Influence of cold deformation on martensite transformation and mechanical properties of Ti-Nb-Ta-Zr alloy

International Nuclear Information System (INIS)

Wang Liqiang; Lu Weijie; Qin Jining; Zhang Fan; Zhang Di

2009-01-01

Ti-35Nb-2Ta-3Zr alloy was fabricated by vacuum consumable arc melting furnace and hot pressing. Microstructure and phase transformation of solution-treated (ST) and cold-rolled (CR) plates of Ti-Nb-Ta-Zr alloy were observed. Different microstructure of strain-induced martensite transformation during cold deformation were investigated. With the increase of reduction of cold rolling, microstructure of α''-phase changed from acicular martensite to butterfly shaped martensite and showed variant crossed and cross-hatched when the reduction of cold rolling was over 60%. Mechanical properties and SEM images of the fracture surface indicated that the alloy fabricated by cold deformation showed favorable strength and plasticity. Owing to the excellent cold workability and biomedical safety of elements of Nb, Ta and Zr, Ti-Nb-Ta-Zr alloy contributed much to medical applications

Cold deformation of ADI castings: Martensitic transformation

International Nuclear Information System (INIS)

Navea, Lilian R; Mannheim, Rodolfo M; Garin, Jorge L

2004-01-01

Research and applications in austempered ductile iron (ADI castings) have recently undergone noticeable progress in the industrialized world, becoming a highly competitive engineering material. The notable properties of these castings derive from their austenitic matrix stabilized by carbon, a thermally stable austenite during the austenizing process but possibly turning into martensite when undergoing plastic deformation. This work aims to study the changing structure of an ADI casting caused by one directional cold lamination. The samples that were studied were obtained from two nodular castings, one without alloying and the other alloyed with Cu, Ni and Mo. The samples were austenized in the first stage of the austempering process at 910 o C for 80 min. Then in the second stage the unalloyed samples were austempered at 410 o C for 10 min and the alloyed samples for 120 min. After the thermal treatment, the test pieces were deformed 0% to 25% by cold lamination. The quantification of the phases was performed using x-ray diffraction and the metallographic study using optic and Scanning Electronic Microscopy. The results show that the martensitic phase obtained by deformation is a very fine structure that evolves into a thicker one when the deformation of the samples increases (CW)

Position-dependent shear-induced austenite– martensite transformation in double-notched TRIP and dual-phase steel samples

NARCIS (Netherlands)

Blondé, R.J.P.; Jimenez-Melero, E.; Anusuya Ponnusami, S.; Zhao, L.; Schell, N.; Brück, E.H.; Van der Zwaag, S.; Van Dijk, N.H.

2014-01-01

While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

Science.gov (United States)

Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

2017-10-01

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

The effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy

International Nuclear Information System (INIS)

Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

2014-01-01

Based on stress-controlled cyclic tension–unloading experiments with different peak stresses, the effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy micro-tubes is investigated and discussed. The experimental results show that the reverse transformation from the induced martensite phase to the austenite phase is gradually restricted by the plastic deformation of the induced martensite phase caused by an applied peak stress that is sufficiently high (higher than 900 MPa), and the extent of such restriction increases with further increasing the peak stress. The residual and peak strains of super-elastic NiTi shape memory alloy accumulate progressively, i.e., transformation ratchetting occurs during the cyclic tension–unloading with peak stresses from 600 to 900 MPa, and the transformation ratchetting strain increases with the increase of the peak stress. When the peak stress is higher than 900 MPa, the peak strain becomes almost unchanged, but the residual strain accumulates and the dissipation energy per cycle decreases very quickly with the increasing number of cycles due to the restricted reverse transformation by the martensite plasticity. Furthermore, a quantitative relationship between the applied stress and the stabilized residual strain is obtained to reasonably predict the evolution of the peak strain and the residual strain. (paper)

Structural properties, deformation behavior and thermal stability of martensitic Ti-Nb alloys

Energy Technology Data Exchange (ETDEWEB)

Boenisch, Matthias

2016-06-10

. Also, experimental evidence indicates a deformation-induced martensite to austenite (α'' → β) conversion. The influence of Nb content on the thermal stability and on the occurrence of decomposition reactions in martensitic Ti-Nb alloys is examined by isochronal differential scanning calorimetry, dilatometry and in-situ synchrotron X-ray diffraction complemented by transmission electron microscopy. The thermal decomposition and transformation behavior exhibits various phase transformation sequences during heating into the β-phase field in dependence of composition. Eventually, the transformation temperatures, interval, hysteresis and heat of the β <-> α'' martensitic transformation are investigated in relation to the Nb content. The results obtained in this study are useful for the development and optimization of β-stabilized Ti-based alloys for structural, Ni-free shape memory and/or superelastic, as well as for biomedical applications.

EBSD characterization of deformed lath martensite in if steel

DEFF Research Database (Denmark)

Lv, Z.A.; Zhang, Xiaodan; Huang, Xiaoxu

2017-01-01

Rolling deformation results in the transformation of a lath martensite structure to a lamellar structure characteristic to that of IF steel cold-rolled to medium and high strains. The structural transition takes place from low to medium strain, and electron backscatter diffraction analysis shows...... and the strength are characterized for lath martensite rolled to a thickness reduction of 30%, showing that large changes in the misorientation take place, while the strain hardening rate is low....

The effects of non-isothermal deformation on martensitic transformation in 22MnB5 steel

International Nuclear Information System (INIS)

Naderi, M.; Saeed-Akbari, A.; Bleck, W.

2008-01-01

In the present paper, the effects of process parameters on phase transformations during non-isothermal deformations are described and discussed. Non-isothermal high temperature compressive deformations were conducted on 22MnB5 boron steel by using deformation dilatometry. Cylindrical samples were uniaxially deformed at different strain rates ranging from 0.05 to 1.0 s -1 to a maximum compressive strain of 50%. Qualitative and quantitative investigations were carried out using surface hardness mapping data as well as dilatation curves. It was observed that a higher initial deformation temperatures resulted in a higher martensite fraction of the microstructure, while a variation in the martensite start temperature was negligible. Another conclusion was that by applying larger amounts of strain as well as higher force levels, not only the martensite start temperature, but also the amount of martensite was reduced. Moreover, it was concluded that using surface hardness mapping technique and dilatometry experiments were very reliable methods to quantify and qualify the coexisting phases

The effects of non-isothermal deformation on martensitic transformation in 22MnB5 steel

Energy Technology Data Exchange (ETDEWEB)

Naderi, M. [Department of Materials Science and Engineering, Faculty of Engineering, Arak University, Shariati Street, Arak (Iran, Islamic Republic of)], E-mail: malek.naderi@iehk.rwth-aachen.de; Saeed-Akbari, A.; Bleck, W. [Department of Ferrous Metallurgy, RWTH Aachen University, Aachen (Germany)

2008-07-25

In the present paper, the effects of process parameters on phase transformations during non-isothermal deformations are described and discussed. Non-isothermal high temperature compressive deformations were conducted on 22MnB5 boron steel by using deformation dilatometry. Cylindrical samples were uniaxially deformed at different strain rates ranging from 0.05 to 1.0 s{sup -1} to a maximum compressive strain of 50%. Qualitative and quantitative investigations were carried out using surface hardness mapping data as well as dilatation curves. It was observed that a higher initial deformation temperatures resulted in a higher martensite fraction of the microstructure, while a variation in the martensite start temperature was negligible. Another conclusion was that by applying larger amounts of strain as well as higher force levels, not only the martensite start temperature, but also the amount of martensite was reduced. Moreover, it was concluded that using surface hardness mapping technique and dilatometry experiments were very reliable methods to quantify and qualify the coexisting phases.

Influence of Plastic Deformation on Martensitic Transformation During Hot Stamping of Complex Structure Auto Parts

Science.gov (United States)

Shen, Yuhan; Song, Yanli; Hua, Lin; Lu, Jue

2017-04-01

The ultra-high strength steel auto parts manufactured by hot stamping are widely applied for weight reduction and safety improvement. During the hot stamping process, hot forming and quenching are performed in one step wherein plastic deformation and phase transformation simultaneously take place and affect each other. Thereinto, the influence of deformation on martensitic transformation is of great importance. In the present paper, the influence of plastic deformation on martensitic transformation during hot stamping of complex structure auto parts was investigated. For this purpose, a B-pillar reinforced panel in B1500HS steel was manufactured by hot stamping, and the process was simulated by finite element software based on a thermo-mechanical-metallurgical coupled model. Considering various deformation degrees, the microstructures and mechanical properties at four typical locations of the hot stamped B-pillar reinforced panel were detected. The results show that the martensitic content and the microhardness increase with the increase in the deformation amount. There are two reasons causing this phenomenon: (1) the increase in mechanical driving force and (2) the increased probability of the martensitic nucleation at crystal defects. The x-ray diffraction analysis indicates the carbon enrichment in retained austenite which results from the carbon diffusion during the low-carbon martensite formation. Furthermore, the carbon content decreases with the increase in the deformation amount, because the deformation of austenite suppresses the carbon diffusion.

Influence of grain structure on the deformation mechanism in martensitic shear reversion-induced Fe-16Cr-10Ni model austenitic alloy with low interstitial content: Coarse-grained versus nano-grained/ultrafine-grained structure

Energy Technology Data Exchange (ETDEWEB)

Challa, V.S.A. [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials Engineering, and Biomedical Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Department of Metallurgical, Materials Engineering, and Biomedical Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Somani, M.C. [Center for Advanced Steels Research, The University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Wang, Z.D. [State Key Laboratory for Rolling and Automation, Northeastern University, 3-11 Wenhua Road, Shenyang 110819 (China)

2016-04-20

Nanograined/ultrafine-grained (NG/UFG) materials characterized by high strength-high ductility combination are excellent vehicles to obtain an unambiguous understanding of deformation mechanisms vis-à-vis their coarse-grained counterparts. In this context, the innovative concept of phase reversion-induced NG/UFG structure enabled achieving high strength besides comparable ductility, for instance, in metastable austenitic stainless steels. In the phase reversion process, severe deformation of austenite at room temperature (typically ~60–80%) transforms face-centered cubic austenite (γ) to body centered cubic martensite (α′). Upon annealing, martensite reverts to austenite leading to extensive grain refinement. The objective of the present study to fundamentally understand the deformation mechanisms in NG/UFG structure in relation to that of the coarse-grained (CG) structure was accomplished by combining depth-sensing nanoscale experiments on an Fe-16Cr-10Ni model austenitic alloy conducted at different strain rates, followed by the study of structural evolution in the deformed zone using transmission electron microscopy (TEM). In the high strength NG/UFG steel (YS~585 MPa), stacking faults and nanotwins contributed to the enhanced ductility (El~35%), while in the case of low strength (YS~260 MPa) coarse-grained (CG) counterpart, ductility was also high (El~40%), but chiefly due to strain-induced martensite, which points to a clear case of grain size effect (and the corresponding level of strength). The distinct change in the deformation mechanism from stacking faults and twinning-induced plasticity (TWIP) in the NG structure to transformation-induced plasticity (TRIP) in the CG structure is elucidated in terms of austenite stability-strain energy relationship. The insights on the relationship between grain structure (and strength) and deformation mechanisms are envisaged to be important in providing a new direction for the futuristic design of high strength

The Investigation on Strain Strengthening Induced Martensitic Phase Transformation of Austenitic Stainless Steel: A Fundamental Research for the Quality Evaluation of Strain Strengthened Pressure Vessel

Science.gov (United States)

Li, Bo; Cai Ren, Fa; Tang, Xiao Ying

2018-03-01

The manufacture of pressure vessels with austenitic stainless steel strain strengthening technology has become an important technical means for the light weight of cryogenic pressure vessels. In the process of increasing the strength of austenitic stainless steel, strain can induce the martensitic phase transformation in austenite phase. There is a quantitative relationship between the transformation quantity of martensitic phase and the basic mechanical properties. Then, the martensitic phase variables can be obtained by means of detection, and the mechanical properties and safety performance are evaluated and calculated. Based on this, the quantitative relationship between strain hardening and deformation induced martensite phase content is studied in this paper, and the mechanism of deformation induced martensitic transformation of austenitic stainless steel is detailed.

Room-Temperature Deformation and Martensitic Transformation of Two Co-Cr-Based Alloys

Science.gov (United States)

Cai, S.; Schaffer, J. E.; Huang, D.; Gao, J.; Ren, Y.

2018-05-01

Deformation of two Co-Cr alloys was studied by in situ synchrotron X-ray diffraction. Both alloys show stress-induced martensite transformation, which is affected by phase stabilities and transformation strains. Crystal structure of WC in Co-20Cr-15W-10Ni is identified. Compared with other phases present, it is elastically isotropic, exhibits high strength, and can elastically withstand strains exceeding 1 pct. Texture change during phase transformation is explained based on the crystal orientation relationship between γ- and ɛ-phases.

Twinning and martensitic transformations in nickel-enriched 304 austenitic steel during tensile and indentation deformations

Energy Technology Data Exchange (ETDEWEB)

Gussev, M.N., E-mail: gussevmn@ornl.gov; Busby, J.T.; Byun, T.S.; Parish, C.M.

2013-12-20

Twinning and martensitic transformation have been investigated in nickel-enriched AISI 304 stainless steel subjected to tensile and indentation deformation. Using electron backscatter diffraction (EBSD), the morphology of α- and ε-martensite and the effect of grain orientation to load axis on phase and structure transformations were analyzed in detail. It was found that the twinning occurred less frequently under indentation than under tension; also, twinning was not observed in [001] and [101] grains. In tensile tests, the martensite particles preferably formed at the deformation twins, intersections between twins, or at the twin-grain boundary intersections. Conversely, martensite formation in the indentation tests was not closely associated with twinning; instead, the majority of martensite was concentrated in the dense colonies near grain boundaries. Martensitic transformation seemed to be obstructed in the [001] grains in both tensile and indentation test cases. Under a tensile stress of 800 MPa, both α- and ε-martensites were found in the microstructure, but at 1100 MPa only α-martensite presented in the specimen. Under indentation, α- and ε-martensite were observed in the material regardless of the stress level.

Effects of pre-deformation on the martensitic transformation and magnetocaloric property in Ni-Mn-Co-Sn ribbons

International Nuclear Information System (INIS)

Ma Sheng-Can; Xuan Hai-Cheng; Zhang Cheng-Liang; Wang Liao-Yu; Cao Qing-Qi; Wang Dun-Hui; Du You-Wei

2010-01-01

This paper investigates the martensitic transformation and magnetocaloric effect in pre-deformed Ni-Mn-Co-Sn ribbons. The experimental results show that the reverse martensitic transformation temperature T M increases with the increasing pre-pressure, suggesting that pre-deformation is another effective way to adjust T M in ferromagnetic shape memory alloys. Large magnetic entropy changes and refrigerant capacities are obtained in these ribbons as well. It also discusses the origin of the enhanced martensitic transformation temperature and magnetocaloric property in pre-deformed Ni-Mn-Co-Sn ribbons

Relationship between local deformation behavior and crystallographic features of as-quenched lath martensite during uniaxial tensile deformation

International Nuclear Information System (INIS)

Michiuchi, M.; Nambu, S.; Ishimoto, Y.; Inoue, J.; Koseki, T.

2009-01-01

Electron backscattering diffraction patterns were used to investigate the relationship between local deformation behavior and the crystallographic features of as-quenched lath martensite of low-carbon steel during uniform elongation in tensile tests. The slip system operating during the deformation up to a strain of 20% was estimated by comparing the crystal rotation of each martensite block after deformation of 20% strain with predictions by the Taylor and Sachs models. The results indicate that the in-lath-plane slip system was preferentially activated compared to the out-of-lath-plane system up to this strain level. Further detailed analysis of crystal rotation at intervals of approximately 5% strain confirmed that the constraint on the operative slip system by the lath structure begins at a strain of 8% and that the local strain hardening of the primary slip systems occurred at approximately 15% strain.

Damping Capacity of High Manganese Austenitic Stainless Steel with a Two Phase Mixed Structure of Martensite and Austenite

International Nuclear Information System (INIS)

Hwang, Tae Hyun; Kang, Chang-Yong

2013-01-01

The damping capacity of high manganese austenitic stainless steel with a two phase mixed structure of deformation-induced martensite and reversed austenite was studied. Reversed austenite with an ultra-fine grain size of less than 0.2 μm was obtained by reversion treatment. The two phase structure of deformation-induced martensite and reversed austenite was obtained by annealing treatment at a range of 500-700 °C and various times in cold rolled high manganese austenitic stainless steel. The damping capacity increased with an increasing annealing temperature and time. In high manganese stainless steel with the two phase mixed structure of martensite and austenite, the damping capacity decreased with an increasing volume fraction of deformation-induced martensite. Thus, the damping capacity was strongly affected by deformation-induced martensite. The results confirmed that austenitic stainless steel with a good combination of strength and damping capacity was obtained from the two phase mixed structure of austenite and martensite.

Variation of martensite lath width and precipitate size during creep deformation in a 10Cr-Mo steel

International Nuclear Information System (INIS)

Kim, S. H.; Song, B. Z.; Lu, W. S.

