15. Recrystailization Behavior of Deformed Austenite in High Strength Microalloyed Pipeline Steel

    Institute of Scientific and Technical Information of China (English)

    YANG Jing-hong; LIU Qing-you; SUN Dong-bai; LI Xiang-yang

    2009-01-01

    Using methods of single-hit hot compression and stress relaxation after deformation on a Gleeble 1500D thermomechanical simulator,the curves of flow stress and stress relaxation,the microstructure and the recrystallization behavior of Nb-V-Ti high strength microalloyed low carbon pipeline steel were studied,and the influence of the thermomechanical treatment parameters on dynamic and static recrystallization of the steel was investigated.It was found that microalloying elements improved the deformation activation energy and produced a retardation of the recrystallization due to the solid solution and precipitation pinning.The deformation conditions such as deformation temperature,strain,and strain rate influenced the recrystallization kinetics and the microstructure respectively.Equations obtained can be used to valuate and predict the dynamic and static recrystallizations.

  16. Effect of solution hardening on the shape memory effect of Fe-Mn based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzaki, K.; Natsume, Y.; Maki, T. [Kyoto Univ. (Japan). Dept. of Materials Science and Engineering; Tomota, Y. [Ibaraki Univ., Hitachi (Japan)

    1995-10-01

    Fe-high Mn-Si alloys, which undergo {gamma} (fcc) to {var_epsilon} (hcp) martensitic transformation, exhibit a pronounced shape memory effect. The origin of shape memory effect of these alloys is the reversion of stress-induced {var_epsilon} martensite. A shape change must hence be accomplish3ed by stress-induced martensitic transformation without permanent slip in austenite ({gamma}) in order to obtain a good shape memory effect. It is clear that the intrusion of permanent slip can be suppressed by increasing the strength of austenite and by decreasing the applied stress required for a shape change due to stress-induced martensitic transformation. It has been reported that the addition of the interstitial elements of C and N as well as the substitutional elements of Mo and V increases the 0.2% proof stress of austenite in Fe-high Mn alloys. However, there have been few studies on the effect of these alloying elements on the shape memory effect of Fe-high Mn based alloys. In the present study, it was aimed to improve the shape memory effect of Fe-high Mn based alloys by the strengthening of austenite through solution hardening due to C and Mo.

  17. High Curie temperatures in (Ga,Mn)N from Mn clustering

    OpenAIRE

    Hynninen, Teemu; Raebiger, Hannes; Ayuela, Andres; von Boehm, J.

    2005-01-01

    The effect of microscopic Mn cluster distribution on the Curie temperature (Tc) is studied using density-functional calculations. We find that the calculated Tc depends crucially on the microscopic cluster distribution, which can explain the abnormally large variations in experimental Tc values from a few K to well above room temperature. The partially dimerized Mn_2-Mn_1 distribution is found to give the highest Tc > 500 K, and in general, the presence of the Mn_2 dimer has a tendency to enh...

  18. Report on Status of Shipment of High Fluence Austenitic Steel Samples for Characterization and Stress Corrosion Crack Testing

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Scarlett R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Leonard, Keith J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    The goal of the Mechanisms of Irradiation Assisted Stress Corrosion Cracking (IASCC) task in the LWRS Program is to conduct experimental research into understanding how multiple variables influence the crack initiation and crack growth in materials subjected to stress under corrosive conditions. This includes understanding the influences of alloy composition, radiation condition, water chemistry and metallurgical starting condition (i.e., previous cold work or heat treatments and the resulting microstructure) has on the behavior of materials. Testing involves crack initiation and growth testing on irradiated specimens of single-variable alloys in simulated Light Water Reactor (LWR) environments, tensile testing, hardness testing, microstructural and microchemical analysis, and detailed efforts to characterize localized deformation. Combined, these single-variable experiments will provide mechanistic understanding that can be used to identify key operational variables to mitigate or control IASCC, optimize inspection and maintenance schedules to the most susceptible materials/locations, and, in the long-term, design IASCC-resistant materials. In support of this research, efforts are currently underway to arrange shipment of “free” high fluence austenitic alloys available through Électricité de France (EDF) for post irradiation testing at the Oak Ridge National Laboratory (ORNL) and IASCC testing at the University of Michigan. These high fluence materials range in damage values from 45 to 125 displacements per atom (dpa). The samples identified for transport to the United States, which include nine, no-cost, 304, 308 and 316 tensile bars, were relocated from the Research Institute of Atomic Reactors (RIAR) in Dimitrovgrad, Ulyanovsk Oblast, Russia, and received at the Halden Reactor in Halden, Norway, on August 23, 2016. ORNL has been notified that a significant amount of work is required to prepare the samples for further shipment to Oak Ridge, Tennessee. The

  19. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    Science.gov (United States)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2016-05-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dissolution during the second, higher temperature, stage. A better homogenization of the material causes an increase in the transformation temperatures for the martensite-to-austenite transformation and a lower retained austenite fraction with less variability after tempering. Furthermore, the martensite-to-austenite transformation was found to be incomplete at the target temperature of 1223 K (950 °C), which is influenced by the previous austenitization treatment and the heating rate. The activation energy for martensite-to-austenite transformation was determined by a modified Kissinger equation to be approximately 400 and 500 kJ/mol for the first and the second stages of transformation, respectively. Both values are much higher than the activation energy found during isothermal treatment in a previous study and are believed to be effective activation energies comprising the activation energies of both mechanisms involved, i.e., nucleation and growth.

  20. Cast alumina forming austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P

    2013-04-30

    An austenitic stainless steel alloy consisting essentially of, in terms of weight percent ranges 0.15-0.5C; 8-37Ni; 10-25Cr; 2.5-5Al; greater than 0.6, up to 2.5 total of at least one element selected from the group consisting of Nb and Ta; up to 3Mo; up to 3Co; up to 1W; up to 3Cu; up to 15Mn; up to 2Si; up to 0.15B; up to 0.05P; up to 1 total of at least one element selected from the group consisting of Y, La, Ce, Hf, and Zr; <0.3Ti+V; <0.03N; and, balance Fe, where the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale comprising alumina, and a stable essentially single phase FCC austenitic matrix microstructure, the austenitic matrix being essentially delta-ferrite free and essentially BCC-phase-free. A method of making austenitic stainless steel alloys is also disclosed.

  1. In Situ Thermo-magnetic Investigation of the Austenitic Phase During Tempering of a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    Science.gov (United States)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2014-12-01

    The formation of austenite during tempering of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was investigated using an in situ thermo-magnetic technique to establish the kinetics of the martensite to austenite transformation and the stability of austenite. The austenite fraction was obtained from in situ magnetization measurements. It was found that during heating to the tempering temperature 1 to 2 vol pct of austenite, retained during quenching after the austenitization treatment, decomposed between 623 K and 753 K (350 °C and 480 °C). The activation energy for martensite to austenite transformation was found by JMAK-fitting to be 233 kJ/mol. This value is similar to the activation energy for Ni and Mn diffusion in iron and supports the assumption that partitioning of Ni and Mn to austenite are mainly rate determining for the austenite formation during tempering. This also indicates that the stability of austenite during cooling after tempering depends on these elements. With increasing tempering temperature the thermal stability of austenite is decreasing due to the lower concentrations of austenite-stabilizing elements in the increased fraction of austenite. After cooling from the tempering temperature the retained austenite was further partially decomposed during holding at room temperature. This appears to be related to previous martensite formation during cooling.

  2. 高镍奥氏体球墨铸铁涡壳的开发%Development of High-Ni Austenitic Ductile Iron Turbine Housing

    Institute of Scientific and Technical Information of China (English)

    高顺; 程凤军; 史朝龙; 莫俊超; 宋彦丞

    2013-01-01

    针对D-3.5和D-5S两种材质的高镍奥氏体球铁涡壳进行了试验研究,认为奥氏体枝晶发达才是高镍球铁出现碎块状石墨和显微缩松难以消除的根本原因.通过MAGMA模拟软件进行了铸造工艺模拟分析,优化了铸造工艺,缩短了开发周期,降低了成本.采用长效的Si-Ba和Si-Sr孕育剂的多次孕育,并加入微量的Sn和Sb元素,同时严格控制化学成分、出铁温度等关键参数,解决了球化不稳定、碎块石墨和显微缩松等问题,成功完成了高镍奥氏体球铁涡壳的开发,掌握了高镍奥氏体球铁的批量生产技术.%Two kinds of high nickel austenite ductile iron (D-3.5 and D-5S) turbocharger housing were researched, and a large number of austenitic dendrites were deem to the basic reason of chunky graphite and porosity. By simulation of casting process with the MAGMA software, the casting process was optimized; development cycle and the cost were reduced. Using long-acting nucleating agent such as Si-Ba and Si-Sr, adding trace of Sn and Sb element, and strictly controlling the key parameters of the chemical composition, the tapping temperature and the pouring temperature, etc., we solved the problems of the spheroidizing instability, chunky graphite and porosity, so successfully completed the development of the austenite ductile iron turbocharger housing and mastered the batch production technology of the high nickel austenite ductile iron.

  3. Large single crystal growth of MnWO4-type materials from high-temperature solutions

    Science.gov (United States)

    Gattermann, U.; Röska, B.; Paulmann, C.; Park, S.-H.

    2016-11-01

    A simple high-temperature growth apparatus was constructed to obtain large crystals of chemically gradient (In, Na)-doped MnWO4solid-solutions. This paper presents the crystal growth and characterisation of both MnWO4and epitaxially grown (In, Na): MnWO4crystals on MnWO4. These large monolithic crystals were made in two steps: A MnWO4 crystal was grown in the crystallographic main direction [001] applying the Czochralski method, followed by the top seeded growth of (In, Na): MnWO4 solid-solutions with an oriented seed crystal of MnWO4. Such a monolithic crystal will serve to fundamental investigation of coupling properties at boundaries between various multiferroic MnWO4-typesolid-solutions.

  4. Structural and magnetic properties of GeMn layers; High Curie temperature ferromagnetism induced by self organized GeMn nano-columns

    Energy Technology Data Exchange (ETDEWEB)

    Devillers, T.; Jamet, M.; Barski, A.; Poydenot, V.; Dujardin, R.; Bayle Guillemaud, P.; Bellet Amalric, E.; Mattana, R. [Departement de Recherche Fondamentale sur la Matiere Condensee, Service de Physique des Materiaux et Microstructures, CEA Grenoble, 17 avenue des Martyrs, 38054 Grenoble Cedex (France); Rothman, J. [Laboratoire d' Electronique de Technologie de l' Information, Laboratoire Infrarouge, CEA Grenoble, 17 avenue des Martyrs, 38054 Grenoble Cedex (France); Cibert, J. [Laboratoire Louis Neel, CNRS, BP166, 38042 Grenoble Cedex 9 (France); Tatarenko, S. [Laboratoire de Spectrometrie Physique, BP 87, 38402 Saint-Martin d' Heres (France)

    2007-01-15

    In this paper we report on the structural and magnetic properties of GeMn layers grown on Ge(001). We show that for the optimized Mn concentration (6%) and for optimized growth temperature (close to 130 C), GeMn samples exhibit a high Curie temperature (higher than 400 K) and Anomalous Hall Effect up to room temperature. Our GeMn layers grown at low temperature (70 C to 130 C) are composed of vertical Mn-rich nano-columns. Samples grown at temperatures higher than 130 C contain GeMn nanoclusters. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Synthesis of Perovskite ScMnO3 under High Temperature and Pressure

    Science.gov (United States)

    Yu, Tian; Gao, Peng; Tyson, Trevor A.

    2012-02-01

    Perovskite type ScMnO3 was synthesized under high temperature and pressure starting with hexagonal ScMnO3. The detail of the structure is examined by synchrotron x-ray diffraction and IR spectroscopy at room temperature. A highly distorted perovskite phase which is similar to the structure of LaMnO3 is identified by XRD Rietveld Refinement. Due to the small Sc ion radius, each Mn site has a distorted MnO6 polyhedron. This work is supported by DOE Grant DE-FG02-07ER46402.

  6. Nitriding Process Characterization of Cold Worked AISI 304 and 316 Austenitic Stainless Steels

    National Research Council Canada - National Science Library

    Waldemar Alfredo Monteiro; Silvio Andre Lima Pereira; Jan Vatavuk

    2017-01-01

    ... (in layer thicknesses). The nitriding processes have formed two layers, one external layer formed by expanded austenite with high nitrogen content, followed by another thinner layer just below formed by expanded austenite...

  7. Crecimiento anormal del grano austenítico en el acero microaleado 38MnSiV55 y determinación de las fuerzas impulsoras y de anclaje

    OpenAIRE

    Medina, S. F.; Chapa, M.; M. Gómez; Quispe, A.; López, V.; Fernández, B.

    2003-01-01

    Several castings of 38MnSiVS5 steel have been manufactured with different titanium and aluminium contents and the austenitic grain size has been determined at temperatures between 900 and 1200 °C. The volume fraction of normal and abnormal grain growth have been quantified. The results show that abnormal growth of the austenitic grain occurs irrespective of the titanium and aluminium contents, due fundamentally to the partial dissolution of TiN precipitates. The steels with high aluminium con...

  8. Bimetallic Co-Mn perovskite fluorides as high-stable electrode materials for supercapacitors.

    Science.gov (United States)

    Shi, Wei; Ding, Rui; Li, Xudong; Xu, Qilei; Ying, Danfeng; Huang, Yongfa; Liu, Enhui

    2017-09-14

    Bimetallic Co-Mn perovskite fluorides (KCoxMn1-xF3, denoted as K-Co-Mn-F) with various Co/Mn ratios (1:0, 12:1, 6:1, 3:1, 1:1, 1:3, 0:1) were prepared via one-pot solvothermal strategy and further used as electrode materials for supercapacitors. The optimal K-Co-Mn-F (Co/Mn=6:1) candidate showed size range of 0.1-1 μm and uniform element distribution, exhibiting the light changes in XRD diffraction peaks and XPS binding energy in comparison for the bare K-Co-F and K-Mn-F due to the structural/electronic effects. Owing to the stronger synergistic effect of Co/Mn redox species, the K-Co-Mn-F (Co/Mn=6:1) electrode exhibited superior specific capacity and rate behavior (113-100 C g-1 at 1-16 A g-1) together with excellent cycling stability (118% for 5000 cycles at 8 A g-1), and the AC//K-Co-Mn-F (Co/Mn=6:1) asymmetric capacitor showed superior energy and power densities (8.0-2.4 Wh Kg-1 at 0.14-8.7 KW Kg-1) along with high cycling stability (90% for 10000 cycles at 5 A g-1). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. High temperature ferromagnetism in cubic Mn-doped ZrO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Nguyen Hoa, E-mail: nguyenhong@snu.ac.kr [Nanomagnetism Laboratory, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Park, Chul-Kwon; Raghavender, A.T. [Nanomagnetism Laboratory, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Ruyter, Antoine [Laboratoire GREMAN, UMR 7347 CNRS - Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); Chikoidze, Ekaterina; Dumont, Yves [Laboratoire GEMaC, UMR 8635 Universite de Versailles St Quentin en Yvelines - CNRS, 45, Av. des Etats-Unis, 78035 Versailles Cedex (France)

    2012-09-15

    Theory has predicted that high temperature ferromagnetism (FM) should be found in cubic fake-diamonds, Mn-doped ZrO{sub 2}. Experimentally, it is shown that Mn-doped ZrO{sub 2} ceramics are not ferromagnetic, but the nanosized Mn-doped ZrO{sub 2} thin films grown on LaAlO{sub 3} substrates can be ferromagnets with T{sub C} above 400 K. The largest saturated magnetic moment (M{sub s}) is huge as of about 230 emu/cm{sup 3} for the Mn{sub 0.05}Zr{sub 0.95}O{sub 2} films, and it decreases as the Mn content increases. The intrinsic FM is strongly associated with the cubic structure of Mn-doped ZrO{sub 2}, and the Mn-Mn interactions via oxygen intermediates are important. No electrical conductivity is observed. Mn-doped ZrO{sub 2} thin films can be truly considered as excellent candidates for spintronic applications. - Highlights: Black-Right-Pointing-Pointer Mn-doped ZrO2 thin films can be ferromagnetic above room temperature. Black-Right-Pointing-Pointer Huge magnetic moment of 13.8 {mu}{sub B} per Mn is found in the sampledoping with 5% of Mn. Black-Right-Pointing-Pointer Magnetic force measurements confirm intrinsic ferromagnetism. Black-Right-Pointing-Pointer Important feedback to the theoretical work. Black-Right-Pointing-Pointer Good candidates for spintronics applications.

  10. A New Resource-Saving, High Chromium and Manganese Super Duplex Stainless Steels 29Cr-12Mn-2Ni-1Mo-xN

    Institute of Scientific and Technical Information of China (English)

    MA Zheng-huan; ZHAO Xiang-juan; GE Chang-sheng; DING Tie-suo; LI Jun; XIAO Xue-shan

    2011-01-01

    A new family of resource saving, high chromium and manganese super duplex stainless steels (DSSs), with a composition in mass percent, % of Cr 0.29, Mn 0.12, Ni 2.0, Mo i. 0, and N 0. 51-0. 68, has been developed by examining the effect of N on the microstructure, mechanical properties and corrosion properties. The results show that these alloys have a balanced ferrite-austenite relation. The austenite volume fraction decreases with the solution treatment temperature, but it increases with an increase in N content. The increases in nitrogen enhance the ultimate tensile strength (UTS) and reduce the ductility of the material slightly. The pitting corrosion potential increases first and then decreases with an increase in nitrogen content when the amount of N arrives to 0.68%. The yield stress and ultimate tensile strength of solution treated samples were more than 680 and 900 MPa, the elongation of experimental alloys are higher than 30%, respectively, what is more, the pitting potentials were beyond 1 100 mV.

  11. Carbon Concentration of Austenite

    Directory of Open Access Journals (Sweden)

    Z. Ławrynowicz

    2007-07-01

    Full Text Available The investigation was carried out to examine the influence of temperature and times of austempering process on the maximum extend towhich the bainite reaction can proceed and the carbon content in retained austenite. It should be noted that a small percentage change in theaustenite carbon content can have a significant effect on the subsequent austempering reaction changing the volume fraction of the phasespresent and hence, the resulting mechanical properties. Specimens were prepared from an unalloyed ductile cast iron, austenitised at 950oCfor 60 minutes and austempered by the conventional single-step austempering process at four temperatures between BS and MS, eg., 250,300, 350 and 400oC. The samples were austempered at these temperatures for 15, 30, 60, 120 and 240 minutes and finally quenched toambient temperature. Volume fractions of retained austenite and carbon concentration in the residual austenite have been observed byusing X-ray diffraction. Additionally, carbon concentration in the residual austenite was calculated using volume fraction data of austeniteand a model developed by Bhadeshia based on the McLellan and Dunn quasi-chemical thermodynamic model. The comparison ofexperimental data with the T0, T0' and Ae3' phase boundaries suggests the likely mechanism of bainite reaction in cast iron is displacive rather than diffusional. The carbon concentration in retained austenite demonstrates that at the end of bainite reaction the microstructure must consist of not only ausferrite but additionally precipitated carbides.

  12. Magnetostructural transition and magnetocaloric effect in highly textured Ni-Mn-Sn alloy

    Science.gov (United States)

    Czaja, P.; Chulist, R.; Szczerba, M. J.; Przewoźnik, J.; Olejnik, E.; Chrobak, A.; Maziarz, W.; Cesari, E.

    2016-04-01

    Ni49.4Mn38.5Sn12.1 near single crystal was obtained by the Bridgman method. At room temperature, it consisted of a mixture of the parent austenite phase with the cubic L21 Heusler structure (ac = 5.984 Å) and modulated, tetragonal martensite phase 4M (at = 4.337 Å, ct = 5.655 Å). Under the application of a magnetic field, the specimen undergoes field induced reverse martensitic transformation, which combined with the Curie transition in austenite leads to the coexistence of direct and inverse magnetocaloric effects. The maximum entropy change at 280 K and under 5 T amounts to 3.4 J.kg-1.K-1 for the structural transition and at 316 K reaches -2.7 J.kg-1.K-1 for the magnetic transformation. The magnetic entropy change occurs over a wide temperature span leading to improved refrigerant capacity of 101 J.kg-1 (5 T). Hysteretic losses are considerably reduced, which is promising with respect to improved cyclic stability of such a material.

  13. Study of retained austenite and nano-scale precipitation and their effects on properties of a low alloyed multi-phase steel by the two-step intercritical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J.; Han, G., E-mail: hangang@mater.ustb.edu.cn; Zhou, W.H.; Zeng, C.Y.; Shang, C.J., E-mail: cjshang@ustb.edu.cn

    2016-03-15

    Microstructure evolution and properties were studied in a low carbon low alloyed hot-rolled bainitic steel by annealing and annealing plus tempering. Microstructure of the hot-rolled steel consists of lath bainite and martensite. By annealing at 720 °C for 30 min and water quenching, multi-phase microstructure consisting of intercritical ferrite, tempered bainite/martensite, retained austenite and fresh martensite was obtained. With increasing annealing temperature to 760 °C, microstructure of the steel consisted of intercritical ferrite, fresh martensite without retained austenite. After the second step of tempering at 680 °C for samples annealed both at 720 °C and 760 °C, ~ 8–9% volume fraction of retained austenite was obtained in the multi-phase microstructure. Moreover, fine precipitates of VC with size smaller than 10 nm and copper precipitates with size of ~ 10–50 nm were obtained after tempering. Results from scanning transmission electron microscopy (STEM) give evidence to support that the partitioning of Mn, Ni and Cu is of significance for retained austenite stabilization. Due to the combined contribution of multiphase microstructure, the transformation-induced-plasticity effect of retained austenite and strengthening effect of nanometer-sized precipitates, yield strength greater than 800 MPa, yield to tensile ratio of 0.9, uniform elongation of ~ 9% and good low temperature impact toughness of 147 J at − 40 °C were achieved. - Highlights: • Stable retained austenite was produced in a low alloyed steel. • Partition of Mn, Ni and Cu was confirmed by STEM for austenite stabilization. • Nano-sized VC and Cu precipitates were achieved by second tempering. • High strength–high toughness with low Y/T ratio was obtained.

  14. Effect of 16Cr Austenite Stainless Steel High Frequency Welding Parameters on Weld Microstructure and Properties%16Cr奥氏体不锈钢高频焊接参数对焊缝组织性能的影响

    Institute of Scientific and Technical Information of China (English)

    毕宗岳; 严培林; 余晗; 汪海涛

    2016-01-01

    In order to analyze the effect of 16Cr stainless steel high frequency welding parameter on weld microstructure and properties, under the different high frequency welding(HFW) parameters,the change of weld microstructure and properties of 16Cr stainless steel were studied by optical microscope(OM), scanning electron microscope(SEM) tensile test and bending test. The results showed that the weld formability of 16Cr austenitic stainless steel becomes better with the increase of welding speed. The content of δ-ferrite in weld show a trend of decrease after an initial increase with the increasing of welding heat input,accompanied by brittle σ-phase precipitation. The weld of 3.4 mm thickness 16Cr austenitic stainless steel has good formability,when welding speed about 10 m/min,welding heat input 2.9 kJ/cm, and with appropriate pressing force and the opening angle. The welded joints have good matching hardness and the weld tensile strength is close to the base material tensile strength. The microstructure of weld is mainly composed of austenite and δ-ferrite. But the welded joints have poor toughness, because of the oxide inclusions in weld.%为了分析16Cr不锈钢高频焊接参数对焊缝组织性能的影响,通过光学显微镜(OM)、扫描电镜(SEM)和拉伸、弯曲试验,分析了不同高频焊接参数下1Cr17Mn6Ni5N 不锈钢(以下简称16Cr不锈钢)焊缝组织与性能的变化情况。结果表明:16Cr奥氏体不锈钢高频焊随着焊接速度的增加,焊缝成形性能变好;焊缝中δ铁素体的含量随焊接热输入的增加先增后减,同时伴随σ脆性相析出;对于壁厚3.4 mm的16Cr奥氏体不锈钢,当焊接速度为10 m/min、焊接热输入为2.9 kJ/cm、并配以适当的挤压力和开口角时,焊缝成形及焊接接头硬度匹配良好,且焊缝抗拉强度接近母材抗拉强度,焊缝显微组织以奥氏体+δ铁素体为主,但由于焊缝存在大量

  15. Investigation of joining techniques for advanced austenitic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Qiao, C.Y.P.; Kikuchi, Y.; Shi, C.; Gill, T.P.S.

    1991-05-01

    Modified Alloys 316 and 800H, designed for high temperature service, have been developed at Oak Ridge National Laboratory. Assessment of the weldability of the advanced austenitic alloys has been conducted at the University of Tennessee. Four aspects of weldability of the advanced austenitic alloys were included in the investigation.

  16. INFLUENCE OF ABNORMAL AUSTENITE GRAIN GRAIN GROWTH IN QUENCHED ABNT 5135 STEEL

    Directory of Open Access Journals (Sweden)

    Camila de Brito Ferreira

    2015-03-01

    Full Text Available Grain size in the steels is a relevant aspect in quenching and tempering heat treatments. It is known that high austenitizing temperature and long time provide an increase in austenitic grain sizes. Likewise, after hardening of low alloy steel, the microstructure consists of martensite and a volume fraction of retained austenite. This paper evaluates the influence of austenite grain size on the volume fraction of retained austenite measured by metallographic analyses and X-ray diffraction. The Mi and Mf temperatures were calculated using an empirical equation and experimentally determined by differential thermal analysis. The mechanical behavior of the steel was evaluated by Vickers microhardness testing. Differently from other results published in the literature that steel hardenability increases with the austenite grain size, it was observed that the increase in austenite grain promotes greater volume fraction of retained austenite after water quenching.

  17. Effect of the carbide phase on the tribological properties of high-manganese antiferromagnetic austenitic steels alloyed with vanadium and molybdenum

    Science.gov (United States)

    Korshunov, L. G.; Kositsina, I. I.; Sagaradze, V. V.; Chernenko, N. L.

    2011-07-01

    Effect of special carbides (VC, M 6C, Mo2C) on the wear resistance and friction coefficient of austenitic stable ( M s below -196°C) antiferromagnetic ( T N = 40-60°C) steels 80G20F2, 80G20M2, and 80G20F2M2 has been studied. The structure and the effective strength (microhardness H surf, shear resistance τ) of the surface layer of these steels have been studied using optical and electron microscopy. It has been shown that the presence of coarse particles of primary special carbides in the steels 80G20F2, 80G20M2, and 80G20F2M2 quenched from 1150°C decreases the effective strength and the resistance to adhesive and abrasive wear of these materials. This is caused by the negative effect of carbide particles on the toughness of steels and by a decrease in the carbon content in austenite due to a partial binding of carbon into the above-mentioned carbides. The aging of quenched steels under conditions providing the maximum hardness (650°C for 10 h) exerts a substantial positive effect on the parameters of the effective strength ( H surf, τ) of the surface layer and, correspondingly, on the resistance of steels to various types of wear (abrasive, adhesive, and caused by the boundary friction). The maximum positive effect of aging on the wear resistance is observed upon adhesive wear of the steels under consideration. Upon friction with enhanced sliding velocities (to 4 m/s) under conditions of intense (to 500-600°C) friction-induced heating, the 80G20F2, 80G20M2, and, especially, 80G20F2M2 steels subjected to quenching and aging substantially exceed the 110G13 (Hadfield) steel in their tribological properties. This is due to the presence in these steels of a favorable combination of high effective strength and friction heat resistance of the surface layer, which result from the presence of a large amount of special carbides in these steels and from a high degree of alloying of the matrix of these steels by vanadium and molybdenum. In the process of friction

  18. Improvement of the Corrosion Resistance of High Alloyed Austenitic Cr-Ni-Mo Stainless Steels by Solution Nitriding

    Institute of Scientific and Technical Information of China (English)

    Christine Eckstein; Heinz- Joachim Spies; Jochen Albrecht

    2004-01-01

    Characteristic features of austenitic steel grades combine a good corrosion resistance with a low hardness, wear resistance and scratch resistance. An interesting possibility for improving the wear behaviour of these steels without loss of their corrosion resistance lies in enriching the near surface region with nitrogen. The process of a solution nitriding allows the rise of the solution of nitrogen in the solid phase. On this state nitrogen increases the corrosion resistance and the tribilogical load-bearing capacity. The aim of the study was, to investigate the improvement of the pitting corrosion behaviour by solution nitriding. A special topic was to observe the effect of nitrogen by different molybdenum content. So austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.06 to 3.6%) had been solution nitrided. The samples could be prepared with various surface content of nitrogen from 0.04 to 0.45% with a step-by-step grinding. The susceptibility against pitting corrosion of these samples had been tested by determination of the stable pitting potential in 0.5M and 1M NaCl at 25℃. For the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen. The influence of nitrogen to all of the determined parameters can be corrosion tests. Additionally surface investigations with an acid elektolyte (0,1M HCl + 0,4M NaCI) were performed. In this case the passivation effective nitrogen content increases markedly with rising molybdenum concentration of the steel.Obviously an interaction of Mo and N is connected with a strongly acid electrolyte.

  19. Neutron Diffraction Investigation of MnAs under High Pressure

    DEFF Research Database (Denmark)

    Andresen, A.F; Fjellvag, H; Lebech, Bente

    1984-01-01

    Powdered MnAs has been investigated by neutron diffraction in a pressure cryostat, at hydrostatic pressures up to 13 kbar and temperatures down to 4.2 K. It has been found that in the orthorhombic MnP type structure, which under pressure is retained at low temperature, a spiral magnetic structure...

  20. Microstructural Developments and Tensile Properties of Lean Fe-Mn-Al-C Lightweight Steels

    Science.gov (United States)

    Sohn, S. S.; Lee, S.; Lee, B.-J.; Kwak, J.-H.

    2014-09-01

    Concepts of Fe-Al-Mn-C-based lightweight steels are fairly simple, but primary metallurgical issues are complicated. In this study, recent studies on lean-composition lightweight steels were reviewed, summarized, and emphasized by their microstructural development and mechanical properties. The lightweight steels containing a low-density element of Al were designed by thermodynamic calculation and were manufactured by conventional industrial processes. Their microstructures consisted of various secondary phases as κ-carbide, martensite, and austenite in the ferrite matrix according to manufacturing and annealing procedures. The solidification microstructure containing segregations of C, Mn, and Al produced a banded structure during the hot rolling. The (ferrite + austenite) duplex microstructure was formed after the annealing, and the austenite was retained at room temperature. It was because the thermal stability of austenite nucleated from fine κ-carbide was quite high due to fine grain size of austenite. Because these lightweight steels have outstanding properties of strength and ductility as well as reduced density, they give a promise for automotive applications requiring excellent properties.

  1. Revealing the extra-high ductility and toughness of micro+duplex medium+Mn steel in a large temperature range from 200 ℃ to -196 ℃

    DEFF Research Database (Denmark)

    Cao, Wenquan; Hu, Jun; Dong, Han

    2014-01-01

    A medium-Mn steel (0.2C5Mn) was processed by intercritical annealing at different temperature (625℃ and 650℃) after forging and hot rolling. The microstructures were characterized by transmission electron microscopy and the mechanical properties were measured by tensile tests and impact tests...... be obtained in the temperature range from 200℃ to -196℃. And significantly delayed transition from ductile to brittle and no less than 200J impact toughness at -40℃ could be obtained in the ART-annealed medium-Mn steel. Based on the analysis of microstructure and mechanical properties, the enhanced ductility...... in the full temperature range could be ascribed to the phase transformation effect of austenite (TRIP effects), while the delayed ductile to brittle transition could be attributed to the enhanced austenite stability....

  2. Polydopamine and MnO2 core-shell composites for high-performance supercapacitors

    Science.gov (United States)

    Hou, Ding; Tao, Haisheng; Zhu, Xuezhen; Li, Maoguo

    2017-10-01

    Polydopamine and MnO2 core-shell composites (PDA@MnO2) for high-performance supercapacitors had been successfully synthesized by a facile and fast method. The morphology, crystalline phase and chemical composition of PDA@MnO2 composites are characterized using SEM, TEM, XRD, EDS and XPS. The performance of PDA@MnO2 composites are further investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte. The PDA@MnO2 core-shell nanostructure composites exhibit a high capacitance of 193 F g-1 at the current density of 1A g-1 and retained over 81.2% of its initial capacitance after 2500 cycles of charge-discharge at 2 A g-1. The results manifest that the PDA@MnO2 composites can be potentially applied in supercapacitors.

  3. Inlfuence of carbon content on microstructure and mechanical properties of Mn13Cr2 and Mn18Cr2 cast steels

    Institute of Scientific and Technical Information of China (English)

    Lu Dingshan; Liu Zhongyi; Li Wei

    2014-01-01

    In this paper, a comparison study was carried out to investigate the inlfuence of carbon content on the microstructure, hardness, and impact toughness of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The study results indicate that both steels' water-quenched microstructures are composed of austenite and a smal amount of carbide. The study also found that, when the carbon contents are the same, there is less carbide in Mn18Cr2 steel than in Mn13Cr2 steel. Therefore, the hardness of Mn18Cr2 steel is lower than that of Mn13Cr2 steel but the impact toughness of Mn18Cr2 steel is higher than that of Mn13Cr2 steel. With increasing the carbon content, the hardness increases and the impact toughness decreases in these two kinds of steels, and the impact toughness of Mn18Cr2 steel substantialy exceeds that of Mn13Cr2 steel. Therefore, the water-quenched Mn18Cr2 steel with high carbon content could be applied to relatively high impact abrasive working conditions, while the as-cast Mn18Cr2 steel could be only used under working conditions of relatively low impact abrasive load due to lower impact toughness.

  4. Evaluation of High-Temperature Tensile Property of Diffusion Bond of Austenitic Alloys for S-CO{sub 2} Cycle Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sunghoon; Sah, Injin; Jang, Chanheui [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-12-15

    To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical CO{sub 2} (S-CO{sub 2}) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the S-CO{sub 2} system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to 650℃. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to 550℃. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.

  5. Austenite and ferrite grain size evolution in plain carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Militzer, M.; Giumelli, A.; Hawbolt, E.B.; Meadowcroft, T.R. [British Columbia Univ., Vancouver, BC (Canada)

    1995-01-01

    Grain size evolution in a 0.17%C, 0.74%Mn plain carbon steel is investigated using a Gleeble 1500 thermomechanical simulator. Austenite grain growth measurements in the temperature range from 900 to 1150{degrees}C have been used to validate the Abbruzzese and Luecke model, which is recommended for simulating grain growth during reheating. For run-out table conditions, the ferrite grain size decreases from 1l{mu}m to 4{mu}m when the cooling rate from the austenite is increased from 1 to 80{degrees}C/s.

  6. Thermomechanical hardening of stable and metastable austenitic steels

    Science.gov (United States)

    Baraz, V. R.; Gladkovskii, S. V.; Ishina, E. A.

    2005-11-01

    Phase composition, mechanical properties, and variation of the density of cold-deformed Fe-Cr-Ni-Mn steels differing in the stability of austenite are studied. A comparative analysis of formation of phase composition and accumulation of discontinuities in the process of drawing of stable and metastable austenitic steels is performed. The effect of post-deformation annealing on the variation of the density and mechanical properties is considered. The capacity for recovery of the density is shown to be correlated with the resistance of the studied thermomechanically hardened steels to fatigue fracture. The determined dependences are explained.

  7. Embrittlement of austenitic stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    David, S.A.; Vitek, J.M. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-31

    The microstructure of type-308 austenitic stainless steel weld metal containing {gamma} and {delta} and ferrite is shown. Typical composition of the weld metal is Cr-20.2, Ni-9.4, Mn-1.7, Si-0.5, C-0.05, N-0.06 and balance Fe (in wt %). Exposure of austenitic stainless steel welds to elevated temperatures can lead to extensive changes in the microstructural features of the weld metal. On exposure to elevated temperatures over a long period of time, a continuous network of M{sub 23}C{sub 6} carbide forms at the austenite/ferrite interface. Upon aging at temperatures between 550--850 C, ferrite in the weld has been found to be unstable and transforms to sigma phase. These changes have been found to influence mechanical behavior of the weld metal, in particular the creep-rupture properties. For aging temperatures below 550 C the ferrite decomposes spinodally into {alpha} and {alpha}{prime} phases. In addition, precipitation of G-phase occurs within the decomposed ferrite. These transformations at temperatures below 550 C lead to embrittlement of the weld metal as revealed by the Charpy impact properties.

  8. Kinetics of the austenite formation during intercritical annealing

    OpenAIRE

    J. Lis; A. Lis

    2008-01-01

    Purpose: of this paper is the effect of the microstructure of the 6Mn16 steel after soft annealing on the kinetics of the austenite formation during next intercritical annealing.Design/methodology/approach: Analytical TEM point analysis with EDAX system attached to Philips CM20 was used to evaluate the concentration of Mn in the microstructure constituents of the multiphase steel,Findings: The increase in soft annealing time from 1-60 hours at 625 °C increases Mn partitioning between ferrite ...

  9. Acoustic emission study of the plastic deformation of quenched and partitioned 35CrMnSiA steel

    Institute of Scientific and Technical Information of China (English)

    Yang Li; Gui-yong Xiao; Lu-bin Chen; Yu-peng Lu

    2014-01-01

    Acoustic emission (AE) monitored tensile tests were performed on 35CrMnSiA steel subjected to different heat treatments. The results showed that quenching and partitioning (Q−P) heat treatments enhanced the combined mechanical properties of high strength and high ductility for commercial 35CrMnSiA steel, as compared with traditional heat treatments such as quenching and tempering (Q−T) and austempering (AT). AE signals with high amplitude and high energy were produced during the tensile deformation of 35CrMnSiA steel with retained austenite (RA) in the microstructure (obtained via Q−P and AT heat treatments) due to an austenite-to-martensite phase transforma-tion. Moreover, additional AE signals would not appear again and the mechanical properties would degenerate to a lower level once RA de-generated by tempering for the Q−P treated steel.

  10. Effect of heat treatment on formability in 0.15C-1.5Si-1.5Mn multiphase cold-rolled steel sheet

    Science.gov (United States)

    Lee, Chang Gil; Kim, Sung-Joon; Song, Byung-Hwan; Lee, Sunghak

    2002-10-01

    The effects of volume fraction and the stability of retained austenite on the formability of a 0.15C-1.5Si-1.5Mn (hereafter all in wt.%) TRIP-aided multiphase cold-rolled steel sheet were investigated after various heat treatments. The steel sheets were intercritically annealed at 800°C, and isothermally treated at 400°C and 430°C. Microstructural observation, tensile tests and limiting dome height (LDH) tests were conducted on the heat-treated sheet specimens, and the changes in retained austenite volume fraction as a function of tensile strain were measured using an X-ray diffractometer. The results showed a plausible relationship between formability and retained austenite stability. Although the same amount of retained austenite was obtained after isothermal holding at different temperatures, better formability was obtained in the specimens with the higher stability of retained austenite. If the stability of the retained austenite is high, the strain-induced transformation of retained austenite to martensite can be stably progressed, resulting in a delay of necking to the high strain region and improvement in formability.