2001-01-01

The relationship between creep deformation and microstructural changes in martensitic 10Cr-MoW steel has been studied. Transmission electron microscopy and image analyser were used to determine the variation of precipitates and martensite lath width size during creep deformation and aging. As precipitates are coarsened during creep deformation, dislocations become easy to move and the recovery proceeds rapidly. This leads to the growth of lath width. The average size of precipitates was linearly increased with creep time. On the other hand the growth rate of lath width is constant until tertiary creep, but the growth of lath width is accelerated during tertiary creep. It has been concluded that the growth behavior of lath width are consistent with creep deformation. Because the growth of lath width is controlled by the coarsening of precipitates it is important to form more stable precipitates in creep condition for improvement of creep properties of martensitie steel. Microstructure of martensitic steel is thermally very stable, so the size of precipitates and martensite lath width are hardly changed during aging

Impact of Martensite Spatial Distribution on Quasi-Static and Dynamic Deformation Behavior of Dual-Phase Steel

Science.gov (United States)

Singh, Manpreet; Das, Anindya; Venugopalan, T.; Mukherjee, Krishnendu; Walunj, Mahesh; Nanda, Tarun; Kumar, B. Ravi

2018-02-01

The effects of microstructure parameters of dual-phase steels on tensile high strain dynamic deformation characteristic were examined in this study. Cold-rolled steel sheets were annealed using three different annealing process parameters to obtain three different dual-phase microstructures of varied ferrite and martensite phase fraction. The volume fraction of martensite obtained in two of the steels was near identical ( 19 pct) with a subtle difference in its spatial distribution. In the first microstructure variant, martensite was mostly found to be situated at ferrite grain boundaries and in the second variant, in addition to at grain boundaries, in-grain martensite was also observed. The third microstructure was very different from the above two with respect to martensite volume fraction ( 67 pct) and its morphology. In this case, martensite packets were surrounded by a three-dimensional ferrite network giving an appearance of core and shell type microstructure. All the three steels were tensile deformed at strain rates ranging from 2.7 × 10-4 (quasi-static) to 650 s-1 (dynamic range). Field-emission scanning electron microscope was used to characterize the starting as well as post-tensile deformed microstructures. Dual-phase steel consisting of small martensite volume fraction ( 19 pct), irrespective of its spatial distribution, demonstrated high strain rate sensitivity and on the other hand, steel with large martensite volume fraction ( 67 pct) displayed a very little strain rate sensitivity. Interestingly, total elongation was found to increase with increasing strain rate in the dynamic regime for steel with core-shell type of microstructure containing large martensite volume fraction. The observed enhancement in plasticity in dynamic regime was attributed to adiabatic heating of specimen. To understand the evolving damage mechanism, the fracture surface and the vicinity of fracture ends were studied in all the three dual-phase steels.

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.

Constitutive modelling of stainless steels for cryogenic applications. Strain induced martensitic transformation

CERN Document Server

Garion, C

2001-01-01

The 300-series stainless steels are metastable austenitic alloys: martensitic transformation occurs at low temperatures and/or when plastic strain fields develop in the structures. The transformation influences the mechanical properties of the material. The present note aims at proposing a set of constitutive equations describing the plastic strain induced martensitic transformation in the stainless steels at cryogenic temperatures. The constitutive modelling shall create a bridge between the material sciences and the structural analysis. For the structures developing and accumulating plastic deformations at sub-zero temperatures, it is of primary importance to be able to predict the intensity of martensitic transformation and its effect on the material properties. In particular, the constitutive model has been applied to predict the behaviour of the components of the LHC interconnections, the so-called bellows expansion joints (the LHC mechanical compensation system).

Deformation mechanisms induced under high cycle fatigue tests in a metastable austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Roa, J.J., E-mail: joan.josep.roa@upc.edu [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edificio C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain); Fargas, G. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); Jiménez-Piqué, E. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edificio C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain); Mateo, A. [CIEFMA-Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain)

2014-03-01

Advanced techniques were used to study the deformation mechanisms induced by fatigue tests in a metastable austenitic stainless steel AISI 301LN. Observations by Atomic Force Microscopy were carried out to study the evolution of a pre-existing martensite platelet at increasing number of cycles. The sub-superficial deformation mechanisms of the austenitic grains were studied considering the cross-section microstructure obtained by Focused Ion Beam and analysed by Scanning Electron Microscopy and Transmission Electron Microscopy. The results revealed no deformation surrounding the pre-existing martensitic platelet during fatigue tests, only the growth on height was observed. Martensite formation was associated with shear bands on austenite, mainly in the {111} plane, and with the activation of the other intersecting austenite {111}〈110〉 slip system. Furthermore, transmission electron microscopy results showed that the nucleation of ε-martensite follows a two stages phase transformation (γ{sub fcc}→ε{sub hcp}→α'{sub bcc})

Influence of hot plastic deformation and cooling rate on martensite and bainite start temperatures in 22MnB5 steel

International Nuclear Information System (INIS)

Nikravesh, M.; Naderi, M.; Akbari, G.H.

2012-01-01

Highlights: ► Reduction of cooling rate, can cause to increase or decrease M s and M f . ► 40% hot plastic deformation hindered the martensitic transformation. ► Hot plastic deformation, caused to decrease M f and M s , while B s increased. ► The critical cooling rate increased 40 °C/s due to apply 40% hot deformation. - Abstract: During hot stamping process, hot forming, cooling and phase transformations are performed in a single step. As a matter of fact, multifunctional phenomena happen and affect each other. Among these phenomena, martensitic and bainitic transformations have the greatest importance. In the current research, the start temperatures of martensite and bainite of 22MnB5 boron steel have been measured in undeformed and 40% deformed conditions, and in various cooling rates from 0.4 °C/s to 100 °C/s by means of deformation dilatometer. It is concluded that, reduction of cooling rate, could bring about an increase or decrease in M s and M f , depending on other phases formation before martensite. Also, hot plastic deformation, hindered the martensitic transformation and decreased M f and M s especially at lower cooling rates, while B s increased. Furthermore, the critical cooling rate, increased about 40 °C/s by applying 40% hot plastic deformation.

Transformation of deformation martensite into austenite in stainless steels at various heating rates

International Nuclear Information System (INIS)

Gojkhenberg, Yu.N.; Shtejnberg, M.M.

1978-01-01

Under isothermal conditions and with continuous preheating at defferent rates, the inverse transformation of deformation martensite that is obtained through reductions to small, medium and great degrees, has been studied. It has been established that depending on the preheat rate, the temperature of the end α → ν of rebuilding varies according to a curve having a maximum. The ascending branch of that curve is connected with the diffusion-controlled shear transformation, whereas the descending branch with the transition to the martensite reaction of austenite formation. As the deformation degree increases, the temperature of the end of the inverse transformation decreases. As a result, recrystallization of austenite proceeds only after completing α → ν transition, when heating the steels deformed to the medium degree at rates of at least 25 deg/sec and after high reductions at rates of at least 0.8 deg/sec

On the role of interlath retained austenite in the deformation of lath martensite

International Nuclear Information System (INIS)

Maresca, F; Kouznetsova, V G; Geers, M G D

2014-01-01

Literature presents extensive experimental evidence of large deformation and ductile fracture behaviour of lath martensite in martensitic and multi-phase high strength steels under quasi-static, uniaxial loading conditions. The physical origin of this apparent ductile behaviour of martensite is not clear, since martensite generally provides a high material strength. The presence of thin films of interlath retained austenite may trigger the observed apparent martensite ductility. The present contribution investigates the role played by interlath retained austenite on the mechanics of lath martensite by means of crystal plasticity simulations. It is shown that independently from the interlath retained austenite volume fraction and the exact lath morphology, localized shearing along the lath habit plane occurs as long as there are enough carriers for plasticity. The austenite film acts like a ‘greasy’ plane on which the stiffer laths can slide. The shearing mechanism is not a mere consequence of the lower flow stress in the austenitic phase, but it is largely due to the orientation relationship between the retained austenite face centred cubic lattice and the body centred cubic lath crystals. (paper)

Influence of hot plastic deformation and cooling rate on martensite and bainite start temperatures in 22MnB5 steel

Energy Technology Data Exchange (ETDEWEB)

Nikravesh, M., E-mail: nikravesh@yahoo.com [Department of Material Science and Engineering, Shahid Bahonar University, Kerman (Iran, Islamic Republic of); Naderi, M. [Department of Mining and Metallurgy, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Akbari, G.H. [Department of Material Science and Engineering, Shahid Bahonar University, Kerman (Iran, Islamic Republic of)

2012-04-01

Highlights: Black-Right-Pointing-Pointer Reduction of cooling rate, can cause to increase or decrease M{sub s} and M{sub f}. Black-Right-Pointing-Pointer 40% hot plastic deformation hindered the martensitic transformation. Black-Right-Pointing-Pointer Hot plastic deformation, caused to decrease M{sub f} and M{sub s}, while B{sub s} increased. Black-Right-Pointing-Pointer The critical cooling rate increased 40 Degree-Sign C/s due to apply 40% hot deformation. - Abstract: During hot stamping process, hot forming, cooling and phase transformations are performed in a single step. As a matter of fact, multifunctional phenomena happen and affect each other. Among these phenomena, martensitic and bainitic transformations have the greatest importance. In the current research, the start temperatures of martensite and bainite of 22MnB5 boron steel have been measured in undeformed and 40% deformed conditions, and in various cooling rates from 0.4 Degree-Sign C/s to 100 Degree-Sign C/s by means of deformation dilatometer. It is concluded that, reduction of cooling rate, could bring about an increase or decrease in M{sub s} and M{sub f}, depending on other phases formation before martensite. Also, hot plastic deformation, hindered the martensitic transformation and decreased M{sub f} and M{sub s} especially at lower cooling rates, while B{sub s} increased. Furthermore, the critical cooling rate, increased about 40 Degree-Sign C/s by applying 40% hot plastic deformation.

Ultrahigh Ductility, High-Carbon Martensitic Steel

Science.gov (United States)

Qin, Shengwei; Liu, Yu; Hao, Qingguo; Zuo, Xunwei; Rong, Yonghua; Chen, Nailu

2016-10-01

Based on the proposed design idea of the anti-transformation-induced plasticity effect, both the additions of the Nb element and pretreatment of the normalization process as a novel quenching-partitioning-tempering (Q-P-T) were designed for Fe-0.63C-1.52Mn-1.49Si-0.62Cr-0.036Nb hot-rolled steel. This high-carbon Q-P-T martensitic steel exhibits a tensile strength of 1890 MPa and elongation of 29 pct accompanied by the excellent product of tensile and elongation of 55 GPa pct. The origin of ultrahigh ductility for high-carbon Q-P-T martensitic steel is revealed from two aspects: one is the softening of martensitic matrix due to both the depletion of carbon in the matensitic matrix during the Q-P-T process by partitioning of carbon from supersaturated martensite to retained austenite and the reduction of the dislocation density in a martensitic matrix by dislocation absorption by retained austenite effect during deformation, which significantly enhances the deformation ability of martensitic matrix; another is the high mechanical stability of considerable carbon-enriched retained austenite, which effectively reduces the formation of brittle twin-type martensite. This work verifies the correctness of the design idea of the anti-TRIP effect and makes the third-generation advanced high-strength steels extend to the field of high-carbon steels from low- and medium-carbon steels.

Stress-induced martensitic transformations in NiTi and NiTi-TiC composites investigated by neutron diffraction

International Nuclear Information System (INIS)

Vaidyanathan, R.; Dunand, D.C.

1999-01-01

Superelastic NiTi (51.0 at.% Ni) specimens reinforced with 0, 10 and 20 vol.% TiC particles were deformed under uniaxial compression while neutron diffraction spectra were collected. The experiments yielded in-situ measurements of the thermoelastic stress-induced transformation. The evolution of austenite/martensite phase fractions and of elastic strains in the reinforcing TiC particles and the austenite matrix were obtained by Rietveld refinement during the loading cycle as the austenite transforms to martensite (and its subsequent back transformation during unloading). Phase fractions and strains are discussed in terms of load transfer in composites where the matrix undergoes a stress-induced phase transformation. (orig.)

Martensite phase stress and the strengthening mechanism in TRIP steel by neutron diffraction.

Science.gov (United States)

Harjo, Stefanus; Tsuchida, Noriyuki; Abe, Jun; Gong, Wu

2017-11-09

Two TRIP-aided multiphase steels with different carbon contents (0.2 and 0.4 mass%) were analyzed in situ during tensile deformation by time-of-flight neutron diffraction to clarify the deformation induced martensitic transformation behavior and its role on the strengthening mechanism. The difference in the carbon content affected mainly the difference in the phase fractions before deformation, where the higher carbon content increased the phase fraction of retained austenite (γ). However, the changes in the relative fraction of martensitic transformation with respect to the applied strain were found to be similar in both steels since the carbon concentrations in γ were similar regardless of different carbon contents. The phase stress of martensite was found much larger than that of γ or bainitic ferrite since the martensite was generated at the beginning of plastic deformation. Stress contributions to the flow stress were evaluated by multiplying the phase stresses and their phase fractions. The stress contribution from martensite was observed increasing during plastic deformation while that from bainitic ferrite hardly changing and that from γ decreasing.

Vacancy clustering behavior in hydrogen-charged martensitic steel AISI 410 under tensile deformation

International Nuclear Information System (INIS)

Sugita, K; Mutou, Y; Shirai, Y

2016-01-01

The formation and accumulation of defects under tensile deformation of hydrogen- charged AISI 410 martensitic steels were investigated by using positron lifetime spectroscopy. During the deformation process, dislocations and vacancy-clusters were introduced and increased with increasing strains. Between hydrogen-charged and uncharged samples with the same tensile strains there was no significant difference in the dislocation density and monovacancy equivalent vacancy density. (paper)

The influence of grain size on the strain-induced martensite formation in tensile straining of an austenitic 15Cr–9Mn–Ni–Cu stainless steel

International Nuclear Information System (INIS)

Kisko, A.; Misra, R.D.K.; Talonen, J.; Karjalainen, L.P.

2013-01-01

In order to improve understanding on the behavior of ultrafine-grained austenitic stainless steels during deformation, the influence of the austenite grain size and microstructure on the strain-induced martensite transformation was investigated in an austenitic 15Cr–9Mn–Ni–Cu (Type 204Cu) stainless steel. By different reversion treatments of the 60% cold-rolled sheet, varying grain sizes from ultrafine (0.5 μm), micron-scale (1.5 μm), fine (4 μm) to coarse (18 μm) were obtained. Some microstructures also contained a mixture of ultrafine or micron-scale and coarse initially cold-worked austenite grains. Samples were tested in tensile loading and deformation structures were analyzed after 2%, 10% and 20% engineering strains by means of martensite content measurements, scanning electron microscope together with a electron backscatter diffraction device and transmission electron microscope. The results showed that the martensite nucleation sites and the rate of transformation vary. In ultrafine grains strain-induced α′-martensite nucleates at grain boundaries and twins, whereas in coarser grains as well as in coarse-grained retained austenite, α′-martensite formation occurs at shear bands, sometimes via ε-martensite. The transformation rate of strain-induced α′-martensite decreases with decreasing grain size to 1.5 μm. However, the rate is fastest in the microstructure containing a mixture of ultrafine and retained cold-worked austenite grains. There the ultrafine grains transform quite readily to martensite similarly as the coarse retained austenite grains, where the previous cold-worked microstructure is still partly remaining

Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steels

International Nuclear Information System (INIS)

Yen, Hung-Wei; Ooi, Steve Woei; Eizadjou, Mehdi; Breen, Andrew; Huang, Ching-Yuan; Bhadeshia, H.K.D.H.; Ringer, Simon P.

2015-01-01

This work explains the occurrence of transformation-induced plasticity via stress-assisted martensite, when designing ultrafine-grained duplex steels. It is found that, when the austenite is reduced to a fine scale of about 300 nm, the initial deformation-induced microstructure can be dominated by parallel lamellae of ε martensite or mechanical twinning, which cannot efficiently provide nucleation sites for strain-induced martensite. Hence, α′ martensite nucleation occurs independently by a stress-assisted process that enhances transformation-induced plasticity in ultrafine-grained austenite. This metallurgical principle was validated experimentally by using a combination of transmission Kikuchi diffraction mapping, transmission electron microscopy and atom probe microscopy, and demonstrated theoretically by the thermodynamics model of stress-assisted martensite

Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

Energy Technology Data Exchange (ETDEWEB)

Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

2015-05-15

A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

International Nuclear Information System (INIS)

Shirdel, M.; Mirzadeh, H.; Parsa, M.H.

2015-01-01

A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

Magnetic properties of cyclically deformed austenite

Energy Technology Data Exchange (ETDEWEB)

Das, Arpan, E-mail: dasarpan1@yahoo.co.in

2014-06-01

In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic γ(fcc) austenite phase to ferromagnetic α{sup /}(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ϵ(hcp), α{sup /}(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band–grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: γ(fcc)→ϵ(hcp), γ(fcc)→ϵ(hcp)→α{sup /}(bcc), γ(fcc)→ deformation twin →α{sup /}(bcc) and γ(fcc)→α{sup /}(bcc). - Highlights: • LCF tests were done at various strain amplitudes of 304LNSS. • Quantification of martensite was done through ferritecope. • Magnetic properties were characterised through VSM. • Correlation of magnetic properties with the cyclic plastic response was done. • TEM was done to investigate the transformation micro-mechanisms.

Nucleation and evolution of strain-induced martensitic (b.c.c.) embryos and substructure in stainless steel: a transmission electron microscope study

International Nuclear Information System (INIS)

Staudhammer, K.P.; Hecker, S.S.; Murr, L.E.

1983-01-01

The deformation of type 304 stainless steel produces a preponderance of strain-induced /chi/ (b.c.c.) martensite, which nucleates as stable embryos at micro-shear band or twin-fault intersections as proposed by Olson and Cohen. The two intersecting micro-shear bands must have a specific defect (fault-displacement) structure, and for stable martensite embryos to form requires a minimal micro-shear band thickness ranging from 50-70 A. The critical nature of nucleation is influenced by the local temperature and strain. The structure, geometry, and morphology of strain-induced martensite embryos is essentially invariant regardless of the strain rate, strain state or temperature. Larger volume fractions of martensite evolve at large strains (greater than or equal to 20%) as a result of embryo coalescence to produce a blocky-type morphology. Martensite embryos and coalesced volume elements of /chi/ are frequently characterized by an irregular non-homogeneous distribution of smaller b.c.c. regimes which result from the irregular satisfaction of the necessary and specific fault-displacement requirements within a larger intersection volume

Strain-Induced Martensitic Transformation and Texture Evolution in Cold-Rolled Co–Cr Alloys

Directory of Open Access Journals (Sweden)

Yusuke Onuki

2018-05-01

Full Text Available Co–Cr alloys have been used in biomedical purposes such as stents and artificial hip joints. However, the difficulty of plastic deformation limits the application of the alloys. During the deformation, Co–Cr alloys often exhibit strain-induced martensitic transformation (SIMT, which is a possible reason for the low formability. The distinct increase in dislocation density in the matrix phase may also result in early fractures. Since these microstructural evolutions accompany the textural evolution, it is crucial to understand the relationship among the SIMT, the increase in dislocations, and the texture evolution. To characterize those at the same time, we conducted time-of-flight neutron diffraction experiments at iMATERIA beamline at the Japan Proton Accelerator Research Complex (J-PARC Materials and Life Science Experimental Facility (MLF, Ibaraki, Japan. The cold-rolled sheets of Co–29Cr–6Mo (CCM and Co–20Cr–15W–10Ni (CCWN alloys were investigated in this study. As expected from the different stacking fault energies, the SIMT progressed more rapidly in the CCM alloy. The dislocation densities of the matrix phases of the CCM and CCWN alloys increased similarly with an increase in the rolling reduction. These results suggest that the difference in deformability between the CCM and CCWN alloys originate not from the strain hardening of the matrix phase but from the growth behaviors of the martensitic phase.

Investigation of strain-induced martensitic transformation in metastable austenite using nanoindentation

International Nuclear Information System (INIS)

Ahn, T.-H.; Oh, C.-S.; Kim, D.H.; Oh, K.H.; Bei, H.; George, E.P.; Han, H.N.

2010-01-01

Strain-induced martensitic transformation of metastable austenite was investigated by nanoindentation of individual austenite grains in multi-phase steel. A cross-section prepared through one of these indented regions using focused ion beam milling was examined by transmission electron microscopy. The presence of martensite underneath the indent indicates that the pop-ins observed on the load-displacement curve during nanoindentation correspond to the onset of strain-induced martensitic transformation. The pop-ins can be understood as resulting from the selection of a favorable martensite variant during nanoindentation.

Investigation of Strain-Induced Martensitic Transformation in Metastable Austenite using Nanoindentation

Energy Technology Data Exchange (ETDEWEB)

Ahn, T.-H. [Seoul National University; Oh, C.-S. [Korean Institute of Materials Science; Kim, D. H. [Seoul National University; Oh, K. H. [Seoul National University; Bei, Hongbin [ORNL; George, Easo P [ORNL; Han, H. N. [Seoul National University

2010-01-01

Strain-induced martensitic transformation of metastable austenite was investigated by nanoindentation of individual austenite grains in multi-phase steel. A cross-section prepared through one of these indented regions using focused ion beam milling was examined by transmission electron microscopy. The presence of martensite underneath the indent indicates that the pop-ins observed on the load-displacement curve during nanoindentation correspond to the onset of strain-induced martensitic transformation. The pop-ins can be understood as resulting from the selection of a favorable martensite variant during nanoindentation.

Deformation mechanisms in ferritic/martensitic steels and the impact on mechanical design

International Nuclear Information System (INIS)

Ghoniem, Nasr M.; Po, Giacomo; Sharafat, Shahram

2013-01-01

Structural steels for nuclear applications have undergone rapid development during the past few decades, thanks to a combination of trial-and-error, mechanism-based optimization, and multiscale modeling approaches. Deformation mechanisms are shown to be intimately related to mechanical design via dominant plastic deformation modes. Because mechanical design rules are mostly based on failure modes associated with plastic strain damage accumulation, we present here the fundamental deformation mechanisms for Ferritic/Martensitic (F/M) steels, and delineate their operational range of temperature and stress. The connection between deformation mechanisms, failure modes, and mechanical design is shown through application of design rules. A specific example is given for the alloy F82H utilized in the design of a Test Blanket Module (TBM) in the International Thermonuclear Experimental Reactor (ITER), where several constitutive equations are developed for design-related mechanical properties

Deformation mechanisms in ferritic/martensitic steels and the impact on mechanical design

Energy Technology Data Exchange (ETDEWEB)

Ghoniem, Nasr M., E-mail: ghoniem@seas.ucla.edu; Po, Giacomo; Sharafat, Shahram

2013-10-15

Structural steels for nuclear applications have undergone rapid development during the past few decades, thanks to a combination of trial-and-error, mechanism-based optimization, and multiscale modeling approaches. Deformation mechanisms are shown to be intimately related to mechanical design via dominant plastic deformation modes. Because mechanical design rules are mostly based on failure modes associated with plastic strain damage accumulation, we present here the fundamental deformation mechanisms for Ferritic/Martensitic (F/M) steels, and delineate their operational range of temperature and stress. The connection between deformation mechanisms, failure modes, and mechanical design is shown through application of design rules. A specific example is given for the alloy F82H utilized in the design of a Test Blanket Module (TBM) in the International Thermonuclear Experimental Reactor (ITER), where several constitutive equations are developed for design-related mechanical properties.

Finite-strain micromechanical model of stress-induced martensitic transformations in shape memory alloys

International Nuclear Information System (INIS)

Stupkiewicz, S.; Petryk, H.

2006-01-01

A micromechanical model of stress-induced martensitic transformation in single crystals of shape memory alloys is developed. This model is a finite-strain counterpart to the approach presented recently in the small-strain setting [S. Stupkiewicz, H. Petryk, J. Mech. Phys. Solids 50 (2002) 2303-2331]. The stress-induced transformation is assumed to proceed by the formation and growth of parallel martensite plates within the austenite matrix. Propagation of phase transformation fronts is governed by a rate-independent thermodynamic criterion with a threshold value for the thermodynamic driving force, including in this way the intrinsic dissipation due to phase transition. This criterion selects the initial microstructure at the onset of transformation and governs the evolution of the laminated microstructure at the macroscopic level. A multiplicative decomposition of the deformation gradient into elastic and transformation parts is assumed, with full account for the elastic anisotropy of the phases. The pseudoelastic behavior of Cu-Zn-Al single crystal in tension and compression is studied as an application of the model

Ultrahigh strength martensite-austenite dual-phase steels with ultrafine structure: The response to indentation experiments

Energy Technology Data Exchange (ETDEWEB)

Misra, R.D.K., E-mail: dmisra@louisiana.edu [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Venkatsurya, P. [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Wu, K.M. [International Research Institute for Steel Technolgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Karjalainen, L.P. [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland)

2013-01-10

In medium to high carbon steels, characterized by martensite-austenite microstructure processed by quenching and partitioning process, martensite potentially provides high strength, while austenite provides work hardening [Fu, Wu, and Misra, DOI: 10.1179/1743284712/068]. Given the significant interest in these steels in the steel community, the paper reports for the first time the nanoscale deformation experiments and accompanying microstructural evolution to obtain micromechanical insights into the deformation behavior of ultrahigh strength-high ductility dual-phase steels with significant retained austenite fraction of {approx}0.35. During deformation experiments with nanoindenter, dislocations were distributed on several slip systems, whereas strain-induced twinned martensite and twinning were the deformation mechanisms in carbon-enriched and thermally stabilized retained austenite. Furthermore, ultrafine dual-phase steels exhibited high strain rate sensitivity.

Martensitic transformations in titanium nickelide subject to sock wave loading

International Nuclear Information System (INIS)

Zel'dovich, V.I.; Shorokhov, E.V.; Gundyrev, V.M.; Khejfets, A.Eh.; Frolova, N.Yu.; Khomskaya, I.V.

2000-01-01

The plates of titanium nickelide (Ti-50.5 at. % Ni) rolled in an austenitic state and subjected to impact shock with pressure of 10 and 50 GPa are under study. Dilatometric and X-ray diffraction studied show that shock wave loading induces anisotropic martensitic transformations in the plates. The anisotropy of transformations is conditioned by directed motion of the substance of the plate in shock waves. Austenitic memory of specimens prior to loading is changed to martensitic one typical of deformation of martensite. Martensitic memory not preserve after the reserve martensitic transformation, the specimens recall the initial state with austenitic memory. The particles of Ti 3 N 4 precipitated phase and the dislocation structure formed in rolling are the carriers of memory [ru

In situ synchrotron analysis of lattice rotations in individual grains during stress-induced martensitic transformations in a polycrystalline CuAlBe shape memory alloy

International Nuclear Information System (INIS)

Berveiller, S.; Malard, B.; Wright, J.; Patoor, E.; Geandier, G.

2011-01-01

Highlights: → 3DXRD, Laue microdiffraction measurements of grain rotation in a shape memory alloy. → During stress-induced martensitic transformation, the austenite grains rotate. → This rotation reverses with the reverse transformation. → The austenite grains splits into various orientations with martensite formation. - Abstract: Two synchrotron diffraction techniques, three-dimensional X-ray diffraction and Laue microdiffraction, are applied to studying the deformation behaviour of individual grains embedded in a Cu 74 Al 23 Be 3 superelastic shape memory alloy. The average lattice rotation and the intragranular heterogeneity of orientations are measured during in situ tensile tests at room temperature for four grains of mean size ∼1 mm. During mechanical loading, all four grains rotate and the mean rotation angle increases with austenite deformation. As the martensitic transformation occurs, the rotation becomes more pronounced, and the grain orientation splits into several sub-domains: the austenite orientation varies on both sides of the martensite variant. The mean disorientation is ∼1 o . Upon unloading, the sub-domains collapse and reverse rotation is observed.

Comparative Study of Hardening Mechanisms During Aging of a 304 Stainless Steel Containing α'-Martensite

Science.gov (United States)

Jeong, S. W.; Kang, U. G.; Choi, J. Y.; Nam, W. J.

2012-09-01

Strain aging and hardening behaviors of a 304 stainless steel containing deformation-induced martensite were investigated by examining mechanical properties and microstructural evolution for different aging temperature and time. Introduced age hardening mechanisms of a cold rolled 304 stainless steel were the additional formation of α'-martensite, hardening of α'-martensite, and hardening of deformed austenite. The increased amount of α'-martensite at an aging temperature of 450 °C confirmed the additional formation of α'-martensite as a hardening mechanism in a cold rolled 304 stainless steel. Additionally, the increased hardness in both α'-martensite and austenite phases with aging temperature proved that hardening of both α'-martensite and austenite phases would be effective as hardening mechanisms in cold rolled and aged 304 stainless steels. The results suggested that among hardening mechanisms, hardening of an α'-martensite phase, including the diffusion of interstitial solute carbon atoms to dislocations and the precipitation of fine carbide particles would become a major hardening mechanism during aging of cold rolled 304 stainless steels.

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain

Energy Technology Data Exchange (ETDEWEB)

Gussev, M.N., E-mail: gussevmn@ornl.gov; Field, K.G.; Busby, J.T.

2014-03-15

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ∼1 μm and depths of several microns were observed at channels with heights greater than ∼150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]–[1 1 1] orientation but not in those along the [1 0 1] orientation.

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain

International Nuclear Information System (INIS)

Gussev, M.N.; Field, K.G.; Busby, J.T.

2014-01-01

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ∼1 μm and depths of several microns were observed at channels with heights greater than ∼150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]–[1 1 1] orientation but not in those along the [1 0 1] orientation

γ→α′ Martensitic transformation and magnetic property of cold rolled Fe–20Mn–4Al–0.3C steel

Energy Technology Data Exchange (ETDEWEB)

Ma, Biao; Li, Changsheng, E-mail: lics@ral.neu.edu.cn; Han, Yahui; Wang, Jikai

2016-12-01

Direct γ→α′ martensitic transformation during cold rolling deformation was investigated for a high-Mn non-magnetic steel. Its influence on magnetic property was also analyzed. The magnetization under rolling reduction less than 50% almost presents a linear increase with the applied magnetic field. With deformation up to 73% and 93% thickness reductions, strain induced α′-martensite transformation starts to occur, causing the steel to be slightly magnetized. The α′-martensite prefers to nucleate directly at either microband–microband or microband-twin intersections without participation of intermediate ε-martensite. The volume fraction of α′-martensite is estimated as 0.070% and 0.17%, respectively, based on the magnetic hysteresis loops. Such a small fraction of ferromagnetic α′-martensite shows little influence on the magnetic induction intensity and low relative permeability. - Highlights: • Magnetic property of high-Mn austenitic steel was examined after cold rolling. • Nucleation mode for direct γ→α′ martensitic transformation was observed and discussed. • Volume fraction of strain induced α′-martensite was estimated by magnetic measurement.

Resistance to small plastic strains during martensite tempering under tension

Energy Technology Data Exchange (ETDEWEB)

Zabil' skij, V.V.; Sarrak, V.I. (AN SSSR, Sverdlovsk. Inst. Fiziki Metallov)

1982-11-01

The mechanism of plastic deformation of martensite of a series of hardened steels (N18, 20KhG, 50KhFA and others) during tempering under tension and the role of residual internal microstresses and phase transformations are studied. It is shown that martensite low resistance to small plastic deformations during tempering under tension which is usually associated with phase transformations depends as well on the level of residual internal microstresses in the martensite structure. The decrease of resistance to deformation in the course of the decomposition of a solid solution is due to weakening of martensitic matrix because of carbon departure from the solid solution and carbide coarsening. An assumption is made that martensite plastic deformation during tempering under tension is realized at the expense of the directed microplastic deformation in the regions of higher concentration of internal stresses.

An investigation of the γ → α martensitic transformation in uranium alloys

International Nuclear Information System (INIS)

Speer, J.G.; Edmonds, D.V.

1988-01-01

A detailed study of the γ → chi martensite transformation in uranium alloys is presented. Five binary uranium-base alloys containing 0.77 Ti, 1.2 Mo, 2.2 Mo, 4.3 Mo and 5.0 Mo, respectively, were examined. As quenched, the U-0.77 Ti and U-1.2 Mo alloys consisted of an orthorhombic α'/sub a/ martensite phase with an acicular morphology. The acicular martensite plates contain deformation twins which result from transformation stresses. The U-2.2 Mo and U-4.3 Mo alloys transformed during quenching to orthorhomic chi'/sub b/ and monoclinic chi'/sub b/ martensite phases, respectively. The banded morphology observed in these two alloys consists of long, parallel martensite plates containing fine arrays of transformation twins. The type I transformation twinning modes were identified as /021/, /130/ and /131/. There was also evidence for a type II /111/ mode. It was found that adjacent bands could contain different kinds of transformation twins. In the U-5.0 Mo alloy, some of the cubic parent phase was retained during water quenching, and chi/γ orientation relationship was determined. The γ phase was completely retained in this alloy by slow cooling from the solution treatment temperature of 800 0 C, and it was found that a martensitic reaction could be induced by deformation. The strain-induced martensite plates contained /021/ transformation twins. The chi/γ orientation relationship was found to be different than the one determined in the quenched condition, and both orientation relationships are irrational. The invariant plane strain theory of martensite crystallography was applied to the twinned martensites, and a number of different parent/product lattice correspondences were considered for the γ → chi transformations. It was concluded that more than one correspondence may be operative during these transformations

Electron microscope study of the genesis of strain-induced martensite embryos

International Nuclear Information System (INIS)

Staudhammer, K.P.; Hecker, S.S.; Murr, L.E.

1984-01-01

Previous work of Olson and Cohen and Murr, et al., is used to describe the genesis of martensite embryos which form at the intersection of microscopic shear bands in deformed type 304 stainless steel. It is shown that the intersection volume included within intersecting shear bands contains irregular and smaller dispersed volume segments forming α' martensite (bcc). These correspond to the satisfaction of specific intersections of stacking faults or partial dislocations on approximately every second (111)/sub fcc/ plane in one direction, and every third (111)/sub fcc/ plane in the other (conjugate) direction. The requisite stacking fault or partial dislocation arrangements are produced in an irregular fashion resulting in α' martensite embryos nucleating in an incomplete and irregular fashion within the intersection volume. 9 references, 2 figures

Numerical simulation of transformation-induced microscopic residual stress in ferrite-martensite lamellar steel

International Nuclear Information System (INIS)

Mikami, Y; Inao, A; Mochizuki, M; Toyoda, M

2009-01-01

The effect of transformation-induced microscopic residual stress on fatigue crack propagation behavior of ferrite-martensite lamellar steel was discussed. Fatigue tests of prestrained and non-prestrained specimens were performed. Inflections and branches at ferrite-martensite boundaries were observed in the non-prestrained specimens. On the other hand, less inflections and branches were found in the prestrained specimens. The experimental results showed that the transformation induced microscopic residual stress has influence on the fatigue crack propagation behavior. To estimate the microscopic residual, a numerical simulation method for the calculation of microscopic residual stress stress induced by martensitic transformation was performed. The simulation showed that compressive residual stress was generated in martensite layer, and the result agree with the experimental result that inflections and branches were observed at ferrite-martensite boundaries.