  11. Synthesis of highly luminescent Mn:ZnSe/ZnS nanocrystals in aqueous media.

    Science.gov (United States)

    Fang, Zheng; Wu, Ping; Zhong, Xinhua; Yang, Yong-Ji

    2010-07-30

    High-quality water-dispersible Mn(2+)-doped ZnSe core/ZnS shell (Mn:ZnSe/ZnS) nanocrystals have been synthesized directly in aqueous media. Overcoating a high bandgap ZnS shell around the Mn:ZnSe cores can bring forward an efficient energy transfer from the ZnSe host nanocrystals to the dopant Mn. The quantum yields of the dopant Mn photoluminescence in the as-prepared water-soluble Mn:ZnSe/ZnS core/shell nanocrystals can be up to 35 +/- 5%. The optical features and structure of the obtained Mn:ZnSe/ZnS core/shell nanocrystals have been characterized by UV-vis, PL spectroscopy, TEM, XRD and ICP elementary analysis. The influences of various experimental variables, including the Mn concentration, the Se/Zn molar ratio as well as the kind and amount of capping ligand used in the core production and shell deposition process, on the luminescent properties of the obtained Mn:ZnSe/ZnS nanocrystals have been systematically investigated.

  12. Double Double Cation Order in the High-Pressure Perovskites MnRMnSbO6.

    Science.gov (United States)

    Solana-Madruga, Elena; Arévalo-López, Ángel M; Dos Santos-García, Antonio J; Urones-Garrote, Esteban; Ávila-Brande, David; Sáez-Puche, Regino; Attfield, J Paul

    2016-08-01

    Cation ordering in ABO3 perovskites adds to their chemical variety and can lead to properties such as ferrimagnetism and magnetoresistance in Sr2 FeMoO6 . Through high-pressure and high-temperature synthesis, a new type of "double double perovskite" structure has been discovered in the family MnRMnSbO6 (R=La, Pr, Nd, Sm). This tetragonal structure has a 1:1 order of cations on both A and B sites, with A-site Mn(2+) and R(3+) cations ordered in columns and Mn(2+) and Sb(5+) having rock salt order on the B sites. The MnRMnSbO6 double double perovskites are ferrimagnetic at low temperatures with additional spin-reorientation transitions. The ordering direction of ferrimagnetic Mn spins in MnNdMnSbO6 changes from parallel to [001] below TC =76 K to perpendicular below the reorientation transition at 42 K at which Nd moments also order. Smaller rare earths lead to conventional monoclinic double perovskites (MnR)MnSbO6 for Eu and Gd.

  13. Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line.

    Science.gov (United States)

    Talha, Mohd; Kumar, Sanjay; Behera, C K; Sinha, O P

    2014-02-01

    The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation.

  14. Swelling and microstructure of austenitic stainless steel ChS-68 CW after high dose neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Porollo, S.I.; Konobeev, Yu.V. [State Scientific Center of Russian Federation - Institute of Physics and Power Engineering (IPPE), Obninsk, Kaluga Region (Russian Federation); Garner, F.A., E-mail: frank.garner@dslextreme.co [Radiation Effects Consulting, 2003 Howell Avenue, Richland, WA 99354 (United States)

    2009-08-15

    Austenitic stainless steel ChS-68 serving as fuel pin cladding was irradiated in the 20% cold-worked condition in the BN-600 fast reactor in the range 56-84 dpa. This steel was developed to replace EI-847 which was limited by its insufficient resistance to void swelling. Comparison of swelling between EI-847 and ChS-68 under similar irradiation conditions showed improvement of the latter steel by an extended transient regime of an additional approx10 dpa. Concurrent with swelling was the development of a variety of phases. In the temperature range 430-460 deg. S where the temperature peak of swelling was located, the principal type of phase generated during irradiation was G-phase, with volume fraction increasing linearly with dose to approx0.5% at 84 dpa. While the onset of swelling is concurrent with formation of G-phase, the action of G-phase cannot be confidently ascribed to significant removal from solution of swelling-suppressive elements such as silicon. A plausible mechanism for the higher resistance to void swelling of ChS-68 as compared with EI-847 may be related to an observed higher stability of faulted dislocation loops in ChS-68 that impedes the formation of a glissile dislocation network. The higher level of boron in ChS-68 is thought to be one contributor that might play this role.

  15. Dynamical recrystallization of high purity austenitic stainless steels; Recristallisation dynamique d'aciers inoxydables austenitiques de haute purete

    Energy Technology Data Exchange (ETDEWEB)

    Gavard, L

    2001-01-01

    The aim of this work is to optimize the performance of structural materials. The elementary mechanisms (strain hardening and dynamical regeneration, germination and growth of new grains) occurring during the hot working of metals and low pile defect energy alloys have been studied for austenitic stainless steels. In particular, the influence of the main experimental parameters (temperature, deformation velocity, initial grain size, impurities amount, deformation way) on the process of discontinuous dynamical recrystallization has been studied. Alloys with composition equal to those of the industrial stainless steel-304L have been fabricated from ultra-pure iron, chromium and nickel. Tests carried out in hot compression and torsion in order to cover a wide range of deformations, deformation velocities and temperatures for two very different deformation ways have allowed to determine the rheological characteristics (sensitivity to the deformation velocity, apparent activation energy) of materials as well as to characterize their microstructural deformations by optical metallography and electron back-scattered diffraction. The influence of the initial grain size and the influence of the purity of the material on the dynamical recrystallization kinetics have been determined. An analytical model for the determination of the apparent mobility of grain boundaries, a semi-analytical model for the dynamical recrystallization and at last an analytical model for the stationary state of dynamical recrystallization are proposed as well as a new criteria for the transition between the refinement state and the state of grain growth. (O.M.)

  16. Yttrium modifying influence on the shape and amount of nonmetallic inclusions in the austenitic high alloy steel

    Directory of Open Access Journals (Sweden)

    Андрій Володимирович Патюпкін

    2016-07-01

    Full Text Available Yttrium influence on the form and amount of non-metallic inclusions in steel 06H23N18M5 was studied. It has been found that yttrium binds oxygen and other elements into heterogeneous compounds, it resulting in the transition of impurities into passive state. Oxide inclusions, sulfide inclusions and globules formed as a result of steel components reactions with oxygen, sulfur and nitrogen dissolved in metal are mostly found in the structure. It was found that by modifying and refining austenitic steels with yttrium service properties of the deposited layer can be adjusted. X-ray diffraction and X-ray spectrum analysis revealed that the modified steel 06H23N18M5 + 0.02% Y has a heterogeneous structure with uniformly distributed inclusions of σ-phase and composite carbides (Fe, Cr, Mo 23C6. It is possible that Y modification resulted in the appearance of chemically resistant intermetallic σ-phase in these steels, for nucleation was facilitated by increasing the number of crystallization centers as dispersed primary yttrium oxy-sulfide compounds

  17. X-ray absorption near edge spectroscopy at the Mn K-edge in highly homogeneous GaMnN diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A. [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Martinez-Criado, G.; Salome, M.; Susini, J. [ESRF, Polygone Scientifique Louis Neel, 6 rue Jules Horowitz, 38000 Grenoble (France); Olguin, D. [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D.F. (Mexico); Dhar, S.; Ploog, K. [Paul Drude Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    We have studied by X-ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga{sub 1-x}Mn{sub x}N (0.06Mn K-edges. In this report, we focus our attention to the X-ray absorption near edge spectroscopy (XANES) results. The comparison of the XANES spectra corresponding to the Ga and Mn edges indicates that Mn is substitutional to Ga in all samples studied. The XANES spectra measured at the Mn absorption edge shows in the near-edge region a double peak and a shoulder below the absorption edge and the main absorption peak after the edge, separated around 15 eV above the pre-edge structure. We have compared the position of the edge with that of MnO (Mn{sup 2+}) and Mn{sub 2}O{sub 3} (Mn{sup 3+}). All samples studied present the same Mn oxidation state, 2{sup +}. In order to interprete the near-edge structure, we have performed ab initio calculations with a 2 x 2 x 1supercell ({proportional_to}6% Mn) using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of Mn anti-bonding t{sub 2g} bands, which are responsible for the pre-edge absorption. The shoulder and main absorption peaks are due to transitions from the valence band 1s-states of Mn to the p-contributions of the conduction bands. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Effect of retained austenite on the dynamic tensile behavior of a novel quenching-partitioning-tempering martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Qingguo; Qin, Shengwei; Liu, Yu [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zuo, Xunwei, E-mail: jeepling@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Nailu [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Huang, Wen [College of Civil Engineering, Shenzhen University, Shenzhen 518060 (China); Rong, Yonghua [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2016-04-26

    The dynamic tensile test with a strain rate of 500 s{sup −1} and the quasi-static tensile test with a strain rate of 5.6×10{sup −4} s{sup −1} were performed for a novel Fe-0.20C-1.49Mn-1.52Si-0.58Cr-0.05 Nb (wt%) quenching-partitioning-tempering (Q-P-T) martensitic steel with high amount of retained austenite, respectively. This low carbon steel was also treated by the traditional quenching and tempering (Q&T) process, and the same experimental tests were performed for the low carbon Q&T martensitic steel with little retained austenite to understand the effect of the retained austenite on the dynamic tensile behavior. The results indicate that compared with the quasi-static tensile test, the high strain rate in the dynamic tensile test raises the strength of the Q-P-T steel. However, the elongation slightly decreases. These results differ from the enhancement in both the strength and elongation of the Q&T steel in the dynamic tensile test. The increase in the strength of the Q-P-T steel in the dynamic tensile test is attributed to the strain rate hardening effect. The slight decrease in the elongation stems mainly from that the suppression of the dislocation absorption of the retained austenite (DARA) effect existing in the quasi-static tensile test, moreover, such a suppression is not effectively complemented by the adiabatic softening of the martensitic matrix in dynamic tensile test. The marked increase in the elongation of the Q&T steel in the dynamic tensile test is only attributed to the adiabatic softening of the martensite matrix because there is no DARA effect in the Q&T steel with little retrained austenite.

  19. Graphene/MnO{sub 2} hybrid nanosheets as high performance electrode materials for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, Anjon Kumar, E-mail: Anjon.K.Mondal@student.uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia); Wang, Bei; Su, Dawei; Wang, Ying; Chen, Shuangqiang [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia); Zhang, Xiaogang [College of Materials Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Wang, Guoxiu, E-mail: Guoxiu.wang@uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia)

    2014-01-15

    Graphene/MnO{sub 2} hybrid nanosheets were prepared by incorporating graphene and MnO{sub 2} nanosheets in ethylene glycol. Scanning electron microscopy and transmission electron microscopy analyses confirmed nanosheet morphology of the hybrid materials. Graphene/MnO{sub 2} hybrid nanosheets with different ratios were investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatic charge–discharge in 1 M Na{sub 2}SO{sub 4} electrolyte. We found that the graphene/MnO{sub 2} hybrid nanosheets with a weight ratio of 1:4 (graphene:MnO{sub 2}) delivered the highest specific capacitance of 320 F g{sup −1}. Graphene/MnO{sub 2} hybrid nanosheets also exhibited good capacitance retention on 2000 cycles. - Highlights: • Graphene/MnO{sub 2} hybrid nanosheets with different ratios were fabricated. • The specific capacitance is strongly dependent on graphene/MnO{sub 2} ratios. • The graphene/MnO{sub 2} hybrid electrode (1:4) exhibited high specific capacitance. • The electrode retained 84% of the initial specific capacitance after 2000 cycles.

  20. Pearlitic Lamellae Spheroidisation During Austenitization and Subsequent Temperature Hold

    Directory of Open Access Journals (Sweden)

    Hauserova D.

    2017-03-01

    Full Text Available Typical processing routes for bearing steels include a soft annealing stage. The purpose of this procedure is to obtain a microstructure containing globular carbides in ferritic matrix. A newly developed process called ASR (Accelerated Spheroidisation and Refinement cuts the carbide spheroidisation times several fold, producing considerably finer globular carbides than conventional soft annealing. Finer microstructure also leads to more homogeneous and finer structure after final hardening process. The present paper explores process of the accelerated spheroidisation (ASR in steel 100CrMnSi6-4 with initial pearlitic structure. Cementite lamellae morphology was observed in different stages of austenitization. The heat treatment was performed using induction heating in quenching dilatometer. There was analysed influence of austenitization temperature and austenitization time on spheroidisation. Hardness and carbide morphology was observed. Deep etching was used to reveal evolution of cementitic lamellae fragmentation. It is favourable process especially in induction treatment of small parts.

  1. Valence state of Mn in Ca-doped LaMnO3 studied by high-resolution Mn K ß emission spectroscopy

    NARCIS (Netherlands)

    Tyson, T.A.; Qian, Q.; Kao, C.-C.; Rueff, J.-P.; Groot, F.M.F. de; Croft, M.; Cheong, S.-W.; Greenblatt, M.; Subramanian, M.A.

    1999-01-01

    Mn K ß x-ray emission spectra provide a direct method to probe the effective spin state and charge density on the Mn atom and is used in an experimental study of a class of Mn oxides. Specifically, the Mn K ß line positions and detailed spectral shapes depend on the oxidation and the spin state of

  2. Valence state of Mn in Ca-doped LaMnO3 studied by high-resolution Mn K ß emission spectroscopy

    NARCIS (Netherlands)

    Tyson, T.A.; Qian, Q.; Kao, C.-C.; Rueff, J.-P.; Groot, F.M.F. de; Croft, M.; Cheong, S.-W.; Greenblatt, M.; Subramanian, M.A.

    2001-01-01

    Mn K ß x-ray emission spectra provide a direct method to probe the effective spin state and charge density on the Mn atom and is used in an experimental study of a class of Mn oxides. Specifically, the Mn K ß line positions and detailed spectral shapes depend on the oxidation and the spin state of t

  3. Magnetostructural transitions in Mn-rich Heusler Mn–Ni–In melt-spun ribbons with enhanced magnetocaloric effect

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongwei; Feng, Shutong; Ren, Jian [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China); Laboratory for Microstructures, Shanghai University, Shanghai 200072 (China); Zhai, Qijie; Fu, Jianxun [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China); Luo, Zhiping [Department of Chemistry and Physics, Fayetteville State University, Fayetteville, NC 28301 (United States); Zheng, Hongxing, E-mail: hxzheng@shu.edu.cn [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072 (China); Laboratory for Microstructures, Shanghai University, Shanghai 200072 (China)

    2015-10-01

    The magnetostructural transition behavior and magnetocaloric effect of Mn-rich Heusler Mn–Ni–In melt-spun ribbons have been investigated in the present study. Experimental results showed that the martensitic transition temperatures decreased by substituting small amounts of Ni with Mn in Mn{sub 49+x}Ni{sub 42−x}In{sub 9} (x=0,1,2). Within a temperature range from 100 K to 380 K, the Mn{sub 49}Ni{sub 41}In{sub 9} underwent a martensitic transformation from a paramagnetic L2{sub 1}-type cubic austenite to a ferromagnetic modulated fourteen-layered monoclinic (14M) martensite, followed with a ferromagnetic→weak-magnetic transition in martensite upon cooling. While for both Mn{sub 50}Ni{sub 41}In{sub 9} and Mn{sub 51}Ni{sub 40}In{sub 9}, the paramagnetic→ferromagnetic transition in austenite occurred prior to the martensitic transformation upon cooling. Under a magnetic field change of 30 kOe, the maximum magnetic entropy changes of the Mn{sub 50}Ni{sub 41}In{sub 9} melt-spun ribbons were found to be 5.7 J/kg K and −2.3 J/kg K in the vicinity of martensitic transformation and magnetic transition of austenite, respectively. An enhanced total effective refrigeration capacity as high as 184.2 J/kg was obtained in the Mn{sub 50}Ni{sub 41}In{sub 9} melt-spun ribbons. - Highlights: • Mn-rich Heusler Mn–Ni–In melt-spun ribbons were investigated in the present study. • The compositional dependence on the magnetostructural transition behavior was clarified. • An enhanced refrigeration capacity as high as 184.2 J/kg was obtained in Mn{sub 50}Ni{sub 41}In{sub 9}.

  4. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada)

    2015-08-15

    The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientation relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld

  5. Austenitic Nickel- and Manganese-Free Fe-15Cr-1Mo-0.4N-0.3C Steel: Tensile Behavior and Deformation-Induced Processes between 298 K and 503 K (25 °C and 230 °C)

    Science.gov (United States)

    Mola, Javad; Ullrich, Christiane; Kuang, Buxiao; Rahimi, Reza; Huang, Qiuliang; Rafaja, David; Ritzenhoff, Roman

    2017-03-01

    The high-temperature austenite phase of a high-interstitial Mn- and Ni-free stainless steel was stabilized at room temperature by the full dissolution of precipitates after solution annealing at 1523 K (1250 °C). The austenitic steel was subsequently tensile-tested in the temperature range of 298 K to 503 K (25 °C to 230 °C). Tensile elongation progressively enhanced at higher tensile test temperatures and reached 79 pct at 503 K (230 °C). The enhancement at higher temperatures of tensile ductility was attributed to the increased mechanical stability of austenite and the delayed formation of deformation-induced martensite. Microstructural examinations after tensile deformation at 433 K (160 °C) and 503 K (230 °C) revealed the presence of a high density of planar glide features, most noticeably deformation twins. Furthermore, the deformation twin to deformation-induced martensite transformation was observed at these temperatures. The results confirm that the high tensile ductility of conventional Fe -Cr-Ni and Fe-Cr-Ni-Mn austenitic stainless steels may be similarly reproduced in Ni- and Mn-free high-interstitial stainless steels solution annealed at sufficiently high temperatures. The tensile ductility of the alloy was found to deteriorate with decarburization and denitriding processes during heat treatment which contributed to the formation of martensite in an outermost rim of tensile specimens.

  6. Austenitic Nickel- and Manganese-Free Fe-15Cr-1Mo-0.4N-0.3C Steel: Tensile Behavior and Deformation-Induced Processes between 298 K and 503 K (25 °C and 230 °C)

    Science.gov (United States)

    Mola, Javad; Ullrich, Christiane; Kuang, Buxiao; Rahimi, Reza; Huang, Qiuliang; Rafaja, David; Ritzenhoff, Roman

    2017-01-01

    The high-temperature austenite phase of a high-interstitial Mn- and Ni-free stainless steel was stabilized at room temperature by the full dissolution of precipitates after solution annealing at 1523 K (1250 °C). The austenitic steel was subsequently tensile-tested in the temperature range of 298 K to 503 K (25 °C to 230 °C). Tensile elongation progressively enhanced at higher tensile test temperatures and reached 79 pct at 503 K (230 °C). The enhancement at higher temperatures of tensile ductility was attributed to the increased mechanical stability of austenite and the delayed formation of deformation-induced martensite. Microstructural examinations after tensile deformation at 433 K (160 °C) and 503 K (230 °C) revealed the presence of a high density of planar glide features, most noticeably deformation twins. Furthermore, the deformation twin to deformation-induced martensite transformation was observed at these temperatures. The results confirm that the high tensile ductility of conventional Fe-Cr-Ni and Fe-Cr-Ni-Mn austenitic stainless steels may be similarly reproduced in Ni- and Mn-free high-interstitial stainless steels solution annealed at sufficiently high temperatures. The tensile ductility of the alloy was found to deteriorate with decarburization and denitriding processes during heat treatment which contributed to the formation of martensite in an outermost rim of tensile specimens.

  7. Effect of Primary Factor on Cavitation Resistance of Some Austenitic Metals

    Institute of Scientific and Technical Information of China (English)

    WANG Zai-you; ZHU Jin-hua

    2003-01-01

    The cavitation resistance of six kinds of austenitic metals was investigated using a rotating disc rig. The research results show that cavitation resistance of the austenitic metals is obviously raised due to cavitation-induced martensite and greatly influenced by mechanism of martensitic transformation. The cavitation resistance of two stress-induced martensite Fe-Mn-Si-Cr shape memory alloys is much better than that of three strain-induced martensite austenitic stainless steels. The Fe-Mn-Si-Cr shape memory alloys possess excellent cavitation resistance mainly because of their excellent elasticity in local small-zone. The first principal factor for cavitation resistance of metastable austenitic metals is unloaded rebounding depth, and the second one is energy dissipation resulted from cavitation-induced martensite.

  8. Novel 1.5 GPa-strength with 50%-ductility by transformation-induced plasticity of non-recrystallized austenite in duplex steels.

    Science.gov (United States)

    Sohn, Seok Su; Song, Hyejin; Jo, Min Chul; Song, Taejin; Kim, Hyoung Seop; Lee, Sunghak

    2017-04-28

    Needs for steel designs of ultra-high strength and excellent ductility have been an important issue in worldwide automotive industries to achieve energy conservation, improvement of safety, and crashworthiness qualities. Because of various drawbacks in existing 1.5-GPa-grade steels, new development of formable cold-rolled ultra-high-strength steels is essentially needed. Here we show a plausible method to achieve ultra-high strengths of 1.0~1.5 GPa together with excellent ductility above 50% by actively utilizing non-recrystallization region and TRansformation-Induced Plasticity (TRIP) mechanism in a cold-rolled and annealed Fe-Mn-Al-C-based steel. We adopt a duplex microstructure composed of austenite and ultra-fine ferrite in order to overcome low-yield-strength characteristics of austenite. Persistent elongation up to 50% as well as ultra-high yield strength over 1.4 GPa are attributed to well-balanced mechanical stability of non-crystallized austenite with critical strain for TRIP. Our results demonstrate how the non-recrystallized austenite can be a metamorphosis in 1.5-GPa-grade steel sheet design.

  9. Grotrian diagrams for highly ionized Manganese, Mn VI through Mn XXV

    OpenAIRE

    白井 稔三; Sugar, J.; Wiese, W. L.

    1997-01-01

    高電離マンガン、Mn VI-Mn XXVの1,535本のスペクトル線をエネルギー準位と遷移の特徴を視覚化するグロトリアン図にまとめた。Bashkin and Stoner[North-Holland,Amsterdam,1975]による通常のグロトリアン図の表示法では、それぞれの遷移を表す線の密度が高くなり過ぎ、全ての遷移を表示できないことがしばしばある。我々のグロトンアン図でも遷移を線で表すが、しかし、遷移の上位準位を必要なだけ繰り返す方法に変更した。その結果、遷移線の高密度化が回避でき、多重項等全ての遷移を表すことができた。...

  10. On the synthesis and microstructure analysis of high performance MnBi

    Science.gov (United States)

    Chen, Yu-Chun; Sawatzki, Simon; Ener, Semih; Sepehri-Amin, Hossein; Leineweber, Andreas; Gregori, Giuliano; Qu, Fei; Muralidhar, Shreyas; Ohkubo, Tadakatsu; Hono, Kazuhiro; Gutfleisch, Oliver; Kronmüller, Helmut; Schütz, Gisela; Goering, Eberhard

    2016-12-01

    Highly anisotropic MnBi powder with over 90 wt% low-temperature phase can be prepared using conventional arc-melting and 2 hour-low energy ball milling (BM) followed by magnetic separation. After proper alignment, the purified Mn55Bi45(Mn45Bi55) powder show remarkable magnetic properties: mass remanence of 71(65) Am2/kg and coercivity of 1.23(1.18) T at 300 K. The nominal maximum energy product of 120 kJ/m3 is achieved in the purified 2h-BM Mn55Bi45 powder, close to theoretical value of 140.8 kJ/m3. The Mn55Bi45(Mn45Bi55) bulk magnets show the highest volume remanence of 0.68(0.57) T at 300 K, while they were consolidated at 573(523) K by a pressure of 200 MPa for 5 minutes using hot-compaction method. In addition to the observed grain size, the coercivity of the hot-compacted samples at 300 K was found to be strongly related to the amount of metallic Mn and Bi residue at the grain-boundary. Our study proves that the magnetic properties of the Mn45Bi55 bulk magnets are stable up to 500 K, and the nominal (BH)max values are still above 40 kJ/m3 at 500 K showing the potential ability for high-temperature applications.

  11. Training of the Ni-Mn-Fe-Ga ferromagnetic shape-memory alloys due cycling in high magnetic field

    Science.gov (United States)

    Cherechukin, A. A.; Khovailo, V. V.; Koposov, R. V.; Krasnoperov, E. P.; Takagi, T.; Tani, J.

    2003-03-01

    The temperature and magnetic field dependences of Ni-Mn-Ga polycrystals deformation are investigated. Ingots were prepared by arc-melting in argon atmosphere and further annealing. A training procedure (cycling across the martensitic transition point) for the two-way shape-memory effect was performed with Ni 2.16Fe 0.04Mn 0.80Ga samples. Changes in sample deformations were noticed with changing the magnetic field at constant temperature. The first cycle deformation increment as compared with the initial value (in austenitic state, at zero field) in the course of the martensitic transition was 0.29%, and 0.41% and 0.48% for the second and third cycles, respectively.

  12. Training of the Ni-Mn-Fe-Ga ferromagnetic shape-memory alloys due cycling in high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Cherechukin, A.A. E-mail: cherechukin@mail.ru; Khovailo, V.V.; Koposov, R.V.; Krasnoperov, E.P.; Takagi, T.; Tani, J

    2003-03-01

    The temperature and magnetic field dependences of Ni-Mn-Ga polycrystals deformation are investigated. Ingots were prepared by arc-melting in argon atmosphere and further annealing. A training procedure (cycling across the martensitic transition point) for the two-way shape-memory effect was performed with Ni{sub 2.16}Fe{sub 0.04}Mn{sub 0.80}Ga samples. Changes in sample deformations were noticed with changing the magnetic field at constant temperature. The first cycle deformation increment as compared with the initial value (in austenitic state, at zero field) in the course of the martensitic transition was 0.29%, and 0.41% and 0.48% for the second and third cycles, respectively.

  13. Formation of Austenite During Intercritical Annealing of Dual-Phase Steels

    Science.gov (United States)

    Speich, G. R.; Demarest, V. A.; Miller, R. L.

    1981-08-01

    The formation of austenite during intercritical annealing at temperatures between 740 and 900 °C was studied in a series of 1.5 pct manganese steels containing 0.06 to 0.20 pct carbon and with a ferrite-pearlite starting microstructure, typical of most dual-phase steels. Austenite formation was separated into three stages: (1) very rapid growth of austenite into pearlite until pearlite dissolution is complete; (2) slower growth of austenite into ferrite at a rate that is controlled by carbon diffusion in austenite at high temperatures (~85O °C), and by manganese diffusion in ferrite (or along grain boundaries) at low temperatures (~750 °C); and (3) very slow final equilibration of ferrite and austenite at a rate that is controlled by manganese diffusion in austenite. Diffusion models for the various steps were analyzed and compared with experimental results.

  14. The Varying Effects of Uniaxial Compressive Stress on the Bainitic Transformation under Different Austenitization Temperatures

    Directory of Open Access Journals (Sweden)

    Mingxing Zhou

    2016-05-01

    Full Text Available In this study, thermal simulation experiments under different austenitization temperatures and different stress states were conducted. High-temperature laser scanning confocal microscopy (LSCM, thermal dilatometry, and scanning electron microscope (SEM were used to quantitatively investigate the effects of the uniaxial compressive stress on bainitic transformation at 330 °C following different austenitization temperatures. The transformation plasticity was also analyzed. It was found that the promotion degree of stress on bainitic transformation increases with the austenitization temperature due to larger prior austenite grain size as well as stronger promoting effect of mechanical driving force on selected variant growth at higher austenitization temperatures. The grain size and the yield strength of prior austenite are other important factors which influence the promotion degree of stress on bainitic transformation, besides the mechanical driving force provided by the stress. Moreover, the transformation plasticity increases with the austenitization temperature.

  15. Isotropic, high coercive field in melt-spun tetragonal Heusler Mn3Ge

    Directory of Open Access Journals (Sweden)

    Adel Kalache

    2016-08-01

    Full Text Available Nanostructured Mn3Ge ribbons with a composition ranging from 77 to 74 at.% Mn were prepared using induction melting, melt-spinning, and subsequent heat treatment. The hard magnetic properties of the ribbons originate from the highly anisotropic tetragonal D022 structure of Mn3Ge. Depending on the composition and the amount of ferrimagnetic Mn5Ge2 as a secondary phase, a coercivity of up to μ0HC = 2.62 T was obtained for the Mn3Ge ribbons. Microstructure investigations by transmission electron microscopy confirmed the formation of the secondary phase. All samples show isotropic coercive fields, i.e., independent of the direction of the applied magnetic field in contrast to already known epitaxial thin films. The Curie temperature was found to be higher than 800 K, which is the temperature of the phase transition from the tetragonal D022 structure to the hexagonal D019 structure.

  16. Isotropic, high coercive field in melt-spun tetragonal Heusler Mn3Ge

    Science.gov (United States)

    Kalache, Adel; Kreiner, Guido; Ouardi, Siham; Selle, Susanne; Patzig, Christian; Höche, Thomas; Felser, Claudia

    2016-08-01

    Nanostructured Mn3Ge ribbons with a composition ranging from 77 to 74 at.% Mn were prepared using induction melting, melt-spinning, and subsequent heat treatment. The hard magnetic properties of the ribbons originate from the highly anisotropic tetragonal D022 structure of Mn3Ge. Depending on the composition and the amount of ferrimagnetic Mn5Ge2 as a secondary phase, a coercivity of up to μ0HC = 2.62 T was obtained for the Mn3Ge ribbons. Microstructure investigations by transmission electron microscopy confirmed the formation of the secondary phase. All samples show isotropic coercive fields, i.e., independent of the direction of the applied magnetic field in contrast to already known epitaxial thin films. The Curie temperature was found to be higher than 800 K, which is the temperature of the phase transition from the tetragonal D022 structure to the hexagonal D019 structure.

  17. Microstructural Features of Austenite Formation in C35 and C45 alloys

    OpenAIRE

    2007-01-01

    The microstructural evolution during continuous heating experiments has been studied for two C-Mn steels with carbon contents in the range 0.35 to 0.45 wt pct using optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). It is shown that the formation of the austenitic phase is possible in pearlite as well as in ferrite regions. Thus, a considerable overlap in time of ferrite-to-austenite and pearlite-to-austenite transformations is likely to occur. An...

  18. Stacking faults and microstrains in strain-hardened surface of nitrogen-alloyed austenitic steel

    Science.gov (United States)

    Narkevich, N.; Syrtanov, M.; Mironov, Yu.; Surikova, N.

    2016-11-01

    X-ray diffractometry has been applied to examine the effect of ultrasonic forging and frictional treatment on structural parameters and oriented microstrains responsible for the generation of residual microstresses in austenitic steel Fe-17Cr-19Mn-0.52N. The maximum stacking fault density α = 0.067 is observed in the steel surface layer of thickness 5 µm after frictional treatment. A decrease in the austenite lattice parameter after deformation treatment is associated with the change in the sign (direction) of residual stresses. Surface deformation treatment induces compression of the austenite lattice along the normal to the surface.

  19. InSb:Mn - A high temperature ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Laehderanta, E.; Lashkul, A.V. [Lappeenranta University of Technology (Finland); Kochura, A.V. [Lappeenranta University of Technology (Finland); South-West State University, Kursk (Russian Federation); Lisunov, K.G. [Lappeenranta University of Technology (Finland); Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev (Moldova, Republic of); Aronzon, B.A. [Lappeenranta University of Technology (Finland); RRC ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Shakhov, M.A. [Lappeenranta University of Technology (Finland); A.F. Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation)

    2014-05-15

    Diluted magnetic semiconductor InSb:Mn exhibits a ferromagnetic behavior up to T ∝ 600 K due to presence of nanosize MnSb precipitates [Kochura et al., J. Appl. Phys. 113, 083905 (2013)]. Transport properties of InSb:Mn, including the resistivity, the magnetoresistance (MR), and the Hall effect, are investigated between T ∝ 1.6 and 300 K in magnetic fields B up to 15 T. The resistivity, ρ(T), displays an upturn with lowering the temperature below T ∝ 10-20 K attributable to the Kondo effect, where the universal Kondo behavior is observed. The Hall resistivity, ρ{sub H}, demonstrates a nonlinear dependence on B up to T ∝ 300 K, suggesting an anomalous contribution due to the effect of the MnSb nanoprecipitates. The relative MR, Δρ(B)/ρ(0), is positive (pMR) above T ∝ 10 K and transforms into a negative one (nMR) with lowering temperature. The Hall effect and pMR are interpreted simultaneously with the two-band model, addressed to presence of the two types of holes with quite different concentrations and mobilities. The dependences of nMR on B and T follow those of the Khosla-Fischer model, taking into account damping of the spin-dependent scattering of charge carriers in magnetic field. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Texture and microstructure of the austenite in multiphased steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Regle, H. [ARCELOR Group, CMC-IRSID, Maizieres-les-Metz (France); Maruyama, N.; Yoshinaga, N. [Nippon Steel Corp. - Technical Development Bureau, Futtsu (Japan)

    2004-07-01

    In this paper we present results obtained in collaboration between NSC and Arcelor on the austenite of a multiphased steel and on a 70%Ni-30Fe alloy. The work concerns the formation of the crystallographic textures during the recrystallisation of austenite, since these textures have a strong influence, after the phase transformation, on the forming properties of the sheets. The microstructure and the textures of the austenite and the FeNi alloy were measured with X-Ray diffraction techniques and with EBSD on a high resolution FEG-SEM. (orig.)

  1. Measurement and tailoring of residual stress in expanded austenite on austenitic stainless steel

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Winther, Grethe

    2017-01-01

    Expanded austenite on stainless steel with a high interstitial nitrogen content is characterized by elasto-plastic accommodation of the large composition-induced lattice expansion leading to huge compressive residual stress. The elasto-plastic accommodation as well as the (steep) concentration...... profile has implications for the measurement strategy to determine lattice strains and associated residual stresses with X-ray diffraction. Lattice strain measurements were performed on nitrided as well as subsequently de-nitrided expanded austenite on AISI 316L stainless steel, for various grazing...... stresses in expanded austenite can be tailored by de-nitriding after nitriding, such that a condition of virtually zero stress at the surface is obtained....

  2. On the crystal structure of Cr2N precipitates in high-nitrogen austenitic stainless steel. III. Neutron diffraction study on the ordered Cr2N superstructure.

    Science.gov (United States)

    Lee, Tae-Ho; Kim, Sung-Joon; Shin, Eunjoo; Takaki, Setsuo

    2006-12-01

    The ordered structure of Cr(2)N precipitates in high-nitrogen austenitic steel was investigated utilizing high-resolution neutron powder diffractometry (HRPD). On the basis of the Rietveld refinement of neutron diffraction patterns, the ordered Cr2N superstructure was confirmed to be trigonal (space group P31m), with lattice parameters a=4.800 (4) and c=4.472 (5) A, as suggested in previous transmission electron microscopy studies [Lee, Oh, Han, Lee, Kim & Takaki (2005). Acta Cryst. B61, 137-144; Lee, Kim & Takaki (2006). Acta Cryst. B62, 190-196]. The occupancies of the N atoms in four crystallographic sites [1(a), 1(b), 2(d) and 2(c) Wyckoff sites] were determined to be 1.00 (5), 0.0, 0.74 (9) and 0.12 (3), respectively, reflecting a partial disordering of N atoms along the c axis. The position of the metal atom was specified to be x=0.346 (8) and z=0.244 (6), corresponding to a deviation from the ideal position (x=0.333 and z=0.250). This deviation caused the ((1/3 1/3)(0))-type superlattice reflection to appear. A comparison between the ideal and measured crystal structures of Cr2N was performed using a computer simulation of selected-area diffraction patterns.

  3. Effect of microstructure on fatigue behavior of advanced high strength steels produced by quenching and partitioning and the role of retained austenite

    Energy Technology Data Exchange (ETDEWEB)

    Diego-Calderón, I. de, E-mail: irenedediego.calderon@imdea.org [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Rodriguez-Calvillo, P. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Lara, A. [Fundació CTM Centre Tecnològic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Molina-Aldareguia, J.M. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain); Petrov, R.H. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Department of Materials Science and Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); De Knijf, D. [Department of Materials Science and Engineering, Ghent University, Technologiepark 903, B-9052 Zwijnaarde (Ghent) (Belgium); Sabirov, I. [IMDEA Materials Institute, Calle Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2015-08-12

    Despite the significant body of research on mechanical properties of quenched and partitioned (Q&P) steels, their fatigue behavior has not been investigated. This work focuses on the effect of microstructure on high cycle fatigue of Q&P steels and microstructural evolution during cyclic loading. It is demonstrated that increased content of retained austenite (RA) improves fatigue limit of Q&P steels that is related to delay of crack propagation due to austenite–martensite phase transformation. Increasing stress amplitude promotes austenite–martensite phase transformation during cycling loading. It is shown that size and crystallographic orientation of RA are the main factors determining its stability, whereas its shape and spatial distribution do not seem to affect it significantly. Fatigue crack initiation during fatigue testing with high stress amplitudes occurs by intergranular cracking, whereas transgranular cracking controls fatigue crack initiation during cycling loading with lower stress amplitudes. Transgranular crack propagation dominates in the second stage of fatigue at all stress amplitudes. The final stage of fatigue is also not affected by the stress amplitude. It is suggested that fatigue life of Q&P steels can be enhanced via improvement of strength of grain/interphase boundaries.

  4. High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

    Science.gov (United States)

    Galanakis, I.

    2015-03-01

    Half-metallic Co2MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co2MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co2MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices.

  5. Stability of Retained Austenite in High-Al, Low-Si TRIP-Assisted Steels Processed via Continuous Galvanizing Heat Treatments

    Science.gov (United States)

    McDermid, J. R.; Zurob, H. S.; Bian, Y.

    2011-12-01

    Two galvanizable high-Al, low-Si transformation-induced plasticity (TRIP)-assisted steels were subjected to isothermal bainitic transformation (IBT) temperatures compatible with the continuous galvanizing (CGL) process and the kinetics of the retained austenite (RA) to martensite transformation during room temperature deformation studied as a function of heat treatment parameters. It was determined that there was a direct relationship between the rate of strain-induced transformation and optimal mechanical properties, with more gradual transformation rates being favored. The RA to martensite transformation kinetics were successfully modeled using two methodologies: (1) the strain-based model of Olsen and Cohen and (2) a simple relationship with the normalized flow stress, ( {{{σ_{{flow}} - σ_{YS} }/{σ_{YS }}}} ) . For the strain-based model, it was determined that the model parameters were a strong function of strain and alloy thermal processing history and a weak function of alloy chemistry. It was verified that the strain-based model in the present work agrees well with those derived by previous workers using TRIP-assisted steels of similar composition. It was further determined that the RA to martensite transformation kinetics for all alloys and heat treatments could be described using a simple model vs the normalized flow stress, indicating that the RA to martensite transformation is stress-induced rather than strain-induced for temperatures above the Ms^{σ }.