Electron backscatter and X-ray diffraction studies on the deformation and annealing textures of austenitic stainless steel 310S

Energy Technology Data Exchange (ETDEWEB)

Nezakat, Majid, E-mail: majid.nezakat@usask.ca [Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3 (Canada); Akhiani, Hamed [Westpower Equipment Ltd., 4451 54 Avenue South East, Calgary, AB T2C 2A2 (Canada); Sabet, Seyed Morteza [Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL 33431 (United States); Szpunar, Jerzy [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 (Canada)

2017-01-15

We studied the texture evolution of thermo-mechanically processed austenitic stainless steel 310S. This alloy was cold rolled up to 90% reduction in thickness and subsequently annealed at 1050 °C. At the early stages of deformation, strain-induced martensite was formed from deformed austenite. By increasing the deformation level, slip mechanism was found to be insufficient to accommodate higher deformation strains. Our results demonstrated that twinning is the dominant deformation mechanism at higher deformation levels. Results also showed that cold rolling in unidirectional and cross rolling modes results in Goss/Brass and Brass dominant textures in deformed samples, respectively. Similar texture components are observed after annealing. Thus, the annealing texture was greatly affected by texture of the deformed parent phase and martensite did not contribute as it showed an athermal reversion during annealing. Results also showed that when the fraction of martensite exceeds a critical point, its grain boundaries impeded the movement of austenite grain boundaries during annealing. As a result, recrystallization incubation time would increase. This caused an incomplete recrystallization of highly deformed samples, which led to a rational drop in the intensity of the texture components. - Highlights: •Thermo-mechanical processing through different cold rolling modes can induce different textures. •Martensite reversion is athermal during annealing. •Higher fraction of deformation-induced martensite can increase the annealing time required for complete recrystallization. •Annealing texture is mainly influenced by the deformation texture of austenite.

Acoustic emission on thermoelastic martensitic transformations in alloys in the course of mechanical loading

International Nuclear Information System (INIS)

Plotnikov, V.A.; Kokhanenko, D.V.

2004-01-01

The connection of the emission process with the process of the deformation accumulation and relaxation in the cycle of the martensitic transformations is studied. The martensitic transformations cycling was investigated by cycling change in the temperature in the Ti 50 Ni 50 Cu 10 alloys. The deformation accumulation and recovery is observed in the alloys undergoing the thermoelastic martensitic transformations under the mechanical loading conditions. The acoustic emission, accompanying the martensitic transformations, reflects the peculiarities of the alloy deformation behavior by the martensitic transformations. The anomalous acoustic effect correlates with the reversible deformation accumulation and does not correlates with the irreversible deformation accumulation [ru

Analysis of martensitic transformation and residual tension in an 304L stainless steel

International Nuclear Information System (INIS)

Alves, Juciane Maria

2014-01-01

The relationship between plastic deformation and the strain induced phase transformation, that provides a practical route to the development of new engineering materials with excellent mechanical properties, characterize the TRIP effect 'Transformation Induced Plasticity'. Among the stainless steels, the metastable 304 L austenitic steel is susceptible to transformation of austenite-martensite phase from tensile tests at room temperature by increments of plastic deformation. It is of great technological and scientific interest the knowledge of the evolution of phase transformation and residual stress from different levels and rates of plastic deformation imposed to the material. It is also important to evaluate the interference of metallographic preparation in quantitative analyzes of this steel. The main techniques used in this study consisted of X-rays diffraction and Ferritoscopy for the quantitation phase, and XRD to residual stress analysis also. As observed, the phase transformation quantification has not suffered significant influence of the metallographic preparation and evolved from increments of plastic deformation due to different stop charges and strain rates, leading to a further strengthening of the austenite matrix. The evaluation of residual stress resulting from the martensitic transformation was susceptible to the metallographic preparation and increased its value on comparison to sample without metallographic preparation. It was also observed that the residual stress decreased with the increase of the fraction of transformed martensite. (author)

A Shear Strain Route Dependency of Martensite Formation in 316L Stainless Steel.

Science.gov (United States)

Kang, Suk Hoon; Kim, Tae Kyu; Jang, Jinsung; Oh, Kyu Hwan

2015-06-01

In this study, the effect of simple shearing on microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. Two different shear strain routes were obtained by twisting cylindrical specimens in the forward and backward directions. The strain-induced martensite phase was effectively obtained by alteration of the routes. Formation of the martensite phase clearly resulted in significant hardening of the steel. Grain-size reduction and strain-induced martensitic transformation within the deformed structures of the strained specimens were characterized by scanning electron microscopy - electron back-scattered diffraction, X-ray diffraction, and the TEM-ASTAR (transmission electron microscopy - analytical scanning transmission atomic resolution, automatic crystal orientation/phase mapping for TEM) system. Significant numbers of twin networks were formed by alteration of the shear strain routes, and the martensite phases were nucleated at the twin interfaces.

Radiation induced microstructural evolution in ferritic/martensitic steels

International Nuclear Information System (INIS)

Kohno, Y.; Kohyama, A.; Asakura, K.; Gelles, D.S.

1993-01-01

R and D of ferritic/martensitic steels as structural materials for fusion reactor is one of the most important issues of fusion technology. The efforts to characterize microstructural evolution under irradiation in the conventional Fe-Cr-Mo steels as well as newly developed Fe-Cr-Mn or Fe-Cr-W low activation ferritic/ martensitic steels have been continued. This paper provides some of the recent results of heavy irradiation effects on the microstructural evolution of ferritic/martensitic steels neutron irradiated in the FFTF/MOTA (Fast Flux Test Facility/Materials Open Test Assembly). Materials examined are Fe-10Cr-2Mo dual phase steel (JFMS: Japanese Ferritic/Martensitic Steel), Fe-12Cr-XMn-1Mo manganese stabilized martensitic steels and Fe-8Cr-2W Tungsten stabilized low activation martensitic steel (F82H). JFMS showed excellent void swelling resistance similar to 12Cr martensitic steel such as HT-9, while the manganese stabilized steels and F82H showed less void swelling resistance with small amount of void swelling at 640-700 K (F82H: 0.14% at 678 K). As for irradiation response of precipitate behavior, significant formation of intermetallic χ phase was observed in the manganese stabilized steels along grain boundaries which is though to cause mechanical property degradation. On the other hand, precipitates identified were the same type as those in unirradiated condition in F82H with no recognition of irradiation induced precipitates, which suggested satisfactory mechanical properties of F82H after the irradiation. (author)

Influence of martensitic transformation on the low-cycle fatigue behaviour of 316LN stainless steel at 77 K

International Nuclear Information System (INIS)

Botshekan, M.; Degallaix, S.; Desplanques, Y.

1997-01-01

Tensile and low-cycle fatigue tests were performed on a 316LN austenitic stainless steel at 300 and 77 K. The tensile and low-cycle fatigue properties were obtained and analysed in terms of influence of temperature on the plastic deformation process, and particularly on the strain-induced martensite formation. The martensite content was measured by a magnetic-at-saturation method. No martensite was detected at 300 K. On the contrary, strain-induced martensite transformation is responsible for the higher tensile elongation at 77 K and for the secondary hardening observed on softening-hardening curves in low-cycle fatigue at 77 K. The induced martensite content in tensile tests is a function of the strain according to Angel's model, and in low-cycle fatigue it is a function of the strain level and of the accumulated plastic strain. (orig.)

Comprehensive Deformation Analysis of a Newly Designed Ni-Free Duplex Stainless Steel with Enhanced Plasticity by Optimizing Austenite Stability

Science.gov (United States)

Moallemi, Mohammad; Zarei-Hanzaki, Abbas; Eskandari, Mostafa; Burrows, Andrew; Alimadadi, Hossein

2017-08-01

A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magnetic phase measurements, X-ray diffraction (XRD) and electron backscattered diffraction were employed to study the plastic deformation behavior and to identify the operating plasticity mechanisms. The results obtained show that the newly designed duplex alloy exhibits some extraordinary mechanical properties, including an ultimate tensile strength of 900 MPa and elongation to fracture of 94 pct due to the synergistic effects of transformation-induced plasticity and twinning-induced plasticity. The deformation mechanism of austenite is complex and includes deformation banding, strain-induced martensite formation, and deformation-induced twinning, while the ferrite phase mainly deforms by dislocation slip. Texture analysis indicates that the Copper and Rotated Brass textures in austenite (FCC phase) and {001} texture in ferrite and martensite (BCC phases) are the main active components during tensile deformation. The predominance of these components is logically related to the strain-induced martensite and/or twin formation.

Atomic force microscopy study of stacking modes of martensitic transformation in Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Liu, D.Z.; Kikuchi, T.; Kajiwara, S.; Shinya, N.

2000-01-01

Stacking modes of thermally induced and stress-induced martensitic transformation in Fe-28Mn-6Si-5Cr shape memory alloys have been studied using atomic force microscopy (AFM). It has been found that thermally induced martensite plates appear with the self-accommodated stacking form, in which all the three possible variants with different left angle 112 right angle shear directions in a {111} plane are activated and formed in parallel but at separate places; i.e. each plate corresponds to one variant. In addition, a plastic deformation band is always induced in austenite between two different variants. On the other hand, stress-induced martensite plates appear with the mono-partial stacking form, i.e. only single variant is activated in a {111} plane in a grain. The difference between stacking modes of thermally induced and stress-induced martensites makes them play a different role in contributing to shape memory effect in Fe-Mn-Si based shape memory alloys. (orig.)

Superelastic NiTi memory alloy micro-tube under tension - nucleation and propagation of martensite band

International Nuclear Information System (INIS)

Li, Z.Q.; Sun, Q.P.

2000-01-01

The superelastic behavior of polycrystalline NiTi shape memory alloy micro-tube under tension is studied experimentally. The nominal stress-strain curve of the micro-tube is recorded. By using a special surface coating it is found that the deformation of the tube is via the nucleation and propagation of stress-induced martensite band. The experiments show that the martensite nucleates in the form of a spiral lens-shaped narrow band that is inclined at 61 to the axis of loading when the stress reaches the peak of stress-strain curve. The width and the length of the band grew gradually with increase of loading and finally joined and merged into a single band. The subsequent deformation of the tube is realized by the propagation of this cylindrical martensite band. (orig.)

Some aspects of thermally induced martensite in Fe-30% Ni-5% Cu alloy

International Nuclear Information System (INIS)

Guener, M.; Gueler, E.; Yasar, E.; Aktas, H.

2007-01-01

Kinetical, morphological, crystallographical and several thermal properties of thermally induced martensite in the austenite phase of Fe-30% Ni-5% Cu alloy were investigated. Scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) techniques were used during study. Kinetics of the transformation was found to be as athermal type. SEM and TEM observations revealed α' (BCC) martensite formation in the austenite phase of alloy by thermal effect. These thermally induced α' martensites exhibited a thin plate-like morphology with twinnings

Modeling mechanical effects on promotion and retardation of martensitic transformation

Energy Technology Data Exchange (ETDEWEB)

Maalekian, Mehran, E-mail: mehran.maalekian@ubc.ca [Department of Materials Engineering, University of British Columbia, 309-6350 Stores Road, Vancouver, B.C. V61Z4 (Canada); Kozeschnik, Ernst [Christian Doppler Laboratory for ' Early Stages of Precipitation' , Institute of Materials Science and Technology, Vienna University of Technology (Austria)

2011-01-25

Research highlights: {yields} Compressive elastic stresses up to 250 MPa are applied in continuous cooling. {yields} Using the thermodynamic data and maximum value of the mechanical driving force the predicted increase in M{sub s} ({approx}0.1 K/MPa) is in agreement with experiment {yields} Austenite was deformed plastically at different temperatures (800 deg. C-1100 deg. C). {yields} High deformation temperature (i.e. 1100 deg. C) as well as low plastic strain (i.e. {epsilon}{sub ave} {approx} 30%) do not affect martensite transformation noticeably, whereas lower deformation temperature (e.g. 900 deg. C) and large plastic strain (i.e. {epsilon}{sub ave} {approx} 70%) retards martensite transformation. {yields} The theory of mechanical stabilization predicts the depression of M{sub s}. - Abstract: The influence of compressive stress and prior plastic deformation of austenite on the martensite transformation in a eutectoid steel is studied both experimentally and theoretically. It is demonstrated that martensite formation is assisted by stress but it is retarded when transformation occurs from deformed austenite. With the quantitative modeling of the problem based on the theory of displacive shear transformation, the explanation of the two opposite roles of mechanical treatment prior to or simultaneously to martensite transformation is presented.

Martensitic transformation, shape memory effects, and other curious mechanical effects

International Nuclear Information System (INIS)

Vandermeer, R.A.

1982-01-01

The objective of this paper is to review tutorially the subject of martensitic transformations in uranium alloys emphasizing their role in the shape memory effect (SME). We examine first what a martensitic transformation is, illustrating some of its characteristics with specific examples. As well as being athermal in nature, as expected, data are presented indicating that martensitic transformations in some uranium alloys also have a strong isothermal component. In addition, a few alloys are known to exhibit thermoelastic martensitic reactions. The SME, which is associated with these, is defined and demonstrated graphically with data from a uranium-6 wt % niobium alloy. Some of the important variables influencing SME behavior are described. Specifically, these are reheat temperature, amount of deformation, crystal structure, and composition. A mechanism for SME is postulated and the association with martensitic transformation is detailed. A self-induced shape instability in the uranium-7.5 wt % niobium-2.5 wt % zirconium alloy with a rationalization of the behavior in terms of texture and lattice parameter change during aging is reviewed and discussed. 24 figures

The effects of strain induced martensite on stress corrosion cracking in AISI 304 stainless steel

International Nuclear Information System (INIS)

Lee, W. S.; Kwon, S. I.

1989-01-01

The effects of strain induced martensite on stress corrosion cracking behavior in AISI 304 stainless steel in boiling 42 wt% MgCl 2 solution were investigated using monotonic SSRT and cyclic SSRT with R=0.1 stress ratio. As the amount of pre-strain increased, the failure time of the specimens in monotonic SSRT test decreased independent of the existence of strain induced martensite. The strain induced martensite seems to promote the crack initiation but to retard the crack propagation during stress corrosion cracking

Modulated martensite: why it forms and why it deforms easily

International Nuclear Information System (INIS)

Kaufmann, S; Niemann, R; Thersleff, T; Roessler, U K; Heczko, O; Buschbeck, J; Holzapfel, B; Schultz, L; Faehler, S

2011-01-01

Diffusionless phase transitions are at the core of the multifunctionality of (magnetic) shape memory alloys, ferroelectrics and multiferroics. Giant strain effects under external fields are obtained in low symmetric modulated martensitic phases. We outline the origin of modulated phases, their connection with tetragonal martensite and consequences owing to their functional properties by analysing the martensitic microstructure of epitaxial Ni-Mn-Ga films from the atomic to the macroscale. Geometrical constraints at an austenite-martensite phase boundary act down to the atomic scale. Hence, a martensitic microstructure of nanotwinned tetragonal martensite can form. Coarsening of twin variants can reduce twin boundary energy, a process we could observe from the atomic to the millimetre scale. Coarsening is a fractal process, proceeding in discrete steps by doubling twin periodicity. The collective defect energy results in a substantial hysteresis, which allows the retention of modulated martensite as a metastable phase at room temperature. In this metastable state, elastic energy is released by the formation of a 'twins within twins' microstructure that can be observed from the nanometre to the millimetre scale. This hierarchical twinning results in mesoscopic twin boundaries. Our analysis indicates that mesoscopic boundaries are broad and diffuse, in contrast to the common atomically sharp twin boundaries of tetragonal martensite. We suggest that the observed extraordinarily high mobility of such mesoscopic twin boundaries originates from their diffuse nature that renders pinning by atomistic point defects ineffective.

Texture developed during deformation of Transformation Induced Plasticity (TRIP) steels

International Nuclear Information System (INIS)

Bhargava, M; Asim, T; Sushil, M; Shanta, C

2015-01-01

Automotive industry is currently focusing on using advanced high strength steels (AHSS) due to its high strength and formability for closure applications. Transformation Induced Plasticity (TRIP) steel is promising material for this application among other AHSS. The present work is focused on the microstructure development during deformation of TRIP steel sheets. To mimic complex strain path condition during forming of automotive body, Limit Dome Height (LDH) tests were conducted and samples were deformed in servo hydraulic press to find the different strain path. FEM Simulations were done to predict different strain path diagrams and compared with experimental results. There is a significant difference between experimental and simulation results as the existing material models are not applicable for TRIP steels. Micro texture studies were performed on the samples using EBSD and X-RD techniques. It was observed that austenite is transformed to martensite and texture developed during deformation had strong impact on limit strain and strain path. (paper)

Texture developed during deformation of Transformation Induced Plasticity (TRIP) steels

Science.gov (United States)

Bhargava, M.; Shanta, C.; Asim, T.; Sushil, M.

2015-04-01

Automotive industry is currently focusing on using advanced high strength steels (AHSS) due to its high strength and formability for closure applications. Transformation Induced Plasticity (TRIP) steel is promising material for this application among other AHSS. The present work is focused on the microstructure development during deformation of TRIP steel sheets. To mimic complex strain path condition during forming of automotive body, Limit Dome Height (LDH) tests were conducted and samples were deformed in servo hydraulic press to find the different strain path. FEM Simulations were done to predict different strain path diagrams and compared with experimental results. There is a significant difference between experimental and simulation results as the existing material models are not applicable for TRIP steels. Micro texture studies were performed on the samples using EBSD and X-RD techniques. It was observed that austenite is transformed to martensite and texture developed during deformation had strong impact on limit strain and strain path.

Kinetic of martensitic transformations induced by hydrogen in the austenite

International Nuclear Information System (INIS)

Oliveira, Sergio P. de; Saavedra, A.; Miranda, P.E.V. de

1986-01-01

The X-ray diffractometry technique was used, with an automatic data acquisition system to determine the kinetics of hydrogen induced martensitic phase transformations in an AISI 304 austenitic stainless steel type, used in nuclear power plants. Hydrogenation was performed cathodically in a 1N sulfuric acid solution, containing 100 mg/l of arsenic trioxide, at 50 0 C, during 2 hours and with a current density of 200 A/m 2 . It was found that the microstructure of the steel plays a role on the generation of hydrogen induced martensitic phases and surface micro cracks. Both kinetics were slower on a pre-cold rolled steel. (Author) [pt

Hysteresis and Power-Law Statistics during temperature induced martensitic transformation

International Nuclear Information System (INIS)

Paul, Arya; Sengupta, Surajit; Rao, Madan

2011-01-01

We study hysteresis in temperature induced martensitic transformation using a 2D model solid exhibiting a square to rhombic structural transition. We find that upon quenching, the high temperature square phase, martensites are nucleated at sites having large non-affineness and ultimately invades the whole of the high temperature square phase. On heating the martensite, the high temperature square phase is restored. The transformation proceeds through avalanches. The amplitude and the time-duration of these avalanches exhibit power-law statistics both during heating and cooling of the system. The exponents corresponding to heating and cooling are different thereby indicating that the nucleation and dissolution of the product phase follows different transformation mechanism.

On a phase field approach for martensitic transformations in a crystal plastic material at a loaded surface

Science.gov (United States)

Schmitt, Regina; Kuhn, Charlotte; Müller, Ralf

2017-07-01

A continuum phase field model for martensitic transformations is introduced, including crystal plasticity with different slip systems for the different phases. In a 2D setting, the transformation-induced eigenstrain is taken into account for two martensitic orientation variants. With aid of the model, the phase transition and its dependence on the volume change, crystal plastic material behavior, and the inheritance of plastic deformations from austenite to martensite are studied in detail. The numerical setup is motivated by the process of cryogenic turning. The resulting microstructure qualitatively coincides with an experimentally obtained martensite structure. For the numerical calculations, finite elements together with global and local implicit time integration scheme are employed.

Martensitic transformations, structure, and strengthness of processed high-nitrogen and high-carbon ferrous alloys

Science.gov (United States)

Kaputkina, L. M.; Prokoshkina, V. G.

2003-10-01

Structures and properties of metastable austenitic alloys Fe-18Cr-16Ni-I2Mn-(0.17 to 0. 50)N, Fe-18Cr-12Mn-(0.48 to 1.12)N, Fe-18Cr-(0.1 to 1.18)N, and Fe-(12 to 20)Ni-(0.6 to 1.3)C, Fe-(6 to 8)Mn-(0.6 to 1.0)C, Fe-(5 to 6)Cr-(4 to 5)Mn-(0.6 to 0.8)C, Fe-6Cr-(1.0 to 1.3)C resulting from martensitic transformations under cooling and cold deformation (CD), as well as following tempering processes, were studied by magnetometry, X-ray and electron microscopy analyses, hardness measurements and mechanical properties tests. Martensite with a b.c.t. lattice was formed in all alloys with M_s{>}-196^circC during cooling. Under CD transformations of γ{to}α, γ{to}\\varepsilon{to}α, or γ{to}\\varepsilon types were realized depending on the alloy composition. Carbon increased but nitrogen decreased stacking fault energy. Thus carbon assists α-martensite formation but nitrogen promotese. As CD level and/or concentration of carbon and nitrogen increase residual stresses resulting from the CD also increase. The martensitic transformation during CD can decrease the residual stresses. Kinetic of tempering of b.c.t. thermal martensite differs from those of CD-induced martensite. In the second case, deformation aging, texture, and residual stresses are more visible. The maximal strengthening under CD takes place in (Mn+N)-steels. (Cr+N) and (Cr+Mn+N)-steels are high-strength, non-magnetic and corrosion resistant and are easily hardened by a low level of plastic deformation.

Plastic Strain Induced Damage Evolution and Martensitic Transformation in Ductile Materials at Cryogenic Temperatures

CERN Document Server

Garion, C

2002-01-01

The Fe-Cr-Ni stainless steels are well known for their ductile behaviour at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damage and strain induced martensitic transformation. Ductile damage is described by the kinetic law of damage evolution. Here, the assumption of isotropic distribution of damage (microcracks and microvoids) in the Representative Volume Element (RVE) is made. Formation of the plastic strain induced martensite (irreversible process) leads to the presence of quasi-rigid inclusions of martensite in the austenitic matrix. The amount of martensite platelets in the RVE depends on the intensity of the plastic strain fields and on the temperature. The evolution of the volume fraction of martensite is governed by a kinetic law based on the accumulated plastic strain. Both of thes...

Effect of tensile pre-strain at different orientation on martensitic transformation and mechanical properties of 316L stainless steel

Science.gov (United States)

Wibowo, F.; Zulfi, F. R.; Korda, A. A.

2017-01-01

Deformation induced martensite was studied in 316L stainless steel through tensile pre-strain deformation in the rolling direction (RD) and perpendicular to the rolling direction (LT) at various %pre-strain. The experiment was carried out at various given %pre-strain, which were 0%, 4.6%, 12%, 17.4%, and 25.2% for the RD, whereas for LT were 0%, 4.6%, 12%, 18%, and 26% for LT. Changes in the microstructure and mechanical properties were observed using optical microscope, tensile testing, hardness testing, and X-ray diffraction (XRD) analysis. The experimental results showed that the volume fraction of martensite was increased as the %pre-strain increased. In the same level of deformation by tensile pre-strain, the volume of martensite for RD was higher than that with LT direction. The ultimate tensile strength (UTS), yield strength (YS), and hardness of the steel were increased proportionally with the increases in %pre-strain, while the value of elongation and toughness were decreased with the increases in %pre-strain.

Comprehensive Deformation Analysis of a Newly Designed Ni-Free Duplex Stainless Steel with Enhanced Plasticity by Optimizing Austenite Stability

DEFF Research Database (Denmark)

Moallemi, Mohammad; Zarei-Hanzaki, Abbas; Eskandari, Mostafa

2017-01-01

A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magnetic......, including an ultimate tensile strength of ~900 MPa and elongation to fracture of ~94 pct due to the synergistic effects of transformation-induced plasticity and twinning-induced plasticity. The deformation mechanism of austenite is complex and includes deformation banding, strain-induced martensite...... formation, and deformation-induced twinning, while the ferrite phase mainly deforms by dislocation slip. Texture analysis indicates that the Copper and Rotated Brass textures in austenite (FCC phase) and {001}〈110〉 texture in ferrite and martensite (BCC phases) are the main active components during...

Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

Science.gov (United States)

Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

2016-01-01

We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α′-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α′ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α′N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance. PMID:27492862

Precipitation behavior in a nitride-strengthened martensitic heat resistant steel during hot deformation

Directory of Open Access Journals (Sweden)

Wenfeng Zhang

2015-09-01

Full Text Available The stress relaxation curves for three different hot deformation processes in the temperature range of 750–1000 °C were studied to develop an understanding of the precipitation behavior in a nitride-strengthened martensitic heat resistant steel (Zhang et al., Mater. Sci. Eng. A, 2015 [1]. This data article provides supporting data and detailed information on how to accurately analysis the stress relaxation data. The statistical analysis of the stress peak curves, including the number of peaks, the intensity of the peaks and the integral value of the pumps, was carried out. Meanwhile, the XRD energy spectrum data was also calculated in terms of lattice distortion.

Orientation dependence of stress-induced martensite formation during nanoindentation in NiTi shape memory alloys

International Nuclear Information System (INIS)

Laplanche, G.; Pfetzing-Micklich, J.; Eggeler, G.

2014-01-01

In the present work we used nanoindentation with a spherical indenter tip to study the formation of stress-induced martensite in NiTi shape memory alloys. Prior to nanoindentation, orientation imaging was performed to select austenite grains with specific crystallographic orientations, including the principal crystallographic directions [0 0 1], [1 0 1] and [1 1 1]. We studied a material where stress-induced martensite is stable at room temperature and found surface patterns with four-, two- and threefold symmetries for the [0 0 1], [1 0 1] and [1 1 1] crystallographic indentation directions, respectively. Atomic force microscopy investigations of the topography showed that the surface patterns were associated with sink-ins. The crystallographic sink-in patterns disappeared during heating, which proved their martensitic origin. Our results provide clear experimental evidence which shows that the crystallographic anisotropy of nanoindentation is governed by the crystallographic anisotropy of the stress-induced formation of martensite

The effect of nitrogen on martensite formation in a Cr-Mn-Ni stainless steel

International Nuclear Information System (INIS)

Biggs, T.; Knutsen, R.D.

1995-01-01

The influence of nitrogen (0 to 0.27 wt%) on martensite formation in an experimental low-nickel stainless-steel alloy (Fe-17Cr-7Mn-4Ni) has been investigated. The alloys containing 0.1 wt% or more nitrogen are fully austenitic at room temperature; those containing less nitrogen consist of a mixture of austenite, martensite and δ-ferrite. The alloys containing less than 0.2 wt% nitrogen are metastable and undergo a transformation from austenite to martensite on deformation. Transmission electron microscopy investigations suggest that, within the nitrogen range considered in this investigation, the addition of nitrogen causes an increase in stacking fault energy which in turn inhibits the nucleation of martensite. As the low-nitrogen alloys (less than 0.2 wt% nitrogen) undergo deformation, ε-martensite (with the [ anti 110] γ and [ anti 12 anti 10] ε zone axes parallel) is observed at the intersection of stacking faults. With increasing strain, the presence of α'-martensite is observed in conjunction with the ε-martensite, and only α'-martensite is observed at very high strains. Both the Nishiyama-Wasserman and Kurdjumov-Sachs orientation relationships are observed between austenite and α'-martensite. The transformation to martensite during deformation causes a significant variation in room-temperature mechanical properties, despite the overall narrow range in composition considered. (orig.)

A micromechanical constitutive model for anisotropic cyclic deformation of super-elastic NiTi shape memory alloy single crystals

Science.gov (United States)

Yu, Chao; Kang, Guozheng; Kan, Qianhua

2015-09-01

Based on the experimental observations on the anisotropic cyclic deformation of super-elastic NiTi shape memory alloy single crystals done by Gall and Maier (2002), a crystal plasticity based micromechanical constitutive model is constructed to describe such anisotropic cyclic deformation. To model the internal stress caused by the unmatched inelastic deformation between the austenite and martensite phases on the plastic deformation of austenite phase, 24 induced martensite variants are assumed to be ellipsoidal inclusions with anisotropic elasticity and embedded in the austenite matrix. The homogeneous stress fields in the austenite matrix and each induced martensite variant are obtained by using the Mori-Tanaka homogenization method. Two different inelastic mechanisms, i.e., martensite transformation and transformation-induced plasticity, and their interactions are considered in the proposed model. Following the assumption of instantaneous domain growth (Cherkaoui et al., 1998), the Helmholtz free energy of a representative volume element of a NiTi shape memory single crystal is established and the thermodynamic driving forces of the internal variables are obtained from the dissipative inequalities. The capability of the proposed model to describe the anisotropic cyclic deformation of super-elastic NiTi single crystals is first verified by comparing the predicted results with the experimental ones. It is concluded that the proposed model can capture the main quantitative features observed in the experiments. And then, the proposed model is further used to predict the uniaxial and multiaxial transformation ratchetting of a NiTi single crystal.

Effect of W Contents on Martensitic Transformation and Shape Memory Effect in Co-Al-W Alloys

Science.gov (United States)

Yang, X.; Qian, B. N.; Peng, H. B.; Wu, B. J.; Wen, Y. H.

2018-04-01

To clarify the effect of W contents on the shape memory effect (SME) in the Co-Al alloys and its influencing mechanism, the SME, martensitic transformation, and deformation behavior were studied in the Co-7Al-xW ( x = 0, 4, 6, 9 wt pct) alloys. The results showed that the additions of W all deteriorated the SME in Co-7Al alloy when deformed at room temperature. However, when deformed in liquid nitrogen, the SME in Co-7Al alloy could be remarkably improved from 43 to 78 pct after the addition of 4 pct W, above which the SME decreased rapidly with the increase of W content although the yield strength of the parent phase rose due to the solution strengthening of W. The deterioration in SME induced by the excessive addition of W could be ascribed to its resulting significant drop of the start temperature of martensitic transformation.

Stepwise transformation behavior of the strain-induced martensitic transformation in a metastable stainless steel

International Nuclear Information System (INIS)

Hedstroem, Peter; Lienert, Ulrich; Almer, Jon; Oden, Magnus

2007-01-01

In situ high-energy X-ray diffraction during tensile loading has been used to investigate the evolution of lattice strains and the accompanying strain-induced martensitic transformation in cold-rolled sheets of a metastable stainless steel. At high applied strains the transformation to α-martensite occurs in stepwise bursts. These stepwise transformation events are correlated with stepwise increased lattice strains and peak broadening in the austenite phase. The stepwise transformation arises from growth of α-martensite embryos by autocatalytic transformation

Analysis of recrystallization behavior of hot-deformed austenite reconstructed from electron backscattering diffraction orientation maps of lath martensite

International Nuclear Information System (INIS)

Kubota, Manabu; Ushioda, Kohsaku; Miyamoto, Goro; Furuhara, Tadashi

2016-01-01

The recrystallization behavior of hot-deformed austenite of a 0.55% C steel at 800 °C was investigated by a method of reconstructing the parent austenite orientation map from an electron backscattering diffraction orientation map of lath martensite. Recrystallized austenite grains were clearly distinguished from un-recrystallized austenite grains. Very good correlation was confirmed between the static recrystallization behavior investigated mechanically by double-hit compression tests and the change in austenite microstructure evaluated by the reconstruction method. The recrystallization behavior of hot-deformed 0.55% C steel at 800 °C is directly revealed and it was observed that by addition of 0.1% V the recrystallization was significantly retarded.

Phase transformation and microstructure evolution of the deformed Ti-30Zr-5Nb shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Qu, Wentao, E-mail: wtqu@xsyu.edu.cn [School of Mechanical Engineering, Xi' an Shiyou University, Xi' an 710065 (China); Sun, Xuguang; Yuan, Bifei [School of Mechanical Engineering, Xi' an Shiyou University, Xi' an 710065 (China); Xiong, Chengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Nie, Yongsheng [Lanzhou Seemine SMA Co. Ltd., Lanzhou 730010 (China)

2017-04-15

The phase transformation and microstructures of the deformed Ti-30Zr-5Nb shape memory alloy were investigated. The X-ray diffraction measurements indicated that the Ti-30Zr-5Nb alloy was composed of a single orthorhombic α″-martensite phase. The alloy exhibited one yielding behavior in the tensile test, with a critical stress of ~ 600 MPa and a tensile strain of approximately 15%. A shape memory recovery accompanied by a permanent strain was exhibited in the deformed alloys when heated at 873 K. The permanent strain increased with increasing pre-strain. The microstructure evolution of the deformed alloy was investigated by transmission electron microscopy. The results showed that the martensite reorientation occurred and the dislocations were generated during deformation. The alloy displayed a reversible martensite transformation start temperature as high as 763 K. However, no strain-induced martensite stabilization was found in the deformed alloy with different pre-strain levels, potentially because the large chemical energy of the Ti-30Zr-5Nb alloy depressed the effects of the elastic energy and the dissipative energy. - Highlights: • Ti-30Zr-5Nb alloy is composed of single orthorhombic α″-martensite phase with M{sub s} of 721 K. • No martensite stabilization has been found in Ti-30Zr-5Nb alloy with different pre-strain. • Ti-30Zr-5Nb shows the maximum shape memory effect of 2.75% with a pre-strain of 8%.

Correlation between microstructure and mechanical properties of stable mixtures formed by austenite and martensite

International Nuclear Information System (INIS)

Eckstein, C.B.