  6. Interaction between recrystallization and strain-induced precipitation in a high Nb- and N-bearing austenitic stainless steel: Influence of the interpass time

    Energy Technology Data Exchange (ETDEWEB)

    Silva, M.B.R., E-mail: marianabdrs@gmail.com [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil); Gallego, J. [Department of Mechanical Engineering, UNESP, Avenida Brasil, 56, 15385-000 Ilha Solteira, SP (Brazil); Cabrera, J.M. [Department of Materials Science and Metallurgical Engineering, Polytechnic University of Catalunya, Avenida Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Balancin, O. [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil); Jorge, A.M., E-mail: moreira@dema.ufscar.br [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil)

    2015-06-18

    In this work, we studied the influence of the interpass time (20 and 5 s) on the interaction between recrystallization and strain-induced precipitation occurring during multiple passes' deformations under continuous cooling conditions in a high niobium- and nitrogen-bearing austenitic stainless steel (ISO 5832-9). The correlation between microstructure evolution and hot mechanical properties was performed by physical simulation using hot torsion tests. The microstructure evolution was analyzed by optical microscopy, transmission electron microscopy and electron back scattered diffraction (EBSD). This technique indicated that dynamic recrystallization occurred at the first passes promoting an excellent grain refinement. On the other hand, shorter interpass time (5 s) allowed higher volume fraction of smallest precipitates than larger interpass time (20 s). After soaking, only TiNbN precipitates were found, whereas, Z-phase (CrNbN) and NbN were formed during thermomechanical processing. Particles with sizes between 20 and 50 nm were effective to pin grain boundaries and dislocations.

  7. α MnMoO₄/graphene hybrid composite: high energy density supercapacitor electrode material.

    Science.gov (United States)

    Ghosh, Debasis; Giri, Soumen; Moniruzzaman, Md; Basu, Tanya; Mandal, Manas; Das, Chapal Kumar

    2014-07-28

    A unique and cost effective hydrothermal procedure has been carried out for the synthesis of hexahedron shaped α MnMoO4 and its hybrid composite with graphene using three different weight percentages of graphene. Characterization techniques, such as XRD, Raman and FTIR analysis, established the phase and formation of the composite. The electrochemical characterization of the pseudocapacitive MnMoO4 and the MnMoO4/graphene composites in 1 M Na2SO4 displayed highest specific capacitances of 234 F g(-1) and 364 F g(-1), respectively at a current density of 2 A g(-1). Unlike many other pseudocapacitive electrode materials our prepared materials responded in a wide range of working potentials of (-)1 V to (+)1 V, which indeed resulted in a high energy density without substantial loss of power density. The highest energy densities of 130 Wh kg(-1) and 202.2 Wh kg(-1) were achieved, respectively for the MnMoO4 and the MnMoO4/graphene composite at a constant power delivery rate of 2000 W kg(-1). The synergistic effect of the graphene with the pseudocapacitive MnMoO4 caused an increased cycle stability of 88% specific capacitance retention after 1000 consecutive charge discharge cycles at 8 A g(-1) constant current density, which was higher than the virgin MnMoO4 with 84% specific capacitance retention.

  8. Mn-Ce oxide as a high-capacity adsorbent for fluoride removal from water.

    Science.gov (United States)

    Deng, Shubo; Liu, Han; Zhou, Wei; Huang, Jun; Yu, Gang

    2011-02-28

    A novel Mn-Ce oxide adsorbent with high sorption capacity for fluoride was prepared via co-precipitation method in this study, and the granular adsorbent was successfully prepared by calcining the mixture of the Mn-Ce powder and pseudo-boehmite. High-resolution transmission electron microscopy (TEM) image showed that the Mn-Ce adsorbent consisted of about 4.5 nm crystals, and X-ray diffraction (XRD) analysis indicated the formation of solid solution by Mn species entering CeO(2) lattices. The surface hydroxyl group density on the Mn-Ce adsorbent was determined to be as high as 15.3 mmol g(-1), mainly responsible for its high sorption capacity for fluoride. Sorption isotherms showed that the sorption capacities of fluoride on the powdered and granular adsorbent were 79.5 and 45.5 mg g(-1) respectively at the equilibrium fluoride concentration of 1 mg L(-1), much higher than all reported adsorbents. Additionally, the adsorption was fast within the initial 1 h. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that the hydroxyl groups on the adsorbent surface were involved in the sorption of fluoride. Both anion exchange and electrostatic interaction were involved in the sorption of fluoride on the Mn-Ce oxide adsorbent. Copyright © 2010 Elsevier B.V. All rights reserved.

  9. Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

    Science.gov (United States)

    Hidalgo, Javier; Santofimia, Maria Jesus

    2016-11-01

    Current trends in steels are focusing on refined martensitic microstructures to obtain high strength and toughness. An interesting manner to reduce the size of martensitic substructure is by reducing the size of the prior austenite grain (PAG). This work analyzes the effect of PAGS refinement by thermal cycling on different microstructural features of as-quenched lath martensite in a 0.3C-1.6Si-3.5Mn (wt pct) steel. The application of thermal cycling is found to lead to a refinement of the martensitic microstructures and to an increase of the density of high misorientation angle boundaries after quenching; these are commonly discussed to be key structural parameters affecting strength. Moreover, results show that as the PAGS is reduced, the volume fraction of retained austenite increases, carbides are refined and the concentration of carbon in solid solution as well as the dislocation density in martensite increase. All these microstructural modifications are related with the manner in which martensite forms from different prior austenite conditions, influenced by the PAGS.

  10. High-Resolution Mn EXAFS of the Oxygen-Evolving Complex inPhotosystem II: Structural Implications for the Mn4Ca Cluster

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Junko; Pushkar, Yulia; Glatzel, Pieter; Lewis, Azul; Sauer,Kenneth; Messinger, Johannes; Bergmann, Uwe; Yachandra, Vittal

    2005-09-06

    The biological generation of oxygen by the oxygen-evolving complex in photosystem II (PS II) is one of natures most important reactions. The recent X-ray crystal structures, while limited by resolutions of 3.2 to 3.5 A, have located the electron density associated with the Mn4Ca complex within the multi-protein PS II complex. Detailed structures critically depend on input from spectroscopic techniques such as EXAFS and EPR/ENDOR, as the XRD resolution does not allow for accurate determination of the position of Mn/Ca or the bridging and terminal ligand atoms. The number and distances of Mn-Mn/Ca/ligand interactions determined from EXAFS provide important constraints for the structure of the Mn cluster. Here we present data from a high-resolution EXAFS method using a novel multi-crystal monochromator that show three short Mn-Mn distances between 2.7 and 2.8 A and hence the presence of three di-mu-oxobridged units in the Mn4Ca cluster. This result imposes clear limitations on the proposed structures based on spectroscopic and diffraction data and provides input for refining such structures.

  11. Cladding of High Mn Steel on Low C Steel by Explosive Welding

    OpenAIRE

    ACARER, Mustafa

    2014-01-01

    High Mn steel containing about 16% Mn was cladded to a low C steel by explosive welding. The experimental results showed that the bonding interface has a wavy morphology; the welding interface has the characteristics of both sharp transition and local melted zones between 2 metals. Hardness increased near the welding interface due to excess plastic deformation in the explosion area and phase transformation from g (f.c.c.) to a (b.c.c.).

  12. Effects of applied stress and plastic strain on. gamma. r reversible. epsilon. martensitic transformation in high Mn alloy polyctystals. Ko Mn tetsu gokin takessho ni okeru. gamma. r reversible. epsilon. martensite hentai ni oyobosu gairyoku to hizumi no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Tomota, Y.; Piao, M.; Hasunuma, T.; Kimura, Y. (Ibaraki Univ., Ibaraki (Japan))

    1990-06-20

    The influences of applied stress and plastic strain on a transformation austenite ({gamma}) to hcp martensite ({epsilon}) were studied on Fe-16wt%Mn, Fe-24wt%Mn, and Fe-24%Mn-6%Si alloy, and a transformation mechanism and a shape memory phenomenon were more deeply examined. As the quenching structure of three kinds of the alloys consists of two phases of {gamma} and {epsilon}, the specimens were cooled after heated above the A {sub f} temperature to keep {gamma} single phase, and then the tensile tests were carried out. Positive temperature dependence was found under the 0.2% proof stress due to stress-induced {gamma}{yields} {epsilon} transformation in each of Fe-Mn alloy and Fe-24%Mn-6%Si alloy. When {gamma} phase of Fe-24%Mn alloy stabilized due to cyclic transformation was stretched at room temperature, the yield stress was remarkably lowered by the stress-induced {gamma}{r arrow}{epsilon} transformation. When the specimens were stretched at 523K under stress which was larger than the yield strength and then cooled, the elongation along the applied stress direction due to martensitic tranformation was recognized. A shape recovery was remarkable in Si content alloys. 22 refs., 5 figs.

  13. High temperature magnetism and microstructure of ferromagnetic alloy Si1-x Mn x

    Science.gov (United States)

    Aronzon, B. A.; Davydov, A. B.; Vasiliev, A. L.; Perov, N. S.; Novodvorsky, O. A.; Parshina, L. S.; Presniakov, M. Yu; Lahderanta, E.

    2017-02-01

    The results of a detailed study of magnetic properties and of the microstructure of SiMn films with a small deviation from stoichiometry are presented. The aim was to reveal the origin of the high temperature ferromagnetic ordering in such compounds. Unlike SiMn single crystals with the Curie temperature ~30 K, considered Si1-x Mn x compounds with x  =  0.5  +Δx and Δx in the range of 0.01-0.02 demonstrate a ferromagnetic state above room temperature. Such a ferromagnetic state can be explained by the existence of highly defective B20 SiMn nanocrystallites. These defects are Si vacancies, which are suggested to possess magnetic moments. The nanocrystallites interact with each other through paramagnons (magnetic fluctuations) inside a weakly magnetic manganese silicide matrix giving rise to a long range ferromagnetic percolation cluster. The studied structures with a higher value of Δx  ≈  0.05 contained three different magnetic phases: (a)—the low temperature ferromagnetic phase related to SiMn; (b)—the above mentioned high temperature phase with Curie temperature in the range of 200-300 K depending on the growth history and (c)—superparamagnetic phase formed by separated noninteracting SiMn nanocrystallites.

  14. The Impact of Retained Austenite Characteristics on the Two-Body Abrasive Wear Behavior of Ultrahigh Strength Bainitic Steels

    Science.gov (United States)

    Narayanaswamy, Balaji; Hodgson, Peter; Timokhina, Ilana; Beladi, Hossein

    2016-10-01

    In the current study, a high-carbon, high-alloy steel (0.79 pct C, 1.5 pct Si, 1.98 pct Mn, 0.98 pct Cr, 0.24 pct Mo, 1.06 pct Al, and 1.58 pct Co in wt pct) was subjected to an isothermal bainitic transformation at a temperature range of 473 K to 623 K (200 °C to 350 °C), resulting in different fully bainitic microstructures consisting of bainitic ferrite and retained austenite. With a decrease in the transformation temperature, the microstructure was significantly refined from ~300 nm at 623 K (350 °C) to less than 60 nm at 473 K (200 °C), forming nanostructured bainitic microstructure. In addition, the morphology of retained austenite was progressively altered from film + blocky to an exclusive film morphology with a decrease in the temperature. This resulted in an enhanced wear resistance in nanobainitic microstructures formed at low transformation temperature, e.g., 473 K (200 °C). Meanwhile, it gradually deteriorated with an increase in the phase transformation temperature. This was mostly attributed to the retained austenite characteristics ( i.e., thin film vs blocky), which significantly altered their mechanical stability. The presence of blocky retained austenite at high transformation temperature, e.g., 623 K (350 °C) resulted in an early onset of TRIPing phenomenon during abrasion. This led to the formation of coarse martensite with irregular morphology, which is more vulnerable to crack initiation and propagation than that of martensite formed from the thin film austenite, e.g., 473 K (200 °C). This resulted in a pronounced material loss for the fully bainitic microstructures transformed at high temperature, e.g., 623 K (350 °C), leading to distinct sub-surface layer and friction coefficient curve characteristics. A comparison of the abrasive behavior of the fully bainitic microstructure formed at 623 K (350 °C) and fully pearlitic microstructure demonstrated a detrimental effect of blocky retained austenite with low mechanical stability on

  15. High spin-polarization in ultrathin Co{sub 2}MnSi/CoPd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Galanakis, I., E-mail: galanakis@upatras.gr

    2015-03-01

    Half-metallic Co{sub 2}MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co{sub 2}MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co{sub 2}MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices. - Highlights: • Ab-initio study of ultrathin Co{sub 2}MnSi/CoPd multilayers. • Large values of spin-polarization at the Fermi are retained. • Route for novel spintronic/magnetoelectronic devices.

  16. High Curie temperature Mn5Ge3 thin films produced by non-diffusive reaction

    Science.gov (United States)

    Assaf, E.; Portavoce, A.; Hoummada, K.; Bertoglio, M.; Bertaina, S.

    2017-02-01

    Polycrystalline Mn5Ge3 thin films were produced on SiO2 using magnetron sputtering and reactive diffusion (RD) or non-diffusive reaction (NDR). In situ X-ray diffraction and atomic force microscopy were used to determine the layer structures, and magnetic force microscopy, superconducting quantum interference device, and ferromagnetic resonance were used to determine their magnetic properties. RD-mediated layers exhibit similar magnetic properties as molecular beam epitaxy-grown monocrystalline Mn5Ge3 thin films, while NDR-mediated layers show magnetic properties similar to monocrystalline C-doped Mn5Ge3Cx thin films with 0.1 ≤ x ≤ 0.2. NDR appears as a complementary metal oxide semi-conductor-compatible efficient method to produce good magnetic quality high-Curie temperature Mn5Ge3 thin films.

  17. Structure transition of multiferroic hexagonal TmMnO3 compound under high pressure

    Science.gov (United States)

    Wang, L. J.; Feng, S. M.; Zhu, J. L.; Liu, Q. Q.; Li, Y. C.; Li, X. D.; Liu, J.; Jin, C. Q.

    2010-06-01

    The high-pressure-induced structure transition in multiferroic hexagonal TmMnO3 (h-TmMnO3) has been investigated using an in situ angle-dispersive synchrotron X-ray diffraction technique in a diamond anvil cell. The experimental results show that the phase transition from ambient hexagonal to orthorhombic structure with space group Pbnm begins around 10.2 GPa. The Rietveld refinement method was used to determine the lattice parameters and lattice compressibility of the h-TmMnO3 compound from 0.8 to 28.6 GPa. The pressure evolution of average bond distances and bond angles between the Mn and O atoms in the ab-plane was obtained. The magnetic properties under different pressures as well as their effect on multiferroic properties are discussed using extrapolations from the empirical relation of magnetic order versus rare-earth ionic radius.

  18. Delayed Fracture Resistance and Mechanical Properties of 30MnSi High Strength Steel

    Institute of Scientific and Technical Information of China (English)

    XIAO Gui-zhi; DI Hong-shuang

    2009-01-01

    To investigate the effect of heat treatment on mechanical properties and delayed fracture resistance of high strength steel,30MnSi prestressed concrete (PC) steel bars are quenched and tempered.Tensile results show that,after 950 ℃ quenching and about 430 ℃ tempering,30MnSi PC steel bars have superior mechanical properties and delayed fracture resistance.Microstructursl observation shows that 30MnSi steel bar is mainly composed of fine tempered sorbite (troostite) with carbide distributed along the lath martensite boundaries.It can be concluded that thermal refining is an effective way to improve mechanical properties and delayed fracture resistance of 30MnSi PC steel bar.

  19. Surface structure and properties of ion-nitrided austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hannula, S.P.; Nenonen, P. (Metallurgy Lab., Technical Research Centre, Espoo (Finland)); Hirvonen, J.P. (Dept. of Physics, Univ. of Helsinki (Finland))

    1989-12-10

    The near surface structure and nitrogen concentration of the low-temperature low-pressure ion-nitrided stainless steels (SS) was studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), nuclear resonance broadening (NRB) and microhardness techniques. The surface nitrogen content as determined by NRB was found to increase with nitriding time such that at long nitriding times the surface nitrogen concentration was higher than for any equilibrium nitride in the Fe-N system. Nitrogen contents were slightly higher for type-304 than for type-316 stainless steels. Simultaneously with increasing surface nitrogen content, a strong shift and broadening of X-ray diffraction peaks occured. In the surface of the nitrided layer expanded austenite as well as {epsilon}-phase analogous to {epsilon}-martensite is formed. At long nitriding times (high nitrogen surface contents) the structure of the surface corresponds to cubic MN{sub 1-x} nitride. At intermediate nitriding times (and nitrogen contents) possibly some {epsilon}'-nitride is also formed. TEM study of the surface layer showed that after long nitriding times the expanded austenite with occasional weak primitive lattice reflections was the dominating phase and the hexagonal {epsilon}-phase was habited as thin platelets on the (111) planes of the nitrogen supersaturated austenite. The hardness of the compound layer can be as high as 25 GPa. The high hardness is suggested to result from nitrogen supersaturation, high dislocation density and thin platelets of {epsilon}-phase in the surface of the compound layer. (orig.).

  20. Structural Diversities in Heterometallic Mn-Ca Cluster Chemistry from the Use of Salicylhydroxamic Acid: {Mn(III)4Ca2}, {Mn(II/III)6Ca2}, {Mn(III/IV)8Ca}, and {Mn(III)8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex.

    Science.gov (United States)

    Alaimo, Alysha A; Koumousi, Evangelia S; Cunha-Silva, Luís; McCormick, Laura J; Teat, Simon J; Psycharis, Vassilis; Raptopoulou, Catherine P; Mukherjee, Shreya; Li, Chaoran; Gupta, Sayak Das; Escuer, Albert; Christou, George; Stamatatos, Theocharis C

    2017-09-05

    One-pot reactions between the [Mn3O(O2CPh)6(py)x](+/0) triangular precursors and either CaBr2·xH2O or CaCl2·6H2O, in the presence of salicylhydroxamic acid (shaH2), have afforded the heterometallic complexes [Mn(III)4Ca2(O2CPh)4(shi)4(H2O)3(Me2CO)] (1) and (pyH)[Mn(II)2Mn(III)4Ca2Cl2(O2CPh)7(shi)4(py)4] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO3)2·4H2O/Ca(NO3)2·4H2O and Mn(O2CPh)2·2H2O/Ca(ClO4)2·4H2O "metal blends" and shaH2, in the presence of external base NEt3, led to the new complexes (NHEt3)2[Mn(III)4Mn(IV)4Ca(OEt)2(shi)10(EtOH)2] (3) and (NHEt3)4[Mn(III)8Ca2(CO3)4(shi)8] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi(3-)), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH2, was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn4Ca2 octahedron bound to an additional Mn2 unit, 3 consists of a Mn8 "ring" surrounding a Ca(II) atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two Ca(II) atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

  1. Synthesis of High-Quality α-MnSe Nanostructures with Superior Lithium Storage Properties.

    Science.gov (United States)

    Li, Na; Zhang, Yi; Zhao, Hongyang; Liu, Zhengqing; Zhang, Xinyu; Du, Yaping

    2016-03-21

    High-quality α-MnSe nanocubes were successfully prepared for the first time by an effective hot injection synthesis strategy. This approach was simple but robust and had been applied to the controllable synthesis of different sizes and diverse morphologies of α-MnSe nanostructures. The crystal phases, compositions, and microstructures of these nanostructures had been systematically characterized with a series of techniques. As a proof-of-concept application, the as-prepared α-MnSe nanocubes were used as an anode material for a lithium ion battery, which exhibited superior rate ability and ultralong cycle stability in half-cell and full-cell tests. Importantly, the phase transition from α-MnSe to β-MnSe during the electrochemical process was proved by ex situ X-ray diffraction and selected area electron diffraction. The excellent electrochemical performance of α-MnSe endowed its potential as an anode material candidate for high performance lithium storage.

  2. On the Role of High Amounts of Mn Element in CdS Structure

    Science.gov (United States)

    Gonullu, Meryem Polat; Kose, Salih

    2017-03-01

    CdS and MnS are technologically important semiconducting materials. In this work, due to the limited ability of these materials separately, a detailed characterization of the new samples formed by the combined use of them has been reported. CdS films, with the incorporation of Mn in a wide range of concentrations, have been produced by a low-cost Ultrasonic Spray Pyrolysis set-up. Spectroscopic Ellipsometry (SE) has been used to determine the thicknesses and optical constants ( n, k) of the samples. It has been determined that samples with high amounts of Mn have lower refractive index values. Absorbance spectra have shown additional band edges along with the one belonging to CdS, for samples with Mn concentrations higher than 50 pct. This has been attributed to a phase separation above this limit. Raman spectroscopy analysis which shows additional Raman peaks belonging to MnS phase also supports these findings. Depending on this phase separation, crystalline structure has been deteriorated. Surface properties of the samples have been investigated by SEM and AFM. Elemental analysis has been performed by EDS. Resistivity measurements performed by a four-probe set-up have shown that samples containing high amount of Mn have lower electrical resistivity values.

  3. The extrinsic PsbO protein modulates the oxidation/reduction rate of the exogenous Mn cation at the high-affinity Mn-binding site of Mn-depleted PSII membranes.

    Science.gov (United States)

    Semin, Boris K; Podkovirina, Tatiana E; Davletshina, Lira N; Timofeev, Kirill N; Ivanov, Il'ya I; Rubin, Andrei B

    2015-08-01

    The oxidation of exogenous Mn(II) cations at the high-affinity (HA) Mn-binding site in Mn-depleted photosystem II (PSII) membranes with or without the presence of the extrinsic PsbO polypeptide was studied by EPR. The six-lines EPR spectrum of Mn(II) cation disappears in the absence of the PsbO protein in membranes under illumination, but there was no effect when PSII preparations bound the PsbO protein. Our study demonstrates that such effect is determined by significant influence of the PsbO protein on the ratio between the rates of Mn oxidation and reduction at the HA site when the membranes are illuminated.

  4. Microstructural changes within similar coronary stents produced from two different austenitic steels.

    Science.gov (United States)

    Weiss, Sabine; Meissner, Andreas; Fischer, Alfons

    2009-04-01

    Coronary heart disease has become the most common source for death in western industrial countries. Since 1986, a metal vessel scaffold (stent) is inserted to prevent the vessel wall from collapsing [Puel, J., Joffre, F., Rousseau, H., Guermonprez, B., Lancelin, B., Valeix, B., Imbert, G., Bounhoure, J.P, 1987. Endo-prothéses coronariennes autoexpansives dans la Préevention des resténoses apés angioplastie transluminale. Archives des Maladies du Coeur et des Vaisseaux, 1311--1312]. Most of these coronary stents are made from CrNiMo-steel (AISI 316L). Due to its austenitic structure, the material shows strength and ductility combined with corrosion resistance and a satisfactory biocompatibility. However, recent studies indicate that Nickel is under discussion as to its allergenic potential. Other typically used materials like Co-Base L605 or Tantalum alloys are relatively expensive and are not used so often. Newly developed austenitic high-nitrogen CrMnMoN-steels (AHNS) may offer an alternative. Traditional material tests revealed that strength and ductility, as well as corrosion resistance and biocompatibility, are as good as or even better than those of 316L [Vogt, J.B., Degallaix, S., Foct J., 1984. Low cycle fatigue life enhancement of 316L stainless steel by nitrogen alloying. International Journal of Fatigue 6 (4), 211-215, Menzel, J., Stein, G., 1996. High nitrogen containing Ni-free austenitic steels for medical applications. ISIJ Intern 36 (7), 893-900, Gavriljuk, V.G., Berns, H., 1999. High nitrogen steels, Springer Verlag, Berlin, Heidelberg]. However, because of a strut diameter of about 100 microm, the cross section consists of about five to ten crystal grains (oligo-crystalline). Thus very few, or even just one, grain can be responsible for the success or failure of the whole stent. During implantation, the structure of coronary artery stents is subjected to distinct inhomogeneous plastic deformation due to crimping and dilation.

  5. Effect of Heat Treatment on Delayed Fracture Resistance of High Strength Steel 30CrMnSi2NiNb

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The steel specimens of nominal composition 0.3C-1.0Cr-1.0Mn-2.0Si-1.0Ni-0.04Nb were quenched and tempered or isothermally quenched from various temperatures. It is found that the steel quenched and tempered with a tensile strength of 1 500-1 600 MPa has a KISCC (critical stress intensity factor) value below 15.0 MPa*m1/2. The steel isothermally quenched with a tensile strength of 1 350-1 750 MPa has a KISCC value about 20.0 MPa*m1/2. In addition, with increase of isothermal quenching temperature, the tensile strength decreases greatly and KISCC value does not pronouncedly change. The microstructure of isothermally quenched specimens is composed of bainite and retained austenite. The delayed fracture resistance is dependent on the stability of austenite, which is in turn related to the retained austenite volume fraction and carbon content in austenite.

  6. Austenitic Oxide Dispersion Strengthened Steels : A Review

    Directory of Open Access Journals (Sweden)

    Lavanya Raman

    2016-06-01

    Full Text Available Materials play an important role in the fast breeder reactors.  Materials used in cladding tube and fuel pins should have better creep and void swelling resistance. To overcome these difficulties, a new class of material known as oxide dispersion strengthened (ODS steels are used. There are two groups of ODS steels, the ferritic and the austenitic ODS steels based on the matrix. The present paper reviews the current status of research in austenitic ODS steels. The interaction of dislocations with finely dispersed incoherent, hard particles that governs the strength and high temperature properties of ODS materials is briefly reviewed. The synthesis route adopted for these ODS steels, which is mostly through powder metallurgy route is also discussed. The role of various oxides such as Y2O3, ZrO2and TiO2and the clusters formed in these ODS steels on the mechanical properties and void swelling characteristics is also discussed.

  7. Utilization of aluminum to obtaining a duplex type stainless steel using high energy ball milling; Obtencao de um aco inoxidavel de estrutura duplex do sistema FeMnAl processado por moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Pavlak, I.E.; Cintho, O.M., E-mail: eng.igorpavlak@yahoo.com.b [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil); Capocchi, J.D.T. [Universidade de Sao Paulo (USP), SP (Brazil)

    2010-07-01

    The obtaining of stainless steel using aluminum in its composition - FeMnAl system, has been researches subject since the sixties, by good mechanical properties and resistance to oxidation presented, when compared with conventional FeNiCr stainless steel system. In another point, the aluminum and manganese are low cost then traditional elements. This work, metallic powders of iron, manganese and pure aluminum, were processed in a Spex type high-energy ball mill in nitrogen atmosphere. The milling products were compressed into pastille form and sintered under inert atmosphere. The final products were characterized by optical and electronic microscopy and microhardness test. The metallographic analysis shows a typical austenite and ferrite duplex type microstructure. The presence of these phases was confirmed according X ray diffraction analysis. (author)

  8. Effects of Mn on the mechanical properties and high temperature oxidation of 9Cr2WVTa steel

    Science.gov (United States)

    Jin, Xiaojie; Chen, Shenghu; Rong, Lijian

    2017-10-01

    The mechanical properties and high temperature oxidation behaviors of 9Cr2WVTa steels with Mn contents in the range of 0.04-0.93 wt% were investigated. There are no obvious differences in the tensile properties at room temperature and high temperature, only a slight reduction in the impact toughness when Mn content reaches 0.93 wt%. Remarkably, the high temperature oxidation resistance is significantly improved with an increase of Mn content. After 500 h of oxidation, a (Fe0.6Cr0.4)2O3 oxide scale is developed on the steel with 0.04 wt% Mn, Mn1.5Cr1.5O4 oxides are occasionally detected when Mn content reaches 0.47 wt%, while a thin compact scale with a mixture of Mn1.5Cr1.5O4 and Cr1.3Fe0.7O3 oxides is formed on the steel containing 0.93 wt% Mn. Addition of Mn promotes the formation of Mn-oxides, which lowers oxygen partial pressure and accelerates external oxidation of Cr. At last, the presence of Mn-Cr spinels and Cr-rich oxides improves the oxidation resistance.

  9. The Strain-Hardening Behavior of Partially Austenitized and the Austempered Ductile Irons with Dual Matrix Structures

    Science.gov (United States)

    Kilicli, Volkan; Erdogan, Mehmet

    2008-04-01

    In the current study, an unalloyed ductile iron containing 3.50 C wt.%, 2.63 Si wt.%, 0.318 Mn wt.%, and 0.047 Mg wt.% was intercritically austenitized (partially austenitized) in two-phase regions (α + γ) at different temperatures for 20 min and then was quenched into salt bath held at austempering temperature of 365 °C for various times to obtain different ausferrite plus proeutectoid ferrite volume fractions. Fine and coarse dual matrix structures (DMS) were obtained from two different starting conditions. Some specimens were also conventionally austempered from 900 °C for comparison. The results showed that a structure having proeutectoid ferrite plus ausferrite (bainitic ferrite + high-carbon austenite (retained or stabilized austenite)) has been developed. Both of the specimens with ˜75% ausferrite volume fraction (coarse structure) and the specimen with ˜82% ausferrite volume fraction (fine structure) exhibited the best combination of high strength and ductility compared to the pearlitic grades, but their ductility is slightly lower than the ferritic grades. These materials also satisfy the requirements for the strength of the quenched and tempered grades and their ductility is superior to this grade. The correlation between the strain-hardening rates of the various austempered ductile iron (ADI) with DMS and conventionally heat-treated ADI microstructures as a function of strain was conducted by inspection of the respective tensile curves. For this purpose, the Crussard-Jaoul (C-J) analysis was employed. The test results also indicate that strain-hardening behavior of ADI with dual matrix is influenced by the variations in the volume fractions of the phases, and their morphologies, the degree of ausferrite connectivity and the interaction intensities between the carbon atoms and the dislocations in the matrix. The ADI with DMS generally exhibited low strain-hardening rates compared to the conventionally ADI.

  10. Significant improvement in Mn2O3 transition metal oxide electrical conductivity via high pressure

    Science.gov (United States)

    Hong, Fang; Yue, Binbin; Hirao, Naohisa; Liu, Zhenxian; Chen, Bin

    2017-01-01

    Highly efficient energy storage is in high demand for next-generation clean energy applications. As a promising energy storage material, the application of Mn2O3 is limited due to its poor electrical conductivity. Here, high-pressure techniques enhanced the electrical conductivity of Mn2O3 significantly. In situ synchrotron micro X-Ray diffraction, Raman spectroscopy and resistivity measurement revealed that resistivity decreased with pressure and dramatically dropped near the phase transition. At the highest pressure, resistivity reduced by five orders of magnitude and the sample showed metal-like behavior. More importantly, resistivity remained much lower than its original value, even when the pressure was fully released. This work provides a new method to enhance the electronic properties of Mn2O3 using high-pressure treatment, benefiting its applications in energy-related fields. PMID:28276479

  11. Crystallographic Reconstruction Study of the Effects of Finish Rolling Temperature on the Variant Selection During Bainite Transformation in C-Mn High-Strength Steels

    Science.gov (United States)

    Bernier, Nicolas; Bracke, Lieven; Malet, Loïc; Godet, Stéphane

    2014-12-01

    The effect of finish rolling temperature on the austenite-( γ) to-bainite ( α) phase transformation is quantitatively investigated in high-strength C-Mn steels using an alternative crystallographic γ reconstruction procedure, which can be directly applied to experimental electron backscatter diffraction mappings. In particular, the current study aims to clarify the respective contributions of the γ conditioning during the hot rolling and the variant selection during the phase transformation to the inherited texture. The results confirm that the sample finish rolled at the lowest temperature [1102 K (829 °C)] exhibits the sharpest transformation texture. It is shown that this sharp texture is exclusively due to a strong variant selection from parent brass {110}, S {213} and Goss {110} grains, whereas the variant selection from the copper {112} grains is insensitive to the finish rolling temperature. In addition, a statistical variant selection analysis proves that the habit planes of the selected variants do not systematically correspond to the predicted active γ slip planes using the Taylor model. In contrast, a correlation between the Bain group to which the selected variants belong and the finish rolling temperature is clearly revealed, regardless of the parent orientation. These results are discussed in terms of polygranular accommodation mechanisms, especially in view of the observed development in the hot-rolled samples of high-angle grain boundaries with misorientation axes between γ and γ.

  12. Interface Migration between Martensite and Austenite during Quenching and Partitioning (Q&P) Process

    Institute of Scientific and Technical Information of China (English)

    Ning ZHONG; Xiaodong WANG; Yonghua RONG; Li WANG

    2006-01-01

    An Fe-0.2C-1.5Si-1.67Mn steel was subjected to quenching and partitioning (Q&P) process, and the interface migration between martensite and austenite at an elevated partitioning temperature was observed. The interface migration is excluded in constrained paraequilibrium (CPE) model. Based on "endpoint" predicted by CPE model the thermodynamic condition of interface migration is analyzed, that is, the difference in the chemical potential of iron in both ferrite (martenisite) and austenite produces the driving force of the iron atoms to migrate from one phase to the other phase. In addition, the interface migration can change the austenite fraction; as a result, the austenite fraction at partitioning temperature may be higher than that at quenching temperature through the interface migration, but this phenomenon cannot be explained by CPE model.

  13. INFLUENCE OF COOLING RATE ON THE OCORRENCE OF RETAINED AUSTENITE IN A STEEL FOR WELDING ELECTRODES

    Directory of Open Access Journals (Sweden)

    Helder Carvalho Ferreira

    2015-07-01

    Full Text Available The effect of cooling rate on the occurrence of retained austenite in a low carbon Si-Mn steel, used for welding electrodes, is measured here by combining the sectioning of Jominy test samples with the measurement of retained austenite by X-ray diffraction. It was observed that the amount of retained austenite increases from zero, as the cooling rate is less than 0.8°C/s, and the structure is mostly ferrite, to a maximum of 6%, where the quantity of bainite is also maximum. This information guides the post-rolling cooling cycle when welding grade is been rolled. The hard phases proportionality with the amount of retained austenite allows, then, the use of X-ray diffraction as an end of the line equipment for quality control, and also permits simplification of heat treatment before wire drawing.

  14. Graphene/LiMn{sub 2}O{sub 4} nanocomposites for enhanced lithium ion batteries with high rate capability

    Energy Technology Data Exchange (ETDEWEB)

    Pyun, Min Ho; Park, Yong Joon, E-mail: yjpark2006@kyonggi.ac.kr

    2015-09-15

    Highlights: • Composites of LiMn{sub 2}O{sub 4} nanoparticles in a graphene matrix were prepared. • The graphene/LiMn{sub 2}O{sub 4} electrode showed enhanced discharge capacity and rate capability. • This is attributed to the high surface area of LiMn{sub 2}O{sub 4} and good electronic conductivity of graphene. - Abstract: Composites of LiMn{sub 2}O{sub 4} nanoparticles in a graphene matrix were prepared to compensate for the low electronic conductivity of the LiMn{sub 2}O{sub 4} cathode. The LiMn{sub 2}O{sub 4} nanoparticles were homogeneously dispersed and attached on the graphene surface by the hydrothermal method. The graphene/LiMn{sub 2}O{sub 4} electrode showed higher discharge capacity and rate capability than a pristine LiMn{sub 2}O{sub 4} electrode. This is attributed to the high surface area of LiMn{sub 2}O{sub 4} nanoparticles and good electronic conductivity because of the presence of graphene. The composites of LiMn{sub 2}O{sub 4} nanoparticles with graphene were also effective in stabilizing the cyclic performance of the LiMn{sub 2}O{sub 4} nanoparticle cathode.

  15. High Temperature Softening Behaviors and Flow Stress Model for a High Molybdenum Austenitic Stainless Steel%高钼奥氏体不锈钢高温软化行为与流变应力模型

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Single-stage and double-stage interrupted hot compression tests for physical simulating hot rolling have been carried out on the THERMECMATSTOR-Z simulator for 00Cr20Ni18Mo6Cu[ N] austenitic stainless steel under high temperature (1223~1373 K) and various strain rates (0.1~60 s- 1 ). The high temperature mechanical behaviors and microstructure evolution of the steel were studied. The activation energies of hot deformation and dynamic, static and metadynamic recrystallization were calculated. Serials of perfect flow stress model considering dynamic recrystallization were established. The predicted result by the model was well agreed with the experiment data.The kinetics of metadynamic and static recrystallization had also been determined.

  16. Erosion-corrosion behavior of austenitic cast iron in an acidic slurry medium

    Science.gov (United States)

    Yang, Ke; Sun, Lan; Liu, Yu-zhen; Fan, Hong-yuan

    2015-06-01

    A series of austenitic cast iron samples with different compositions were cast and a part of nickel in the samples was replaced by manganese for economic reason. Erosion-corrosion tests were conducted under 2wt% sulfuric acid and 15wt% quartz sand. The results show that the matrix of cast irons remains austenite after a portion of nickel is replaced with manganese. (Fe,Cr)3C is a common phase in the cast irons, and nickel is the main alloying element in high-nickel cast iron; whereas, (Fe,Mn)3C is observed with the increased manganese content in low-nickel cast iron. Under erosion-corrosion tests, the weight-loss rates of the cast irons increase with increasing time. Wear plays a more important role than corrosion in determining the weight loss. It is indicated that the processes of weight loss for the cast irons with high and low nickel contents are different. The erosion resistance of the cast iron containing 7.29wt% nickel and 6.94wt% manganese is equivalent to that of the cast iron containing 13.29wt% nickel.

  17. Direct Observations of the (Alpha to Gamma) Transformation at Different Input Powers in the Heat Affected Zone of 1045 C-Mn Steel Arc Welds Observed by Spatially Resolved X-Ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, T A; Elmer, J W

    2005-03-16

    Spatially Resolved X-Ray Diffraction (SRXRD) experiments have been performed during Gas Tungsten Arc (GTA) welding of AISI 1045 C-Mn steel at input powers ranging from 1000 W to 3750 W. In situ diffraction patterns taken at discreet locations across the width of the heat affected zone (HAZ) near the peak of the heating cycle in each weld show regions containing austenite ({gamma}), ferrite and austenite ({alpha}+{gamma}), and ferrite ({alpha}). Changes in input power have a demonstrated effect on the resulting sizes of these regions. The largest effect is on the {gamma} phase region, which nearly triples in width with increasing input power, while the width of the surrounding two phase {alpha}+{gamma} region remains relatively constant. An analysis of the diffraction patterns obtained across this range of locations allows the formation of austenite from the base metal microstructure to be monitored. After the completion of the {alpha} {yields} {gamma} transformation, a splitting of the austenite peaks is observed at temperatures between approximately 860 C and 1290 C. This splitting in the austenite peaks results from the dissolution of cementite laths originally present in the base metal pearlite, which remain after the completion of the {alpha} {yields} {gamma} transformation, and represents the formation of a second more highly alloyed austenite constituent. With increasing temperatures, carbon, originally present in the cementite laths, diffuses from the second newly formed austenite constituent to the original austenite constituent. Eventually, a homogeneous austenitic microstructure is produced at temperatures of approximately 1300 C and above, depending on the weld input power.

  18. Phase Transformations in Austenitic 0Cr18Ni10Ti Steel Irradiated with High-Energy Heavy Ions

    CERN Document Server

    Hofmann, A; Semina, V K

    2000-01-01

    Radiation-induced segregation and phase transformations in 0Cr18Ni10Ti steel irradiated with high-energy heavy Ar^{+6} ions at 625^o up to 1 dpa (from 0.01 to 1 dpa) have been studied. It was found that ion irradiation accelerates carbide precipitation and EDX-analysis showed irradiation-induced segregation near grain boundaries.

  19. High performance hydrogen sensor based on Mn implanted ZnO nanowires array fabricated on ITO substrate.

    Science.gov (United States)

    Renitta, A; Vijayalakshmi, K

    2017-08-01

    In the present research, we propose a novel approach for the detection of hydrogen gas using Mn implanted ZnO nanowires fabricated onto ITO coated glass substrate by chemical spray pyrolysis deposition. The effect of Mn concentration on the structural, optical and morphological properties of ZnO films were investigated. X-ray diffraction studies showed that the Mn implanted ZnO films were grown as a polycrystalline hexagonal wurtzite phase without any impurities. The (101) peak position of ZnO-Mn films was shifted towards a lower angle with increasing Mn concentration. The optical band gap decreased from 3.45eV to 3.23eV with increasing Mn content. PL spectra, revealed sharp and strong near band edge emission which suggests that ZnO nanowires exhibit high crystalline quality. FE-SEM images of Mn implanted ZnO show perfectly aligned nanowires for all the films fabricated on ITO. The material (Zn, O, Mn) was confirmed by EDX spectra. The hydrogen sensing mechanism of the Mn implanted ZnO nanowire sensor was also discussed. It was found that H2 response was significantly enhanced by more than one order of magnitude with increasing Mn doping concentrations. The studied ZnO-Mn films coated on ITO substrate can be used as a low cost and easy-fabrication hydrogen sensing material. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. High-Resolution Structure of the Photosynthetic Mn4Ca Catalyst from X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yachandra, Vittal; Yano, Junko; Kern, Jan; Pushkar, Yulia; Sauer, Kenneth; Glatzel, Pieter; Bergmann, Uwe; Messinger, Johannes; Zouni, Athina; Yachandra, Vittal K.

    2007-08-01

    The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, are described. Issues of X-ray damage especially at the metal sites in the Mn4Ca cluster are discussed. The structure of the Mn4Ca catalyst at high-resolution which has so far eluded attempts of determination by X-ray diffraction, EXAFS and other spectroscopic techniques has been addressed using polarized EXAFS techniques applied to oriented PS II membrane preparations and PS II single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and K? emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.

  1. Microwave-assisted synthesis of high-voltage nanostructured LiMn1.5Ni0.5O4 spinel: tuning the Mn3+ content and electrochemical performance

    CSIR Research Space (South Africa)

    Jafta, CJ

    2013-08-01

    Full Text Available on the Mn3+ concentration and electrochemistry of the LiMn1.5Ni0.5O4 spinel. It is shown that microwave is capable of tuning the Mn3+ content of the spinel for enhanced electrochemical performance (high capacity, high capacity retention, excellent rate...

  2. Effects of Mn and Cu on the Mechanical Properties of a High Strength Low Alloy NiCrMoV Steel

    Institute of Scientific and Technical Information of China (English)

    A.Abdollah-zadeh; M. Belbasy

    2005-01-01

    The present study focuses on the effects of Mn and Cu on the mechanical properties, in particular, strength and toughness of a low alloy steel containing Ni, Cr, Mo and V. Specimens with different amounts of Mn (0.23%~0.85%)and Cu (0.15%~0.45%) were cast and forged, and then austenitized at 870℃ for 1 h, followed by oil quenching. All specimens were tempered at 650℃ for 1 h. The results show that as the amounts of Mn and Cu increase respectively from 0.35% to 0.85% and from 0.15% to 0.45%, the yield and tensile strength increase. The highest impact energies were observed in the specimen with 0.35% Mn and in the specimen with 0.25% Cu. The impact energy decreases with increasing the Mn and Cu from 0.35% to 0.85% and from 0.25% to 0.45%, respectively. Furthermore, the variation of Mn and Cu does not cause a considerable change in the tempered martensite microstructure. The optimum strength and toughness is observed in 0.35% Mn containing steel and in the 0.25% Cu containing steel.

  3. Effect of pressure and high magnetic field on phase transitions and magnetic properties of Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} and Ni{sub 2}MnSn Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kaštil, J., E-mail: kastil@fzu.cz [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Kamarád, J. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Isnard, O. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Skourski, Y. [Hochfeld-Magnetlabor Dresden (HLD), HZ Dresden-Rossendorf, D-01314 Dresden (Germany); Míšek, M.; Arnold, Z. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic)

    2015-11-25

    Complex study of magnetic, magnetocaloric and structural properties of the Ni{sub 2}MnSn and Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} compounds was performed. The stoichiometric single-crystal of Ni{sub 2}MnSn was prepared by Czochralski method. The remarkable pressure effect on the martensitic magnetization and the martensite-austenite transition temperature T{sub M–A} was observed in the Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} compound. The coefficient dT{sub M–A}/dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} was further substantially decreased by external pressure, in contrast with pressure almost insensitive magnetization of the stoichiometric Ni{sub 2}MnSn single-crystal. The pulse magnetic field of 58 T invoked the structural transition at temperature 180 K that is of about 100 K below T{sub M–A} of Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} at zero field. An anomalous increase of resistivity of the compound has been observed at temperature range below T{sub M–A}, however, it does not copy the sharp change of magnetization at T{sub M–A}. The obtained results indicate the important role of interatomic distances on the magnetic ordering and electronic structure of the studied Heusler alloys and are in agreement with the Jahn-Teller mechanism of the martensitic transition in these compounds. - Highlights: • Samples of Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} and single crystal of Ni{sub 2}MnSn compounds were prepared. • Significant decrease of magnetization of Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52} by pressure, dlnM/dp = −18.7·10{sup −3}GPa{sup −1}. • Negligible pressure effect on magnetization of the Ni{sub 2}MnSn single-crystal. • Large increase of T{sub M–A} under pressure, dT{sub M–A}/dp = 18 K/GPa in the Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52}. • High magnetoresistance and moderate MCE were measured on Ni{sub 1.92}Mn{sub 1.56}Sn{sub 0.52}.

  4. Microstructure and mechanical properties of 980MPa grade Fe-Mn-Al-C lightweight steel

    Science.gov (United States)

    Jiang, Yinghua; Xie, Chunqian

    2017-06-01

    Fe-Mn-Al-C lightweight high strength steel, adding more Mn, Al and C elements into conventional AHSS, shows amazing mechanical properties, corrosion resistant and weight reduction than conventional AHSS. The mechanical properties and microstructure of Fe-15Mn-6.8Al-0.9C-0.2Ti steel after annealing process were investigated. The results show that the microstructures consisted of secondary phases TiC precipitate and ferrite in the austenite matrix. The tensile strength and elongation of the steel are 985MPa and 36%, respectively. The density is 6.86g/cm3. Continuous strain hardening behavior provides Fe-Mn-Al-C lightweight steel with perfect combination of strength and ductility.

  5. Ferroelectricity of multiferroic hexagonal TmMnO3 ceramics synthesized under high pressure

    Science.gov (United States)

    Wang, L. J.; Feng, S. M.; Zhu, J. L.; Yu, R. C.; Jin, C. Q.; Yu, W.; Wang, X. H.; Li, L. T.

    2007-10-01

    Dense hexagonal TmMnO3 ceramics were synthesized by solid-state reaction technique combined with high-pressure treatment which significantly increased the density of ceramic samples. The crystal structure of the hexagonal TmMnO3 oxide was refined by using Rietveld analysis based on powder x-ray diffraction experiment. We observed obvious dielectric peaks through dielectric measurement on the specimen subjected to postannealing in oxygen atmosphere. A ferroelectric-paraelectric transition around 348°C is identified. Polarization-electric field hysteresis (P-E ) loop measurement proved the ferroelectricity of the sample at room temperature.

  6. PHASE TRANSITION IN LAYERED PEROVSKITE LIKE MANGANATE Ca3Mn2O7 UNDER HIGH PRESSURE

    Institute of Scientific and Technical Information of China (English)

    J.L.ZHU; L.C.CHEN; R.C.YU; F.Y.LI; J.LIU; C.Q.JIN

    2001-01-01

    In situ high pressure energy dispersive X-ray diffraction measurements on layered perovskite-like manganate Ca3Mn2O7 under pressures up to 35 GPa have been Performed by using diamond anvil cell with synchrotron radiation.The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks.The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35GPa.One was at about 1.3GPa with the crystal structure changing from tetragonalt go orthorhombic.The other was at about 9.5GPa with the crystal structure changing form orthorhombic back to another tetragonal.

  7. Nickel-free austenitic stainless steels for medical applications

    Directory of Open Access Journals (Sweden)

    Ke Yang and Yibin Ren

    2010-01-01

    Full Text Available The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels.

  8. Nanostructure formation during relatively high temperature growth of Mn-doped GaAs by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Del Río-De Santiago, A.; Méndez-García, V.H. [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico); Martínez-Velis, I.; Casallas-Moreno, Y.L. [Physics Department, CINVESTAV-IPN, Apdo. Postal 14470 D. F. México, México (Mexico); López-Luna, E. [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico); Yu Gorbatchev, A. [IICO-UASLP, Av. Karakorum 1470, Lomas 4a. Sección, San Luis Potosí, S.L.P. 78210, México (Mexico); López-López, M. [Physics Department, CINVESTAV-IPN, Apdo. Postal 14470 D. F. México, México (Mexico); Cruz-Hernández, E., E-mail: esteban.cruz@uaslp.mx [CIACyT-UASLP, Sierra Leona Av. # 550, Lomas 2a Secc, San Luis Potosí, S.L.P. 78210, México (Mexico)

    2015-04-01

    Highlights: • The formation of different kind of nanostructures in GaMnAs layers depending on Mn concentration at relative HT-MBE is reported. In this Mn% range, it is found the formation of nanogrooves, nanoleaves, and nanowires. • It is shown the progressive photoluminescence transitions from purely GaAsMn zinc blende (for Mn% = 0.01) to a mixture of zinc blende and wurtzite GaAsMn (for Mn% = 0.2). • A critical thickness for the Mn catalyst effect was determined by RHEED. - Abstract: In the present work, we report on molecular beam epitaxy growth of Mn-doped GaAs films at the relatively high temperature (HT) of 530 °C. We found that by increasing the Mn atomic percent, Mn%, from 0.01 to 0.2, the surface morphology of the samples is strongly influenced and changes from planar to corrugated for Mn% values from 0.01 to 0.05, corresponding to nanostructures on the surface with dimensions of 200–300 nm and with the shape of leave, to nanowire-like structures for Mn% values above 0.05. From reflection high-energy electron diffraction patterns, we observed the growth mode transition from two- to three-dimensional occurring at a Mn% exceeding 0.05. The optical and electrical properties were obtained from photoluminescence (PL) and Hall effect measurements, respectively. For the higher Mn concentration, besides the Mn related transitions at approximately 1.41 eV, PL spectra sharp peaks are present between 1.43 and 1.49 eV, which we related to the coexistence of zinc blende and wurtzite phases in the nanowire-like structures of this sample. At Mn% of 0.04, an increase of the carrier mobility up to a value of 1.1 × 10{sup 3} cm{sup 2}/Vs at 77 K was found, then decreases as Mn% is further increased due to the strengthening of the ionized impurity scattering.

  9. A study of austenitization of SG iron

    Indian Academy of Sciences (India)

    Uma Batra; Pankaj Tandon; Kulbir Kaur

    2000-10-01

    Austenitization process of three SG irons with varying compositions and as cast matrix microstructure has been studied at three austenitization temperatures of 850, 900 and 950C for different time periods. Microstructure, hardness and X-ray diffraction have been used to reveal the nature of dependence of the process on austenitization temperature, time and as cast structure. The optimum austenitization time is maximum for ferritic and minimum for pearlitic matrix.

  10. Recrystallization Modelling of Hot Deformed Si-Mn TRIP Steel

    Institute of Scientific and Technical Information of China (English)

    ZHU Li-juan; WU Di; ZHAO Xian-ming

    2007-01-01

    By means of hot compression single and double hit experiments, the kinetics of dynamic and static recrystallization in hot-rolled Si-Mn TRIP steel was studied, and the emphasis was put on the influence of high silicon content. The results show that the calculated parameters are consistent with the experimental ones, and addition of silicon retards both dynamic and static recrystallization as well as increases the flow stress of austenite, and the non-recrystallization zone can be enlarged by increasing the silicon contents.

  11. High pressure X-ray diffraction study of SrMnO3 perovskite

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-Xin; QIN Shan; WU Xiang; JIANG Jian-Zhong; Kikegawa Takumi; SHI Guang-Hai

    2011-01-01

    Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO 3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressu

  12. High-performance asymmetric supercapacitor based on graphene hydrogel and nanostructured MnO2.

    Science.gov (United States)

    Gao, Hongcai; Xiao, Fei; Ching, Chi Bun; Duan, Hongwei

    2012-05-01

    We have successfully fabricated an asymmetric supercapacitor with high energy and power densities using graphene hydrogel (GH) with 3D interconnected pores as the negative electrode and vertically aligned MnO(2) nanoplates on nickel foam (MnO(2)-NF) as the positive electrode in a neutral aqueous Na(2)SO(4) electrolyte. Because of the desirable porous structure, high specific capacitance and rate capability of GH and MnO(2)-NF, complementary potential window of the two electrodes, and the elimination of polymer binders and conducting additives, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-2.0 V and exhibits an energy density of 23.2 Wh kg(-1) with a power density of 1.0 kW kg(-1). Energy density of the asymmetric supercapacitor is significantly improved in comparison with those of symmetric supercapacitors based on GH (5.5 Wh kg(-1)) and MnO(2)-NF (6.7 Wh kg(-1)). Even at a high power density of 10.0 kW kg(-1), the asymmetric supercapacitor can deliver a high energy density of 14.9 Wh kg(-1). The asymmetric supercapacitor also presents stable cycling performance with 83.4% capacitance retention after 5000 cycles.

  13. Electrochemical study of a novel high performance supercapacitor based on MnO{sub 2}/nitrogen-doped graphene nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Naderi, Hamid Reza, E-mail: hrnaderi@ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Norouzi, Parviz, E-mail: norouzi@khayam.ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Biosensor Research Center, Endocrinology & Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Ganjali, Mohammad Reza, E-mail: ganjali@khayam.ut.ac.ir [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Biosensor Research Center, Endocrinology & Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2016-03-15

    Graphical abstract: - Highlights: • MnO{sub 2} nanoparticles was prepared by sonochemical method. • MnO{sub 2} are anchored on the surface of nitrogen-doped reduced graphene oxide (NRGO). • MnO{sub 2}/NRGO nanocomposite show high capacitance, good rate and cycling performance. • The nanocomposite electrode exhibits specific capacitance of 522 F g{sup −1} in 2 mV s{sup −1}. • The electrode reveals 97% retention of initial capacitance after 4000 cycles. - Abstract: A new nanocomposite was synthesized via deposition of MnO{sub 2} on Nitrogen-doped reduced graphene (MnO{sub 2}/NRGO) by sonochemical method, in which, the particles of manganese oxide were uniformly distributed on NRGO sheets. The structure and morphology of MnO{sub 2}/NRGO nanocomposites are characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical supercapacitive performance of the nanocomposite was investigated by cyclic voltammetry (CV), continuous cyclic voltammetry (CCV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) methods. The MnO{sub 2}/NRGO nanocomposite shows enhanced specific capacitance of 522 F g{sup −1} at 2 mV s{sup −1} and its high synergistic effect was compared with MnO{sub 2}/RGO. The high specific capacitance and exceptionally high cyclic stability of MnO{sub 2}/NRGO attributes to the doping of nitrogen and uniform dispersion of MnO{sub 2} particles on NRGO. The CCV showed that the capacity retention for MnO{sub 2}/NRGO and MnO{sub 2}/RGO still maintained at 96.3% and 93% after 4000 CVs. The improved supercapacitive performance enables this nanocomposite as efficient electrode material for supercapacitor electrodes.

  14. Synthesis and high-efficiency methylene blue adsorption of magnetic PAA/MnFe2O4 nanocomposites

    Science.gov (United States)

    Wang, Wei; Ding, Zui; Cai, Minhan; Jian, Haitao; Zeng, Zhiqiao; Li, Feng; Liu, J. Ping

    2015-08-01

    MnFe2O4 nanoparticles and polyacrylic acid PAA/MnFe2O4 nanocomposites were synthesized by a hydrothermal method and ultrasonic mixing process. The obtained materials were characterized by XRD, FTIR, SEM, TEM, and VSM. XRD patterns indicate that the synthesized MnFe2O4 nanoparticles have a single cubic spinel phase. SEM images confirm the existence of three types of basic morphology of MnFe2O4 nanoparticles: octahedral, flower-like, and plate-like particles. High saturation magnetization Ms (up to 74.6 emu/g) of the as-synthesized MnFe2O4 nanoparticles was obtained. Experiments demonstrate that the variation of the hydrothermal reaction time does not remarkably affect the magnetic properties of MnFe2O4 nanoparticles. In PAA/MnFe2O4 nanocomposites, the coating of PAA leads to a slight decrease in magnetization of MnFe2O4 nanoparticles. Additionally, PAA coating greatly enhances the adsorption properties of MnFe2O4 nanoparticles for Methylene Blue (MB) dye. Especially, the removal efficiency reaches 96.3%. This research indicates that the as-synthesized PAA/MnFe2O4 nanocomposites exhibit excellent magnetic properties and can be taken as a promising adsorbent for removal of MB dye in industrial scale.

  15. High-pressure phase transition and properties of spinel ZnMn2O4

    DEFF Research Database (Denmark)

    Åbrink, S.; Waskowska, A.; Gerward, Leif

    1999-01-01

    X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high-pressure beh...... of the Mn3+ ions is moved to the d(x2-y2) level, which is revealed as an abrupt fall of observed magnitude of the distortion of the bulk crystal above P-c. [S0163-1829(99)08341-1].......X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high......-pressure behavior of ZnMn2O4 was investigated up to 52 GPa using the energy-dispersive x-ray diffraction technique and synchrotron radiation. The structural first-order phase transition from the body-centered to primitive-tetragonal cell takes place at P-c = 23 GPa. The high-pressure phase is metastable down...

  16. High-field magnetization of Heusler compound Fe2Mn1 -xVxSi

    Science.gov (United States)

    Hiroi, Masahiko; Tazoko, Tomoya; Sano, Hiroaki; Shigeta, Iduru; Koyama, Keiichi; Kondo, Akihiro; Kindo, Koich; Manaka, Hirotaka; Terada, Norio

    2017-01-01

    Fe2MnSi exhibits a ferromagnetic transition at TC˜230 K and another transition to a phase with antiferromagnetic components at TA˜60 K. By substituting V for Mn, so as to obtain Fe2Mn1 -xVxSi , TA is revealed to decrease with x and then vanish around x ˜0.2 . In this study, the phase boundary of the transition at TA in the high-field range is found for 0 ≤x ≤0.15 with pulsed fields up to ˜70 T. The magnetization of Fe2Mn1 -xVxSi slowly increases even at the highest field of ˜70 T, though it occurs more gradually as x increases. We compare the magnetization for 0 ≤x ≤0.20 at 62 T with the Slater-Pauling rule, which holds when a Heusler compound is a half-metal, and find fairly good agreement. This suggests an intimate relation between the high-field phase and the half-metallic electronic structure, and that at the high-field limit the phase approaches the half-metallic state, which has been predicted by band-structure calculations.

  17. Structure and substructure of austenite formed during heating of quenched and thermomechanically strengthened steels

    Energy Technology Data Exchange (ETDEWEB)

    Bernshtejn, M.L.; Kaputkina, L.M.; Prokoshkin, S.D.; Lyuttsau, A.V.; Prokoshkina, V.G. (Moskovskij Inst. Stali i Splavov (USSR))

    1982-06-01

    Mechanism of ..cap alpha.. ..-->.. ..gamma.. transformation in chromium and chromium-nickel steels, peculiarities of substructure formation of austenite formed at repeated heating after quenching and high-temperature thermomechanical treatment and its stability to recrystallization in steels with different martensite morphology and temperature of the initial stage of austenite formation are investigated.

  18. Nonstoichiometric perovskite CaMnO(3-δ) for oxygen electrocatalysis with high activity.

    Science.gov (United States)

    Du, Jing; Zhang, Tianran; Cheng, Fangyi; Chu, Wangsheng; Wu, Ziyu; Chen, Jun

    2014-09-01

    Perovskite oxides offer efficient and cheap electrocatalysts for both oxygen reduction reactions and oxygen evolution reactions (ORR/OER) in diverse oxygen-based electrochemical technologies. In this study, we report a facile strategy to enhance the electrocatalytic activity of CaMnO3 by introducing oxygen defects. The nonstoichiometric CaMnO(3-δ) (0 < δ ≤ 0.5) was prepared through thermal reduction of pristine perovskite microspheres and nanoparticles, which were synthesized from thermal-decomposition of carbonate precursors and the Pechini route, respectively. The as-prepared samples were analyzed by chemical titration, structural refinement, thermogravimetric analysis, and energy spectrometry. In 0.1 M KOH aqueous solution, the nonstoichiometric CaMnO(3-δ) with δ near 0.25 and an average Mn valence close to 3.5 exhibited the highest ORR activity (36.7 A g(-1) at 0.70 V vs RHE, with onset potential of 0.96 V), which is comparable to that of benchmark Pt/C. Density functional theory (DFT) studies and electrical conductivity measurement revealed that the enhanced ORR kinetics is due to facilitated oxygen activation and improved electrical properties. Besides high activity, the nonstoichiometric perovskite oxides showed respectable catalytic stability. Furthermore, the moderate oxygen-defective CaMnO(3-δ) (δ ≈ 0.25) favored the OER because of the improved electrical conductivity. This study makes nonstoichiometric CaMnO(3-δ) a promising active, inexpensive bifunctional catalytic material for reversible ORR and OER.

  19. MnO2-Carbon nanotube composite for high-areal-density supercapacitors with high rate performance

    Science.gov (United States)

    Wang, Ke; Gao, Shan; Du, Zhaolong; Yuan, Anbao; Lu, Wei; Chen, Liwei

    2016-02-01

    Practical supercapacitor devices require high areal capacitance and areal power density, and thus demand high utilization of active material and good rate performance under high areal mass loading. However, ion transport in high-mass-loading electrodes can be a challenge, which leads to deteriorate specific capacitance and rate performance. In this paper, a well-dispersed porous MnO2-carbon nanotube (CNT) composite was prepared for use as a supercapacitor electrode material. The small MnO2 nanoparticles and porous CNT network facilitated fast electron/ion transfer kinetics in the electrode. With a mass loading as high as 6.4 mg cm-2 on the electrode, the MnO2-CNT composite exhibited an excellent areal capacitance of 1.0 F cm-2 at 0.2 A g-1 (1.28 mA cm-2), with a retention of 77% even at a high current density of 20 A g-1 (128 mA cm-2). The electrode exhibited a high power density of 45.2 kW kg-1 (0.29 W cm-2) while maintaining a reasonable energy density of 16.7 Wh kg-1 (106 μWh cm-2). No apparent fading was observed even after 3000 charge/discharge cycles at 1 A g-1. This porous and evenly distributed MnO2-CNT composite has great potential for practical applications in supercapacitors.

  20. Influence of austenitizing temperature on apparent morphologies of as-quenched microstructures of steels

    Institute of Scientific and Technical Information of China (English)

    LIU Yue-jun; LI Yi-min; HUANG Bai-yun

    2006-01-01

    The effects of austenitizing temperature on the morphologies and substructures of as-quenched microstructure were investigated by using 13 medium and high carbon steels. The formation reasons of various morphologies of martensite quenched at different austenitizing temperatures were also studied. The results show that the packet martensite in medium and high carbon steels quenched at higher austenitizing temperature is entirely different from that in as-quenched low carbon steels, which is still plate martensite, and not lath martensite. All the change laws of as-quenched microstructures in medium and high carbon steels are identical with an increase in austenitizing temperature, and the austenitizing temperature can merely change the combined morphology of martensitic platelets,but cannot alter the type of product of martensitic transformation in commercial steels.

  1. Mn-stabilized zirconia: from imitation diamonds to a new potential high-Tc ferromagnetic spintronics material.

    Science.gov (United States)

    Ostanin, S; Ernst, A; Sandratskii, L M; Bruno, P; Däne, M; Hughes, I D; Staunton, J B; Hergert, W; Mertig, I; Kudrnovský, J

    2007-01-05

    From the basis of ab initio electronic structure calculations which include the effects of thermally excited magnetic fluctuations, we predict Mn-stabilized cubic zirconia to be ferromagnetic above 500 K. We find this material, which is well known both as an imitation diamond and as a catalyst, to be half-metallic with the majority and minority spin Mn impurity states lying in zirconia's wide gap. The Mn concentration can exceed 40%. The high-Tc ferromagnetism is robust to oxygen vacancy defects and to how the Mn impurities are distributed on the Zr fcc sublattice. We propose this ceramic as a promising future spintronics material.

  2. High Tc ferrimagnetic organic-inorganic hybrid materials with MnII-L-MnII and MnII-NC-NbIV linkages (L=pyrazine, pyrazine-N,N'-dioxide, bipyrimidine).

    Science.gov (United States)

    Podgajny, Robert; Pinkowicz, Dawid; Korzeniak, Tomasz; Nitek, Wojciech; Rams, Michał; Sieklucka, Barbara

    2007-11-26

    A series of heterobimetallic, cyano-bridged 3D inorganic-organic hybrid networks with MnII-L-MnII and MnII-NC-NbIV linkages are reported. Reaction of [Mn(H2O)6]2+ with [Nb(CN)8]4- in the presence of organic linker L (pyrazine (pyz), pyrazine-N,N'-dioxide (pzdo), and 2,2'-bipyrimidine (bpym)) in H2O affords {MnII2(pz)2(H2O)4[NbIV(CN)8]}.pz.3H2O (1), {MnII2(pzdo)(H2O)4[NbIV(CN)8]}.5H2O (2), and {MnII2(bpym)(H2O)2[NbIV(CN)8]} (3), respectively. 1-3 were examined by X-ray crystallography and vibrational and magnetochemical studies. 1 is characterized by the coexistence of 3D inorganic cyano-bridged and 1D organic [Mn-(micro-pyz)]n2n+ sublattices along with the presence of monocoordinated and crystallization molecules of pyrazine. Assemblies 2 and 3 exhibit dimeric {MnII2-(micro-L)}4+ coordination motifs. The magnetic behavior of heterobimetallic 1-3 complexes is dominated by antiferromagnetic coupling between MnII and NbIV centers mediated by cyano bridges, resulting in long-range ferrimagnetic ordering with a high TC of 27 (1), 37 (2), and 50 K (3). The magneto-structural correlation leads to the conclusion that the magnitude of TC is related to the type of coordination polyhedra of [Nb(CN)8] moieties (SAPR (1), intermediate between SAPR and DD (2), and DD (3)), the relative number of cyano bridges per Mn2Nb unit, and coexistence of inorganic and organic connectivity. FC/ZFC responses appear to be sensitive to the degree of organic connectivity. The discussion of magneto-structural correlation is based on the spin-density properties of adequate heterobimetallic systems containing octacyanometalates.

  3. 高氮奥氏体钢的韧脆转变与层错能的关系%Study on relationship between ductile to brittle transition and stacking fault energy of high nitrogen containing austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    马玉喜

    2011-01-01

    在60℃至室温范围内,采用夏比冲击试验测定材料的韧一脆转变温度,并通过对冲击断口的X-射线测试层错能等方法,对几种不同含氮量奥氏体不锈钢在低温下发生韧一脆转变的现象进行了研究.结果表明:在超高氮奥氏体钢中,随氮质量分数的增加该钢种发生韧一脆转变的温度上升,层错能减少,韧性越来越差.%The DBTT of super-high nitrogen containing austenitic stainless steels was tested at temperatures between room-temperature and -60 ℃ by Charpy-type test, and its ductility and brittleness transition were investigated under low temperature by XRD method. The results show that the ductile to brittle transition temperature (DBTT) of high nitrogen containing austenitic stainless steels depends on the nitrogen content in the steel, and the DBTT is shifted from low temperature to high temperature. In addition,with the increase of nitrogen content, the stacking fault energy is decreased and the ductility is getting worse.

  4. Carbide precipitation in austenitic stainless steel carburized at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, F. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)]. E-mail: frank.ernst@case.edu; Cao, Y. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Michal, G.M. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)

    2007-04-15

    Low-temperature gas-phase carburization can significantly improve the surface mechanical properties and corrosion resistance of austenitic stainless steel by generating a single-phase 'case' with concentrations of interstitially dissolved carbon exceeding the equilibrium solubility limit by orders of magnitude. Upon prolonged treatment, however, carbides (mostly {chi}, M{sub 5}C{sub 2}) can precipitate and degrade the properties. High-resolution and spatially resolved analytical transmission electron microscopy revealed the precise carbide-austenite orientation relationship, a highly coherent interface, and that precipitation only occurs when (i) the carbon-induced lattice expansion of the austenite has reached a level that substantially reduces volume-misfit stress and (ii) diffusional transport of nickel, chromium, and iron - enhanced by structural defects - can locally reduce the nickel concentration to the solubility limit of nickel in {chi}-carbide.

  5. Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line

    Energy Technology Data Exchange (ETDEWEB)

    Talha, Mohd [Centre of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University) Varanasi 221005, Uttar Pradesh (India); Kumar, Sanjay [Centre of Advanced Study, Department of Zoology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh (India); Behera, C.K. [Centre of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University) Varanasi 221005, Uttar Pradesh (India); Sinha, O.P., E-mail: opsinha.met@itbhu.ac.in [Centre of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University) Varanasi 221005, Uttar Pradesh (India)

    2014-02-01

    The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation. - Graphical abstract: Effect of cold working on in-vitro biocompatibility of indigenized Ni-free nitrogen bearing austenitic stainless steels was explored using Dalton's Lymphoma cell line. Cell proliferation and cell adhesion increase by increasing the degree of cold working and nitrogen content in steel indicating that indigenized material is more biocompatible and no negative effect of cold working on these steels. - Highlights: • Effect of cold working on biocompatibility of Ni-free austenitic stainless steels • Cell proliferation and adhesion increase with nitrogen and degree of cold working. • Contact angle values decrease with nitrogen and degree of cold working.

  6. Creep properties and microstructure of the new wrought austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Vlasak, T.; Hakl, J.; Novak, P. [SVUM a.s., Prague (Czech Republic); Vyrostkova, A. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Materials Research

    2010-07-01

    The contribution is oriented on the new wrought austenitic steel BGA4 (Cr23Ni15Mn6Cu3W1.5NbVMo) developed by the British Corus Company. Our main aim is to present creep properties studied in SVUM a.s. Prague during COST 536 programme. The dependencies of the creep strength, strength for specific creep strain and minimum creep strain rate were evaluated on the basis of long term creep tests carried out at temperature interval (625; 725) C. Important part of a paper is metallographic analysis. (orig.)

  7. Translocation of Cd and Mn from Bark to Leaves in Willows on Contaminated Sediments: Delayed Budburst Is Related to High Mn Concentrations

    Directory of Open Access Journals (Sweden)

    Bart Vandecasteele

    2015-04-01

    Full Text Available Changes in the hydrology of sediments in tidal marshes or landfills may affect the uptake of metals in the vegetation. Leaf and stem samples of Salix cinerea (grey sallow were collected during four consecutive growing seasons at six contaminated plots on a polluted dredged sediment landfill and one plot on an uncontaminated reference site. The first three contaminated plots were already emerged in the first half of the first growing season, while the other three were submerged in the first year, but became increasingly dry over the study period. Foliar and stem cutting concentrations for Cd, Zn and Mn increased on the latter three plots over the four years. Willow bark contained high concentrations of Cd, Zn and Mn. In two consecutive greenhouse experiments with willow cuttings from different origins (uncontaminated and contaminated sites and grown under different soil conditions (uncontaminated and contaminated, we observed an important translocation of Mn from bark to shoots. In a third experiment with willow cuttings collected on soils with a range of heavy metal concentrations and, thus, with a broad range of Cd (4–67 mg/kg dry matter, Zn (247–660 mg/kg dry matter and Mn (38–524 mg/kg dry matter concentrations in the bark, high Mn concentrations in the bark were found to affect the budburst of willow cuttings, while no association of delayed budburst with Cd and Zn concentrations in the bark was found. We conclude that wood and, especially, bark are not a sink for metals in living willows. The high Mn concentrations in the bark directly or indirectly caused delayed or restricted budburst of the willow cuttings.

  8. Tuning the Morphologies of MnO/C Hybrids by Space Constraint Assembly of Mn-MOFs for High Performance Li Ion Batteries.

    Science.gov (United States)

    Sun, Dan; Tang, Yougen; Ye, Delai; Yan, Jun; Zhou, Haoshen; Wang, Haiyan

    2017-02-15

    Morphology controllable fabrication of electrode materials is of great significance but is still a major challenge for constructing advanced Li ion batteries. Herein, we propose a novel space constraint assembly approach to tune the morphology of Mn(terephthalic acid) (PTA)-MOF, in which benzonic acid was employed as a modulator to adjust the available MOF assembly directions. As a result, Mn(PTA)-MOFs with microquadrangulars, microflakes, and spindle-like microrods morphologies have been achieved. MnO/C hybrids with preserved morphologies were further obtained by self-sacrificial and thermal transformation of Mn(PTA)-MOFs. As anodes for Li ion batteries, these morphologies showed great influence on the electrochemical properties. Owing to the abundant porous structure and unique architecture, the MnO/C spindle-like microrods demonstrated superior electrochemical properties with a high reversible capacity of 1165 mAh g(-1) at 0.3 A g(-1), excellent rate capability of 580 mAh g(-1) at 3 A g(-1), and no considerable capacity loss after 200 cycles at 1 A g(-1). This strategy could be extended to engineering the morphology of other MOF-derived functional materials in various structure-dependent applications.

  9. Texture Dependent Young's Modulus in Austenitic Cladding

    OpenAIRE

    1988-01-01

    In Austenitic claddings of pressure vessel steel columnar grains with a 〈100〉-fiber axis oriented perpendicular to the surface have been previously observed. The fiber axis is parallel to the steepest temperature gradient. Since high temperature gradients also exist in the plane of cladding, preferred orientation should be found there.This was proved with {111}- and {220}-pole figures taken of the cladding in addition to {200}-pole figures. From these pole figures it could be concluded that t...

  10. Covalent magnetism, exchange interactions and anisotropy of the high temperature layered antiferromagnet MnB₂.

    Science.gov (United States)

    Khmelevskyi, S; Mohn, P

    2012-01-11

    The investigation of the electronic structure and magnetism for the compound MnB(2) with crystal structure type AlB(2) has been revisited to resolve contradictions between various experimental and theoretical results present in the literature. We find that MnB(2) exhibits an interesting example of a Kübler's covalent magnetism (Williams et al 1981 J. Appl. Phys. 52 2069). The covalent magnetism also appears to be the source of some disagreement between the calculated values of the magnetic moments and those given by neutron diffraction experiments. We show that this shortcoming is due to the atomic sphere approximation applied in earlier calculations. The application of the disordered local moment approach and the calculation of the inter-atomic exchange interactions within the Liechtenstein formalism reveal strong local moment antiferromagnetism with a high Néel temperature predicted from Monte Carlo simulations. A fully relativistic band structure calculation and then the application of the torque method yields a strong in-plane anisotropy of the Mn magnetic moments. The agreement of these results with neutron diffraction studies rules out any possible weak itinerant electron magnetism scenarios as proposed earlier for MnB(2).

  11. Observation of the TWIP + TRIP Plasticity-Enhancement Mechanism in Al-Added 6 Wt Pct Medium Mn Steel

    Science.gov (United States)

    Lee, Seawoong; Lee, Kyooyoung; De Cooman, Bruno C.

    2015-06-01

    The intercritically annealed Fe-0.15 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl and Fe-0.30 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl medium Mn steels were found to have improved mechanical properties due to the TWIP and TRIP plasticity-enhancing mechanisms being activated in succession during tensile deformation. The increase of the C content from 0.15 to 0.30 pct resulted in ultra-high strength properties and a strength-ductility balance of approximately 65,000 MPa-pct, i.e., equivalent to the strength-ductility balance of high Mn TWIP steel with a fully austenitic microstructure.

  12. Magnetic properties of Mn1.9Cu0.1Sb under high pressure

    Science.gov (United States)

    Matsumoto, Yoshihiro; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Hiroi, Masahiko; Mitsui, Yoshifuru; Koyama, Keiichi

    2016-08-01

    Magnetization measurements were carried out for polycrystalline Mn1.9Cu0.1Sb in magnetic fields up to 5 T in the 10-300 K temperature range under high pressures up to 1 GPa in order to investigate the magnetic properties and the thermal transformation arrest (TTA) phenomenon under high pressures. The spin-reorientation temperature increased from 202 K for 0.1 MPa to 244 K for 1 GPa, whereas the transition temperature from the ferrimagnetic (FRI) to antiferromagnetic (AFM) state did not drastically change at ˜116 K. The magnetic relaxation behavior from the FRI to AFM state was observed in 10 < T ≤ 70 K, which was analyzed using the Kohlrausch-Williams-Watts model. Obtained results indicated that the TTA phenomenon of Mn1.9Cu0.1Sb was suppressed by the application of high pressures.

  13. L10-MnGa based magnetic tunnel junction for high magnetic field sensor

    Science.gov (United States)

    Zhao, X. P.; Lu, J.; Mao, S. W.; Yu, Z. F.; Wang, H. L.; Wang, X. L.; Wei, D. H.; Zhao, J. H.

    2017-07-01

    We report on the investigation of the magnetic tunnel junction structure designed for high magnetic field sensors with a perpendicularly magnetized L10-MnGa reference layer and an in-plane magnetized Fe sensing layer. A large linear tunneling magnetoresistance ratio up to 27.4% and huge dynamic range up to 5600 Oe have been observed at 300 K, with a low nonlinearity of 0.23% in the optimized magnetic tunnel junction (MTJ). The field response of tunneling magnetoresistance is discussed to explain the field sensing properties in the dynamic range. These results indicate that L10-MnGa based orthogonal MTJ is a promising candidate for a high performance magnetic field sensor with a large dynamic range, high endurance and low power consumption.

  14. Microstructure Changes during Cavitation Erosion for a Steel with Metastable Austenite

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The characteristics of microstructure changes during cavitation erosion (CE) were investigatedby the use of XRD and TEM analyses for steel (ZG0Cr13Mn8N) with metastable austenite.The results show that the microstructure of the surface layer of the specimens consists of α'-martensite, metastable austenite and a few ε-martensite before CE. CE obviously increases dislocation density and straight or planar dislocations on the surface, and induces γ → ε, ε → α'and γ → α'-martensitic transformation.