1982-03-01

The influence of martensite in mechanical properties of stable mixtures formed by austenite and martensite was studied by varying the amount of martensite in the mixtures. Microstructural parameters were determined by Optical Quantitative Metallography and used to establish the correlation between the mechanical response of the mixtures in tension and their microstructures. The 'in situ' deformation of each phase in mixtures was determined experimentally in terms of the rule of mixtures. It is shown that the partitioning of the deformation depends on the amount of martensite in the mixture and that it tends to a condition of isostrain at higher martensite volume fractions. Optical observation of fractured specimens showed that the beginning of the fracture process may related to regions of the austenite grain boundaries where they meet martensite plates. (Author) [pt

Effect of martensitic phase transformation on the hardening behavior and texture evolution in a 304L stainless steel under compression at liquid nitrogen temperature

Energy Technology Data Exchange (ETDEWEB)

Cakmak, Ercan [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States); Vogel, Sven C. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Choo, Hahn, E-mail: hchoo@utk.edu [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States)

2014-01-01

The martensitic phase transformation behavior and its relations with the macroscopic hardening rate and the evolutions in the crystallographic texture of the constituent phases were studied for a 304L stainless steel that exhibits the transformation induced plasticity (TRIP) phenomenon. Time-of-flight neutron diffraction was used to measure the evolutions of phase fractions and texture in terms of pole figures as a function of the applied compressive strain at the liquid nitrogen temperature (77 K). The phase transformation analyses show that the hcp-martensite phase fraction reaches a significant level of about 22 wt% at 15% applied strain and remains constant. The bcc-martensite phase fraction increases continuously with the deformation that correlates well with the macroscopic hardening behavior. Furthermore, the texture analyses show that transformation has dominant effect on the bcc-martensite texture evolution with little influence from subsequent plastic deformation at current testing conditions.

Effect of martensitic phase transformation on the hardening behavior and texture evolution in a 304L stainless steel under compression at liquid nitrogen temperature

International Nuclear Information System (INIS)

Cakmak, Ercan; Vogel, Sven C.; Choo, Hahn

2014-01-01

The martensitic phase transformation behavior and its relations with the macroscopic hardening rate and the evolutions in the crystallographic texture of the constituent phases were studied for a 304L stainless steel that exhibits the transformation induced plasticity (TRIP) phenomenon. Time-of-flight neutron diffraction was used to measure the evolutions of phase fractions and texture in terms of pole figures as a function of the applied compressive strain at the liquid nitrogen temperature (77 K). The phase transformation analyses show that the hcp-martensite phase fraction reaches a significant level of about 22 wt% at 15% applied strain and remains constant. The bcc-martensite phase fraction increases continuously with the deformation that correlates well with the macroscopic hardening behavior. Furthermore, the texture analyses show that transformation has dominant effect on the bcc-martensite texture evolution with little influence from subsequent plastic deformation at current testing conditions

Deformation of shape memory alloys associated with twinned domain re-configurations

International Nuclear Information System (INIS)

Liu Yong; Van Humbeeck, J.; Xie Zeliang; Delaey, L.

1999-01-01

Most of the applications of shape memory alloys (SMAs) imply deformation of martensite; it is therefore one of the fundamental research topics on the shape memory effect. So far, several classifications of the deformation mechanisms have been made as a function of deformation amplitude. However, the deformation details of martensitic SMAs are still not yet satisfactorily understood and these classifications need to be refined, because several incoherencies have been found lately by mechanical testing and transmission electron microscopy (TEM) observations. The present work summarizes some new results on the deformation mechanisms of martensitic NiTi SMAs under tension. As a result, the deformation process of martensite twins as a function of the deformation strain amplitude is refined. (orig.)

Plastic strain induced damage evolution and martensitic transformation in ductile materials at cryogenic temperatures

International Nuclear Information System (INIS)

Garion, C.; Skoczen, B.T.

2002-01-01

The Fe-Cr-Ni stainless steels are well known for their ductile behavior at cryogenic temperatures. This implies development and evolution of plastic strain fields in the stainless steel components subjected to thermo-mechanical loads at low temperatures. The evolution of plastic strain fields is usually associated with two phenomena: ductile damage and strain induced martensitic transformation. Ductile damage is described by the kinetic law of damage evolution. Here, the assumption of isotropic distribution of damage (microcracks and microvoids) in the Representative Volume Element (RVE) is made. Formation of the plastic strain induced martensite (irreversible process) leads to the presence of quasi-rigid inclusions of martensite in the austenitic matrix. The amount of martensite platelets in the RVE depends on the intensity of the plastic strain fields and on the temperature. The evolution of the volume fraction of martensite is governed by a kinetic law based on the accumulated plastic strain. Both of these irreversible phenomena, associated with the dissipation of plastic power, are included into the constitutive model of stainless steels at cryogenic temperatures. The model is tested on the thin-walled corrugated shells (known as bellows expansion joints) used in the interconnections of the Large Hadron Collider, the new proton storage ring being constructed at present at CERN

Low temperature tensile deformation and acoustic emission signal characteristics of AISI 304LN stainless steel

Energy Technology Data Exchange (ETDEWEB)

Barat, K.; Bar, H.N. [Material Science and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Mandal, D. [Material Processing and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Roy, H., E-mail: himadri9504@gmail.com [NDT and Metallurgy Group, CSIR-Central Mechanical Engineering Research Institute, Durgapur 713209 (India); Sivaprasad, S.; Tarafder, S. [Material Science and Technology Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India)

2014-03-01

This investigation examines low temperature tensile deformation behavior of AISI 304LN stainless steel along with synergistic analysis of acoustic emission signals. The tensile tests are done at a range of temperatures starting from 283 K till 223 K. The fracture surfaces of the broken specimens are investigated using scanning electron microscope. The amount of deformation induced martensite is measured using a feritscope. The obtained results reveal that with decrease in test temperature, both strength and ductility increase. The increase in strength and ductility with decreasing temperature is explained in terms of void morphologies and formation of deformation induced martensite. The rapid increment in strength and ductility at 223 K is associated with the burst of martensitic transformation at that temperature; which has been clarified from acoustic emission signals. An additional initiative has been taken to model the evolution of martensite formation from the observed cumulative emission counts using a non linear logarithmic functional form. The fitted curves from the recorded acoustic emission cumulative count data are found to be better correlated compared to earlier obtained results. However, at 223 K normal non-linear logarithmic fit is not found suitable due to presence of burst type signals at intervals, therefore; piecewise logarithmic function to model acoustic emission bursts is proposed.

Quantitative analysis of stress-induced martensites by in situ transmission electron microscopy superelastic tests in Cu-Al-Ni shape memory alloys

International Nuclear Information System (INIS)

No, M.L.; Ibarra, A.; Caillard, D.; San Juan, J.

2010-01-01

Stress-induced martensite nucleation and further growing, in Cu-Al-Ni shape memory alloys, have been studied during in situ superelastic tests in the transmission electron microscope. Two kinds of martensite, β 3 ' and γ 3 ' , are induced and can coexist under stress, both exhibiting in a high density of stacking faults. The interface plane and the orientation relationships between the different variants of such martensites have been determined, and the atomic configurations of the lattices across the interface have been described. Finally, in light of the results, selection rules for the stress-induced promoted martensites at the nano-scale have been established, being determined by the shear direction and the basal plane of the martensite lattice.

Direct evidence for stress-induced transformation between coexisting multiple martensites in a Ni–Mn–Ga multifunctional alloy

International Nuclear Information System (INIS)

Huang, L; Cong, D Y; Dong, Y H; Zhang, Y; Wang, Y D; Wang, Z L; Nie, Z H; Ren, Y

2015-01-01

The structural response of coexisting multiple martensites to stress field in a Ni–Mn–Ga multifunctional alloy was investigated by the in situ high-energy x-ray diffraction technique. Stress-induced transformation between coexisting multiple martensites was observed at 110 K, at which five-layered modulated (5M), seven-layered modulated (7M) and non-modulated (NM) martensites coexist. We found that a tiny stress of as low as 0.5 MPa could trigger the transformation from 5M and 7M martensites to NM martensite and this transformation is partly reversible. Besides the transformation between coexisting multiple martensites, rearrangement of martensite variants also occurs during loading, at least at high stress levels. The present study is instructive for designing advanced multifunctional alloys with easy actuation. (paper)

The effect of alloying and treatment on martensite transformation during deformation in Fe-Cr-Mn steels with unstable austenite

International Nuclear Information System (INIS)

Malinov, L.S.; Konop, V.I.; Sokolov, K.N.

1977-01-01

The effect is studied of alloying with chromium (6-10%), silicon (1-2%), molybdenum (1-3%), and copper (2%), the heat treatment conditions, and the deformation conditions, or the martensitic transformation and mechanical properties of Fe-Cr-Mn steels of the transitional class based on 0G8AM2S. It is shown that appropriate alloying and treatment, taking into account the degree of stability of the austenite, can ensure a complex of high mechanical properties of the steels investigated. For instance, the treatment of steel 0Kh10AG8MD2S by the technique: hardening+ 40% deformation at 400 deg C + 10% deformation at room temperature has yielded the following mechanical properties: sigmasub(B)=150 kgf/mm 2 , sigmasub(T)=110 kgf/mm 2 , sigma=18%, psi=32%

Stress- and Magnetic Field-Induced Martensitic Transformation at Cryogenic Temperatures in Fe-Mn-Al-Ni Shape Memory Alloys

Science.gov (United States)

Xia, Ji; Xu, Xiao; Miyake, Atsushi; Kimura, Yuta; Omori, Toshihiro; Tokunaga, Masashi; Kainuma, Ryosuke

2017-12-01

Stress-induced and magnetic-field-induced martensitic transformation behaviors at low temperatures were investigated for Fe-Mn-Al-Ni alloys. The magnetic-field-induced reverse martensitic transformation was directly observed by in situ optical microscopy. Magnetization measurements under pulsed magnetic fields up to 50 T were carried out at temperatures between 4.2 and 125 K on a single-crystal sample; full magnetic-field-induced reverse martensitic transformation was confirmed at all tested temperatures. Compression tests from 10 to 100 K were conducted on a single-crystal sample; full shape recovery was obtained at all tested temperatures. It was found that the temperature dependence of both the critical stress and critical magnetic field is small and that the transformation hysteresis is less sensitive to temperature even at cryogenic temperatures. The temperature dependence of entropy change during martensitic transformation up to 100 K was then derived using the Clausius-Clapeyron relation with critical stresses and magnetic fields.

Nanoscale multiphase phase field approach for stress- and temperature-induced martensitic phase transformations with interfacial stresses at finite strains

Science.gov (United States)

Basak, Anup; Levitas, Valery I.

2018-04-01

A thermodynamically consistent, novel multiphase phase field approach for stress- and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic models (KMs) for the transformation deformation gradient tensors are assumed: (i) In KM-I the transformation deformation gradient tensor is a linear function of the Bain tensors for the variants. (ii) In KM-II the natural logarithms of the transformation deformation gradient is taken as a linear combination of the natural logarithm of the Bain tensors multiplied with the interpolation functions. (iii) In KM-III it is derived using the twinning equation from the crystallographic theory. The instability criteria for all the phase transformations have been derived for all the kinematic models, and their comparative study is presented. A large strain finite element procedure has been developed and used for studying the evolution of some complex microstructures in nanoscale samples under various loading conditions. Also, the stresses within variant-variant boundaries, the sample size effect, effect of penalizing the triple junctions, and twinned microstructures have been studied. The present approach can be extended for studying grain growth, solidifications, para↔ferro electric transformations, and diffusive phase transformations.

Martensitic transformation in SUS304 steels with the same Ni equivalent

International Nuclear Information System (INIS)

Ueda, T.; Okino, Y.; Takahashi, S.; Echigoya, J.; Kamada, Y.

2003-01-01

The behavior of martensitic transformation due to plastic deformation at room temperature was investigated in SUS304 austenitic stainless steels with the same nickel equivalent. The absolute volume of the martensitic phase was obtained by saturation magnetization. We discuss the shapes of the martensitic phase caused by different values of coercive force. Martensitic transformation depends on the applied stress but is independent of nickel content with same nickel equivalent. We investigated applications to nondestructive testing on the basis of the present study. (author)

Hot Deformation Behavior of 1Cr12Ni3Mo2VN Martensitic Stainless Steel

Science.gov (United States)

He, Xiaomao; Jiang, Peng; Zhou, Leyu; Chen, Chao; Deng, Xiaochun

2017-08-01

1Cr12Ni3Mo2VN is a new type of martensitic stainless steel for the last-stage blades of large-capacity nuclear and thermal power turbines. The deformation behavior of this steel was studied by thermal compression experiments that performed on a Gleeble-3500 thermal simulator at a temperature range of 850°C to 1200°C and a strain rate of 0.01s-1 to 20s-1. When the deformation was performed at high temperature and low strain rate, a necklace type of microstructures was observed, the plastic deformation mechanism is grain boundary slip and migration, when at low temperature and lower strain rate, the slip bands were observed, the mechanism is intracrystalline slips, and when at strain rate of 20s-1, twins were observed, the mechanism are slips and twins. The Arrhenius equation was applied to describe the constitutive equation of the flow stress. The accuracy of the equation was verified by using the experimental data and the correlation coefficient R2 = 0.9786, and the equation can provide reasonable data for the design and numerical simulation of the forging process.

The mechanism of bcc α′ nucleation in single hcp ε laths in the fcc γ → hcp ε → bcc α′ martensitic phase transformation

International Nuclear Information System (INIS)

Yang, Xu-Sheng; Sun, Sheng; Zhang, Tong-Yi

2015-01-01

High Resolution Transmission Electron Microscopy (HRTEM) and Molecular Dynamics (MD) simulations were conducted here to study the plastic deformation induced γ (fcc) → ε (hcp) → α′ (bcc) martensitic transformation in 304 stainless steels for the α′ nucleation from single hcp-ε laths. Results elucidate that the underlying microscopic mechanism for the α′ nucleation from single hcp-ε laths obeys the Bogers–Burgers–Olson–Cohen “3T/8–T/3” model. In particular, the atomic-scale observations clearly show the Kurdyumov–Sachs (K–S) lattice orientation relation (OR) and Pitsch OR at the γ/α′ interfaces, the lattice rotation inside an α′ martensitic inclusion, the transition lattice and the reverse shear-shuffling induced continuous lattice elastic deformation at the diffuse ε/α′ interface, which caters the 3T/8 and T/3 shears and sheds atomic process insight into the mechanism of the martensitic transformation

Deformation-Induced Microstructural Banding in TRIP Steels

Science.gov (United States)

Celotto, S.; Ghadbeigi, H.; Pinna, C.; Shollock, B. A.; Efthymiadis, P.

2018-05-01

Microstructure inhomogeneities can strongly influence the mechanical properties of advanced high-strength steels in a detrimental manner. This study of a transformation-induced plasticity (TRIP) steel investigates the effect of pre-existing contiguous grain boundary networks (CGBNs) of hard second-phases and shows how these develop into bands during tensile testing using in situ observations in conjunction with digital image correlation (DIC). The bands form by the lateral contraction of the soft ferrite matrix, which rotates and displaces the CGBNs of second-phases and the individual features within them to become aligned with the loading direction. The more extensive pre-existing CGBNs that were before the deformation already aligned with the loading direction are the most critical microstructural feature for damage initiation and propagation. They induce micro-void formation between the hard second-phases along them, which coalesce and develop into long macroscopic fissures. The hard phases, retained austenite and martensite, were not differentiated as it was found that the individual phases do not play a role in the formation of these bands. It is suggested that minimizing the presence of CGBNs of hard second-phases in the initial microstructure will increase the formability.

Continuous AFM observation of martensitic transformation and its reversion in training cycles of Fe-Mn-Si based shape memory alloys

International Nuclear Information System (INIS)

Liu, D.Z.; Kikuchi, T.; Kajiwara, S.; Shinya, N.

2000-01-01

The effect of thermomechanical treatment (so-called ''training'') cycles on stress-induced martensitic transformation and its reversion has been studied by atomic force microscopy (AFM) to make clear the origin of improvement of shape memory effect (SME) due to training in Fe-Mn-Si based shape memory alloys (SMAs). It was found that training cycles make martensite plates tend to grow on the primary shear system, i.e., on the most favorable shear system for the fcc to hcp martensitic transformation. In addition, training cycles lead to a more uniform distribution of thin martensite plates in a grain. Martensitic plates with the above characteristics are easier to be reverted back to parent phase when heated, and then nearly perfect SME is obtained. AFM observation shows that the key factor to realize perfect SME in Fe-Mn-Si based SMAs is to produce the uniform distribution of thin martensite plates on the primary shear system when deformed by external stress. (orig.)

Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

International Nuclear Information System (INIS)

Molnar, P.; Sittner, P.; Novak, V.; Lukas, P.