  15. Synthesis of colloidal Mn2+:ZnO quantum dots and high-TC ferromagnetic nanocrystalline thin films.

    Science.gov (United States)

    Norberg, Nick S; Kittilstved, Kevin R; Amonette, James E; Kukkadapu, Ravi K; Schwartz, Dana A; Gamelin, Daniel R

    2004-08-04

    We report the synthesis of colloidal Mn(2+)-doped ZnO (Mn(2+):ZnO) quantum dots and the preparation of room-temperature ferromagnetic nanocrystalline thin films. Mn(2+):ZnO nanocrystals were prepared by a hydrolysis and condensation reaction in DMSO under atmospheric conditions. Synthesis was monitored by electronic absorption and electron paramagnetic resonance (EPR) spectroscopies. Zn(OAc)(2) was found to strongly inhibit oxidation of Mn(2+) by O(2), allowing the synthesis of Mn(2+):ZnO to be performed aerobically. Mn(2+) ions were removed from the surfaces of as-prepared nanocrystals using dodecylamine to yield high-quality internally doped Mn(2+):ZnO colloids of nearly spherical shape and uniform diameter (6.1 +/- 0.7 nm). Simulations of the highly resolved X- and Q-band nanocrystal EPR spectra, combined with quantitative analysis of magnetic susceptibilities, confirmed that the manganese is substitutionally incorporated into the ZnO nanocrystals as Mn(2+) with very homogeneous speciation, differing from bulk Mn(2+):ZnO only in the magnitude of D-strain. Robust ferromagnetism was observed in spin-coated thin films of the nanocrystals, with 300 K saturation moments as large as 1.35 micro(B)/Mn(2+) and T(C) > 350 K. A distinct ferromagnetic resonance signal was observed in the EPR spectra of the ferromagnetic films. The occurrence of ferromagnetism in Mn(2+):ZnO and its dependence on synthetic variables are discussed in the context of these and previous theoretical and experimental results.

  16. The mechanical stability of retained austenite in low-alloyed TRIP steel under shear loading

    Energy Technology Data Exchange (ETDEWEB)

    Blondé, R., E-mail: r.j.p.blonde@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Jimenez-Melero, E., E-mail: enrique.jimenez-melero@manchester.ac.uk [Dalton Cumbrian Facility, The University of Manchester, Westlakes Science and Technology Park, Moor Row, Cumbria CA24 3HA (United Kingdom); Zhao, L., E-mail: lie.zhao@tudelft.nl [Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Schell, N., E-mail: norbert.schell@hzg.de [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max Planck Strasse 1, 21502 Geesthacht (Germany); Brück, E., E-mail: e.h.bruck@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Zwaag, S. van der, E-mail: s.vanderzwaag@tudelft.nl [Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands); Dijk, N.H. van, E-mail: n.h.vandijk@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

    2014-01-31

    The microstructure evolution during shear loading of a low-alloyed TRIP steel with different amounts of the metastable austenite phase and its equivalent DP grade has been studied by in-situ high-energy X-ray diffraction. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing simultaneously the evolution of the austenite phase fraction and its carbon concentration, the load partitioning between the austenite and the ferritic matrix and the texture evolution of the constituent phases. Our results show that for shear deformation the TRIP effect extends over a significantly wider deformation range than for simple uniaxial loading. A clear increase in average carbon content during the mechanically-induced transformation indicates that austenite grains with a low carbon concentration are least stable during shear loading. The observed texture evolution indicates that under shear loading the orientation dependence of the austenite stability is relatively weak, while it has previously been found that under tensile load the {110}〈001〉 component transforms preferentially. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between the interstitial carbon concentration in the austenite, the grain orientation and the load partitioning.

  17. High-pressure compressibility and vibrational properties of (Ca,Mn)CO 3

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jin; Caracas, Razvan; Fan, Dawei; Bobocioiu, Ema; Zhang, Dongzhou; Mao, Wendy L.

    2016-12-01

    Knowledge of potential carbon carriers such as carbonates is critical for our understanding of the deep-carbon cycle and related geological processes within the planet. Here we investigated the high-pressure behavior of (Ca,Mn)CO3 up to 75 GPa by synchrotron single-crystal X-ray diffraction, laser Raman spectroscopy, and theoretical calculations. MnCO3-rich carbonate underwent a structural phase transition from the CaCO3-I structure into the CaCO3-VI structure at 45–48 GPa, while CaCO3-rich carbonate transformed into CaCO3-III and CaCO3-VI at approximately 2 and 15 GPa, respectively. The equation of state and vibrational properties of MnCO3-rich and CaCO3-rich carbonates changed dramatically across the phase transition. The CaCO3-VI-structured CaCO3-rich and MnCO3-rich carbonates were stable at room temperature up to at least 53 and 75 GPa, respectively. The addition of smaller cations (e.g., Mn2+, Mg2+, and Fe2+) can enlarge the stability field of the CaCO3-I phase as well as increase the pressure of the structural transition into the CaCO3-VI phase.

  18. Solution-Processed Graphene/MnO 2 Nanostructured Textiles for High-Performance Electrochemical Capacitors

    KAUST Repository

    Yu, Guihua

    2011-07-13

    Large scale energy storage system with low cost, high power, and long cycle life is crucial for addressing the energy problem when connected with renewable energy production. To realize grid-scale applications of the energy storage devices, there remain several key issues including the development of low-cost, high-performance materials that are environmentally friendly and compatible with low-temperature and large-scale processing. In this report, we demonstrate that solution-exfoliated graphene nanosheets (∼5 nm thickness) can be conformably coated from solution on three-dimensional, porous textiles support structures for high loading of active electrode materials and to facilitate the access of electrolytes to those materials. With further controlled electrodeposition of pseudocapacitive MnO2 nanomaterials, the hybrid graphene/MnO2-based textile yields high-capacitance performance with specific capacitance up to 315 F/g achieved. Moreover, we have successfully fabricated asymmetric electrochemical capacitors with graphene/MnO 2-textile as the positive electrode and single-walled carbon nanotubes (SWNTs)-textile as the negative electrode in an aqueous Na 2SO4 electrolyte solution. These devices exhibit promising characteristics with a maximum power density of 110 kW/kg, an energy density of 12.5 Wh/kg, and excellent cycling performance of ∼95% capacitance retention over 5000 cycles. Such low-cost, high-performance energy textiles based on solution-processed graphene/MnO2 hierarchical nanostructures offer great promise in large-scale energy storage device applications. © 2011 American Chemical Society.

  19. Magnetic nature of the austenite-martensite phase transition and spin glass behaviour in nanostructured Mn2Ni1.6Sn0.4 melt-spun ribbons

    Science.gov (United States)

    Singh, Nidhi; Borgohain, Barsha; Srivastava, A. K.; Dhar, Ajay; Singh, H. K.

    2016-03-01

    Nanocrystalline ribbons of inverse Heusler alloy Mn2Ni1.6Sn0.4 have been synthesised by melt spinning of the arc-melted bulk precursor. The single-phase ribbons crystallize into a cubic structure and exhibit very fine crystallite size of phase transition that begins at M S ≈ 249 K and finishes at M f ≈ 224 K. During warming, the reverse AFM-M to FM-A transitions begins at A s ≈ 240 K and finishes at A f ≈ 261 K. A re-entrant FM transition is observed in the M-phase at T_{{CM}} ≈ 145 K. These transitions are also confirmed by temperature-dependent resistivity ( ρ- T) measurements. The hysteretic behaviour of M- T and ρ- T in the temperature regime spanned by the A-M transition is a manifestation of the first-order phase transition. M- T and ρ- T data also provide unambiguous evidence in favour of spin glass at T AC susceptibility measurements, confirms the existence of canonical spin glass at T phase.

  20. Petrogenetic significance of high Fe/Mn ratios of the Cenozoic basalts from Eastern China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Cenozoic basalts from eastern China show commonly high Fe/Mn ratios (average = 68.6 ± 11.5) coupled with OIB-type trace element signature. The Cenozoic basalts form the northern margin and the southern margin of the North China Craton are studied in detail. Model calculations point out that the coupling feature of high Fe/Mn ratio with OIB-type trace element signature of these basalts cannot be produced by neither pyroxene/olivine crystallization nor remelting of previously melted mantle, but require partial melting of a garnet pyroxenite-rich mantle source. Combining these features of the Cenozoic basalts with the Phanerozoic lithospheric evolution of the eastern China, we suggest that the Cenozoic basalts were derived from a garnet pyroxenite-rich mantle source associated with continental crust delamination or oceanic crust subduction.

  1. Petrogenetic significance of high Fe/Mn ratios of the Cenozoic basalts from Eastern China

    Institute of Scientific and Technical Information of China (English)

    ZHANG BinHui; LIU YongSheng; GAO Shan

    2008-01-01

    The Cenozoic basalts from eastern China show commonly high Fe/Mn ratios (average = 68.6 卤 11.5) coupled with OIB-type trace element signature. The Cenozoic basalts form the northern margin and the southern margin of the North China Craton are studied in detail. Model calculations point out that the coupling feature of high Fe/Mn ratio with OIB-type trace element signature of these basalts cannot be produced by neither pyroxene/olivine crystallization nor remelting of previously melted mantle, but require partial melting of a garnet pyroxenite-rich mantle source. Combining these features of the Cenozoic basalts with the Phanerozoic lithospheric evolution of the eastern China, we suggest that the Cenozoic basalts were derived from a garnet pyroxenite-rich mantle source associated with continental crust delamination or oceanic crust subduction.

  2. Giant magnetoresistance of novel ferromagnets AMg4Mn6O15 (A=K, Rb, and Cs) with highly symmetric structure

    Science.gov (United States)

    Tanaka, Yudai; Sato, Hirohiko

    2017-04-01

    A novel family of cubic manganese oxides, AMg4Mn6O15 (A=K, Rb, and Cs), were discovered. In this type of structure, the MnO6 octahedra share edges, constructing a highly symmetric framework where Mn atoms form a three-dimensional network of truncated octahedra. The crystallographic site of Mn is unique and the average oxidation state of Mn is 3.5, indicating a mixed-valence electronic state where Mn3+ and Mn4+ sites are completely indistinguishable. These compounds become ferromagnetic with fully polarized magnetic moments of Mn ions. The ferromagnetic transition temperature TC is 170 K, that is considerably high for manganese oxides. The electric resistivity of KMg4Mn6O15 is about 105 Ωcm at 300 K and exhibits a non-metallic temperature dependence. It reveals a large negative magnetoresistance; about 40% of the resistivity is suppressed by 5 T of magnetic field at TC.

  3. Wear behavior of austenite containing plate steels

    Science.gov (United States)

    Hensley, Christina E.

    As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

  4. Effect of Ti doping on high pressure behavior of BiMn{sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, K. K., E-mail: kkpandey@barc.gov.in; Poswal, H. K., E-mail: kkpandey@barc.gov.in; Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 40008 (India); Kumar, Ravi [Centre for Materials Science and Engineering, National Institute of Technology, Hamirpur-177005 (India)

    2014-04-24

    Our high pressure x-ray diffraction studies on BiMn{sub 1.5}Ti{sub 0.5}O{sub 5} show iso-structural phase transition above 12 GPa similar to the one observed in undoped BiMn{sub 2}O{sub 5}; however anisotropic compressional behavior is found to be more enhanced in the doped case. Unlike undoped system, an anomalous lattice expansion along c axis has been observed in BiMn{sub 1.5}Ti{sub 0.5}O{sub 5} above 12 GPa; whereas the b lattice parameter has been found to be more compressible as compared to BiMn{sub 2}O{sub 5}. As doping with Ti reduces the magnetic interactions among Mn ions, the observed changes are suggestive of having adverse magnetic implications in the observed iso-structural phase transition.

  5. Influence of Mn-dopant on the properties of {alpha}-FeOOH particles precipitated in highly alkaline media

    Energy Technology Data Exchange (ETDEWEB)

    Krehula, Stjepko [Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia); Music, Svetozar [Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia)]. E-mail: music@irb.hr

    2006-12-21

    The effects of Mn-dopant on the formation of solid solutions {alpha}-(Fe, Mn)OOH in dependence on the initial concentration ratio r = [Mn]/([Mn] + [Fe]), as well as on the size and morphology of the corresponding particles were investigated using Moessbauer and FT-IR spectroscopies, high-resolution scanning electron microscopy (FE SEM) and an energy dispersive X-ray analyser (EDS). The value of the hyperfine magnetic field of 34.9 T, as recorded for the reference {alpha}-FeOOH sample at RT, decreased linearly up to 21.4 T for sample with r = 0.1667. Only a paramagnetic doublet at RT was recorded for sample with r = 0.2308, a ferrite phase was additionally found for r = 0.3333. Fe-OH bending IR bands, {delta} {sub OH} and {gamma} {sub OH}, were influenced by the Mn-substitution as manifested through their gradual shifts. FE SEM micrographs showed a great elongation of the starting acicular particles along the c-axis with an increase in Mn-doping. For r = 0.1667 and 0.2308 star-shaped and dendritic twin {alpha}-(Fe, Mn)OOH particles were observed. The length of these {alpha}-(Fe, Mn)OOH particles decreased, whereas their width increased. The {alpha}-Fe{sub 2}O{sub 3} phase was not detected in any of the samples prepared.

  6. High-efficiency super capacitors based on hetero-structured α-MnO{sub 2} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ghouri, Zafar Khan [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shaheer Akhtar, M. [New & Renewable Energy Material Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of); Zahoor, Awan [Department of Chemical Engineering, NED University of Engineering & Technology, University Road, Karachi 75270 (Pakistan); Barakat, Nasser A.M., E-mail: nasser@jbnu.ac.kr [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Chemical Engineering, Faculty of Engineering, El-Minia University, El-Minia (Egypt); Han, Weidong [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Park, Mira [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kim, Hak Yong, E-mail: khy@jbnu.ac.kr [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2015-09-05

    Highlights: • Hetero-structured α-MnO{sub 2} nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg{sup −1} with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO{sub 2}) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO{sub 2} nanorods. Supercapacitive performance of the hetero-structured α-MnO{sub 2} nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO{sub 2} hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO{sub 6}] structure yield a significantly high specific capacitance of 298 Fg{sup −1} at 5 mV s{sup −1} and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO{sub 2} electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.

  7. Variations in the microstructure and properties of Mn-Ti multiple-phase steel with high strength under different tempering temperatures

    Science.gov (United States)

    Li, Dazhao; Li, Xiaonan; Cui, Tianxie; Li, Jianmin; Wang, Yutian; Fu, Peimao

    2015-03-01

    There are few relevant researches on coils by tempering, and the variations of microstructure and properties of steel coil during the tempering process also remain unclear. By using thermo-mechanical control process(TMCP) technology, Mn-Ti typical HSLA steel coils with yield strength of 920 MPa are produced on the 2250 hot rolling production line. Then, the samples are taken from the coils and tempered at the temperatures of 220 °C, 350 °C, and 620 °C respectively. After tempering the strength, ductility and toughness of samples are tested, and meanwhile microstructures are investigated. Precipitates initially emerge inside the ferrite laths and the density of the dislocation drops. Then, the lath-shaped ferrites begin to gather, and the retained austenite films start to decompose. Finally, the retained austenite films are completely decomposed into coarse and short rod-shape precipitates composed of C and Ti compounds. The yield strength increases with increasing tempering temperature due to the pinning effect of the precipitates, and the dislocation density decreases. The yield strength is highest when the steel is tempered at 220 °C because of pinning of the precipitates to dislocations. The total elongation increases in all samples because of the development of ferrites during tempering. The tensile strength and impact absorbed energy decline because the effect of impeding crack propagation weakens as the retained austenite films completely decompose and the precipitates coarsen. This paper clarifies the influence of different tempering temperatures on phase transformation characteristics and process of Mn-Ti typical multiphase steels, as well as its resulting performance variation rules.

  8. Variations in the Microstructure and Properties of Mn-Ti Multiple-phase Steel with High Strength under Different Tempering Temperatures

    Institute of Scientific and Technical Information of China (English)

    LI Dazhao; LI Xiaonan; CUI Tianxie; LI Jianmin; WANG Yutian; FU Peimao

    2015-01-01

    There are few relevant researches on coils by tempering, and the variations of microstructure and properties of steel coil during the tempering process also remain unclear. By using thermo-mechanical control process(TMCP) technology, Mn-Ti typical HSLA steel coils with yield strength of 920 MPa are produced on the 2250 hot rolling production line. Then, the samples are taken from the coils and tempered at the temperatures of 220 ℃, 350 ℃, and 620 ℃ respectively. After tempering the strength, ductility and toughness of samples are tested, and meanwhile microstructures are investigated. Precipitates initially emerge inside the ferrite laths and the density of the dislocation drops. Then, the lath-shaped ferrites begin to gather, and the retained austenite films start to decompose. Finally, the retained austenite films are completely decomposed into coarse and short rod-shape precipitates composed of C and Ti compounds. The yield strength increases with increasing tempering temperature due to the pinning effect of the precipitates, and the dislocation density decreases. The yield strength is highest when the steel is tempered at 220 ℃ because of pinning of the precipitates to dislocations. The total elongation increases in all samples because of the development of ferrites during tempering. The tensile strength and impact absorbed energy decline because the effect of impeding crack propagation weakens as the retained austenite films completely decompose and the precipitates coarsen. This paper clarifies the influence of different tempering temperatures on phase transformation characteristics and process of Mn-Ti typical multiphase steels, as well as its resulting performance variation rules.

  9. Characterization of High Dose Mn, Fe, and Ni implantation into p-GaN

    CERN Document Server

    Pearton, S J; Thaler, G; Abernathy, C R; Theodoropoulou, N; Hebard, A F; Chu, S N G; Wilson, R G; Zavada, J M; Polyakov, A Y; Osinsky, A V; Norris, P E; Chow, P P; Wowchack, A M; Hove, J M V; Park, Y D

    2002-01-01

    The magnetization of p-GaN or p-AlGaN/GaN superlattices was measured after implantation with high doses (3-5x10 sup 1 sup 6 cm sup - sup 2) of Mn, Fe, or Ni and subsequent annealing at 700-1000 deg. C. The samples showed ferromagnetic contributions below temperatures ranging from 190-250 K for Mn to 45-185 K for Ni and 80-250 K for Fe. The use of superlattices to enhance the hole concentration did not produce any change in ferromagnetic ordering temperature. No secondary phase formation was observed by x-ray diffraction, transmission electron microscopy, or selected area diffraction pattern analysis for the doses we employed.

  10. Investigation of high temperature annealing effectiveness for recovery of radiation-induced structural changes and properties of 18Cr-10Ni-Ti austenitic stainless steels

    Science.gov (United States)

    Gurovich, B. A.; Kuleshova, E. A.; Frolov, A. S.; Maltsev, D. A.; Prikhodko, K. E.; Fedotova, S. V.; Margolin, B. Z.; Sorokin, A. A.

    2015-10-01

    A complex study of structural state and properties of 18Cr-10Ni-Ti austenitic stainless steel after irradiation in BOR-60 fast research reactor (in the temperature range 330-400 °C up to damaging doses of 145 dpa) and in VVER-1000 light water reactor (at temperature ∼320 °C and damaging doses ∼12-14 dpa) was performed. The possibility of recovery of structural-phase state and mechanical properties to the level almost corresponding to the initial state by the recovery annealing was studied. The principal possibility of the recovery annealing of pressurized water reactor internals that ensures almost complete recovery of its mechanical properties and microstructure was shown. The optimal mode of recovery annealing was established: 1000 °C during 120 h.

  11. High capacity MnOx:ZrO2 sorbent for elementary mercury capture: preparation, characterization and comparison to other sorbents

    Science.gov (United States)

    Lakatos, J.; Snape, C. E.

    2017-02-01

    Manganese oxide-zirconia type (MnOx:ZrO2) sorbents were prepared using the sol-gel technique by co precipitation ZrO(NO3)2.xH2O and Mn(NO3)2 xH2O. The heat treatment below 500°C resulted a high surface area solid structure which consists of amorphous Mn2O3 (Bixbyite) and amorphous ZrO2 phases. This material was found a high capacity oxidative sorbent for mercury removal from gas streams.

  12. In-Situ Alignment of MnBi Crystals Induced by High Magnetic Field above Curie Temperature

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-Sheng; ZHANG Jin-Cang; REN Zhong-Ming; CAO Shi-Xun

    2007-01-01

    @@ Above Curie temperature, MnBi crystals are aligned in situ along the c-axis in a Bi matrix by a high fabrication magnetic field Hf of 10 T. Magnetic testing shows a pronounced anisotropy in magnetization in directions normal and parallel to the fabrication field, resulting from the alignment. The successful alignment may result from the fact that the easy magnetization direction is along the c-axis of MnBi and the high fabrication field of 10 T is large enough to rotate the MnBi crystal to this direction even though the temperature is above the Curie temperature.

  13. Kinetics of decomposition of undercooled austenite formed in the critical range of temperatures

    Science.gov (United States)

    Shveikin, V. P.; Khotinov, V. A.; Farber, V. M.

    2007-11-01

    Using dilatometric and microstructural methods, the thermokinetic diagrams of decomposition of undercooled austenite formed upon heating in the intercritical temperature range have been constructed for a group of steels with 0.05 0.10% C, 0.15 1.63% Mn, 0.17 1.18% Si, and 0.003% B. The effect of the compositions of the steels, temperature of heating in the two-phase region, and rate of subsequent cooling on the kinetics of the formation of austenite and products of its decomposition has been considered. The carbon content in austenite at different temperatures of its formation has been estimated from the position of the temperature of the onset of the martensitic transformation.

  14. The effect of austenitizing treatments on the microstructure and creep properties of commercial and high purity 1/2Cr-1/2Mo-1/4V steels

    Energy Technology Data Exchange (ETDEWEB)

    Varma, R.K.; Tipler, H.R.

    1980-08-01

    Techniques used to produce specimens with specific creep properties from two types of 1/2 Cr 1/2 Mo 1/4 V steel, i.e., high purity and commercial purity, having different hardening and grain growth characteristics are described. The production of steels with identical microstructures was desired to provide material for an investigation of the effect of complex stresses in creep. Material for samples was produced by hot rolling at 1050 C. In general the high purity steel has better hardening characteristics and is also more prone to grain growth. Consequently, it was necessary to investigate the effects of various austenitizing conditions and of different rates of cooling on the microstructures obtained. The results of unlaxial creep tests are consistent with those previously obtained on similar steels. (ESA)

  15. Solid Solution Nitriding Technology of 15Cr-7.5Mn-2.6Mo Duplex Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    FU Rui-dong; ZHAO Pin; WANG Chun-Yu; QIU Liang; ZHENG Yang-zeng

    2004-01-01

    Solid solution nitriding technologies of 15Cr-7.5Mn-2.6Mo duplex stainless steel were investigated by using of orthogonal tests. The results show that the best technology would be the processes of 1050℃× 2h + 1150℃× 3h +1050℃× 2h + 1150℃× 4h under pure N2 with PN2=0.15MPa. The high nitrogen austenitic case with the depth of1.62mm can be obtained. Orthogonal tests show that the type of atmosphere has the most notable effect on solid solution nitriding process; the pressure in the furnace and the nitriding processes has a notable effect. X-ray diffraction analyses results indicate that the main phases in the cases of the solution-nitrided samples cooled in the furnace are high nitrogen austenite, CrN, Fe3O4 and nitrogen containing ferrite. In the other samples experienced solid solution nitriding and solution treatment the obtained phase in the cases is high nitrogen austenite only. The results show that solid solution nitriding is a process that nitrogen absolutely diffuses in the austenite. The diffusing activation energy in the conditions of PN2 = 0.15MPa and 1050℃~ 1200℃ is 186.6K J/mol.

  16. High-temperature characteristics of 20MnB4 and 30MnB4 micro-addition cold upsetting steels and C45 and C70 high-carbon-steels

    Directory of Open Access Journals (Sweden)

    S. Sawicki

    2016-10-01

    Full Text Available The paper analyzes the high-temperature plasticity characteristics of 20MnB4 and 30MnB4 with micro-additives, intended for cold upsetting and high-carbon steels C45 and C70 in the “solid phase-liquid” during heating and cooling. The investigation was conducted to determine the plastic formability of the examined alloy under hot plastic working conditions. Experiments were carried out on the simulator Gleeble 3800 with the aim of determining the susceptibility of 20MnB4, 30MnB4, C45 and C70 steels to cracking at high temperature. The nil strength (NST, nil ductility (NDT and ductility recovery temperatures (DRT, and the fracture toughness factor and the BRT (brittleness temperature range have been determined.

  17. Effect of Chemical Composition on Structure and Corrosion Resistance of Ni-Mn-Cu Cast Iron

    Directory of Open Access Journals (Sweden)

    Medyński D.

    2016-09-01

    Full Text Available In the paper, a relationship between chemical composition of Ni-Mn-Cu cast iron and its structure, hardness and corrosion resistance is determined. The examinations showed a decrease of thermodynamic stability of austenite together with decreasing nickel equivalent value, in cast iron solidifying according to both the stable and the metastable systems. As a result of increasing degree of austenite transformation, the created martensite caused a significant hardness increase, accompanied by small decline of corrosion resistance. It was found at the same time that solidification way of the alloy and its matrix structure affect corrosion resistance to a much smaller extent than the nickel equivalent value, in particular concentration of elements with high electrochemical potential.

  18. Electronic properties and native point defects of high efficient NO oxidation catalysts SmMn2O5

    Science.gov (United States)

    Li, Hao-Bo; Yang, Zhi; Liu, Jieyu; Yao, Xiaolong; Xiong, Ka; Liu, Hui; Wang, Wei-Hua; Lu, Feng; Wang, Weichao

    2016-11-01

    Mn-based oxide SmMn2O5 exhibits great catalytic performance in NO oxidation [Wang et al., Science 337, 832 (2012)]. Nevertheless, the fundamental understanding of SmMn2O5 properties is so far not fully accessible. Here, the SmMn2O5 nanoparticles are synthesized through hydrothermal methods, and the pure phase of triclinic SmMn2O5 is characterized by high-resolution tunneling electron microscope and X-ray diffraction. Furthermore, the X-ray photoelectron spectroscopy, absorption, photoluminescence spectra (PL), and density functional theory based first-principles calculations are employed to explore the fundamental electronic structures of pristine and defective SmMn2O5. Combined with band structure calculations, light absorption, and PL spectra, we first show that SmMn2O5 presents an insulating behavior with an indirect band gap of ˜1.0 eV. Between the two types of crystal fields, i.e., octahedral and tetrahedral, the later one contributes to the dz2 of the valence band edge, resulting in superior catalytic performance of NO oxidation. Furthermore, the native point defects in SmMn2O5 are first reported. Among the various native point defects, we demonstrate that oxygen vacancy (VO) shows the lowest formation energy in oxygen poor conditions, while the oxygen interstitial (Oi) and Mn vacancies are energetically favorable in oxygen rich situations. In other words, SmMn2O5 could be potentially utilized as an oxygen storage material.

  19. Spinel LiMn2O4 nanohybrid as high capacitance positive electrode material for supercapacitors

    Science.gov (United States)

    Wang, F. X.; Xiao, S. Y.; Zhu, Y. S.; Chang, Z.; Hu, C. L.; Wu, Y. P.; Holze, R.

    2014-01-01

    A LiMn2O4 nanohybrid consisting of nanotubes, nanorods and nanoparticles has been synthesized using α-MnO2 nanotubes from hydrothermal reaction as a precursor. It is characterized with X-ray diffraction, field emission scanning electron and transmission electron microscopy. A formation mechanism is proposed. As a positive electrode material for supercapacitors, it exhibits a high specific discharge capacitance of 415 F g-1 at 0.5 A g-1 in 0.5 mol l-1 Li2SO4 aqueous solution. Even at 10 A g-1, it still has a specific discharge capacitance of 208 F g-1. The energy density of the asymmetric supercapacitor using activated carbon as the negative electrode and LiMn2O4-nanohybrid as the positive electrode in the aqueous solution in the voltage range of 0-1.8 V presents 29.8 Wh kg-1 at power density of 90 W kg-1. In addition, the cycling behavior of the asymmetric supercapacitor is good.

  20. High temperature far-infrared dynamics of orthorhombic NdMnO3: emissivity and reflectivity.

    Science.gov (United States)

    Massa, Néstor E; del Campo, Leire; Meneses, Domingos De Sousa; Echegut, Patrick; Martínez-Lope, María Jesús; Alonso, José Antonio

    2013-06-12

    We report on near normal far- and mid-infrared emission and reflectivity of NdMnO3 perovskite from room temperature to sample decomposition above 1800 K. At 300 K the number of infrared active phonons is in close agreement with the 25 calculated for the orthorhombic D(2h)(16)-Pbnm (Z = 4) space group. Their number gradually decreases as we approach the temperature of orbital disorder at ~1023 K where the orthorhombic O' lower temperature cooperative phase coexists with the cubic orthorhombic O. At above ~1200 K, the three infrared active phonons coincide with that expected for cubic Pm-3m (Z = 1) in the high temperature insulating regime. Heating samples in dry air triggers double exchange conductivity by Mn(3+) and Mn(4+) ions and a small polaron mid-infrared band. Fits to the optical conductivity single out the octahedral antisymmetric and symmetric vibrational modes as the main phonons in the electron-phonon interactions at 875 K. For 1745 K, it is enough to consider the symmetric stretching internal mode. An overdamped defect induced Drude component is clearly outlined at the highest temperatures. We conclude that rare earth manganite eg electrons are prone to spin, charge, orbital, and lattice couplings in an intrinsic orbital distorted perovskite lattice, favoring embryonic low energy collective excitations.

  1. Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating

    Science.gov (United States)

    Ye, Qingfeng; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Li, Ruifeng; Huang, Jian; Wu, Yixiong

    2017-02-01

    Equimolar CrMnFeCoNi high entropy alloy (HEA) is one of the most notable single phase multi-component alloys up-to-date with promising mechanical properties at cryogenic temperatures. However, the study on the corrosion behavior of CrMnFeCoNi HEA coating has still been lacking. In this paper, HEA coating with a nominal composition of CrMnFeCoNi is fabricated by laser surface alloying and studied in detail. Microstructure and chemical composition are determined by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are used to investigate the corrosion behavior. The coating forms a simple FCC phase with an identical dendritic structure composed of Fe/Co/Ni-rich dendrites and Mn/Ni-rich interdendrites. Both in 3.5 wt.% NaCl solution and 0.5 M sulfuric acid the coating exhibits nobler corrosion resistance than A36 steel substrate and even lower icorr than 304 stainless steel (304SS). EIS plots coupled with fitted parameters reveal that a spontaneous protective film is formed and developed during immersion in 0.5 M sulfuric acid. The fitted Rt value reaches its maximum at 24 h during a 48 h' immersion test, indicating the passive film starts to break down after that. EDS analysis conducted on a corroded surface immersed in 0.5 M H2SO4 reveals that corrosion starts from Cr-depleted interdendrites.

  2. Colloidal Organolead Halide Perovskite with a High Mn Solubility Limit: A Step Toward Pb-Free Luminescent Quantum Dots.

    Science.gov (United States)

    Arunkumar, Paulraj; Gil, Kyeong Hun; Won, Seob; Unithrattil, Sanjith; Kim, Yoon Hwa; Kim, Ha Jun; Im, Won Bin

    2017-09-07

    Organolead halide perovskites have emerged as a promising optoelectronic material for lighting due to its high quantum yield, color-tunable, and narrow emission. Despite their unique properties, toxicity has intensified the search for ecofriendly alternatives through partial or complete replacement of lead. Herein, we report a room-temperature synthesized Mn(2+)-substituted 3D-organolead perovskite displacing ∼90% of lead, simultaneously retaining its unique excitonic emission, with an additional orange emission of Mn(2+) via energy transfer. A high Mn solubility limit of 90% was attained for the first time in lead halide perovskites, facilitated by the flexible organic cation (CH3NH3)(+) network, preserving the perovskite structure. The emission intensities of the exciton and Mn were influenced by the halide identity that regulates the energy transfer to Mn. Homogeneous emission and electron spin resonance characteristics of Mn(2+) indicate a uniform distribution of Mn. These results suggest that low-toxicity 3D-CH3NH3Pb1-xMnxBr3-(2x+1)Cl2x+1 nanocrystals may be exploited as magnetically doped quantum dots with unique optoelectronic properties.

  3. Mn(II)-based porous metal-organic framework showing metamagnetic properties and high hydrogen adsorption at low pressure.

    Science.gov (United States)

    Han, Zheng-Bo; Lu, Rui-Yun; Liang, Yan-Fang; Zhou, Yan-Ling; Chen, Qing; Zeng, Ming-Hua

    2012-01-02

    A Mn(II)-based homometallic porous metal-organic framework, Mn(5)(btac)(4)(μ(3)-OH)(2)(EtOH)(2)·DMF·3EtOH·3H(2)O (1, btac = benzotriazole-5-carboxylate), has been solvothermally synthesized and structurally characterized by elemental analysis, thermogravimetric analysis, and X-ray crystallographic study. 1 is a 3D neutral framework featuring 1D porous channels constructed by {Mn-OH-Mn}(n) chains and btac linkers. Magnetic studies show that 1 is a 3D metamagnet containing 1D {Mn-OH-Mn}(n) ferrimagnetic chains. High-pressure H(2) adsorption measurement at 77 K reveals that activated 1 can absorb 0.99 wt % H(2) at 0.5 atm and reaches a maximum of 1.03 wt % at 5.5 atm. The steep H(2) absorption at lower pressure (98.2% of the storage capacity at 0.5 atm) is higher than the corresponding values of some MOFs (MIL-100 (16.1%), MOF-177 (57.1%), and MOF-5 (22.2%)). Furthermore, activated 1 can adsorb CO(2) at room temperature and 275 K. The adsorption enthalpy is 22.0 kJ mol(-1), which reveals the high binding ability for CO(2). Detailed gas sorption implies that the exposed Mn(II) coordination sites in the activated 1 play an important role to improve its adsorption capacities.

  4. Role of quaternary additions on dislocated martensite, retain austenite and mechanical properties of Fe/Cr/C structural steels

    Energy Technology Data Exchange (ETDEWEB)

    Rao, B.V.N.

    1978-02-01

    The influence of quaternary alloy additions of Mn and Ni to Fe/Cr/C steels which have been designed to provide superior mechanical properties has been investigated. Transmission electron microscopy and x-ray analysis revealed increasing amounts of retained austenite with Mn up to 2 w/o and with 5 w/o Ni additions after quenching from 1100/sup 0/C. This is accompanied by a corresponding improvement in toughness properties of the quaternary alloys. In addition, the generally attractive combinations of strength and toughness in these quaternary alloys is attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. Grain-refining resulted in a further increase in the amount of retained austenite.

  5. Molecular dynamics simulations of spinels: LiMn2O4 and Li4Mn5O12 at high temperatures

    Science.gov (United States)

    Ledwaba, R. S.; Matshaba, M. G.; Ngoepe, P. E.

    2015-04-01

    Energy storage technologies are critical in addressing the global challenge of clean sustainable energy. Spinel lithium manganates have attracted attention due to their electrochemical properties and also as promising cathode materials for lithium-ion batteries. The current study focused on the effects of high temperatures on the materials, in order to understand the sustainability in cases where the battery heats up to high temperature and analysis of lithium diffusion aids in terms of intercalation host compatibility. It is also essential to understand the high temperature behaviour and lithium ion host capability of these materials in order to perform the armorphization and recrystalization of spinel nano-architectures. Molecular dynamics simulations carried out to predict high temperature behaviour of the spinel systems. The NVE ensemble was employed, in the range 300 - 3000K. The melting temperature, lithium-ion diffusion and structural behaviour were monitored in both supercell systems. LiMn2O4 indicated a diffusion rate that increased rapidly above 1500K, just before melting (˜1700K) and reached its maximum diffusion at 2.756 × 10-7 cm2s-1 before it decreased. Li4Mn5O12 indicated an exponential increase above 700K reaching 8.303 × 10-7 cm2s-1 at 2000K and allowing lithium intercalation even above its melting point of around 1300K. This indicated better structural stability of Li4Mn5O12 and capability to host lithium ions at very high temperatures (up to 3000 K) compared to LiMn2O4.

  6. Shear strain in Nd0.5Ca0.5MnO3 at high pressures.

    Science.gov (United States)

    Arulraj, Anthony; Dinnebier, Robert E; Carlson, Stefan; Hanfland, Michael; van Smaalen, Sander

    2005-04-29

    High-pressure x-ray powder diffraction has been measured on the half doped rare earth manganite Nd0.5Ca0.5MnO3 up to a pressure of 15 GPa. We report the presence of a quantifiable amount of shear distortion of the MnO6 octahedra in Nd0.5Ca0.5MnO3 at high pressures. The lattice strain of Nd0.5Ca0.5MnO3 is minimal at a crossover pressure of p* approximately 7 GPa, with the same lattice strain above and below this pressure achieved by shear and Jahn-Teller-type distortions, respectively. The increase in shear strain with increasing pressure provides a mechanism for the insulating behavior of manganites at high pressures that has not been considered before.

  7. Free-standing and flexible LiMnTiO4/carbon nanotube cathodes for high performance lithium ion batteries

    Science.gov (United States)

    Bao, Yinhua; Zhang, Xingyu; Zhang, Xu; Yang, Le; Zhang, Xinyi; Chen, Haosen; Yang, Meng; Fang, Daining

    2016-07-01

    A flexible, free-standing, and light-weight LiMnTiO4/MWCNT electrode has been prepared by vacuum filtration method for the first time. The as-prepared flexible LiMnTiO4/MWCNT electrode possesses a three-dimensional braiding structure in which LiMnTiO4 particles are well embedded in the twining CNT networks. The novel LiMnTiO4/MWCNT electrodes show tensile strength of 1.34 MPa and 2.04 MPa, when the percentages of MWCNTs reach to 30% and 50%, respectively. This novel flexible electrode exhibits a superior electrochemical property, especially at rate capability and cycling stability. The LiMnTiO4/MWCNT electrode can deliver capacity of 161 mAh g-1 (86.4% retention) after 50 cycles at 0.5C rate. Since the high conductivity from MWCNT networks, the LiMnTiO4/MWCNT electrode can still maintain a capacity of 77 mAh g-1 at 5C rate, which is much higher than that of the conventional electrode fabricated by slurry casting method on Al foil. The features of free-standing, light-weight, and excellent electrochemical performance indicate the potential of using the LiMnTiO4/MWCNT cathode in new-generation flexible lithium ion batteries.

  8. Electrochemical characterization of nano V, Ti doped MnO2 in primary lithium manganese dioxide batteries with high rate

    Science.gov (United States)

    Sun, Yang; Wang, Shengping; Dai, Yu; Lei, Xinrong

    2016-10-01

    The nano-sized γ-MnO2 precursor is synthesized using a room temperature, liquid-phase reaction route with the assistance of ultrasonic waves. The MnO2 precursor as an electrode material in lithium manganese dioxide primary batteries displays a low capacity of 140mAhg-1 (45.5% for the theoretical capacity of MnO2) at 20mAg-1. Therefore, the doped MnO2 with cationic V or/and Ti are prepared at high temperature. After the heat treatment, the γ phase precursor powder gradually converts into the β-MnO2 and exhibits a higher specific surface area with a larger pore volume and pore size, providing significantly more electrochemically active sites for the redox reaction. The doped MnO2 matrix has advantage of the ideal lattice parameters and the higher conductivity, resulting in an enhancement of the Li+ diffusion kinetics in the tunnel structure. Especially for co-doped MnO2 with V and Ti, the modified material shows an outstanding electrochemical capacity of 190mAhg-1 (61.7% for the theoretical capacity) at 20mAg-1 and 169mAhg-1 for a higher power output of 100mAg-1.

  9. Analysis of high frequency power loss of MnZn power ferrite%MnZn功率铁氧体高频功耗特性分析

    Institute of Scientific and Technical Information of China (English)

    黄晓东; 余忠; 孙科; 蒋晓娜; 李雪; 安文; 兰中文

    2012-01-01

    采用氧化物陶瓷工艺制备了2~4MHz频段高频开关电源用MnZn功率铁氧体,通过对铁氧体断面显微结构、密度和磁特性的测试,研究了Fe2O3含量对MnZn功率铁氧体功率损耗特性的影响.结果表明,随着Fe2O3含量的增加,晶粒尺寸逐渐减小,常温下3MHz、10mT高频损耗(PCV)先增大后减小,Fe2O3含量从58mol%增加到59 mol%时,损耗下降非常明显,而在100℃时,铁氧体的剩余损耗逐渐降低,导致总损耗随着Fe2O3含量的增加而减小.随着频率的升高,剩余损耗(Pr)占总损耗的比重逐渐增加,成为损耗的主要部分,而磁滞损耗(Ph)占总损耗的比重逐渐降低,涡流损耗(Pe)所占比重变化不明显.%MnZn power ferrites used for 2-4MHz high frequency switch power supply were prepared by conventional oxide ceramic process. The influence of Fe2O3 content on the core losses of MnZn power ferrites was investigated by means of characterizing the fracture surface micrograph, density and magnetic properties. The results indicated that the average grain size decreases, while the core losses(Pcv) of MnZn power ferrites increase first and decrease subsequently with increasing Fe2O3 content at 3MHz, 10mT and room temperature, and especially from 58mol% to 59mol% of Fe2O3 content, the core losses decrease obviously. At high temperature of 100℃, the core losses of MnZn power ferrites gradually decrease with increasing Fe2O3 content. The ratio of residual loss (Pr) and hysteresis loss (Ph) to the total core loss gradually increases and decreases, respectively, and Pr gradually becomes the main part of the core losses, while the ratio of eddy current loss(Pe) to the total core losses changes little with the increase of frequency.

  10. The study of high Curie temperature ferromagnetism properties in Mn-doped SiC thin film

    Directory of Open Access Journals (Sweden)

    Chaoyang Kang

    2015-01-01

    Full Text Available Mn-doped 3C-SiC film has been prepared onto the Si (111 substrate by employing a molecular beam epitaxy method. The experimental analysis establishes that the prepared sample shows the ferromagnetic property with a relatively high Curie temperature (Tc of 355 K, which is an exciting phenomenon on account of the scarceness in the SiC-based diluted magnetic semiconductor. The analysis derived from the X-ray diffraction and absorption spectroscopy patterns indicates that Mn atoms should react with Si atoms and then form Mn4Si7 compounds. Combined with the theoretical simulation, it is speculated that a new alloy phase of Mn4Si7Cx maybe appear, which should be responsible for the exceptionally high Tc ferromagnetic behavior in the sample.

  11. Combined Intercritical Annealing and Q&P Processing of Medium Mn Steel

    Science.gov (United States)

    De Cooman, Bruno C.; Lee, Seon Jong; Shin, Sunmi; Seo, Eun Jung; Speer, John G.

    2016-10-01

    The microstructure and mechanical properties of intercritically annealed medium Mn steel are dependent on the selection of the intercritical annealing (IA) temperature. While the yield strength (YS) decreases with increasing IA temperature, the ultimate tensile strength increases with increasing IA temperature. Strain aging phenomena, both static and dynamic, are also often observed. The present contribution shows that, by combining IA with the quench and partitioning processing of the intercritical austenite, it is possible to obtain non-aging mechanical properties which combine a high YS with an ultra-high tensile strength. These properties are particularly suitable for automotive parts related to passenger safety.

  12. Accurate modelling of anisotropic effects in austenitic stainless steel welds

    Science.gov (United States)

    Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.

    2014-02-01

    The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a `steering' of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterers are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.

  13. Investigation of high spin-polarization, magnetic, electronic and half-metallic properties in RuMn{sub 2}Ge and RuMn{sub 2}Sb Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Dinesh C.; Bhat, Idris Hamid, E-mail: idu.idris@gmail.com

    2015-03-15

    Highlights: • The present materials show magnetism and are ferromagnetic. • The materials show high spin-polarization and follow Slater–Pauling rule. • The materials are half-metallic and can be used as spintronic materials. - Abstract: Half-metallic ferromagnets RuMn{sub 2}Ge and RuMn{sub 2}Sb have been studied in stable F-43m phase. The optimized equilibrium lattice constants in F-43m phase were found to be 5.90 Å and 6.10 Å for RuMn{sub 2}Ge and RuMn{sub 2}Sb, respectively. The materials exhibit half-metallic city with an energy gap in the spin-down channel of 0.38 eV for RuMn{sub 2}Ge and 0.4 eV for RuMn{sub 2}Sb. The calculated total magnetic moments of 2.0 μ{sub B} per unit cell for RuMn{sub 2}Ge and 3.0 μ{sub B} per unit cell for RuMn{sub 2}Sb are in good agreement with Slater–Pauling rule. The magnetic moments of Mn-I and Mn-II mainly contribute to the total magnetic moment of the materials and are antiparallel to each other, hence predicting the signature of ferrimagnetism in RuMn{sub 2}Z alloys. The shifting of bands towards lower energies in spin-down channel for RuMn{sub 2}Sb may be due to the strong covalent character of bonding than RuMn{sub 2}Ge.

  14. Composition-dependent variation of magnetic properties and interstitial ordering in homogeneous expanded austenite

    DEFF Research Database (Denmark)

    Brink, Bastian K.; Ståhl, Kenny; Christiansen, Thomas Lundin;

    2016-01-01

    The crystal structure and magnetic properties of austenitic stainless steel with a colossal interstitial content, so-called expanded austenite, are currently not completely understood. In the present work, the magnetic properties of homogeneous samples of expanded austenite, as prepared by lowera......The crystal structure and magnetic properties of austenitic stainless steel with a colossal interstitial content, so-called expanded austenite, are currently not completely understood. In the present work, the magnetic properties of homogeneous samples of expanded austenite, as prepared...... by lowerature nitriding of thin foils, were investigated with magnetometry and Mössbauer spectroscopy. At room temperature, expanded austenite is paramagnetic for relatively low and for relatively high nitrogen contents (yN = 0.13 and 0.55, respectively, where yN is the interstitial nitrogen occupancy), while...... ferromagnetism is observed for intermediate nitrogen loads. Spontaneous volume magnetostriction was observed in the ferromagnetic state and the Curie temperature was found to depend strongly on the nitrogen content. For the first time, X-ray diffraction evidence for the occurrence of long-range interstitial...

  15. High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn{sub 3}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Laffont, L., E-mail: Lydia.laffont@ensiacet.fr [Institut Carnot, Laboratoire CIRIMAT (equipe MEMO), CNRS UMR 5085, ENSIACET, 4 allee Emile Monso, BP 74233, 31432 Toulouse cedex 4 (France); Gibot, P. [Laboratoire de Reactivite et Chimie des Solides CNRS UMR 6007, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens cedex 9 (France)

    2010-11-15

    Manganese oxides particularly Mn{sub 3}O{sub 4} Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn{sub 3}O{sub 4}, a bivalent oxide, for which a precise characterization is necessary and for which the determination of the valency proves to be essential. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and particularly High Resolution Electron Energy Loss Spectroscopy (HREELS) allow us to perform these measurements on the nanometer scale. Well crystallized 10-20 nm sized Mn{sub 3}O{sub 4} particles with sphere-shaped morphology were thus successfully synthesized. Meticulous EELS investigations allowed the determination of a Mn{sup 3+}/Mn{sup 2+} ratio of 1.5, i.e. slightly lower than the theoretical value of 2 for the bulk Hausmannite manganese oxide. This result emphasizes the presence of vacancies on the tetrahedral sites in the structure of the as-synthesized nanomaterial. - Research Highlights: {yields}Mn{sub 3}O{sub 4} bulk and nano were studied by XRD, TEM and EELS. {yields}XRD and TEM determine the degree of crystallinity and the narrow grain size. {yields}HREELS gave access to the Mn{sup 3+}/Mn{sup 2+} ratio. {yields}Mn{sub 3}O{sub 4} nano have vacancies on the tetrahedral sites.

  16. Reduction Kinetics of MnO from High-Carbon Ferromanganese Slags by Carbonaceous Materials in Ar and CO Atmospheres

    Science.gov (United States)

    Safarian, J.; Tranell, G.; Kolbeinsen, L.; Tangstad, M.; Gaal, S.; Kaczorowski, J.

    2008-10-01

    The kinetics of MnO reduction from synthetic and industrial high-carbon ferromanganese slags were investigated using a sessile drop technique at 1600 °C. The effects of the reductant type, ambient atmosphere, and slag composition on the MnO reduction were illuminated. Six different types of carbonaceous reductants were used as substrates for small slag droplets, which were reacted in a CO or Ar atmosphere, with the reaction studied in situ. The cross sections of the reacted slag-carbon samples were subsequently studied by electron-probe microanalysis (EPMA), to find the extent of the MnO reduction as a function of the reaction time. It was found that the rate of the MnO reduction is affected by both the type of reductant and the ambient atmosphere. It was observed that the MnO reduction rate from synthetic slag by cokes produced from single coals is lower than that from industrial cokes. Reduction rates obtained when charcoal was used as the reductant were higher than when coke was used, while the CO atmosphere yielded a faster initial MnO reduction than did the Ar atmosphere. It was found that the faster reduction rates in the CO atmosphere are related to the MnO reduction by CO gas. A newly developed kinetic method was applied, to calculate the rate constants for the MnO reduction by carbon and CO that considered the reaction interfaces. It was indicated that the rate of the MnO reduction by CO is less than that by carbon; however, the contribution of these reductants to slag reduction is very dependent on their contact with the slag.

  17. Application of advanced austenitic alloys to fossil power system components

    Energy Technology Data Exchange (ETDEWEB)

    Swindeman, R.W.

    1996-06-01

    Most power and recovery boilers operating in the US produce steam at temperatures below 565{degrees}C (1050{degrees}F) and pressures below 24 MPa (3500 psi). For these operating conditions, carbon steels and low alloy steels may be used for the construction of most of the boiler components. Austenitic stainless steels often are used for superheater/reheater tubing when these components are expected to experience temperatures above 565{degrees}C (1050{degrees}F) or when the environment is too corrosive for low alloys steels. The austenitic stainless steels typically used are the 304H, 321H, and 347H grades. New ferritic steels such as T91 and T92 are now being introduced to replace austenitic: stainless steels in aging fossil power plants. Generally, these high-strength ferritic steels are more expensive to fabricate than austenitic stainless steels because the ferritic steels have more stringent heat treating requirements. Now, annealing requirements are being considered for the stabilized grades of austenitic stainless steels when they receive more than 5% cold work, and these requirements would increase significantly the cost of fabrication of boiler components where bending strains often exceed 15%. It has been shown, however, that advanced stainless steels developed at ORNL greatly benefit from cold work, and these steels could provide an alternative to either conventional stainless steels or high-strength ferritic steels. The purpose of the activities reported here is to examine the potential of advanced stainless steels for construction of tubular components in power boilers. The work is being carried out with collaboration of a commercial boiler manufacturer.

  18. High pressure X-ray diffraction study of SrMnO3 perovskite

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-Xin; QIN Shan; WU Xiang; JIANG Jian-Zhong; SHI Guang-Hai

    2011-01-01

    Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is β> β. The isothermal bulk modulus K=266(4) GPa is also obtained by fitting the pressure- volume data using the Murnaghan equation of state.

  19. Testing of austenite-ferrite-compounds of the materials X 3 CrNiMoN 17 13 (1.4910) and X 10 CrMoVNb 9 1 (1.4903) for application in modern high-temperature power plants; Erprobung von Austenit-Ferrit-Verbindungen der Werkstoffe X 3 CrNiMoN 17 13 (1.4910) und X 10 CrMoVNb 9 1 (1.4903) fuer den Einsatz in modernen Hochtemperaturkraftwerken

    Energy Technology Data Exchange (ETDEWEB)

    Muesch, H. [VEW Energie AG, Kraftwerk Bochum (Germany); Meyer, H.; Remmert, H.; Schlueter, N. [VEW Energie AG, Hamm (Germany)

    1997-10-01

    Conventional coal-fired power plants with steam temperatures over 560 C require superheater systems of austenitic materials (e.g. 1.4910) in the steam generator. Since the high-pressure pipework is manufactured from ferritic-martensitic material (e.g. 1.4903), more or less numerous austenite-ferrite-compounds are necessary according to each type of design. Three years ago, tests commenced on compounding P91 and austenite components (tubes and forged bars of the materials 1.4903 and 1.4910) in accordance with the HIP diffusion welding process. Initial tests and appropriate examinations of the seams indicated that excellent mechanical engineering properties are attainable if the whole compound is finally subjected to a heat treatment. Current ISO-stress tests and creep tests with hitherto more than 8000 hours are yielding values which are only slightly below the average values of the steel 1.4903. The HIP process is, however, relatively expensive. As a cost-effective procedure designed for series production, the friction welding process has been tested since the beginning of 1995 at the instigation of VEW. The initial results are to be regarded as satisfactory. (orig.) [Deutsch] Konventionelle Kohlekraftwerke mit Dampftemperaturen ueber 560 C erfordern im Dampferzeuger Ueberhitzersysteme aus austenitischen Werkstoffen (z.B. 1.4910). Da die Hochdruckleitungen aus ferritisch-martensitischem Werkstoff (z.B. 1.4903) hergestellt werden, sind je nach konstruktiver Gestaltung mehr oder weniger zahlreiche Austenit-Ferrit-Verbindungen notwendig. Vor drei Jahren begannen Versuche, P91- und Austenitbauteile (Rohre und Schmiedestaebe der Werkstoffe 1.4903 und 1.4910) nach dem HIP-Diffusionsschweissverfahren zu verbinden. Erste Versuche und entsprechende Untersuchungen der Naehte ergaben, dass gute mechanisch-technologische Eigenschaften erzielbar sind, wenn die gesamte Verbindung abschliessend einer Verguetung unterzogen wird. Laufende Iso-Stress-Versuche und Zeitstandversuche

  20. Wire-type MnO2/Multilayer graphene/Ni electrode for high-performance supercapacitors

    Science.gov (United States)

    Hu, Minglei; Liu, Yuhao; Zhang, Min; Wei, Helin; Gao, Yihua

    2016-12-01

    Commercially available wearable energy storage devices need a wire-type electrode with high strength, conductivity and electrochemical performance, as well as stable structure under deformation. Herein, we report a novel wire-type electrode of hierarchically structure MnO2 on Ni wire with multilayer graphene (MGr) as a buffer layer to enhance the electrical conductivity of the MnO2 and interface contact between the MnO2 and Ni wire. Thus, the wire-type MnO2/MGr/Ni electrode has a stable and high quality interface. The wire-type supercapacitor (WSC) based on wire-type MnO2/MGr/Ni electrode exhibits good electrochemical performance, high rate capability, extraordinary flexibility, and superior cycle lifetime. Length (area, volumetric) specific capacitance of the WSC reaches 6.9 mF cm-1 (73.2 mF cm-2, 9.8 F cm-3). Maximum length (volumetric) energy density of the WSC based on MnO2/MGr/Ni reaches 0.62 μWh cm-1 (0.88 mWh cm-3). Furthermore, the WSC has a short time constant (0.5-400 ms) and exhibits minimal change in capacitance under different bending shapes.

  1. Mn 3 O 4 −Graphene Hybrid as a High-Capacity Anode Material for Lithium Ion Batteries

    KAUST Repository

    Wang, Hailiang

    2010-10-13

    We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Selective growth of Mn3O 4 nanoparticles on RGO sheets, in contrast to free particle growth in solution, allowed for the electrically insulating Mn3O4 nanoparticles to be wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ∼900 mAh/g, near their theoretical capacity, with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn 3O4 nanoparticles grown atop. The Mn3O 4/RGO hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials. © 2010 American Chemical Society.

  2. Low-dimensional magnetic properties of orthorhombic MnV2O6 : A nonstandard structure stabilized at high pressure

    Science.gov (United States)

    Hneda, M. L.; da Cunha, J. B. M.; Gusmão, M. A.; Neto, S. R. Oliveira; Rodríguez-Carvajal, J.; Isnard, O.

    2017-01-01

    This paper presents the physical properties of a nonstandard orthorhombic form of MnV2O6 , including a comparison with the isostructural orthorhombic niobate MnNb2O6 , and with the usual MnV2O6 monoclinic polymorph. Orthorhombic (P b c n ) MnV2O6 is obtained under extreme conditions of high pressure (6.7 GPa) and high temperature (800 ∘C ). A negative Curie-Weiss temperature θCW is observed, implying dominant antiferromagnetic interactions at high temperatures, in contrast to the positive θCW of the monoclinic form. Specific-heat measurements are reported down to 1.8 K for all three compounds, and corroborate the magnetic-transition temperatures obtained from susceptibility data. Orthorhombic MnV2O6 presents a transition to an ordered antiferromagnetic state at TN=4.7 K. Its magnetic structure, determined by neutron diffraction, is unique among the columbite compounds, being characterized by a commensurate propagation vector k =(0 ,0 ,1/2 ) . It presents antiferromagnetic chains running along the c axis, but with a different spin pattern in comparison to the chains observed in MnNb2O6 . By a comparative discussion of our observations in this three compounds, we are able to highlight the interplay between competing interactions and dimensionality that yield their magnetic properties.

  3. Expanded austenite; crystallography and residual stress

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

    2009-01-01

    The identity of expanded austenite as developing during low temperature nitriding and/or carburizing of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article recent results obtained with i) homogeneous samples of various uniform...

  4. Synthesis of aluminum-rich coatings on new high-temperature cast austenitic steel CF8C-Plus by a pack cementation process

    Science.gov (United States)

    Hall, Alex Keith

    2011-12-01

    In this research, a pack cementation process is developed for coating the newly developed cast austenitic steel CF8C-Plus. The developed coating process is capable of producing pack particle free coatings on large fatigue test specimens in a horizontal laboratory tube furnace as well as smaller oxidation and creep test samples. Several methods for the production of the pack powder free Al-rich coating are presented and evaluated for samples of both sizes. The developed coating is intended to compete with coatings of a similar quality produced with chemical vapor deposition and slurry coating methods. Additionally, because CF8C-Plus has only recently become available there is currently no available data on the effect of the fabrication of an Al-rich coating on the substrates properties. This research used advanced characterization methods to evaluate the coating surface and cross-sectional features. These methods include scanning electron microscopy, X-ray diffraction, electron probe microanalysis and energy dispersive spectroscopy analysis. This is the first time that this information has been made available to the scientific community. Also, the oxidation performance of the coating will be tested and compared to other coatings developed with CVD and slurry coating methods and the preliminary results of the effect of the coating on the alloys fatigue performance will be presented.

  5. Analytical modeling of the thermomechanical behavior of ASTM F-1586 high nitrogen austenitic stainless steel used as a biomaterial under multipass deformation.

    Science.gov (United States)

    Bernardes, Fabiano R; Rodrigues, Samuel F; Silva, Eden S; Reis, Gedeon S; Silva, Mariana B R; Junior, Alberto M J; Balancin, Oscar

    2015-06-01

    Precipitation-recrystallization interactions in ASTM F-1586 austenitic stainless steel were studied by means of hot torsion tests with multipass deformation under continuous cooling, simulating an industrial laminating process. Samples were deformed at 0.2 and 0.3 at a strain rate of 1.0s(-1), in a temperature range of 900 to 1200°C and interpass times varying from 5 to 80s. The tests indicate that the stress level depends on deformation temperature and the slope of the equivalent mean stress (EMS) vs. 1/T presents two distinct behaviors, with a transition at around 1100°C, the non-recrystallization temperature (Tnr). Below the Tnr, strain-induced precipitation of Z-phase (NbCrN) occurs in short interpass times (tpass<30s), inhibiting recrystallization and promoting stepwise stress build-up with strong recovery, which is responsible for increasing the Tnr. At interpass times longer than 30s, the coalescence and dissolution of precipitates promote a decrease in the Tnr and favor the formation of recrystallized grains. Based on this evidence, the physical simulation of controlled processing allows for a domain refined grain with better mechanical properties.

  6. Alumina-Forming Austenitics: A New Approach to Thermal and Degradation Resistant Stainless Steels for Industrial Use

    Energy Technology Data Exchange (ETDEWEB)

    David A Helmick; John H Magee; Michael P Brady

    2012-05-31

    A series of developmental AFA alloys was selected for study based on: 25 Ni wt.% (alloys A-F), 20 wt% Ni (alloys G-H), and 12 Ni wt.% (alloys I-L). An emphasis in this work was placed on the lower alloy content direction for AFA alloys to reduce alloy raw material cost, rather than more highly alloyed and costly AFA alloys for higher temperature performance. Alloys A-D explored the effects of Al (3-4 wt.%) and C (0.05-0.2 wt.%) in the Fe-25Ni-14Cr-2Mn-2Mo-1W-1Nb wt.% base range; alloys E and F explored the effects of removing costly Mo and W additions in a Fe-25Ni-14Cr-4Al-2.5Nb-2Mn-0.2C base, alloys G and H examined Nb (1-2.5wt.%) and removal of Mo, W in a Fe-20Ni-14Cr-3Al-2Mn-0.2 C wt.% base; and alloys I-L examined effects of C (0.1-0.2 wt.%) and Mn (5-10 wt.%) on a low cost Fe-14Cr-12Ni-3Cu-2.5Al wt.% base (no Mo, W additions). Creep testing resulted in elemental trends that included the beneficial effect of higher carbon and lower niobium in 20-25%Ni AFA alloys and, the beneficial of lower Mn in 12%Ni AFA alloys. Corrosion tests in steam and sulfidation-oxidation environments showed, in general, these alloys were capable of a ten-fold improvement in performance when compared to conventional austenitic stainless steels. Also, corrosion test results in metal-dusting environments were promising and, warrant further investigation.

  7. Plasma Nitriding of Austenitic Stainless Steel with Severe Surface Deformation Layer

    Institute of Scientific and Technical Information of China (English)

    JI Shi-jun; GAO Yu-zhou; WANG Liang; SUN Jun-cai; HEI Zu-kun

    2004-01-01

    The dc glow discharge plasma nitriding of austenite stainless steel with severe surface deformation layer is used to produce much thicker surface modified layer. This kind of layers has useful properties such as a high surface hardness of about 1500 Hv 0.1 and high resistance to frictional wear. This paper presents the structures and properties of low temperature plasma nitrided austenitic stainless steel with severe surface deformation layer.

  8. The Influence of Saturation of Cast Iron Austenite with Carbon on the Ausferrite Transformation

    Directory of Open Access Journals (Sweden)

    T. Giętka

    2007-07-01

    Full Text Available Austenitizing during quench hardening of the ductile cast iron influences the content of carbon in austenite depending on the soaking heat. On the other hand, the saturation of austenite impacts its transformation in the ausferritizing process of a metal matrix and forming of microstructure. Ductile cast iron with the ferrite matrix was hardened with isothermal transformation in the range of ausferritizing in temperature tpi = 400 i 300 0C and the range of time τpi = 7,5 �� 240 min. Specimens were gradually austenitized. They were soaked in the nominal temperature tγ = 950 0C, then precooled to the temperature tγ’ = 850 and 800 0C. Microstructure was investigated, there were also defined the proportion of austenite in the matrix of the cast iron and the content of carbon in it and hardness and impact strength in unnotched specimens. It was stated, that the precooling temperature deciding on the content of carbon in austenite influences kinetics of the ausferritic transformation, the content of carbon in the γ phase and impact strength and, in a less degree, hardness. As a result of gradual austenitizing the cast iron after quench hardening, in some conditions of treatment, reached mechanical properties corresponding, according to the ASTM A 897 standard, with high grades of ADI. Chilling in the range of austenitizing in temperature 850 and 800 0C led to the decrease of carbon in austenite what influenced positively on the matrix microstructure and properties of the ADI. Investigations in this range will be continued.

  9. The formation of twinned austenite in Fe-10Cr-10Ni-2W maraging steel

    Energy Technology Data Exchange (ETDEWEB)

    Suk, J.I.; Hong, S.H.; Nam, S.W. (Dept. of Minerals Science and Engineering, Korea Advanced Inst. of Science and Technology, P.O. Box 150, Cheongyang, Seoul (KR))

    1991-12-01

    The precipitation hardening mechanisms in high strength maraging steels have been studied in detail by many investigators, but limited information is available on the formation of austenite during aging. Some investigations have been concerned with the understanding of the effect of reverted austenite formed during aging on the mechanical properties. However, only a few investigations have been reported on the morphology and crystallographic feature of austenite. Shiang and Wayman first reported the twin-related and coupled morphology of Widmanstatten austenite plates which were frequently observed in maraging steel. In addition, Ameyama et al. reported the morphology and crystallographic features of austenite formed in ferrite grain during aging in a two-phase stainless steel, and found that each side of the austenite pair of twins satisfies the Kurdjumov-Sachs (K-S) orientation relationship with the parent phase. The morphology and crystallographic features of the reverted austenite formed during aging of Fe-10Cr-10Ni-2W stainless maraging steel have been investigated in this paper. The major strengthening precipitate in Fe-10Cr-10Ni-2W maraging steels has been identified as the rod-shaped {eta}-Ni{sub 3}Ti phase in our previous study. The peculiar morphology of the austenite, i.e., twinned austenite, also has been found in our studies of maraging steel in the Fe-10Cr-10Ni-2W lath martensite. In addition, computer simulation of the diffraction pattern is used to confirm the orientation relationships, such as the Kurdjumov-Sachs (K-S) relationship, the Nishiyama-Wasserman (N-W) relationship and the twin relationship by comparisons with the experimentaly observed results.

  10. High pressure effects on a trimetallic Mn(II/III) SMM.

    Science.gov (United States)

    Prescimone, Alessandro; Sanchez-Benitez, Javier; Kamenev, Konstantin V; Moggach, Stephen A; Lennie, Alistair R; Warren, John E; Murrie, Mark; Parsons, Simon; Brechin, Euan K

    2009-09-28

    A combined study of the high pressure crystallography and high pressure magnetism of the complex [Mn3(Hcht)2(bpy)4](ClO4)3.Et2O.2MeCN (1.Et2O.2MeCN) (H3cht is cis,cis-1,3,5-cyclohexanetriol) is presented in an attempt to observe and correlate pressure induced changes in its structural and physical properties. At 0.16 GPa the complex 1.Et2O.2MeCN loses all associated solvent in the crystal lattice, becoming 1. At higher pressures structural distortions occur changing the distances between the metal centres and the bridging oxygen atoms making the magnetic exchange between the manganese ions weaker. No significant variations are observed in the Jahn-Teller axis of the only Mn(III) present in the structure. High pressure dc chiMT plots display a gradual decrease in both the low temperature value and slope. Simulations show a decrease in J with increasing pressure although the ground state is preserved. Magnetisation data do not show any change in |D|.

  11. Desempenho de duas espécies de eucalipto em solo com elevados teores de Mn Performance of two eucalyptus species in soil with high levels of Mn

    Directory of Open Access Journals (Sweden)

    Marcio O. L. Magalhães

    2012-01-01

    Full Text Available Atualmente, é considerável o interesse no desenvolvimento de estratégias que sejam eficientes e duráveis na remediação de solos contaminados com metais pesados. Objetivou-se, com este trabalho, avaliar o desenvolvimento de duas espécies Eucalyptus urophylla e Eucalyptus saligna, cultivadas em substrato contaminado com Mn coletado em área próxima ao Porto de Itaguaí e ao local de disposição de resíduo perigoso da Cia Mercantil e Industrial Ingá em Itaguaí, RJ. O substrato foi tratado com dois resíduos industriais, um com característica alcalina (escória de aciaria e outro com alto teor de óxido de ferro (carepa de laminação. Verificou se que o substrato não tratado apresentava alto teor de Mn nas frações fitodisponíveis, valores esses tóxicos para as espécies estudadas. Os tratamentos causaram redução nas concentrações de Mn em solução e trocável (frações fitodisponiveis e aumento nas fases mais estáveis. A menor dose de Escória de Aciaria foi suficiente para que ocorresse diminuição nas concentrações de Mn em solução, sendo este efeito evidenciado pelo desenvolvimento das plantas e na maior dose de Escória de Aciaria o crescimento das espécies estudadas foi maior. O Eucalyptus urophylla apresentou maior desenvolvimento e maior extração deste elemento.Currently, there is considerable interest in developing strategies that are efficient and durable in the remediation of soils contaminated with heavy metals. This study aimed to evaluate the development of Eucalyptus urophylla and Eucalyptus saligna grown in contaminated substrate with Mn collected in the area near the Port of Itaguaí and location of disposal of hazardous waste of Cia Mercantil and Industrial Inga in Itaguaí. The substrate was treated with two industrial waste, with a characteristic alkaline (slag of melt shop and another with high content of iron oxide (lamination of scale. It was found that the untreated substrate, had a high

  12. Silica fertilization and nano-MnO₂ amendment on bacterial community composition in high arsenic paddy soils.

    Science.gov (United States)

    Shao, Jihai; He, Yaxian; Zhang, Huiling; Chen, Anwei; Lei, Ming; Chen, Junfeng; Peng, Liang; Gu, Ji-Dong

    2016-03-01

    Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other.

  13. Ag incorporated Mn3O4/AC nanocomposite based supercapacitor devices with high energy density and power density.

    Science.gov (United States)

    Nagamuthu, S; Vijayakumar, S; Muralidharan, G

    2014-12-14

    Silver incorporated Mn3O4/amorphous carbon (AC) nanocomposites are synthesized by a green chemistry method. X-ray diffraction studies revealed the structural changes in Mn3O4/AC nanocomposites attributable to the addition of silver. Cyclic voltammetry, charge-discharge and ac-impedance studies indicated that the Ag-Mn3O4/AC-5 electrode was the most suitable candidate for supercapacitor applications. From the galvanostatic charge-discharge studies, a higher specific capacitance of 981 F g(-1) at a specific current of 1 A g(-1) was obtained. An Ag-Mn3O4/AC-symmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as an anode as well as a cathode, and an asymmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as a cathode and an activated carbon as an anode have been fabricated. The symmetric device exhibits a specific cell capacitance of 72 F g(-1) at a specific current of 1 A g(-1) whereas the asymmetric device delivers a specific cell capacitance of 180 F g(-1) at a high current rate of 10 A g(-1). The asymmetric supercapacitor device yields a high energy density of 81 W h kg(-1). This is higher than that of lead acid batteries and comparable with that of nickel hydride batteries.

  14. Symmetrical MnO2-carbon nanotube-textile nanostructures for wearable pseudocapacitors with high mass loading

    KAUST Repository

    Hu, Liangbing

    2011-11-22

    While MnO2 is a promising material for pseudocapacitor applications due to its high specific capacity and low cost, MnO2 electrodes suffer from their low electrical and ionic conductivities. In this article, we report a structure where MnO2 nanoflowers were conformally electrodeposited onto carbon nanotube (CNT)-enabled conductive textile fibers. Such nanostructures effectively decrease the ion diffusion and charge transport resistance in the electrode. For a given areal mass loading, the thickness of MnO2 on conductive textile fibers is much smaller than that on a flat metal substrate. Such a porous structure also allows a large mass loading, up to 8.3 mg/cm2, which leads to a high areal capacitance of 2.8 F/cm2 at a scan rate of 0.05 mV/s. Full cells were demonstrated, where the MnO2-CNT-textile was used as a positive electrode, reduced MnO2-CNT-textile as a negative electrode, and 0.5 M Na2SO4 in water as the electrolyte. The resulting pseudocapacitor shows promising results as a low-cost energy storage solution and an attractive wearable power. © 2011 American Chemical Society.

  15. Influence of retained austenite on the grain size of austenite after reaustenitization of steels for heavy forgings

    Energy Technology Data Exchange (ETDEWEB)

    Peters, H.J.; Tacke, G.; Hougardy, H.P.

    1989-01-01

    In this investigation the grain size of austenite reaustenitization of different microstructures containing different volume fractions of retained austenite was determined. The austenite grain size after austenitization of martensite and lower bainite was coarse for heating rates lower than a minimum value, which is dependent on the chemical composition. In this case, the austenite forms by rapid growth of retained austenite in the initial microstructure. At heating rates higher than the critical value, formation of austenite starts at the ferrite-carbide phase boundaries giving a fine austenite grain. The formation of austenite from microstructures free of retained austenite, such as pearlite, always occurred by nucleation on the ferrite-carbide interphase resulting in fine austenite grains. (orig.).

  16. High power nano-LiMn2O4 cathode materials with high-rate pulse discharge capability for lithium-ion batteries

    Institute of Scientific and Technical Information of China (English)

    Chen Ying-Chao; Xie Kai; Pan Yi; Zheng Chun-Man; Wang Hua-Lin

    2011-01-01

    Nano-LiMn2O4 cathode materials with nano-sized particles are synthesized via a citric acid assisted sol-gel route. The structure, the morphology and the electrochemical properties of the nano-LiMn2O4 are investigated. Compared with the micro-sized LiMn2O4, the nano-LiMn2O4 possesses a high initial capacity (120 mAh/g) at a discharge rate of 0.2 C (29.6 mA/g). The nano-LiMn2O4 also has a good high-rate discharge capability, retaining 91% of its capacity at a discharge rate of 10 C and 73% at a discharge rate of 40 C. In particular, the nano-LiMn2O4 shows an excellent high-rate pulse discharge capability. The cut-off voltage at the end of 50-ms pulse discharge with a discharge rate of 80 C is above 3.40 V, and the voltage returns to over 4.10 V after the pulse discharge. These results show that the prepared nano-LiMn2O4 could be a potential cathode material for the power sources with the capability to deliver very high-rate pulse currents.

  17. Effect of microstructure on the stability of retained austenite in transformation-induced-plasticity steels

    Science.gov (United States)

    Timokhina, I. B.; Hodgson, P. D.; Pereloma, E. V.

    2004-08-01

    Two Fe-0.2C-1.55Mn-1.5Si (in wt pct) steels, with and without the addition of 0.039Nb (in wt pct), were studied using laboratory rolling-mill simulations of controlled thermomechanical processing. The microstructures of all samples were characterized by optical metallography, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The microstructural behavior of phases under applied strain was studied using a heat-tinting technique. Despite the similarity in the microstructures of the two steels (equal amounts of polygonal ferrite, carbide-free bainite, and retained austenite), the mechanical properties were different. The mechanical properties of these transformation-induced-plasticity (TRIP) steels depended not only on the individual behavior of all these phases, but also on the interaction between the phases during deformation. The polygonal ferrite and bainite of the C-Mn-Si steel contributed to the elongation more than these phases in the C-Mn-Si-Nb-steel. The stability of retained austenite depends on its location within the microstructure, the morphology of the bainite, and its interaction with other phases during straining. Granular bainite was the bainite morphology that provided the optimum stability of the retained austenite.

  18. The Role of κ-Carbides as Hydrogen Traps in High-Mn Steels

    Directory of Open Access Journals (Sweden)

    Tobias A. Timmerscheidt

    2017-07-01

    Full Text Available Since the addition of Al to high-Mn steels is known to reduce their sensitivity to hydrogen-induced delayed fracture, we investigate possible trapping effects connected to the presence of Al in the grain interior employing density-functional theory (DFT. The role of Al-based precipitates is also investigated to understand the relevance of short-range ordering effects. So-called E21-Fe3AlC κ-carbides are frequently observed in Fe-Mn-Al-C alloys. Since H tends to occupy the same positions as C in these precipitates, the interaction and competition between both interstitials is also investigated via DFT-based simulations. While the individual H–H/C–H chemical interactions are generally repulsive, the tendency of interstitials to increase the lattice parameter can yield a net increase of the trapping capability. An increased Mn content is shown to enhance H trapping due to attractive short-range interactions. Favorable short-range ordering is expected to occur at the interface between an Fe matrix and the E21-Fe3AlC κ-carbides, which is identified as a particularly attractive trapping site for H. At the same time, accumulation of H at sites of this type is observed to yield decohesion of this interface, thereby promoting fracture formation. The interplay of these effects, evident in the trapping energies at various locations and dependent on the H concentration, can be expressed mathematically, resulting in a term that describes the hydrogen embrittlement.

  19. Highly sensitive and selective detection of phosphate using novel highly photoluminescent water-soluble Mn-doped ZnTe/ZnSe quantum dots.

    Science.gov (United States)

    Song, Yu; Li, Yang; Liu, Yunling; Su, Xingguang; Ma, Qiang

    2015-11-01

    Herein, the facile method with high selectivity for phosphate ion (Pi) sensing using novel Type-II core/shell Mn: ZnTe/ZnSe quantum dots (QDs) was reported. This was the first time that Mn: ZnTe/ZnSe QDs with highlighted optical properties were used for sensing. The water-soluble Mn: ZnTe/ZnSe QDs with a high quantum yield of 7% were synthesized by aqueous synthetic method. Compared with traditional ZnSe QDs or Mn: ZnSe QDs, the smaller effective band gap, longer wavelength and lower ionization potential (high valence band edge) for effective hole localization made Type-II core/shell Mn: ZnTe/ZnSe QDs to be stable and had high photoluminescence (PL). Only Mg(2+) was found to be able to enhance Mn: ZnTe/ZnSe QDs PL selectively. The mechanism of fluorescence enhancement was attributed to the passivated surface nonradiative relaxation centers of Mn: ZnTe/ZnSe QDs. In the presence of Pi anion, the PL intensity got quenched due to the aggregation species of QDs via electrostatic attraction between Pi and Mg(2+) on the surface of Mn: ZnTe/ZnSe QDs. Therefore, the quenching effect can be used to detect Pi selectively. The PL was observed to be linearly proportional to the Pi analyte concentration in the range from 0.67 to 50.0 μmol/L, with a detection limit of 0.2μ mol/L (S/N=3). The novel "on-off" fluorescence nanosensor for Pi detection was sensitive and convenient in the real analysis application. The reported analytical method of Mn: ZnTe/ZnSe QDs is highly sensitive and selective, which can corroborate the extension of its usages in chemo/ biosensing and bioimaging. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Precipitation Effect on Mechanical Properties and Phase Stability of High Manganese Steel

    Science.gov (United States)

    Bae, Cheoljun; Kim, Rosa; Lee, Un-Hae; Kim, Jongryoul

    2017-09-01

    High manganese (Mn) steels are attractive for automotive applications due to their excellent tensile strength and superior elongation. However, the relatively low yield strength of Mn steels compared to other advanced high-strength steels is a critical problem limiting their use in structural parts. In order to increase the yield strength, the precipitation hardening effect of Mn steels was investigated by the addition of carbide-forming elements. Changes in the austenite phase stability were also evaluated in terms of stacking fault energy (SFE). As a result, fine V(C,N) precipitates were found to increase the yield strength effectively but to lower the SFE by the consumption of matrix carbons. For achieving precipitation hardening without sacrificing austenite stability, the soluble carbon content was discussed.