2008-01-01

A neutron single crystal diffraction method for inspecting the quality of martensite single crystals is introduced. True interface-free martensite single crystals are indispensable for, e.g. measurement of elastic constants of phases by ultrasonic techniques. The neutron diffraction method was used to detect and distinguish the presence of individual lattice correspondence variants of the 2H orthorhombic martensite phase in Cu-Al-Ni as well as to follow the activity of twinning processes during the deformation test on the martensite variant single crystals. When preparing the martensite single variant prism-shaped crystals by compression deformation method, typically a small fraction of second unwanted martensitic variant (compound twin) remains in the prism samples. Due to the very low stress (∼1 MPa) for the compound twinning in many shape memory alloys, it is quite difficult not only to deplete the martensite prisms of all internal interfaces but mainly to keep them in the martensite single variant state for a long time needed for further investigations

Effect of strain-induced martensitic transformation on high cycle fatigue behavior in cyclically-prestrained type 304

International Nuclear Information System (INIS)

Uematsu, Yoshihiko; Kakiuchi, Toshifumi; Akita, Masayuki; Nakajima, Masaki; Nakamura, Yuki; Yajima, Takumi

2013-01-01

The effects of the cyclic prestrain on the fatigue behavior in type 304 austenitic stainless steel were investigated. Rotating bending fatigue tests have been performed in laboratory air using the specimens subjected to ±5% cyclic prestrain at room temperature (R.T.) and -5°C. Martensitic phase volume fraction of the prestrained specimen at -5°C was 48% and larger than 3.8% at R.T. The prestrained specimens exhibited higher fatigue strengths than the as-received ones, and larger volume fraction of martensitic phase resulted in the higher fatigue limit. EBSD analysis revealed that the martensitic phases were more uniformly distributed in the austenitic matrix in the cyclically-prestrained specimens than in the monotonically-prestrained ones. Fatigue crack initiation from inclusion was observed only in the cyclically-prestrained specimens at -5°C. High volume fraction and uniform distribution of martensitic phase induced the transition of crack initiation mechanism and led to the higher fatigue limit. In type 304 stainless steel with high volume fraction of strain-induced martensitic phase, the prediction of fatigue limit based on Vickers hardness could give unconservative results. (author)

Martensitic phase transformations in the nanostructured surface layers induced by mechanical attrition treatment

International Nuclear Information System (INIS)

Ni Zhichun; Wang Xiaowei; Wu Erdong; Liu Gang

2005-01-01

Conversion electron Moessbauer spectroscopy (CEMS) and x-ray diffraction (XRD) analysis have been used to investigate the relationship between characteristics of phase transformation and the treatment time in surface nanocrystallized 316L stainless steel induced by surface mechanical attrition treatment (SMAT). A similar trend of development of the martensitic phase upon the treatment time has been observed from both CEMS and XRD measurements. However, in the CEMS measurement, two types of martensite phase with different magnetic hyperfine fields are revealed. Based on a random distribution of the non-iron coordinating atoms, a three-element theoretical model is developed to illustrate the difference of two types of martensite phase. The calculated results indicate the segregation of the non-iron atoms associated with SMAT treatment

Analysis of martensitic transformation and residual tension in an 304L stainless steel; Analise da transformacao martensitica e tensao residual em um aco inoxidavel 304L

Energy Technology Data Exchange (ETDEWEB)

Alves, Juciane Maria

2014-07-01

The relationship between plastic deformation and the strain induced phase transformation, that provides a practical route to the development of new engineering materials with excellent mechanical properties, characterize the TRIP effect 'Transformation Induced Plasticity'. Among the stainless steels, the metastable 304 L austenitic steel is susceptible to transformation of austenite-martensite phase from tensile tests at room temperature by increments of plastic deformation. It is of great technological and scientific interest the knowledge of the evolution of phase transformation and residual stress from different levels and rates of plastic deformation imposed to the material. It is also important to evaluate the interference of metallographic preparation in quantitative analyzes of this steel. The main techniques used in this study consisted of X-rays diffraction and Ferritoscopy for the quantitation phase, and XRD to residual stress analysis also. As observed, the phase transformation quantification has not suffered significant influence of the metallographic preparation and evolved from increments of plastic deformation due to different stop charges and strain rates, leading to a further strengthening of the austenite matrix. The evaluation of residual stress resulting from the martensitic transformation was susceptible to the metallographic preparation and increased its value on comparison to sample without metallographic preparation. It was also observed that the residual stress decreased with the increase of the fraction of transformed martensite. (author)

Transformation-Induced Creep and Creep Recovery of Shape Memory Alloy.

Science.gov (United States)

Takeda, Kohei; Tobushi, Hisaaki; Pieczyska, Elzbieta A

2012-05-22

If the shape memory alloy is subjected to the subloop loading under the stress-controlled condition, creep and creep recovery can appear based on the martensitic transformation. In the design of shape memory alloy elements, these deformation properties are important since the deflection of shape memory alloy elements can change under constant stress. The conditions for the progress of the martensitic transformation are discussed based on the kinetics of the martensitic transformation for the shape memory alloy. During loading under constant stress rate, temperature increases due to the stress-induced martensitic transformation. If stress is held constant during the martensitic transformation stage in the loading process, temperature decreases and the condition for the progress of the martensitic transformation is satisfied, resulting in the transformation-induced creep deformation. If stress is held constant during the reverse transformation stage in the unloading process, creep recovery appears due to the reverse transformation. The details for these thermomechanical properties are investigated experimentally for TiNi shape memory alloy, which is most widely used in practical applications. The volume fraction of the martensitic phase increases in proportion to an increase in creep strain.

Creep deformation and rupture behaviour of 9Cr–1W–0.2V–0.06Ta Reduced Activation Ferritic–Martensitic steel

International Nuclear Information System (INIS)

Vanaja, J.; Laha, K.; Mythili, R.; Chandravathi, K.S.; Saroja, S.; Mathew, M.D.

2012-01-01

Highlights: ► Creep tests on broad temperature and stress ranges were carried out. ► Microstructural instability on creep and thermal exposures were studied using TEM. ► Creep damage tolerance factor of the material was estimated. - Abstract: This paper presents the creep deformation and rupture behaviour of indigenously produced 9Cr–1W–0.2V–0.06Ta Reduced Activation Ferritic–Martensitic (RAFM) steel for fusion reactor application. Creep studies were carried out at 773, 823 and 873 K over a stress range of 100–300 MPa. The creep deformation of the steel was found to proceed with relatively shorter primary regime followed by an extended tertiary regime with virtually no secondary regime. The variation of minimum creep rate of the material with applied stress followed a power law relation, ε m = Aσ n , with stress exponent value ‘n’ decreasing with increase in temperature. The product of minimum creep rate and creep rupture life was found to obey the modified Monkman–Grant relation. The time to onset of tertiary stage of deformation was directly proportional to rupture life. TEM studies revealed relatively large changes in martensitic sub-structure and coarsening of precipitates in the steel on creep exposure as compared to thermal exposure. Microstructural degradation was considered as the prime cause of extended tertiary stage of creep deformation, which was also reflected in the damage tolerance factor λ with a value more than 2.5. In view of the microstructural instability of the material on creep exposure, the variation of minimum creep rate with stress and temperature did not obey Dorn's equation modified by invoking Lagneborg and Bergman's concepts of back stress.

Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi

International Nuclear Information System (INIS)

Katanchi, B.; Choupani, N.; Khalil-Allafi, J.; Baghani, M.

2017-01-01

Phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress induced martensite phase transformation in a superelastic NiTi (50.8% Ni) shape memory alloy was investigated by using the photo-stress method. First, the material's fabrication procedure has been described and then the material was studied using the metallurgical tests such as differential scanning calorimetry and X-ray diffraction to characterize the material features and the mechanical tensile test to investigate the superelastic behavior. As a new method in observation of the phase transformation, photo-stress pictures showed the formation of stress induced martensite in a superelastic dog-bone specimen during loading and subsequently it's disappearing during unloading. Finally, finite element analysis was implemented using the constitutive equations derived based on the Boyd-Lagoudas phenomenological model.

Photostress analysis of stress-induced martensite phase transformation in superelastic NiTi

Energy Technology Data Exchange (ETDEWEB)

Katanchi, B. [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Choupani, N., E-mail: choupani@sut.ac.ir [Mechanical Engineering Faculty, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Khalil-Allafi, J. [Research Center for Advance Materials, Faculty of Materials Engineering, Sahand University of Technology, Tabriz (Iran, Islamic Republic of); Baghani, M. [School of Mechanical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of)

2017-03-14

Phase transformation in shape memory alloys is the most important factor in their unique behavior. In this paper, the formation of stress induced martensite phase transformation in a superelastic NiTi (50.8% Ni) shape memory alloy was investigated by using the photo-stress method. First, the material's fabrication procedure has been described and then the material was studied using the metallurgical tests such as differential scanning calorimetry and X-ray diffraction to characterize the material features and the mechanical tensile test to investigate the superelastic behavior. As a new method in observation of the phase transformation, photo-stress pictures showed the formation of stress induced martensite in a superelastic dog-bone specimen during loading and subsequently it's disappearing during unloading. Finally, finite element analysis was implemented using the constitutive equations derived based on the Boyd-Lagoudas phenomenological model.

A phase-field study of the physical concepts of martensitic transformations in steels

International Nuclear Information System (INIS)

Yeddu, Hemantha Kumar; Borgenstam, Annika; Hedström, Peter; Ågren, John

2012-01-01

Highlights: ► Critical driving forces associated with martensitic transformation are estimated. ► Plastic relaxation rate affects the transformation and microstructure evolution. ► Low relaxation rate promotes multi-domained martensitic microstructure. ► High relaxation rate promotes growth of a single martensite domain. ► The model predicts the final habit plane of martensite to be (−2 1 1) γ . - Abstract: A 3D elastoplastic phase-field model is employed to study various driving forces associated with martensitic transformations, plastic deformation behavior as well as the habit plane concept. Usage of thermodynamic parameters corresponding to Fe–0.3%C alloy in conjunction with anisotropic physical parameters of steels as the simulation parameters have yielded the results in reasonable agreement with experimental observations. From the simulation results, it is concluded that there exist three critical driving forces that control the transformation and also that the plastic deformation behavior of the material greatly affects the transformation. The model predicts the initial habit plane of the first infinitesimal unit of martensite as (−1 1 1). The model also predicts that, as the transformation progresses, the above mentioned martensite domain rotates and finally orients along the new habit plane of (−2 1 1).

The mechanism of strength and deformation in Gum Metal

International Nuclear Information System (INIS)

Furuta, T.; Kuramoto, S.; Morris, J.W.; Nagasako, N.; Withey, E.; Chrzan, D.C.

2013-01-01

“Gum Metal” refers to β-Ti alloys that achieve exceptional elastic elongation and, with a specific alloy composition, appear to deform via a dislocation-free mechanism involving elastic instability at the limit of strength. This paper describes the current status of research on its strength, deformation mechanism and the possible role of stress-induced martensite. The theoretical basis for deformation at ideal strength is presented. The relevant experimental data is then discussed, including ex situ nanoindentation behavior and in situ pillar compression observed by transmission electron microscopy

Ultrasound-induced martensitic transition in ferromagnetic Ni2.15Mn0.81Fe0.04Ga shape memory alloy

International Nuclear Information System (INIS)

Buchelnikov, V.; Dikshtein, I.; Grechishkin, R.; Khudoverdyan, T.; Koledov, V.; Kuzavko, Y.; Nazarkin, I.; Shavrov, V.; Takagi, T.

2004-01-01

The experimental observation of direct and reverse martensitic transformation due to ultrasound processing of Ni-Mn-Ga alloy is discussed. It was found that martensite-austenite as well as austenite-martensite structural transitions can be induced by the intense ultrasound at constant temperature. During the experiments low magnetic field susceptibility measurements and optical detection of twin domains arising due to martensitic transformation were performed in situ. The non-thermal nature of the effect is confirmed making use of the pulsed ultrasound technique

Numerical Study of the Plasticity-Induced Stabilization Effect on Martensitic Transformations in Shape Memory Alloys

Science.gov (United States)

Junker, Philipp; Hempel, Philipp

2017-12-01

It is well known that plastic deformations in shape memory alloys stabilize the martensitic phase. Furthermore, the knowledge concerning the plastic state is crucial for a reliable sustainability analysis of construction parts. Numerical simulations serve as a tool for the realistic investigation of the complex interactions between phase transformations and plastic deformations. To account also for irreversible deformations, we expand an energy-based material model by including a non-linear isotropic hardening plasticity model. An implementation of this material model into commercial finite element programs, e.g., Abaqus, offers the opportunity to analyze entire structural components at low costs and fast computation times. Along with the theoretical derivation and expansion of the model, several simulation results for various boundary value problems are presented and interpreted for improved construction designing.

Grain-resolved analysis of localized deformation in nickel-titanium wire under tensile load.

Science.gov (United States)

Sedmák, P; Pilch, J; Heller, L; Kopeček, J; Wright, J; Sedlák, P; Frost, M; Šittner, P

2016-08-05

The stress-induced martensitic transformation in tensioned nickel-titanium shape-memory alloys proceeds by propagation of macroscopic fronts of localized deformation. We used three-dimensional synchrotron x-ray diffraction to image at micrometer-scale resolution the grain-resolved elastic strains and stresses in austenite around one such front in a prestrained nickel-titanium wire. We found that the local stresses in austenite grains are modified ahead of the nose cone-shaped buried interface where the martensitic transformation begins. Elevated shear stresses at the cone interface explain why the martensitic transformation proceeds in a localized manner. We established the crossover from stresses in individual grains to a continuum macroscopic internal stress field in the wire and rationalized the experimentally observed internal stress field and the topology of the macroscopic front by means of finite element simulations of the localized deformation. Copyright © 2016, American Association for the Advancement of Science.

Martensite. gamma. -->. cap alpha. transformations in various purity Fe-Ni-Mo alloys

Energy Technology Data Exchange (ETDEWEB)

Nikitina, I.I.; Rozhkova, A.S. (Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR))

1982-06-01

Kinetics of isothermal and athermal ..gamma.. ..-->.. ..cap alpha.. martensitic transitions in the Fe-25.5% Ni-4.5% Mo alloys with different degree of purity is studied. The determinant role of dislocation blocking by interstitials in stabilization of isothermal martensitic transformation is displayed. Presented are the data permitting to consider that the character of martensitic transition kinetics is determined by the ratio of the process moving force and resistance to microplastic deformation.

Leaf-like dislocation substructures and the decrease of martensitic start temperatures: A new explanation for functional fatigue during thermally induced martensitic transformations in coarse-grained Ni-rich Ti–Ni shape memory alloys

International Nuclear Information System (INIS)

Zhang Jian; Somsen, Christoph; Simon, Tobias; Ding Xiangdong; Hou Sen; Ren Shuai; Ren Xiaobing; Eggeler, Gunther

2012-01-01

During repeatedly imposed thermally induced martensitic transformations in Ti–Ni shape memory alloys, the martensite start temperature M s decreases. This has been rationalized on the basis of a scenario where an increasing dislocation density makes it more and more difficult for martensite to form. However, it is not clear why dislocations which form because they accommodate the growth of martensite during the first cooling cycle should act as obstacles during subsequent transformation cycles. In the present work we use diffraction contrast transmission electron microscopy to monitor the formation of unique leaf-like dislocation substructures which form as the martensite start temperature decreases during thermal cycling. We interpret our microstructural results on the basis of a microstructural scenario where dislocations play different roles with respect to the propagation of a big martensite needle in one transformation cycle and the nucleation and growth of new martensite needles in the following cycles. As a consequence, chestnut-leaf-like dislocation arrays spread out in different crystallographic directions.

Vibration mitigation by the reversible fcc/hcp martensitic transformation during cyclic tension-compression loading of an Fe-Mn-Si-based shape memory alloy

International Nuclear Information System (INIS)

Sawaguchi, Takahiro; Sahu, Puspendu; Kikuchi, Takehiko; Ogawa, Kazuyuki; Kajiwara, Setsuo; Kushibe, Atsumichi; Higashino, Masahiko; Ogawa, Takatoshi

2006-01-01

The present work concerns the damping behavior of an Fe-28Mn-6Si-5Cr-0.5NbC (mass%) shape memory alloy determined by low cycle fatigue tests, and the corresponding deformation mechanism under cyclic tension-compression loading. The specific damping capacity increases with increasing strain amplitude and reaches saturation at ∼80%, above the strain amplitude of 0.4%. Quantitative X-ray diffraction analyses and microstructural observations using atomic force microscopy revealed that a significant amount of the tensile stress-induced ε martensite is reversely transformed into the austenite by subsequent compression; in other words, the stress-induced 'reverse' martensitic transformation takes place in the alloy

Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

Directory of Open Access Journals (Sweden)

Heinz Werner Höppel

2012-02-01

Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

The γ-ε martensitic transformation: a model for stress induced variant and its interaction with grain boundary

International Nuclear Information System (INIS)

Guenin, G.

1995-01-01

The γ (f.c.c.) to ε (h.c.p.) martensitic transformation occurs through the Shockley a/6 left angle 211 right angle faulting every second {111} plane of the f.c.c. structure. A stress induced thin single variant corresponds to a single a/6 left angle 211 right angle faulting vector and leads to a large homogeneous shear (0.35) in amplitude. The tip of such a plate is composed of a set of identical Shockley partial dislocations with large mutual interactions. This work is a presentation of a model which describes the martensite morphology of stress induced ε martensite in shape memory Fe-Mn-Si based alloys. The model includes the formation mechanism of the plate (Seeger's like) and its growth inside a limited grain. The mutual interaction of Shockley dislocations and their interaction with the grain boundary is semi quantitatively described; it leads to a lenticular shape of ε martensite thin plates. The model is able to explain the behaviour of this kind of alloys concerning the superelastic effect and the shape memory. (orig.)

Martensitic transition near room temperature and the temperature- and magnetic-field-induced multifunctional properties of Ni49CuMn34In16 alloy

Science.gov (United States)

Sharma, V. K.; Chattopadhyay, M. K.; Khandelwal, A.; Roy, S. B.

2010-11-01

A near room-temperature martensitic transition is observed in the ferromagnetic austenite state of Ni50Mn34In16 alloy with 2% Cu substitution at the Ni site. Application of magnetic field in the martensite state induces a reverse martensitic transition in this alloy. dc magnetization, magnetoresistance and strain measurements in this alloy reveal that associated with this martensitic transition there exist a large magnetocaloric effect, a large magnetoresitance and a magnetic-field temperature-induced strain. This NiMnIn alloy system thus is an example of an emerging class of magnetic materials whose physical properties can be tuned by suitable chemical substitutions, to achieve magnetic-field and temperature-induced multifunctional properties at and around room temperature

Influence of strain-induced martensitic transformation on fatigue short crack behaviour in an austenitic stainless steel

International Nuclear Information System (INIS)

Baffie, N.; Stolarz, J.; Magnin, Th.