  1. HYDROGEN-ASSISTED FRACTURE IN FORGED TYPE 304L AUSTENITIC STAINLESS STEEL

    Energy Technology Data Exchange (ETDEWEB)

    Switzner, Nathan; Neidt, Ted; Hollenbeck, John; Knutson, J.; Everhart, Wes; Hanlin, R. [University of Missouri-Kansas City; Bergen, R. [Precision Metal Products; Balch, D. K. [Sandia Natl Laboratory

    2012-09-06

    Austenitic stainless steels generally have good resistance to hydrogen-assisted fracture; however, structural designs for high-pressure gaseous hydrogen are constrained by the low strength of this class of material. Forging is used to increase the low strength of austenitic stainless steels, thus improving the efficiency of structural designs. Hydrogen-assisted racture, however, depends on microstructural details associated with manufacturing. In this study, hydrogen-assisted fracture of forged type 304L austenitic stainless steel is investigated. Microstructural variation in multi-step forged 304L was achieved by forging at different rates and temperatures, and by process annealing. High internal hydrogen content in forged type 304L austenitic stainless steel is achieved by thermal precharging in gaseous hydrogen and results in as much as 50% reduction of tensile ductility.

  2. Rational design of MnO/carbon nanopeapods with internal void space for high-rate and long-life li-ion batteries.

    Science.gov (United States)

    Jiang, Hao; Hu, Yanjie; Guo, Shaojun; Yan, Chaoyi; Lee, Pooi See; Li, Chunzhong

    2014-06-24

    Searching the long-life MnO-based materials for lithium ion batteries (LIBs) is still a great challenge because of the issue related to the volumetric expansion of MnO nanoparticles (NPs) or nanowires (NWs) during lithiation. Herein, we demonstrate an unexpected result that a peapod-like MnO/C heterostructure with internal void space can be facilely prepared by annealing the MnO precursor (MnO-P) NW/polydopamine core/shell nanostructure in an inert gas, which is very different from the preparation of typical MnO/C core/shell NWs through annealing MnO NW/C precursor nanostructure. Such peapod-like MnO/C heterostructure with internal void space is highly particular for high-performance LIBs, which can address all the issues related to MnO dissolution, conversion, aggregation and volumetric expansion during the Li(+) insertion/extraction. They are highly stable anode material for LIBs with a very high reversible capacity (as high as 1119 mAh g(-1) at even 500 mA g(-1)) and fast charge and discharge capability (463 mAh g(-1) at 5000 mA g(-1)), which is much better than MnO NWs (38 mAh g(-1) at 5000 mA g(-1)) and MnO/C core/shell NWs (289 mAh g(-1) at 5000 mA g(-1)). Such nanopeapods also show excellent rate capability (charged to 91.6% in 10.6 min using the constant current mode). Most importantly, we found that MnO/C nanopeapods show no capacity fading even after 1000 cycles at a high current density of 2000 mA g(-1), and no morphology change. The present MnO/C nanopeapods are the most efficient MnO-based anode materials ever reported for LIBs.

  3. Magnetic and magneto-transport studies of substrate effect on the martensitic transformation in a NiMnIn shape memory alloy

    Directory of Open Access Journals (Sweden)

    Andrei Sokolov

    2016-05-01

    Full Text Available The effect of substrates on the magnetic and transport properties of Ni2Mn1.5In0.5 ultra-thin films were studied theoretically and experimentally. High quality 8-nm films were grown by laser-assisted molecular beam epitaxy deposition. Magneto-transport measurements revealed that the films undergo electronic structure transformation similar to those of bulk materials at the martensitic transformation. The temperature of the transformation depends strongly on lattice parameters of the substrate. To explain this behavior, we performed DFT calculations on the system and found that different substrates change the relative stability of the ferromagnetic (FM austenite and ferrimagnetic (FiM martensite states. We conclude that the energy difference between the FM austenite and FiM martensite states in Ni2Mn1.5In0.5 films grown on MgO (001 substrates is ΔE = 0.20 eV per NiMnIn f.u, somewhat lower compared to ΔE = 0.24 eV in the bulk material with the same lattice parameters. When the lattice parameters of Ni2Mn1.5In0.5 film have values close to those of the MgO substrate, the energy difference becomes ΔE = 0.08 eV per NiMnIn f.u. These results suggest the possibility to control the martensitic transition in thin films through substrate engineering.

  4. Magnetic and magneto-transport studies of substrate effect on the martensitic transformation in a NiMnIn shape memory alloy

    Science.gov (United States)

    Sokolov, Andrei; Kirianov, Eugene; Zlenko, Albina; Quetz, Abdiel; Aryal, Anil; Pandey, Sudip; Dubenko, Igor; Stadler, Shane; Ali, Naushad; Al-Aqtash, Nabil; Sabirianov, Renat

    2016-05-01

    The effect of substrates on the magnetic and transport properties of Ni2Mn1.5In0.5 ultra-thin films were studied theoretically and experimentally. High quality 8-nm films were grown by laser-assisted molecular beam epitaxy deposition. Magneto-transport measurements revealed that the films undergo electronic structure transformation similar to those of bulk materials at the martensitic transformation. The temperature of the transformation depends strongly on lattice parameters of the substrate. To explain this behavior, we performed DFT calculations on the system and found that different substrates change the relative stability of the ferromagnetic (FM) austenite and ferrimagnetic (FiM) martensite states. We conclude that the energy difference between the FM austenite and FiM martensite states in Ni2Mn1.5In0.5 films grown on MgO (001) substrates is ΔE = 0.20 eV per NiMnIn f.u, somewhat lower compared to ΔE = 0.24 eV in the bulk material with the same lattice parameters. When the lattice parameters of Ni2Mn1.5In0.5 film have values close to those of the MgO substrate, the energy difference becomes ΔE = 0.08 eV per NiMnIn f.u. These results suggest the possibility to control the martensitic transition in thin films through substrate engineering.

  5. Development of high-strength, low-cost wrought Mg–2.0 mass% Zn alloy with high Mn content

    Directory of Open Access Journals (Sweden)

    Fusheng. Pan

    2016-12-01

    Full Text Available Mg–Zn–Mn-based alloys have received considerable attention because of their high creep resistance, strength, and good corrosion resistance. The alloying element Mn in Mg–Zn-based alloys is commonly less than 1 wt%. In the present study, the effect of high Mn content (1 wt% and 2 wt% on the microstructures and mechanical properties of Mg–2Zn–0.3Sr extruded alloy was investigated. The results revealed that the high Mn content significantly increased the ultimate tensile strength, tensile yield strength, compress yield strength, and yield asymmetry of the alloy without affecting its ductility. The dynamically recrystallized (DRXed grains of Mg–2Zn–0.3Sr were remarkably refined because of the large amount of fine Mn precipitates in the homogenized alloy. The improved strengths were mainly attributed to the fine DRXed grains according to the Hall–Petch effect and to the large amount of spherical and Mn precipitates through the precipitation and dispersion strengthening. The fine DRXed grains and numerous Mn precipitates effectively suppressed the extension twining, substantially enhanced the compress yield strength, and resulted in improved anisotropy.

  6. Crack growth in an austenitic stainless steel at high temperature; Propagation de fissure a haute temperature dans un acier inoxydable austenitique

    Energy Technology Data Exchange (ETDEWEB)

    Polvora, J.P

    1998-12-31

    This study deals with crack propagation at 650 deg C on an austenitic stainless steel referenced by Z2 CND 17-12 (316L(NN)). It is based on an experimental work concerning two different cracked specimens: CT specimens tested at 650 deg C in fatigue, creep and creep-fatigue with load controlled conditions (27 tests), tube specimens containing an internal circumferential crack tested in four points bending with displacement controlled conditions (10 tests). Using the fracture mechanics tools (K, J and C* parameters), the purpose here is to construct a methodology of calculation in order to predict the evolution of a crack with time for each loading condition using a fracture mechanics global approach. For both specimen types, crack growth is monitored by using a specific potential drop technique. In continuous fatigue, a material Paris law at 650 deg C is used to correlate crack growth rate with the stress intensity factor range corrected with a factor U(R) in order to take into account the effects of crack closure and loading ratio R. In pure creep on CT specimens, crack growth rate is correlated to the evolution of the C* parameter (evaluated experimentally) which can be estimated numerically with FEM calculations and analytically by using a simplified method based on a reference stress approach. A modeling of creep fatigue growth rate is obtained from a simple summation of the fatigue contribution and the creep contribution to the total crack growth. Good results are obtained when C* parameter is evaluated from the simplified expression C*{sub s}. Concerning the tube specimens tested in 4 point bending conditions, a simulation based on the actual A 16 French guide procedure proposed at CEA. (authors) 104 refs.

  7. Crack initiation at high temperature on an austenitic stainless steel; Amorcage de fissure a haute temperature dans un acier inoxydable austenitique

    Energy Technology Data Exchange (ETDEWEB)

    Laiarinandrasana, L.

    1994-11-25

    The study deals with crack initiation at 600 and 650 degrees Celsius, on an austenitic stainless steel referenced by Z2 CND 17 12. The behaviour laws of the studied plate were update in comparison with existing data. Forty tests were carried out on CT specimens, with continuous fatigue with load or displacement controlled, pure creep, pure relaxation, creep-fatigue and creep-relaxation loadings. The practical initiation definition corresponds to a small crack growth of about the grain size. The time necessary for the crack to initiate is predicted with fracture mechanics global and local approaches, with the helps of microstructural observations and finite elements results. An identification of a `Paris`law` for continuous cyclic loading and of a unique correlation between the initiation time and C{sup *}{sub k} for creep tests was established. For the local approach, crack initiation by creep can be interpreted as the reaching of a critical damage level, by using a damage incremental rule. For creep-fatigue tests, crack growth rates at initiation are greater than those of Paris`law for continuous fatigue. A calculation of a transition time between elastic-plastic and creep domains shows that crack initiation can be interpreted whether by providing Paris`law with an acceleration term when the dwell period is less than the transition time, or by calculating a creep contribution which relies on C{sup *}{sub k} parameter when the dwell period and/or the initiation times are greater than the transition time. Creep relaxation tests present crack growth rates at initiation which are less than those for `equivalent` creep-fatigue tests. These crack growth rates when increasing hold time, but also when temperature decreases. Though, for hold times which are important enough and at lower temperature, there is no effect of the dwell period insofar as crack growth rate is equal to continuous fatigue Paris law predicted ones. (Abstract Truncated)

  8. A highly sensitive hydrogen peroxide amperometric sensor based on MnO{sub 2}-modified vertically aligned multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Xu Bin; Ye Minling; Yu Yuxiang [Nano Science Research Center, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, Guangdong (China); Zhang Weide, E-mail: zhangwd@scut.edu.cn [Nano Science Research Center, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, Guangdong (China)

    2010-07-26

    In this report, a highly sensitive amperometric sensor based on MnO{sub 2}-modified vertically aligned multiwalled carbon nanotubes (MnO{sub 2}/VACNTs) for determination of hydrogen peroxide (H{sub 2}O{sub 2}) was fabricated by electrodeposition. The morphology of the nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer and X-ray diffraction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were applied to investigate the electrochemical properties of the MnO{sub 2}/VACNTs nanocomposite electrode. The mechanism for the electrochemical reaction of H{sub 2}O{sub 2} at the MnO{sub 2}/VACNTs nanocomposite electrode was also discussed. In borate buffer (pH 7.8, 0.20 M), the MnO{sub 2}/VACNTs nanocomposite electrode exhibits a linear dependence (R = 0.998) on the concentration of H{sub 2}O{sub 2} from 1.2 x 10{sup -6} M to 1.8 x 10{sup -3} M, a high sensitivity of 1.08 x 10{sup 6} {mu}A M{sup -1} cm{sup -2} and a detection limit of 8.0 x 10{sup -7} M (signal/noise = 3). Meanwhile, the MnO{sub 2}/VACNTs nanocomposite electrode is also highly resistant towards typical inorganic salts and some biomolecules such as acetic acid, citric acid, uric acid and D-(+)-glucose, etc. In addition, the sensor based on the MnO{sub 2}/VACNTs nanocomposite electrode was applied for the determination of trace of H{sub 2}O{sub 2} in milk with high accuracy, demonstrating its potential for practical application.

  9. Fabrication of Ni-Mn Microprobe Structure with Low Internal Stress and High Hardness by Employing DC Electrodeposition

    Directory of Open Access Journals (Sweden)

    Kuan-Hui Cheng

    2014-01-01

    Full Text Available Due to its widely tunable mechanical property and incompatibility with most solders, Ni-Mn alloy can become a viable candidate in the fabrication of testing probe for microelectronic devices. In this study, the electrodeposition of Ni-Mn alloy in nickel sulphamate electrolyte with the addition of manganese sulphate was investigated under direct current (DC power source. The effects of current density and Mn2+ concentration in the electrolyte on the coating composition, cathodic efficiency, microstructure and mechanical properties were explored. The results showed that the raise of the Mn2+ concentration in the electrolyte alone did not effectively increase the Mn content in the coating but reduce the cathodic efficiency. On the other hand, increasing the current density facilitated the codeposition of the Mn and rendered the crystallite from coarse columnar grain to the refined one. Thus, both hardness and internal stress of the coating increased. The fabrication of testing probes at 1 A/dm2 was shown to satisfy the high hardness, low internal stress, reasonable fatigue life, and nonsticking requirements for this microelectronic application.

  10. Truncated octahedral LiMn{sub 2}O{sub 4} cathode for high-performance lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Bo-Mi; Kim, Si-Jin; Lee, Young-Woo; Park, Han-Chul; Kim, Da-Mi; Park, Kyung-Won, E-mail: kwpark@ssu.ac.kr

    2015-05-05

    Spinel-type LiMn{sub 2}O{sub 4} has been studied as a promising cathode candidate capable of replacing LiCoO{sub 2} in lithium-ion batteries. Here we demonstrate LiMn{sub 2}O{sub 4} powders prepared by a calcination process as a function of temperature and time. LiMn{sub 2}O{sub 4} structure electrode prepared at 700 °C for 10 h forms a truncated octahedral structure consisting of {111} and {100} surfaces. In particular, the truncated octahedral structure exhibits the crystal orientation toward dominant {111} surfaces of octahedral structure to minimize Mn dissolution and a particular portion of {100} surfaces of the truncated structure to stabilize the electrode. The truncated octahedral structure shows excellent discharge capacity (∼132.14 mAh g{sup −1} at 1 C), high capacity retention (∼100%) and durable cycling performance (after 100 cycle) compared to the octahedral shaped electrodes. In particular, the truncated octahedral structure of LMO-700-10h exhibits the crystal orientation toward majority {111} surfaces of octahedral structure and minority {100} surfaces. - Highlights: • LiMn{sub 2}O{sub 4} nanostructure materials were prepared for Li-ion batteries. • LiMn{sub 2}O{sub 4} nanostructure materials were controlled by calcination temperatures. • The truncated octahedral nanostructure consists of {111} and {100} surfaces. • The truncated octahedral structure shows an excellent performance.

  11. Membranes of MnO Beading in Carbon Nanofibers as Flexible Anodes for High-Performance Lithium-Ion Batteries

    Science.gov (United States)

    Zhao, Xin; Du, Yuxuan; Jin, Lei; Yang, Yang; Wu, Shuilin; Li, Weihan; Yu, Yan; Zhu, Yanwu; Zhang, Qinghua

    2015-01-01

    Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO2 nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO2 nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g−1 after 150 discharge/charge cycles at 0.1 A g−1, a good rate capability (406.1 mAh g−1 at 3  A g−1) and an excellent cycling performance (655 mAh g−1 over 280 cycles at 0.5 A g−1). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode. PMID:26374601

  12. Dynamic mechanical analyze of superelastic CuMnAl shape memory alloy

    Science.gov (United States)

    (Dragoș Ursanu, A. I.; Stanciu, S.; Pricop, B.; Săndulache, F.; Cimpoeșu, N.

    2016-08-01

    A new shape memory alloy was obtain from high purity Cu, Mn and Al elements using a induce furnace. The intelligent material present negative transformation temperatures and an austenite like state at room temperature. The austenite state of CuMnAl shape memory alloy present superelasticity property. Five kilograms ingot was obtain of Cu10Mn10Al alloy. From the base material (melted state) were cut samples with 6 mm thickness using a mechanical saw. After an homogenization heat treatment the samples were hot rolled through four passes with a reduction coefficient of 20%. Experimental lamellas were obtained with 1.5 mm thickness and 90x10 mm length and width. After the hot rolled treatment the materials were heat treated at 800°C for 20 minutes and chilled in water. Four samples, one just laminated and three heat treated by aging, were analyzed with a Netzsch DMA equipment to establish the elastic modulus and the internal friction values of the materials. Metallic materials microstructure was analyzed using a scanning electron microscope Vega Tescan LMH II type. After the aging heat treatment a decrease of internal friction is observed on the entire analyze range which is assigned to formation of Al-based precipitates that block the internal movement of the alloy characteristic phases.

  13. Engineering single crystalline Mn3O4 nano-octahedra with exposed highly active {011} facets for high performance lithium ion batteries.

    Science.gov (United States)

    Huang, Shao-Zhuan; Jin, Jun; Cai, Yi; Li, Yu; Tan, Hai-Yan; Wang, Hong-En; Van Tendeloo, G; Su, Bao-Lian

    2014-06-21

    Well shaped single crystalline Mn3O4 nano-octahedra with exposed highly active {011} facets at different particle sizes have been synthesized and used as anode materials for lithium ion batteries. The electrochemical results show that the smallest sized Mn3O4 nano-octahedra show the best cycling performance with a high initial charge capacity of 907 mA h g(-1) and a 50th charge capacity of 500 mA h g(-1) at a current density of 50 mA g(-1) and the best rate capability with a charge capacity of 350 mA h g(-1) when cycled at 500 mA g(-1). In particular, the nano-octahedra samples demonstrate a much better electrochemical performance in comparison with irregular shaped Mn3O4 nanoparticles. The best electrochemical properties of the smallest Mn3O4 nano-octahedra are ascribed to the lower charge transfer resistance due to the exposed highly active {011} facets, which can facilitate the conversion reaction of Mn3O4 and Li owing to the alternating Mn and O atom layers, resulting in easy formation and decomposition of the amorphous Li2O and the multi-electron reaction. On the other hand, the best electrochemical properties of the smallest Mn3O4 nano-octahedra can also be attributed to the smallest size resulting in the highest specific surface area, which provides maximum contact with the electrolyte and facilitates the rapid Li-ion diffusion at the electrode/electrolyte interface and fast lithium-ion transportation within the particles. The synergy of the exposed {011} facets and the smallest size (and/or the highest surface area) led to the best performance for the Mn3O4 nano-octahedra. Furthermore, HRTEM observations verify the oxidation of MnO to Mn3O4 during the charging process and confirm that the Mn3O4 octahedral structure can still be partly maintained after 50 discharge-charge cycles. The high Li-ion storage capacity and excellent cycling performance suggest that Mn3O4 nano-octahedra with exposed highly active {011} facets could be excellent anode materials for

  14. a Study Into the Effects of AN Austenitic Weld on Ultrasonic Array Imaging Performance

    Science.gov (United States)

    Hunter, A. J.; Drinkwater, B. W.; Zhang, J.; Wilcox, P. D.

    2011-06-01

    An industrial application of ultrasonic array imaging is the inspection of austenitic welds with high inhomogeneity and anisotropy. These result in attenuation and perturbation of the signals that adversely affects imaging performance. Here, the effects of perturbations introduced by an austenitic weld on array imaging performance are investigated experimentally. It is shown that three major factors contribute to the degradation of image quality: timing errors, phase errors, and multi-path propagation and scattering.

  15. Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

    Science.gov (United States)

    Bansod, Ankur V.; Patil, Awanikumar P.; Moon, Abhijeet P.; Khobragade, Nilay N.

    2016-09-01

    Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.

  16. Structural and magnetic stability of high energy ball milled Co{sub 2}MnSi

    Energy Technology Data Exchange (ETDEWEB)

    Vinesh, A., E-mail: attatappa85@gmail.com [Department of Physics, Amity School of Applied Sciences, Amity University Haryana, Gurgaon 122413 (India); Sudheesh, V.D. [Department of Physics, MohanlalSukhadia University Udaipur, Rajasthan 313001 (India); Sebastian, Varkey [Department of Physics, Nimalagiri College, Nirmalagiri, Kannur, Kerala 670701 (India); Lakshmi, N.; Venugopalan, K. [Department of Physics, MohanlalSukhadia University Udaipur, Rajasthan 313001 (India)

    2015-07-15

    Structural and magnetic properties of ball milled Co{sub 2}MnSi have been studied and compared with that of ordered bulk sample. The milled sample (with average size determined using the Williamson–Hall method) shows that the chemical ordering for this sample is very stable and is little effected by high energy ball milling. However, the reduction in the saturation magnetic moment of the milled sample shows that there is spin disordering induced on ball milling – attributable to the formation of a magnetically dead layer at the surface of the nano-sized samples. The ordered sample (unmilled) has a saturation moment value of 4.4 µ{sub B} per formula unit at room temperature and is in agreement with the prediction of Slater Pauling curve. On milling it reduces to ~3 µ{sub B} per formula unit at room temperature with an accompanying increase in the coercivity, retentivity and squareness factor. - Highlights: • We studied the magnetic and structural properties of bulk and ball milled Co{sub 2}MnSi. • Structural disordering is minimal even at 36 nm. • Constant value of T{sub C} shows strong ferromagnetic interaction in smaller particles. • Formation of magnetically dead surface layer results reduction in magnetic moment. • Variation of magnetic parameters is systematic with variation in milling time/size.

  17. MnBi particles with high energy density made by spark erosion

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, PK; Jin, SH; Berkowitz, AE

    2014-05-07

    We report on the properties of low-temperature phase (LTP)-MnBi particles produced by the rapid-quenching technique of spark-erosion. The as-prepared powder consists of amorphous, crystalline, and superparamagnetic particles, mostly as porous aggregates. The major fraction of the powder consists of 20-30 nm particles. A short anneal crystallizes the amorphous particles producing a high moment, >90% of theoretical M-S, albeit with H-C of a few kOe. If lightly milled, the agglomerates are broken up to yield H-C of 1 T. These findings are supported by the x-ray diffraction pattern showing broadened peaks of the predominant LTP-MnBi phase. The combination of spark erosion, milling, and annealing has produced randomly oriented particles with (BH)(MAX) similar to 3.0 MGOe. The particles are expected to show record energy product when aligned along their crystallographic easy axes. (C) 2014 AIP Publishing LLC.

  18. MnBi particles with high energy density made by spark erosion

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Phi-Khanh, E-mail: phi@ucsd.edu; Jin, Sungho [Materials Science and Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Center for Magnetic Recording Research, University of California, San Diego, La Jolla, California 92093 (United States); Berkowitz, Ami E. [Physics Department, University of California, San Diego, La Jolla, California 92093 (United States); Center for Magnetic Recording Research, University of California, San Diego, La Jolla, California 92093 (United States)

    2014-05-07

    We report on the properties of low-temperature phase (LTP)-MnBi particles produced by the rapid-quenching technique of spark-erosion. The as-prepared powder consists of amorphous, crystalline, and superparamagnetic particles, mostly as porous aggregates. The major fraction of the powder consists of 20–30 nm particles. A short anneal crystallizes the amorphous particles producing a high moment, >90% of theoretical M{sub S}, albeit with H{sub C} of a few kOe. If lightly milled, the agglomerates are broken up to yield H{sub C} of 1 T. These findings are supported by the x-ray diffraction pattern showing broadened peaks of the predominant LTP-MnBi phase. The combination of spark erosion, milling, and annealing has produced randomly oriented particles with (BH){sub MAX} ∼ 3.0 MGOe. The particles are expected to show record energy product when aligned along their crystallographic easy axes.

  19. Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2016-09-15

    To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

  20. Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes.

    Science.gov (United States)

    Ma, Zhipeng; Shao, Guangjie; Fan, Yuqian; Wang, Guiling; Song, Jianjun; Shen, Dejiu

    2016-04-13

    Poor electrical conductivity and mechanical instability are two major obstacles to realizing high performance of MnO2 as pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. We herein report the fabrication of a hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin δ-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong α-MnO2 nanowires. The first specific capacitance of hierarchical core-shell nanostructure reached 153.8 F g(-1) at the discharge current density of as high as 20 A g(-1), and the cycling stability is retained at 98.1% after 10,000 charge-discharge cycles, higher than those in the literature. The excellent rate capacity and stability of the hierarchical core-shell nanostructures can be attributed to the structural features of the two MnO2 crystals, in which a 1D α-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D δ-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.

  1. The Change of Austenitic Stainless Steel Elements Content in the Inner Parts of VVER-440 Reactor during Operation

    Science.gov (United States)

    Smutný, Vladimír; Hep, Jaroslav; Novosad, Petr

    2009-08-01

    Neutron activation induces the element transmutation in materials surrounding the reactor active core. The objective of the present paper is to calculate and evaluate the change of austenitic stainless steel 08Ch18N10T elements content through neutron induced activation, in inner parts of VVER-440 - in the baffle and in the barrel. Particularly the content changes of Mn in austenitic stainless steel. The neutron flux density and then the neutron activation of austenitic stainless steel elements in parts at the core are calculated. Neutron activation represents a measure of austenitic stainless steel elements transmutation. The power distribution is determined as an average value of several cycles power distribution in the middle of a cycle for the NPP Dukovany. The power distribution is calculated with the code MOBY-DICK [1]. The neutron flux density is calculated with the code TORT [2]. The neutron activation of austenitic stainless steel elements in the baffle and in the barrel is calculated with the system EASY-2007 containing the code FISPACT-2007 [3]. The calculation of the changing austenitic stainless steel elements content is performed depending on the moment of the supposed end of reactor operation - 40 years. There is also necessary monitoring and benchmarking of steel element content change, because the neutron flux calculation, particularly in thermal region, shows a considerable uncertainty, e.g. [4]. The motivation for this work is the study focused to stress corrosion cracking of austenitic stainless steels induced by radiation inside PWR and BWR, e.g. [5]. The paper could be a suggestion to estimation of austenitic stainless steel corrosion damage induced by neutrons in inner parts of VVER-440 reactor.

  2. Structural, microstructural and magnetocaloric investigations in high-energy ball milled NiMnGa powders

    Science.gov (United States)

    de Santanna, Y. V. B.; de Melo, M. A. C.; Santos, I. A.; Coelho, A. A.; Gama, S.; Cótica, L. F.

    2008-11-01

    In this paper, structural, microstrucutural and magnetocaloric properties of Ni 2.18Mn 0.82Ga alloys submitted to high-energy ball milling are reported. A 7-layered orthorhombic martensitic ( Pnnm) phase was detected in post-milling annealed samples, which reached a microstrucuture composed predominantly by nanograins. The magnetocaloric effect is strongly weakened in comparison with as-cast samples of similar composition. This effect can be attributed to the absence of the mesoscale twin-related martensitic variants in the nanostructurated powders. However, post-milled samples annealed at 1123 K for 4 h present relative cooling powers as high as those observed for manganites. Therefore, these materials can be considered as potential candidates for use as regenerators in prototypal magnetic refrigerators.

  3. Study on austenitic nitrocarburizing without compound layer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X. [Univ. of Petroleum, Dongying, Shandong (China); Kong, C.; Qiao, Y. [Shandong Polytechnic Univ., Jinan, Shandong (China)

    1995-12-31

    This paper presents an advanced austenitic nitrocarburizing process. Medium-carbon steel was used in austenitic nitrocarburizing with methanol/ammonia atmospheres. A particular hardened case without compound layer was obtained at 680 C processing temperature and a moderate nitrogen potential level and for steel 45 nitrocarburized, there is a fine-grain region beneath the austenite case. The forming and developing mechanism of the fine-grain region was analyzed and the microhardness profiles of the layer before and after ageing were determined. Having the advantages of shorter processing time and a superior hardened case, this treatment is expected to supersede the conventional ferritic nitrocarburizing process in many wear resistance applications.

  4. Mathematical Model of the Processoof Pearlite Austenitization

    Directory of Open Access Journals (Sweden)

    Olejarczyk-Wożeńska I.

    2014-10-01

    Full Text Available The paper presents a mathematical model of the pearlite - austenite transformation. The description of this process uses the diffusion mechanism which takes place between the plates of ferrite and cementite (pearlite as well as austenite. The process of austenite growth was described by means of a system of differential equations solved with the use of the finite difference method. The developed model was implemented in the environment of Delphi 4. The proprietary program allows for the calculation of the rate and time of the transformation at an assumed temperature as well as to determine the TTT diagram for the assigned temperature range.

  5. Stress distribution in unstable austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kubler, R.; Inal, K.; Berveiller, M. [LPMM, UMR CNRS, ENSAM, Metz (France)

    2002-07-01

    Tensile tests performed on unstable austenitic material lead to formation of martensite. Therefore, plasticity and transformation occur at the same time leading to inelastic strain and consequently internal stresses. The present work focuses on the stress distribution in each phase of a two-phase material with an evolving microstructure. Experimental results based on X-ray diffraction are presented to give a trend of the evolution of stress distribution inside austenite and martensite during a tensile test at -60 C. After unloading, first results show compression in martensite and tension in austenite. It is also noticed that mechanical anisotropy is enhanced in both phases. (orig.)

  6. Microstructure and magnetic performance of Ni-substituted high density MnZn ferrite

    Institute of Scientific and Technical Information of China (English)

    YU Zhong; LAN Zhongwen; CHEN Shengming; SUN Yueming; SUN Ke

    2006-01-01

    The effects of NiO on microstructure and magnetic properties of Mn-Zn ferrite with a nominal composition of Zn0.32Mn0.60-xNixFe2.08O4 were investigated. The calcined powder of Mn-Zn ferrite was characterized by X-ray diffraction (XRD), the fracture surface of Mn-Zn ferrite was checked by scanning electronic microscope (SEM), and then the magnetic properties were measured. As a result, the substitution of Ni can cause the crystallattice constant of MnZn ferrite to decline, and the grain size to decrease, therefore improve the magnetic performance of MnZn ferrite whose density exceeds 5.0 g·cm-3.

  7. Influence of Austenitizing Heat Treatment on the Properties of the Tempered Type 410-1Mo Stainless Steel

    Science.gov (United States)

    Mabruri, E.; Syahlan, Z. A.; Sahlan; Prifiharni, S.; Anwar, M. S.; Chandra, S. A.; Romijarso, T. B.; Adjiantoro, B.

    2017-05-01

    The modified 410-1Mo stainless steel has been developed with higher tensile strength and elongation compared to the standard 410 stainless steel. This paper reports the influence of austenitizing temperature on the microstructure, hardness, impact resistance and corrosion resistance of the modified 410-1Mo steel. The steel samples were prepared by a process sequence of induction melting, hot forging, annealing, hardening, and tempering. The microstructure of the tempered steels revealed additional phase of delta ferrite at pre-austenitizing temperatures of 950 to 1050 °C and disappeared at a temperature of 1100 °C. The steels which underwent pre-austenitizing at 1100 °C showed the largest sized lath martensite and the largest amount of retained austenite. The tempered steels maintained hardness at austenitizing temperatures of 950 °C to 1000 °C and showed an increasing hardness at austenitizing temperatures from 1000 to 1100 °C. At a range of austenitizing temperatures, it was investigated that the steels exhibited higher impact resistance at 1050 °C. The tempered steels that were pre-austenitized at 950 °C and 1100 °C showed the lowest pitting potential due to the existence of carbides and coarse-high carbon martensite, respectively.

  8. Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization

    Institute of Scientific and Technical Information of China (English)

    Wan-song Li; Hong-ye Gao; Hideharu Nakashima; Satoshi Hata; Wen-huai Tian

    2016-01-01

    In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron micros-copy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austeni-tized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.

  9. Fundamental study of the austenite formation and decomposition in low-silicon, aluminum added TRIP steels

    Science.gov (United States)

    Garcia-Gonzalez, Jose Enrique

    2005-11-01

    TRIP (Transformation Induced Plasticity) steels are under development for automotive applications that require high strength and excellent formability. Conventional TRIP steels consist of a multiphase microstructure comprised of a ferrite matrix with a dispersion of bainite and metastable retained austenite. The high ductility exhibited by these steels results from the transformation of the metastable retained austenite to martensite during straining. In conventional TRIP steel processing, the multiphase microstructure is obtained by controlled cooling from the alpha + gamma region to an isothermal holding temperature. During this holding, bainite forms and carbon is rejected out into the austenite, which lowers the Ms temperature and stabilizes the austenite to room temperature. In this research project, a fundamental study of a low-Si, Mo-Nb added cold rolled TRIP steel with and without Al additions was conducted. In this study, the recrystallization of cold-rolled ferrite, the formation of austenite during intercritical annealing and the characteristics of the decomposition of the intercritically annealed austenite by controlled cooling rates were systematically assessed. Of special interest were: (i) the effect of the initial hot band microstructure, (ii) the formation of epitaxial ferrite during cooling from the intercritical annealing temperature to the isothermal holding temperature, (iii) the influence of the intercritically annealed austenite on the formation of bainite during the isothermal holding temperature, and (iv) the influence of the processing variables on the type, amount, composition and stability of the retained austenite. During this research study, techniques such as OM, SEM, EBSD, TEM, XRD and Magnetometry were used to fully characterize the microstructures. Furthermore, a Gleeble 3500 unit at US Steel Laboratories was used for dilatometry studies and to simulate different CGL processing routes, from which specimens were obtained to evaluate

  10. Study of Ferrite During Refinement of Prior Austenite Grains in Microalloyed Steel Continuous Casting

    Science.gov (United States)

    Liu, Jiang; Wen, Guanghua; Tang, Ping

    2017-08-01

    The formation of coarse prior austenite grain is a key factor to promote transverse crack, and the susceptibility to the transverse crack can be reduced by refining the austenite grain size. In the present study, the high-temperature confocal laser scanning microscope (CLSM) was used to simulate two types of double phase-transformation technologies. The distribution and morphology of ferrites under different cooling conditions were analyzed, and the effects of ferrite distribution and morphology on the double phase-transformation technologies were explored to obtain the suitable double phase-change technology for the continuous casting process. The results indicate that, under the thermal cycle TH0 [the specimens were cooled down to 913 K (640 °C) at a cooling rate of 5.0 K/s (5.0 °C/s)], the width of prior austenite grain boundaries was thick, and the dislocation density at grain boundaries was high. It had strong inhibition effect on crack propagation; under the thermal cycle TH1 [the specimens were cooled down to 1073 K (800 °C) at a cooling rate of 5.0 K/s (5.0 °C/s) and then to 913 K (640 °C) at a cooling rate of 1.0 K/s (1.0 °C/s)], the width of prior austenite grain boundary was thin, and the dislocation density at grain boundaries was low. It was beneficial to crack propagation. After the first phase change, the developed film-like ferrite along the austenite grain boundaries improved the nucleation conditions of new austenitic grains and removed the inhibition effect of the prior austenite grain boundaries on the austenite grain size.

  11. Extended x-ray absorption fine structure investigation of annealed carbon expanded austenite

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas L.; Somers, Marcel A. J.;

    2012-01-01

    Carbon expanded austenite synthesized through carburizing of austenitic stainless steel powder at 380°C was annealed at 470°C and investigated with extended X-ray absorption fine structure (EXAFS) and synchrotron powder diffraction (SPD). SPD showed that the samples consisted of carbon expanded...... austenite and Hägg carbide, Ξ-M5C2. EXAFS showed that the Cr atoms were mainly present in environments similar to the carbides Hägg Ξ-M5C2 and M23C6. The environments of the Fe and Ni atoms were concluded to be largely metallic austenite. Light optical micrograph of stainless steel AISI 316 gas......-carburized in a temperature regime around 470°C. The surface zone is converted into carbon expanded austenite; the high interstitial content of carbon dissolved in the surface results in highly favorable materials properties. In the present article the local atomic environment of (annealed) carbon expanded austenite...

  12. Computational design of precipitation strengthened austenitic heat-resistant steels

    Science.gov (United States)

    Lu, Qi; Xu, Wei; van der Zwaag, Sybrand

    2013-09-01

    A new genetic alloy design approach based on thermodynamic and kinetic principles is presented to calculate the optimal composition of MX carbonitrides precipitation strengthened austenitic heat-resistant steels. Taking the coarsening of the MX carbonitrides as the process controlling the life time for steels in high temperature use, the high temperature strength is calculated as a function of steel chemistry, service temperature and time. New steel compositions for different service conditions are found yielding optimal combinations of strength and stability of the strengthening precipitation for specific applications such as fire-resistant steels (short-time property guarantee) and creep-resistant steels (long-time property guarantee). Using the same modelling approach, the high temperature strength and lifetime of existing commercial austenitic creep-resistant steels were also calculated and a good qualitative agreement with reported experimental results was obtained. According to the evaluation parameter employed, the newly defined steel compositions may have higher and more stable precipitation strengthening factors than existing high-temperature precipitate-strengthened austenite steels.

  13. Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage

    Science.gov (United States)

    Shan, Xiaoqiang; Charles, Daniel S.; Lei, Yinkai; Qiao, Ruimin; Wang, Guofeng; Yang, Wanli; Feygenson, Mikhail; Su, Dong; Teng, Xiaowei

    2016-11-01

    Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (~1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn5O8 pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn5O8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn2+/Mn4+ redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8.

  14. Bivalence Mn5O8 with hydroxylated interphase for high-voltage aqueous sodium-ion storage.

    Science.gov (United States)

    Shan, Xiaoqiang; Charles, Daniel S; Lei, Yinkai; Qiao, Ruimin; Wang, Guofeng; Yang, Wanli; Feygenson, Mikhail; Su, Dong; Teng, Xiaowei

    2016-11-15

    Aqueous electrochemical energy storage devices have attracted significant attention owing to their high safety, low cost and environmental friendliness. However, their applications have been limited by a narrow potential window (∼1.23 V), beyond which the hydrogen and oxygen evolution reactions occur. Here we report the formation of layered Mn5O8 pseudocapacitor electrode material with a well-ordered hydroxylated interphase. A symmetric full cell using such electrodes demonstrates a stable potential window of 3.0 V in an aqueous electrolyte, as well as high energy and power performance, nearly 100% coulombic efficiency and 85% energy efficiency after 25,000 charge-discharge cycles. The interplay between hydroxylated interphase on the surface and the unique bivalence structure of Mn5O8 suppresses the gas evolution reactions, offers a two-electron charge transfer via Mn(2+)/Mn(4+) redox couple, and provides facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8.

  15. Spongelike Nanosized Mn 3 O 4 as a High-Capacity Anode Material for Rechargeable Lithium Batteries

    KAUST Repository

    Gao, Jie

    2011-07-12

    Mn3O4 has been investigated as a high-capacity anode material for rechargeable lithium ion batteries. Spongelike nanosized Mn 3O4 was synthesized by a simple precipitation method and characterized by powder X-ray diffraction, Raman scattering and scanning electron microscopy. Its electrochemical performance, as an anode material, was evaluated by galvanostatic discharge-charge tests. The results indicate that this novel type of nanosized Mn3O4 exhibits a high initial reversible capacity (869 mA h/g) and significantly enhanced first Coulomb efficiency with a stabilized reversible capacity of around 800 mA h/g after over 40 charge/discharge cycles. © 2011 American Chemical Society.

  16. Magnetic hardening of high-energy ball-milled nanocrystalline LaMn{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Elmali, Ayhan [Department of Physics Engineering, Faculty of Engineering, Ankara University, 06100 Besevler-Ankara (Turkey)], E-mail: elmali@eng.ankara.edu.tr; Tekerek, Simsek; Dincer, Ilker; Elerman, Yalcin [Department of Physics Engineering, Faculty of Engineering, Ankara University, 06100 Besevler-Ankara (Turkey); Theissmann, Ralf [Institute for Materials Science, Darmstadt Technology University, Petersenstr. 23, 64287 Darmstadt (Germany); Institute for NanoTechnology, Forschungszentrum Karlsruhe (Germany); Ehrenberg, Helmut [Institute for Materials Science, Darmstadt Technology University, Petersenstr. 23, 64287 Darmstadt (Germany); Institute for Solid State and Materials Research, Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden (Germany); Fuess, Hartmut [Institute for Materials Science, Darmstadt Technology University, Petersenstr. 23, 64287 Darmstadt (Germany)

    2008-02-15

    Nanocrystalline LaMn{sub 2}Si{sub 2} powders have been obtained by high-energy ball milling for 30 min from bulk alloys. After milling a high coercivity about 6 kOe is observed at 10 K in contrast to neglectable coercivity for the bulk LaMn{sub 2}Si{sub 2} at 5 K. The average grain size of the optimum particles which is obtained from X-ray diffraction pattern and HRTEM picture is about 20 nm. The magnetic hardening is observed for the nanocrystalline LaMn{sub 2}Si{sub 2,} reflected in the coercivity field strength of 6 kOe at 10 K.

  17. Facile synthesis of hierarchical micro/nanostructured MnO material and its excellent lithium storage property and high performance as anode in a MnO/LiNi0.5Mn1.5O(4-δ) lithium ion battery.

    Science.gov (United States)

    Xu, Gui-Liang; Xu, Yue-Feng; Fang, Jun-Chuan; Fu, Fang; Sun, Hui; Huang, Ling; Yang, Shihe; Sun, Shi-Gang

    2013-07-10

    Hierarchical micro/nanostructured MnO material is synthesized from a precursor of MnCO3 with olive shape that is obtained through a facile one-pot hydrothermal procedure. The hierarchical micro/nanostructured MnO is served as anode of lithium ion battery together with a cathode of spinel LiNi0.5Mn1.5O(4-δ) material, which is synthesized also from the precursor of MnCO3 with olive shape through a different calcination process. The structures and compositions of the as-prepared materials are characterized by TGA, XRD, BET, SEM, and TEM. Electrochemical tests of the MnO materials demonstrate that it exhibit excellent lithium storage property. The MnO material in a MnO/Li half cell can deliver a reversible capacity of 782.8 mAh g(-1) after 200 cycles at a rate of 0.13 C, and a stable discharge capacity of 350 mAh g(-1) at a high rate of 2.08 C. Based on the outstanding electrochemical property of the MnO material and the LiNi0.5Mn1.5O(4-δ) as well, the MnO/LiNi0.5Mn1.5O(4-δ) full cell has demonstrated a high discharge specific energy ca. 350 Wh kg(-1) after 30 cycles at 0.1 C with an average high working voltage at 3.5 V and a long cycle stability. It can release a discharge specific energy of 227 Wh kg(-1) after 300 cycles at a higher rate of 0.5 C. Even at a much higher rate of 20 C, the MnO/LiNi0.5Mn1.5O(4-δ) full cell can still deliver a discharge specific energy of 145.5 Wh kg(-1). The excellent lithium storage property of the MnO material and its high performance as anode in the MnO/LiNi0.5Mn1.5O(4-δ) lithium ion battery is mainly attributed to its hierarchical micro/nanostructure, which could buffer the volume change and shorten the diffusion length of Li(+) during the charge/discharge processes.

  18. High Curie temperature of Ce-Fe-Si compounds with ThMn12 structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, C; Pinkerton, FE; Herbst, JF

    2015-01-15

    We report the discovery of ternary CeFe(12-x)Si(x)compounds possessing the ThMn12 structure. The samples were prepared by melt spinning followed by annealing. In contrast to other known Ce Fe-based binary and ternary compounds, CeFe12-xSix compounds exhibit exceptionally high Curie temperatures whose values increase with added Si substitution. The highest T. = 583 K in CeFe10Si2 rivals that of the well-established Nd2Fe14B compound. We ascribe the T-c behavior to a combination of Si-induced 3d band structure changes and partial Ce3+ stabilization. (C) 2014 Published by Elsevier Ltd.

  19. Effect of Additives on Magnetic Properties of High Frequency MnZn Power Ferrite

    Institute of Scientific and Technical Information of China (English)

    YU Zhong; LAN Zhongwen; WANG Jingmei; ZHANG Yidong; WANG Haocai

    2004-01-01

    The effect of additives,such as CaO and V2O5 on the magnetic properties of high frequency MnZn power ferrite is studied by the conventional ceramic process.As a result,the grain boundary resistivity increases and the power loss declines with the addition of CaO enriched at the grain boundary.By adding an optimum amount of V2O5 which acts indirectly via liquid phase formation and influences the microstructural development during sintering,the crystalline grain of ferrite was refined,the porosity decreases,the amount of grain boundary and the grain boundary resistivity increased,so the power loss is suppressed.

  20. High spin polarization in CoFeMnGe equiatomic quaternary Heusler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Bainsla, Lakhan [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Magnetic Materials Unit, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Suresh, K. G., E-mail: suresh@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Nigam, A. K. [Department of Condensed Matter and Materials Science, Tata Institute of Fundamental Research, Mumbai 400005 (India); Manivel Raja, M. [Defence Metallurgical Research Laboratory, Hyderabad 500058 (India); Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hono, K. [Magnetic Materials Unit, National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2014-11-28

    We report the structure, magnetic property, and spin polarization of CoFeMnGe equiatomic quaternary Heusler alloy. The alloy was found to crystallize in the cubic Heusler structure (prototype LiMgPdSn) with considerable amount of DO{sub 3} disorder. Thermal analysis result indicated the Curie temperature is about 750 K without any other phase transformation up to melting temperature. The magnetization value was close to that predicted by the Slater-Pauling curve. Current spin polarization of P = 0.70 ± 0.01 was deduced using point contact andreev reflection measurements. The temperature dependence of electrical resistivity has been fitted in the temperature range of 5–300 K in order to check for the half metallic behavior. Considering the high spin polarization and Curie temperature, this material appears to be promising for spintronic applications.

  1. The effect of strain rate on the impact strength of the high-Mn steel

    Directory of Open Access Journals (Sweden)

    A. Śmiglewicz

    2015-10-01

    Full Text Available In the paper, results of impact bending tests of a high-manganese steel of Fe – 30 wt.%, Mn – 9 wt.%, Al – 0,65 wt.%, C grade are presented. The tests were carried out using a flywheel machine, suitable for dynamic stretching and impact bending tests in the range of linear velocity of the forcing element from 5 ÷ 40 m/s. The obtained test results were compared with the results of impact resistance of the studied steel determined using Charpy machine. Structural investigations were carried out using scanning transmission electron microscopy. Surfaces of fractures formed in the break point during bending tests were analyzed, and they indicate a presence of mixed transcrystalline fractures with a predominance of plastic fractures.

  2. High-temperature Electric Properties of Polycrystalline La-doped CaMnO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Jinle Lan; Yuanhua Lin; Ao Mei; Cewen Nan; Yong Liu; Boping Zhang; Jingfeng Li

    2009-01-01

    Polycrystalline La-doped CaMnO3 ceramics have been prepared by a solid-state sintering method. Analysis of microstructure and phase composition indicates that the addition of La can prohibit the further growth of grain, and no impurity phase appears. The results revealed that the La doping can lead to a large change of the activation energy (from 0.22 to 0.02 eV), and thus result in a marked increase in electric conductivity of 2-4 orders of magnitude. The power factor can reach about 1.5×10-4 W·m-1·K-2 in a wide temperature range, which potentially make them attractive for n-type high-temperature thermoelectric materials.

  3. A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen

    Science.gov (United States)

    Appleby, A. John; Dhar, Y. J.; Murphy, O. J.; Srinivasan, Supramaniam

    1989-01-01

    The nickel-hydrogen secondary battery system is now the one of choice for use in GEO satellites. It offers superior energy density to that of nickel-cadmium, with a lifetime that is at least comparable in terms of both cycle life and overall operating life. While the number of deep cycles required for GEO use is small, LEO satellites with long lifetimes (5 to 10 years) will require secondary battery systems allowing 30,000 to 60,000 useful cycles which are characterized by an approximately 2C charge rate and C average discharge rate. Recent work has shown that birnessite MnO2 doped with bismuth oxide can be cycled at very high rates (6C) over a very large number of cycles (thousands) at depths-of-discharge in the 85 to 90 percent range, based on two electrons, which discharge at the same potential in a flat plateau. The potential is about 0.7 V vs. hydrogen, with a cut-off at 0.6 V. At first sight, this low voltage would seem to be a disadvantage, since the theoretical energy density will be low. However, it permits the use of lightweight materials that are immune from corrosion at the positive. The high utilization and low equivalent weight of the active material, together with the use of teflon-bonded graphite for current collection, result in very light positives, especially when these are compared with those in a derated nickel-hydrogen system. In addition, the weight of the pressure vessel falls somewhat, since the dead volume is lower. Calculations show that a total system will have 2.5 times the Ah capacity of a derated nickel-hydrogen LEO battery, so that the energy density, based on 1.2 V for nickel-hydrogen and 0.7 V for MnO2-hydrogen, will be 45 percent higher for comparable cycling performance.

  4. Influence of original microstructure on the transformation behavior and mechanical properties of ultra-high-strength TRIP-aided steel

    Institute of Scientific and Technical Information of China (English)

    Hong-xiang Yin; Ai-min Zhao; Zheng-zhi Zhao; Xiao Li; Shuang-jiao Li; Han-jiang Hu; Wei-guang Xia

    2015-01-01

    The transformation behavior and tensile properties of an ultra-high-strength transformation-induced plasticity (TRIP) steel (0.2C–2.0Si–1.8Mn) were investigated by different heat treatments for automobile applications. The results show that F-TRIP steel, a tradi-tional TRIP steel containing as-cold-rolled ferrite and pearlite as the original microstructure, consists of equiaxed grains of intercritical ferrite surrounded by discrete particles of M/RA and B. In contrast, M-TRIP steel, a modified TRIP-aided steel with martensite as the original mi-crostructure, containing full martensite as the original microstructure is comprised of lath-shaped grains of ferrite separated by lath-shaped martensite/retained austenite and bainite. Most of the austenite in F-TRIP steel is granular, while the austenite in M-TRIP steel is lath-shaped. The volume fraction of the retained austenite as well as its carbon content is lower in F-TRIP steel than in M-TRIP steel, and austenite grains in M-TRIP steel are much finer than those in F-TRIP steel. Therefore, M-TRIP steel was concluded to have a higher austenite stability, re-sulting in a lower transformation rate and consequently contributing to a higher elongation compared to F-TRIP steel. Work hardening be-havior is also discussed for both types of steel.

  5. Abnormal austenite-ferrite transformation behavior in pure iron

    Institute of Scientific and Technical Information of China (English)

    LIU Yongchang; F.Sommer; E.J. Mittemeijer

    2004-01-01

    The austenite → ferrite transformation is the most important reaction route in the manufacture of Fe-based materials. Here the austenite (γ) → ferrite (α)transformation of pure iron was systematically explored by high-resolution dilatometry. Abnormal transformation kinetics, multi-peak discontinuous reaction, was recognized in pure iron according to the variation of the ferrite-formation rate. The occurrence the one or the other type of γ→α trans formation strongly depends on the grain size: the transformation type changes from abnormal to normal (single-peak continuous reaction) with decreasing grain size. The inherent reason for the occurrence of abnormal transformation could be attributed to the repeated nucleation in front of the moving γ/α interface induced by the accumulation of elastic and plastic accommodation energy.

  6. Laser borided composite layer produced on austenitic 316L steel

    Science.gov (United States)

    Mikołajczak, Daria; Kulka, Michał; Makuch, Natalia

    2016-12-01

    Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides) and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  7. Laser borided composite layer produced on austenitic 316L steel

    Directory of Open Access Journals (Sweden)

    Mikołajczak Daria

    2016-12-01

    Full Text Available Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  8. Carbide Dissolution during Intercritical Austenitization in Bearing Steel

    Institute of Scientific and Technical Information of China (English)

    LI Hui; MI Zhenli; ZHANG Xiaolei; TANG Di; WANG Yide

    2014-01-01

    In order to investigate the carbide dissolution mechanism of high carbon-chromium bearing steel during the intercritical austenitization, the database of TCFE7 of Thermo-calc and MOBFE of DICTRA software were used to calculate the elements diffusion kinetic and the evolution law of volume fraction of carbide. DIL805A dilatometer was used to simulate the intercritical heat treatment. The microstructure was observed by scanning electron microscopy(SEM), and the micro-hardness was tested. The experimental results indicate that the dissolution of carbide is composed of two stages:initial austenite growth governed by carbon diffusion which sharply moves up the micro-hardness of quenched martensite, and subsequent growth controlled by diffusion of Cr elements in M3C. The volume fraction of M3C decreases with the increasing holding time, and the metallographic analysis shows a great agreement with values calculated by software.

  9. COLD ROLLING ORTHODONTIC WIRES OF AUSTENITIC STAINLESS STEEL AISI 304

    Directory of Open Access Journals (Sweden)

    Rodrigo Santos Messner

    2013-03-01

    Full Text Available Austenitic stainless steels wires are widely used in the final stages of orthodontic treatment. The objective of this paper is to study the process of conformation of rectangular wires from round wires commercial austenitic stainless steel AISI 304 by the process of cold rolling. The wire quality is evaluated by means of dimensional analysis, microhardness measurements, tensile strength and fractographic analysis of the wires subjected to tensile tests. Also a study on the application of finite element method to simulate the process, comparing the force and rolling stress obtained in the rolling is done. The simulation results are consistent with those obtained in the actual process and the rolled wires show ductile fracture, tensile strength and dimensional variations appropriate to orthodontic standards. The fracture morphology shows the model cup-cone type besides the high deformation and hardness inherent in the cold rolling process.

  10. Red emission generation through highly efficient energy transfer from Ce(3+) to Mn(2+) in CaO for warm white LEDs.

    Science.gov (United States)

    Feng, Leyu; Hao, Zhendong; Zhang, Xia; Zhang, Liangliang; Pan, Guohui; Luo, Yongshi; Zhang, Ligong; Zhao, Haifeng; Zhang, Jiahua

    2016-01-28

    CaO:Ce(3+),Mn(2+) phosphors with various Mn(2+) concentrations were synthesized by a solid state reaction method. Efficient energy transfer from Ce(3+) to Mn(2+) was observed and it allows the emission color of CaO:Ce(3+),Mn(2+) to be continuously tuned from yellow (contributed by Ce(3+)) to red (by Mn(2+)) with an increase in Mn(2+) concentration and upon blue light excitation. The red emission becomes dominant when the Mn(2+) concentration is ≥0.014 with an energy transfer efficiency higher than 87% which can reach as high as 94% for a Mn(2+) concentration of only 0.02. A critical distance of 10.5 Å for the Ce(3+)-Mn(2+) energy transfer was determined. A faster decrease of Ce(3+) luminescence intensity in comparison with its lifetime was observed on increasing the Mn(2+) concentration. The analysis of this feature reveals that the Ce(3+) excitation energy can be completely transferred to Mn(2+) if the Ce(3+)-Mn(2+) distance is shorter than 7.6 Å. A warm white LED was fabricated through integrating an InGaN blue LED chip and a blend of two phosphors (YAG:Ce(3+) yellow phosphor and CaO:0.007Ce(3+),0.014Mn(2+) red phosphor) into a single package, which has CIE chromaticity coordinates of (x = 0.37, y = 0.35), a correlated color temperature of 3973 K and a color rendering index of 83.1. The results indicate that CaO:Ce(3+),Mn(2+) may serve as a potential red phosphor for blue LED based warm white LEDs.

  11. Structural and magnetic properties of DyMn{sub 2}D{sub 6} synthesized under high deuterium pressure

    Energy Technology Data Exchange (ETDEWEB)

    Paul-Boncour, V [Laboratoire de Chimie Metallurgique des Terres Rares, CNRS, 2-8 rue H Dunant, 94320 Thiais (France); Filipek, S M; Wierzbicki, R [Institute of Physical Chemistry, PAS, Ul. Kasprzaka 44/52, 01224 Warsaw (Poland); Andre, G; Bouree, F [Laboratoire Leon Brillouin, CEA-CNRS, CEA/Saclay, 91191 Gif-sur-Yvette (France); Guillot, M [LCMI, CNRS-MPI, BP166, 38042 Grenoble Cedex 9 (France)], E-mail: paulbon@glvt-cnrs.fr

    2009-01-07

    DyMn{sub 2}D{sub 6} has been prepared by applying high gaseous deuterium pressure on DyMn{sub 2}. This phase is isostructural with other RMn{sub 2}D{sub 6} (R = Y, Er) compounds and crystallizes with a K{sub 2}PtCl{sub 6} type structure having an ordered anion and a partially disordered cation arrangement because Dy and half the Mn atoms are randomly substituted in the same 8c site. The reverse susceptibility follows a Curie-Weiss law with an effective moment of 10 {mu}{sub B} similar to that of DyMn{sub 2}. Short range magnetic order, corresponding to ferromagnetic correlations, is observed in the neutron patterns up to 10 K and can be attributed to Dy-Dy interactions. The decomposition of the deuteride into Mn and DyD{sub 2}, studied by thermal gravimetric analysis, occurs between 470 and 650 K. A further deuterium desorption takes place above 920 K.

  12. Possible martensitic transformation and ferrimagnetic properties in Heusler alloy Mn{sub 2}NiSn

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Ying-Ni, E-mail: duanyingni@163.com [Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Fan, Xiao-Xi; Kutluk, Abdugheni [Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830011, Xinjiang (China); Du, Xiu-Juan [School of Applied Science, Taiyuan University of Science and Technology, Taiyuan 030024, Shanxi (China); Zhang, Zheng-Wei [Chemistry and Chemical Engineering Laboratory, The Xinjiang Technical Institute of Physics & Chemistry, Chinese Academy of Sciences, Urumqi 830011, Xinjiang (China); Song, Yu-Ling [College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, Henan (China)

    2015-07-15

    The electronic structure and magnetic properties of Hg{sub 2}CuTi-type Mn{sub 2}NiSn have been studied by performing the first-principle calculations. It is found that the phase transformation from the cubic to the tetragonal structure reduces the total energy, indicating that the martensitic phase is more stable and the phase transition from austenite to martensite may happen at low temperature for Hg{sub 2}CuTi-type Mn{sub 2}NiSn. Concerning the magnetism of Hg{sub 2}CuTi-type Mn{sub 2}NiSn, both austenitic and martensitic phases are suggested to be ferrimagnets. Furthermore, martensitic transformation decreases the magnetic moment per formula unit compared with austenitic phase. The results are helpful to accelerate the use of Mn{sub 2}NiSn alloys in the series for magnetic shape memory applications. - Highlights: • It is found that the phase transition from austenite to martensite may happen at low temperature for Mn{sub 2}NiSn with the Hg{sub 2}CuTi-type structure. • Both austenitic and martensitic Mn{sub 2}NiSn are ferrimagnets. • Martensitic transformation decreases the magnetization.

  13. First-principles study of helium, carbon, and nitrogen in austenite, dilute austenitic iron alloys, and nickel

    Science.gov (United States)

    Hepburn, D. J.; Ferguson, D.; Gardner, S.; Ackland, G. J.

    2013-07-01

    An extensive set of first-principles density functional theory calculations have been performed to study the behavior of He, C, and N solutes in austenite, dilute Fe-Cr-Ni austenitic alloys, and Ni in order to investigate their influence on the microstructural evolution of austenitic steel alloys under irradiation. The results show that austenite behaves much like other face-centered cubic metals and like Ni in particular. Strong similarities were also observed between austenite and ferrite. We find that interstitial He is most stable in the tetrahedral site and migrates with a low barrier energy of between 0.1 and 0.2 eV. It binds strongly into clusters as well as overcoordinated lattice defects and forms highly stable He-vacancy (VmHen) clusters. Interstitial He clusters of sufficient size were shown to be unstable to self-interstitial emission and VHen cluster formation. The binding of additional He and V to existing VmHen clusters increases with cluster size, leading to unbounded growth and He bubble formation. Clusters with n/m around 1.3 were found to be most stable with a dissociation energy of 2.8 eV for He and V release. Substitutional He migrates via the dissociative mechanism in a thermal vacancy population but can migrate via the vacancy mechanism in irradiated environments as a stable V2He complex. Both C and N are most stable octahedrally and exhibit migration energies in the range from 1.3 to 1.6 eV. Interactions between pairs of these solutes are either repulsive or negligible. A vacancy can stably bind up to two C or N atoms with binding energies per solute atom up to 0.4 eV for C and up to 0.6 eV for N. Calculations in Ni, however, show that this may not result in vacancy trapping as VC and VN complexes can migrate cooperatively with barrier energies comparable to the isolated vacancy. This should also lead to enhanced C and N mobility in irradiated materials and may result in solute segregation to defect sinks. Binding to larger vacancy clusters

  14. Effect of graphite nodule count and Mn content on successive austempering process of austempered ductile iron; ADI no chikuji austemper ho ni oyobosu kokuen tsubusu to Mn ryo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Oide, T.; Ahmadabadi, M.; Saito, M. [Tohoku University, Sendai (Japan). Faculty of Engineering

    1995-02-25

    Shock test was executed for a test piece where the combination of a wide range of austempering conditions was selected and the effective graphite nodule count in the successive austempering process method, the range of Mn amount, etc. were discussed. The low and high graphite nodule counts of sample were 82 - 114 and 229 - 364 piece/mm{sup 2}, respectively. The low and high Mn were 0.26 - 0.65 % and 0.96 - 1.05 %, respectively. The heat treatment cycle was retained to be 1173K, 648K, and 588K in argon gas atmosphere. The Sharpy shock test and organization observation were performed for each test piece, thus revealing that a higher toughness value than that obtained by normal treatment could be obtained by the HLAT method; the better the graphite nodulation count was, the higher the toughness was; it was effective that the Mn was approximately 0.6 %; the influence given to the shock energy value was extremely larger by residual austenite volume than the untransformed austenite module. 7 refs., 12 figs., 2 tabs.

  15. Homogeneous formation of epsilon carbides within the austenite during the isothermal transformation of a ductile iron at 410 °C

    Science.gov (United States)

    Gutierrez, I.; Aranzabal, J.; Castro, F.; Urcola, J. J.

    1995-05-01

    The transformation of a ductile iron at 410 °C for different times, after austenitization for 30 minutes at 900 °C, is analyzed in detail. Upper bainite and a high volume fraction of austenite are formed for intermediate annealing times. A certain amount of martensite is observed after quenching not only for short transformation times but also for intermediate times. The formation of the martensite on cooling after intermediate transformation times is due to the decrease in carbon concentration of the retained austenite because of the homogeneous precipitation of epsilon carbides within. This homogeneous precipitation of epsilon carbide inside austenite is unambiguously observed. The epsilon carbide, pre-precipitated in austenite, which transforms to martensite on cooling, continues growing in the martensite after transformation. For long times of austempering at 410 °C, some complex large carbides or silicocarbides are formed, probably from the epsilon carbide, which result in the total decomposition of austenite.

  16. Barley cultivar MN 698, high malting quality for the state of Rio Grande do Sul

    Directory of Open Access Journals (Sweden)

    Caierão Eduardo

    2006-01-01

    Full Text Available MN 698 is a new cultivar developed by AmBev that resulted from a cross between the cultivars MN 599 and MN 635. MN 698 shows a grain yield potential higher than 4t ha-1, has early cycle and is moderately resistant to lodging. Its spike is uniform and produces around 20 grains well-distributed. MN 698 shows a medium tillering capacity (two to three per plant, and is characterized by the presence of anthocyanin in the culm basis, arists, and glumes. It is the national cultivar with the highest quality and represents an important advance for this cereal in Brazil, combining interests of both the producer and the industrial sector.

  17. Mixed Mg-Mn ferrites for high frequency applications processed by citrate precursor technique

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Gagan; Chand, Jagdish; Verma, Satish; Singh, M, E-mail: bhargava_phy_hpu@yahoo.co.i [Department of Physics, Himachal Pradesh University, Shimla, 171005 India (India)

    2009-08-07

    Mg{sub 0.9}Mn{sub 0.1}In{sub x}Fe{sub 2-x} O{sub 4} (x = 0.1 and 0.2) and Mg{sub 0.9}Mn{sub 0.1}Al{sub y}Fe{sub 2-y} O{sub 4} (y = 0.1, 0.5 and 0.7) ferrites, with improved initial permeability and extremely low relative loss factor (RLF), were synthesized by the citrate precursor technique. Structural studies were made by using the x-ray diffraction technique and scanning electron microscopy (SEM), which confirm the formation of single-phase spinel structure. The size of the particle was of the order of {approx}0.5 {mu}m for the samples sintered at 1200 {sup 0}C, which is smaller than that obtained for ferrite powders by the conventional ceramic method. The magnetic properties such as initial permeability and RLF with frequency, in the range 0.1-20 MHz, at different temperatures have been investigated. Initial permeability ({mu}{sub i}) attains a very high value, 17342, for the In{sup 3+} doped ferrite series and for the Al{sup 3+} doped ferrite series the maximum value is 3785. The RLF was found to have low values and is of the order of 10{sup -5}-10{sup -4} in the frequency range 0.1-20 MHz. In addition to this, an increase in the value of {mu}{sub i} was observed with the rise in the temperature for all the series of ferrites.

  18. Functional Carbon Nanotube/Mesoporous Carbon/MnO2 Hybrid Network for High-Performance Supercapacitors

    Directory of Open Access Journals (Sweden)

    Tao Tao

    2014-01-01

    Full Text Available A functional carbon nanotube/mesoporous carbon/MnO2 hybrid network has been developed successfully through a facile route. The resulting composites exhibited a high specific capacitance of 351 F/g at 1 A g−1, with intriguing charge/discharge rate performance and cycling stability due to a synergistic combination of large surface area and excellent electron-transport capabilities of MnO2 with the good conductivity of the carbon nanotube/mesoporous carbon networks. Such composite shows great potential to be used as electrodes for supercapacitors.

  19. Phase transition in layered perovskite-like manganate Ca3Mn2O7 under high pressure

    Institute of Scientific and Technical Information of China (English)

    朱嘉林; 陈良辰; 禹日成; 李凤英; 刘景; 靳常青

    2002-01-01

    In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.

  20. High temperature EPR study of the M3Fe4V6O24 (M = Cu, Zn, Mg and Mn

    Directory of Open Access Journals (Sweden)

    Guskos Niko

    2016-09-01

    Full Text Available Electron paramagnetic resonance (EPR spectra of M3Fe4V6O24 (M = Cu, Zn, Mg and Mn compounds in high temperature range (293 K to 493 K have been investigated. The role of magnetic (Cu, Mn and non-magnetic (Zn, Mg ions in M3Fe4V6O24 structure in formation of magnetic resonance spectra was studied. Temperature dependence of EPR parameters: resonance field, linewidth and integrated intensity were examined. Similarities and differences in temperature behavior of these parameters has been discussed in terms of different relaxation mechanisms and magnetic interactions in the spin systems. An important role of additional magnetic ions (M = Mn or Cu in the M3Fe4V6O24 structure has been identified and its consequences considered.

  1. Transformation of delta ferrite into sigma phase in metastable austenitic stainless steels after long-term high-temperature service exposure; Umwandlung von Deltaferrit in Sigma-Phase in metastabilen rostfreien austenitischen Staehlen nach Langzeitbeanspruchung durch Hochtemperaturen

    Energy Technology Data Exchange (ETDEWEB)

    Neidel, Andreas; Fischer, Boromir; Riesenbeck, Susanne; Cagliyan, Erhan [Siemens AG, Berlin (Germany). Werkslaboratorien

    2014-04-01

    A service temperature increase of turbine exhaust casing liners of heavy-duty industrial gas turbines, driven by the need to raise thermal efficiencies, motivated a number of ageing trials. Casing liners are often made of metastable austenitic stainless steels, suitable for high temperature applications. Alloys such as 321SS and 347SS might contain, in the as-cast condition, rather large amounts of delta ferrite, if not further processed by rolling or forging, easily in excess of 15 %. Even rolled sheet and bar might contain significant volume fractions of that phase if welded, up to 15 % or so in the heat affected zone (HAZ) immediately adjacent to the fusion line, and in the weld metal. It is known from the literature and from field experience that delta ferrite might decompose into sigma phase after long-term service exposure at elevated temperatures. This may embrittle the material and can be detrimental to mechanical properties. It could also deleteriously affect creep strength. The main aim of ageing trials described in this paper was to study the phase stability of delta ferrite under simulated service conditions. The results are correlated to metallographic testing results, obtained from examining actual service components of heavy-duty gas turbine engines in the field. (orig.)

  2. Characterization of TiC-FeCrMn Cermets Produced by Powder Metallurgy Method

    Directory of Open Access Journals (Sweden)

    Märt Kolnes

    2015-09-01

    Full Text Available TiC-NiMo cermets combine relatively low density with high hardness. Because nickel is known as a toxin and allergen and allergy to nickel is a phenomenon which has assumed growing importance in recent years there has been a flurry of activity to find alternatives to the nickel binder in cermets. It is also the global research and technical development trend in the powder metallurgy cermets industry. In present research TiC-based cermets with FeCrMn binder system were fabricated. Three different sintering conditions were used (vacuum sintering, sinter/HIP and sintering under low Ar pressure. Because of high vapor pressure of manganese different sintering conditions and technologies were investigated to depress the Mn-loss during sintering. Chemical composition of TiC-FeCrMn cermets after different sintering conditions were analyzed by energy-dispersive X-ray spectroscopy (EDS and mechanical properties – hardness and fracture toughness were evaluated on the samples. Results of research showed that Ni-free TiC-based CrMn-steels bonded cermets compare unfavorably with cermets bonded with CrNi austenitic steels in terms of fracture toughness and corrosion resistance. Noticeable Mn-loss during vacuum sintering can be avoided when sintering under low Ar gas pressure.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7364

  3. Thermal and mechanical stability of retained austenite in aluminum-containing multiphase TRIP steels

    CERN Document Server

    Zwaag, S; Kruijver, S O; Sietsma, J

    2002-01-01

    Stability of retained austenite is the key issue to understand transformation-induced plasticity (TRIP) effect. In this work, both thermal stability and mechanical stability are investigated by thermo-magnetic as well as in situ conventional X-ray diffraction and micro synchrotron radiation diffraction measurements. The thermal stability in a 0.20C-1.52Mn-0.25Si-0.96Al (wt%) TRIP steel is studied in the temperature range between 5 and 300 K under a constant magnetic field of 5T. It is found that almost all austenite transforms thermally to martensite upon cooling to 5K and M sub s and M sub f temperatures are analyzed to be 355 and 115 K. Transformation kinetics on the fraction versus temperature relation are well described by a model based on thermodynamics. From the in situ conventional X-ray and synchrotron diffraction measurements in a 0.17C-1.46Mn-0.26Si-1.81Al (wt%) steel, the volume fraction of retained austenite is found to decrease as the strain increases according to Ludwigson and Berger relation. T...

  4. Electrochemically active MnO2 coated Li1.2Ni0.18Co0.04Mn0.58O2 cathode with highly improved initial coulombic efficiency

    Science.gov (United States)

    Jin, Yanling; Xu, Youlong; Sun, Xiaofei; Xiong, Lilong; Mao, Shengchun

    2016-10-01

    Lithium-rich layered oxide is known to be one of the most promising positive electrode materials for lithium ion batteries due to its large capacity and high energy density. However, low initial coulombic efficiency is currently an urgent problem hindering its practical application. In this work, electrochemically active MnO2 coating was used to improve the coulombic efficiency of Li1.2Ni0.18Co0.04Mn0.58O2. Firstly, the pristine material was synthesized via co-precipitation following by solid-state calcination. Then MnO2-coated Li1.2Ni0.18Co0.04Mn0.58O2 was prepared by heat treatment of the mixture of pristine powder and manganese nitrate. During first discharging, lithium ions can intercalate into not only the delithiated Li1.2Ni0.18Co0.04Mn0.58O2 but also the MnO2 coating, thus noticeably improves the coulombic efficiency and discharge capacity. The initial efficiency is enhanced from 61.2% (pristine) to 84.4%, 88.8% and 95.4%, respectively, for 10 wt.%, 15 wt.% and 20 wt.% MnO2 coated Li1.2Ni0.18Co0.04Mn0.58O2 at 20 mA g-1. Furthermore, the 15 wt.% MnO2 coated sample delivers an initial discharge capacity as high as 294.4 mAh g-1.

  5. The sub-zero Celsius treatment of precipitation hardenable semi-austenitic stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Somers, Marcel A. J.

    2015-01-01

    A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite...

  6. Changes in the passive layer of corrugated austenitic stainless steel of low nickel content due to exposure to simulated pore solutions

    Energy Technology Data Exchange (ETDEWEB)

    Bautista, A. [Departamento de Ciencia e Ingenieria de Materiales e Ingenieria Quimica, Universidad Carlos III de Madrid, Avda Universidad no. 30, 28911 Leganes, Madrid (Spain)], E-mail: mbautist@ing.uc3m.es; Blanco, G.; Velasco, F. [Departamento de Ciencia e Ingenieria de Materiales e Ingenieria Quimica, Universidad Carlos III de Madrid, Avda Universidad no. 30, 28911 Leganes, Madrid (Spain); Gutierrez, A.; Soriano, L. [Departamento de Fisica Aplicada and Instituto de Ciencia de Materiales Nicolas Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Cantoblanco, Madrid (Spain); Takenouti, H. [UPR-15 du CNRS, UPMC, 4 place Jussieu, 75252 Paris Cedex 05 (France)

    2009-04-15

    In this work, changes undergone at the passive layer of a new type of corrugated austenitic stainless steel (low Ni, high Mn 204Cu type) when exposed to solutions simulating that contained in the pores of concrete have been studied. Changes in the nature of the passive layer have been characterized by X-ray photoelectronic spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Particular focus has been put on the influence of the presence of chlorides and/or carbonation in the solution. Changes in the passive layer due to the passivation treatment that is often applied to corrugated stainless steels during manufacturing processes have also been considered. The results obtained on the 204Cu type steel have been compared with those obtained on more traditional, high Ni, austenitic AISI 304 grade and duplex SAF 2205 grade. During the immersion in simulated pore solutions, 204Cu type suffers more intense redox processes than other studied stainless steels. Moreover, it shows less Cr-rich protective passive layers in these media.

  7. Diagnostic experimental results on the hydrogen embrittlement of austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Gavriljuk, V.G.; Shivanyuk, V.N.; Foct, J

    2003-03-14

    Three main available hypotheses of hydrogen embrittlement are analysed in relation to austenitic steels based on the studies of the hydrogen effect on the interatomic bonds, phase transformations and microplastic behaviour. It is shown that hydrogen increases the concentration of free electrons, i.e. enhances the metallic character of atomic interactions, although such a decrease in the interatomic bonding cannot be a reason for brittleness and rather assists an increased plasticity. The hypothesis of the critical role of the hydrogen-induced {epsilon} martensite was tested in the experiment with the hydrogen-charged Si-containing austenitic steel. Both the fraction of the {epsilon} martensite and resistance to hydrogen embrittlement were increased due to Si alloying, which is at variance with the pseudo-hydride hypothesis. The hydrogen-caused early start of the microplastic deformation and an increased mobility of dislocations, which are usually not observed in the common mechanical tests, are revealed by the measurements of the strain-dependent internal friction, which is consistent with the hypothesis of the hydrogen-enhanced localised plasticity. An influence of alloying elements on the enthalpy E{sub H} of hydrogen migration in austenitic steels is studied using the temperature-dependent internal friction and a correlation is found between the values of E{sub H} and hydrogen-caused decrease in plasticity. A mechanism for the transition from the hydrogen-caused microplasticity to the apparent macrobrittle fracture is proposed based on the similarity of the fracture of hydrogenated austenitic steels to that of high nitrogen steels.

  8. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    Science.gov (United States)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  9. Microstructural Features During Strain Induced Ferrite Transformation in 08 and 20Mn Steels

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 20Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume fraction of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of ~1.5 ferrite grains less than 3m and 2m can be obtained in 08 and 20Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 20Mn was mainly due to strain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 20Mn.

  10. Retained austenite thermal stability in a nanostructured bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Avishan, Behzad, E-mail: b_avishan@sut.ac.ir [Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Garcia-Mateo, Carlos, E-mail: cgm@cenim.csic.es [Department of Physical Metallurgy, National Centre for Metallurgical Research (CENIM-CSIC), MATERALIA Research Group, Avda. Gregorio del Amo, 8, 28040, Madrid (Spain); Yazdani, Sasan, E-mail: yazdani@sut.ac.ir [Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Caballero, Francisca G., E-mail: fgc@cenim.csic.es [Department of Physical Metallurgy, National Centre for Metallurgical Research (CENIM-CSIC), MATERALIA Research Group, Avda. Gregorio del Amo, 8, 28040, Madrid (Spain)

    2013-07-15

    The unique microstructure of nanostructured bainite consists of very slender bainitic ferrite plates and high carbon retained austenite films. As a consequence, the reported properties are opening a wide range of different commercial uses. However, bainitic transformation follows the T{sub 0} criteria, i.e. the incomplete reaction phenomena, which means that the microstructure is not thermodynamically stable because the bainitic transformation stops well before austenite reaches an equilibrium carbon level. This article aims to study the different microstructural changes taking place when nanostructured bainite is destabilized by austempering for times well in excess of that strictly necessary to end the transformation. Results indicate that while bainitic ferrite seems unaware of the extended heat treatment, retained austenite exhibits a more receptive behavior to it. - Highlights: • Nanostructured bainitic steel is not thermodynamically stable. • Extensive austempering in these microstructures has not been reported before. • Precipitation of cementite particles is unavoidable at longer austempering times. • TEM, FEG-SEM and XRD analysis were used for microstructural characterization.

  11. Development of Cast Alumina-Forming Austenitic Stainless Steels

    Science.gov (United States)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-11-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  12. Development of Cast Alumina-Forming Austenitic Stainless Steels

    Science.gov (United States)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-09-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  13. Mechanical and Transformation Behaviors of a C-Mn-Si-Al-Cr TRIP Steel under Stress