2000-01-01

The influence of martensitic transformation induced by cyclic straining on the mechanisms of low cycle fatigue damage in a metastable austenitic stainless steel with different grain sizes has been investigated using macroscopic measurements and microscopic observations of short crack evolutions. The amount of martensite formed during cyclic straining increases with increasing plastic strain amplitude and cumulative plastic strain but the dominant parameter is the grain size of austenite. The fine microstructure (D = 10 μm) with maximum martensite fraction of about 20% is characterised by a better fatigue resistance than the coarse one (D 40μm and only 2% of martensite) for the same plastic strain amplitude. Martensitic transformation is found to radically modify the cyclic response of the alloy and consequently the damage mechanisms. Indeed, both short crack nucleation and growth take place exclusively in the transformed regions. A mechanism of short crack propagation based on the γ→ α' transformation assisted by stress concentration at the crack tip is proposed. The indirect influence of grain boundaries in the austenite on crack propagation in the martensite is demonstrated. The better fatigue resistance of metastable alloys with fine granular structure can thus be understood. (authors)

Effect of hardness of martensite and ferrite on void formation in dual phase steel

DEFF Research Database (Denmark)

Azuma, M.; Goutianos, Stergios; Hansen, Niels

2012-01-01

The influence of the hardness of martensite and ferrite phases in dual phase steel on void formation has been investigated by in situ tensile loading in a scanning electron microscope. Microstructural observations have shown that most voids form in martensite by evolving four steps: plastic...... deformation of martensite, crack initiation at the martensite/ferrite interface, crack propagation leading to fracture of martensite particles and void formation by separation of particle fragments. It has been identified that the hardness effect is associated with the following aspects: strain partitioning...... between martensite and ferrite, strain localisation and critical strain required for void formation. Reducing the hardness difference between martensite and ferrite phases by tempering has been shown to be an effective approach to retard the void formation in martensite and thereby is expected to improve...

Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

Science.gov (United States)

Rodak, K.; Pawlicki, J.; Tkocz, M.

2012-05-01

The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ- α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

International Nuclear Information System (INIS)

Rodak, K; Pawlicki, J; Tkocz, M

2012-01-01

The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ– α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

Science.gov (United States)

Benafan, Othmane

2012-01-01

The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

Determination of the crystallographic parameters of cubic-to-tetragonal martensitic transformation using the infinitesimal deformation approach and wechsler, lieberman, and read theory

Science.gov (United States)

Navruz, N.

2001-02-01

The aim of the present study is to discuss the infinitesimal deformation (ID) approach’s application and practical applicability. Therefore, ID theory was reformulated and applied to the face centered cubic (fcc) to body centered tetragonal (bct) martensitic transformation for the case of the (110) [bar 110] slip system as the lattice invariant shear (LIS). The analytical solutions for the habit plane orientation, the magnitude of the lattice invariant shear, the orientation relation between parent and product phases, etc. were derived for fcc to bct martensitic transformation in an Fe-7 pct Al-2 pct C alloy. In order to compare with phenomenological theory’s results, crystallographic parameters were also calculated by using Wechsler, Lieberman, and Read (W-L-R) phenomenological theory. Agreement between the two results obtained from ID approach and W-L-R theory was found to be excellent.

Effect of Si on the reversibility of stress-induced martensite in Fe-Mn-Si shape memory alloys

Energy Technology Data Exchange (ETDEWEB)

Stanford, N. [Centre for Material and Fibre Innovation, Deakin University, Geelong, Victoria 3217 (Australia); Dunne, D.P., E-mail: druce_dunne@uow.edu.au [Faculty of Engineering, University of Wollongong, Wollongong, NSW 2522 (Australia)

2010-12-15

Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a-vis shape memory. This paper examines the effect of Si on the morphology and the crystallography of the martensite in the Fe-Mn-Si system. It is concluded that the addition of Si increases the c/a ratio of the martensite, reduces the transformation volume change and decreases the atomic spacing difference between the parallel close-packed directions in the austenite-martensite interface (habit) plane. It is proposed that, in addition to austenite strengthening, Si enhances reversibility by reducing the volume change and the interfacial atomic mismatch between the martensite and the austenite. Although shape memory is improved, transformation reversibility remains limited by the necessary misfit dislocations that accommodate the atomic spacing differences in the interface.

Effect of Si on the reversibility of stress-induced martensite in Fe-Mn-Si shape memory alloys

International Nuclear Information System (INIS)

Stanford, N.; Dunne, D.P.

2010-01-01

Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a-vis shape memory. This paper examines the effect of Si on the morphology and the crystallography of the martensite in the Fe-Mn-Si system. It is concluded that the addition of Si increases the c/a ratio of the martensite, reduces the transformation volume change and decreases the atomic spacing difference between the parallel close-packed directions in the austenite-martensite interface (habit) plane. It is proposed that, in addition to austenite strengthening, Si enhances reversibility by reducing the volume change and the interfacial atomic mismatch between the martensite and the austenite. Although shape memory is improved, transformation reversibility remains limited by the necessary misfit dislocations that accommodate the atomic spacing differences in the interface.

Evolution behavior of nanohardness after thermal-aging and hydrogen-charging on austenite and strain-induced martensite in pre-strained austenitic stainless steel

Science.gov (United States)

Zheng, Yuanyuan; Zhou, Chengshuang; Hong, Yuanjian; Zheng, Jinyang; Zhang, Lin

2018-05-01

Nanoindentation has been used to study the effects of thermal-aging and hydrogen on the mechanical property of the metastable austenitic stainless steel. Thermal-aging at 473 K decreases the nanohardness of austenite, while it increases the nanohardness of strain-induced ɑ‧ martensite. Hydrogen-charging at 473 K increases the nanohardness of austenite, while it decreases the nanohardness of strain-induced ɑ‧ martensite. The opposite effect on austenite and ɑ‧ martensite is first found in the same pre-strained sample. This abnormal evolution behavior of hardness can be attributed to the interaction between dislocation and solute atoms (carbon and hydrogen). Carbon atoms are difficult to move and redistribute in austenite compared with ɑ‧ martensite. Therefore, the difference in the diffusivity of solute atoms between austenite and ɑ‧ martensite may result in the change of hardness.

Theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena

Science.gov (United States)

Jin, Yongmei M.; Wang, Yu U.; Ren, Yang

2015-12-01

Pre-martensitic phenomena, also called martensite precursor effects, have been known for decades while yet remain outstanding issues. This paper addresses pre-martensitic phenomena from new theoretical and experimental perspectives. A statistical mechanics-based Grüneisen-type phonon theory is developed. On the basis of deformation-dependent incompletely softened low-energy phonons, the theory predicts a lattice instability and pre-martensitic transition into elastic-phonon domains via 'phonon spinodal decomposition.' The phase transition lifts phonon degeneracy in cubic crystal and has a nature of phonon pseudo-Jahn-Teller lattice instability. The theory and notion of phonon domains consistently explain the ubiquitous pre-martensitic anomalies as natural consequences of incomplete phonon softening. The phonon domains are characterised by broken dynamic symmetry of lattice vibrations and deform through internal phonon relaxation in response to stress (a particular case of Le Chatelier's principle), leading to previously unexplored new domain phenomenon. Experimental evidence of phonon domains is obtained by in situ three-dimensional phonon diffuse scattering and Bragg reflection using high-energy synchrotron X-ray single-crystal diffraction, which observes exotic domain phenomenon fundamentally different from usual ferroelastic domain switching phenomenon. In light of the theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena, currently existing alternative opinions on martensitic precursor phenomena are revisited.

Defects induced by swift heavy ions in the 18R martensite of Cu-Zn-Al alloy

International Nuclear Information System (INIS)

Zelaya, Eugenia; Tolley, Alfredo; Condo, Adriana; Lovey, Francisco; Schumacher, G

2003-01-01

The swift heavy ion incidence over the surface of a given material produces a strong energy deposition in a nanometric scale.Swift heavy ions, of the order of one thousand of MeV, deposit their energy as electronic excitations.This highly localized deposition can induce metastable transformations within the material. For example, in martensitic NiTi alloys irradiated with swift heavy ions, it has been observed changes on the martensitic transformation temperature and amorphous areas induced by the irradiation.In this work, the effects produced by swift heavy ions on the martensitic 18R structure of Cu-Zn-Al alloy (Cu - 12.17 Zn - 17.92 Al, in %at) were analyzed.Crystalline samples were irradiated in a direction close to the [2 1 0] of 18R with Xe + 230 MeV, Au + of 350 MeV and Kr + of 200 MeV ion beams.Defects of the order of nanometers induced by the irradiation were observed by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM).It was also observed, that the average size of the irradiation defects induced by Au + ion is larger than those induced by Xe + and Kr + ions.In this case, no relationship between the observed defects and the energy deposition was found in the 23 keV/nn to 48 keV/nn range

Microstructure evolution and deformation mechanism change in 0.98C-8.3Mn-0.04N steel during compressive deformation

International Nuclear Information System (INIS)

Wang, T.S.; Hou, R.J.; Lv, B.; Zhang, M.; Zhang, F.C.

2007-01-01

The microstructure evolution and the deformation mechanism change in 0.98C-8.3Mn-0.04N steel during compressive deformation at room temperature have been studied as a function of the reduction in the range of 20-60%. Experimental results show that with the reduction increasing the microstructure of the deformed sample changes from dislocation substructures into the dominant twins plus dislocations. This suggests that the plastic deformation mechanism changes from the dislocation slip to the dominant deformation twinning. The minimum reduction for deformation twins starting is estimated to be at between 30 and 40%. With the reduction further increases to more than 40%, the deformation twinning is operative and the thickness of deformation twins gradually decreases to nanoscale and shear bands occur. These high-density twins can be curved by the formation of shear bands. In addition, both transmission electron microscopy and X-ray diffraction examinations confirm the inexistence of deformation-induced martensites in these deformed samples

Hydrogen embrittlement of austenitic stainless steels revealed by deformation microstructures and strain-induced creation of vacancies

International Nuclear Information System (INIS)

Hatano, M.; Fujinami, M.; Arai, K.; Fujii, H.; Nagumo, M.

2014-01-01

Hydrogen embrittlement of austenitic stainless steels has been examined with respect to deformation microstructures and lattice defects created during plastic deformation. Two types of austenitic stainless steels, SUS 304 and SUS 316L, uniformly hydrogen-precharged to 30 mass ppm in a high-pressure hydrogen environment, are subjected to tensile straining at room temperature. A substantial reduction of tensile ductility appears in hydrogen-charged SUS 304 and the onset of fracture is likely due to plastic instability. Fractographic features show involvement of plasticity throughout the crack path, implying the degradation of the austenitic phase. Electron backscatter diffraction analyses revealed prominent strain localization enhanced by hydrogen in SUS 304. Deformation microstructures of hydrogen-charged SUS 304 were characterized by the formation of high densities of fine stacking faults and ε-martensite, while tangled dislocations prevailed in SUS 316L. Positron lifetime measurements have revealed for the first time hydrogen-enhanced creation of strain-induced vacancies rather than dislocations in the austenitic phase and more clustering of vacancies in SUS 304 than in SUS 316L. Embrittlement and its mechanism are ascribed to the decrease in stacking fault energies resulting in strain localization and hydrogen-enhanced creation of strain-induced vacancies, leading to premature fracture in a similar way to that proposed for ferritic steels

Martensite in steels: its significance, recent developments and trends

International Nuclear Information System (INIS)

Schulz-Beenken, A.S.

1997-01-01

Martensite is generally known as a hard but brittle microstructure. This is only true for high carbon plate martensite. Recently developed steels with a lath martensite microstructure offer an excellent toughness at yield strength of 1000 MPa yield strength. A transformation into lath martensite by glide as invariant shear mechanism is only possible at a carbon content below 0,03%. The source of both high strength and good toughness is the high dislocation density and the narrow lath width off less than 1 μm. By a thermomechanical treatment, that leads to a finer lath structure both strength and ductility can be improved to a yield strength of 1150 MPa and an elongation of 18%. As, unlike high carbon plate martensite, the hardness of lath martensite is not achieved by the distortion of the tetragonal cell by carbon atoms, the hardness of lath martensite remains stable up during an annealing treatment up to 600 C. This thermal stability of the lath martensit microstructure makes an additional increase of hardness by the precipitation of different types of intermetallic phases possible. The increase of the hardness from 300 HV to 600 HV by precipitation without volume changes and good cold deformability reveals many new application in manufacturing. In plate martensite too, comparatively high toughness values can be achieved, if carbon is replaced by nitrogen. The refining influence of nitrides on the austenite grain sizes and the precipitation of fine nitrides during the annealing process leads to impact values three times higher than those of comparable high carbon plate martensite. (orig.)

A multi-scale model of martensitic transformation plasticity

NARCIS (Netherlands)

Kouznetsova, V.G.; Geers, M.G.D.

2008-01-01

The remarkable mechanical engineering properties of many advanced steels, e.g. TRIP steels and metastable austenitic stainless steels, are related to their complex microstructural behaviour, resulting from the interaction between plastic deformation of the phases and the austenite to martensite

Activation volume of martensitic ODS steel

Energy Technology Data Exchange (ETDEWEB)

Kim, D. W.; Noh, S.; Kim, T. K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Apparent activation volume as a function of temperature is 86b{sup 3}-42b{sup 3}. Activation volume decreases with increasing temperature. Activation volume changes scarcely with decreasing strain rate. Strain rate sensitivity increases with increasing temperature and decreasing strain rate. Nano-sized oxide dispersion strengthened (ODS) martensitic steel has a high strength, low thermal expansion coefficient, high thermal conductivity, and a good swelling resistance. Martensitic ODS steel is a candidate material for fuel cladding of sodium cooled fast breeder reactor (SFR). The plastic flow stress is determined through the interaction of dislocations with the obstacles encountered inside lattice. Dislocation movement through the lattice or past an obstacle requires surmounting of the energy barrier by a combination of applied stress and thermal activation. The plastic deformation of materials is a thermally activated process dependent upon time, temperature, and strain rate. Characterization of the rate controlling mechanism for plastic deformation due to dislocation motion in crystalline materials is done by the assessment of activation volume based on thermal activation analysis.

Tents and tunnels on martensitic films

International Nuclear Information System (INIS)

Bhattacharya, K.; Hane, K.F.; James, R.D.; Palmstroem, C.J.

1999-01-01

In this paper we outline a strategy for producing certain deformable structures - tents and tunnels - on epitaxially grown martensitic single crystal films. These structures are intended to be the basic building blocks of micropumps and microactuators. We give specific predictions for the systems Ni 2 MnGa, PbTiO 3 and Cu-Zn-Al. (orig.)

Creep deformation of high Cr-Mo ferritic/martensitic steels by material softening

International Nuclear Information System (INIS)

Kim, Sung Ho; Song, B. J.; Ryu, Woo Seog

2005-01-01

High Cr (9-12%Cr) ferritic/martensitic steels represent a valuable alternative to austenitic stainless steel for high temperature applications up to 600 .deg. C both in power and petrochemical plant, as well as good resistance to oxidation and corrosion. Material softening is the main physical phenomenon observed in the crept material. Thermally-induced change (such as particle coarsening or matrix solute depletion) and strain-induced change (such as dynamic subgrain growth) of microstructure degraded the alloy strength. These microstructural changes during a creep test cause the material softening, so the strength of the materials decreased. Many researches have been performed for the microstructural changes during a creep test, but the strength of crept materials has not been measured. In the present work, we measured the yield and tensile strength of crept materials using Indentationtyped Tensile Test System (AIS 2000). Material softening was quantitatively evaluated with a creep test condition, such as temperature and applied stress

Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...... demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Magnetic-field-induced martensitic transformation of off-stoichiometric single-crystal Ni2MnGa

International Nuclear Information System (INIS)

Inoue, Kazuko; Yamaguchi, Yasuo; Shishido, Toetsu; Ishii, Yoshinobu; Yamauchi, Hiroki

2009-01-01

The effect of a magnetic field on the martensitic transformation of an off-stoichiometric Heusler type Ni 2.16 Mn 0.78 Ga 1.06 single crystal has been revealed by neutron diffraction. The alloy undergoes a martensitic transformation at room temperature, which is nearly coincident with its Curie temperature. Splitting of the cubic (020) peak on the reciprocal lattice cubic c * -plane was traced at 293 K by a triple-axis neutron spectrometer under an increasing magnetic field of up to 10 T. It was found that the magnetic field causes the martensitic transformation from the cubic structure to the orthorhombic structure, which is the same as that caused by decreasing the temperature without a magnetic field. The increase in the magnetic field to 10 T appears to correspond to a decrease in temperature of nearly 12 K, i.e., from 293 to 281 K. The present experiment suggests the possibility of realizing a magnetic-field-induced shape memory alloy. (author)

Creep characteristics of precipitation hardened carbon free martensitic alloys

International Nuclear Information System (INIS)

Muneki, S.; Igarashi, M.; Abe, F.

2000-01-01

A new attempt has been demonstrated using carbon free Fe-Ni-Co martensitic alloys strengthened by Laves phase such as Fe 2 W or Fe 2 Mo to achieve homogeneous creep deformation at high temperatures under low stress levels. Creep behavior of the alloys is found to be completely different from that of the conventional high-Cr ferritic steels. The alloys exhibit gradual change in the creep rate with strain both in the transient and acceleration creep regions, and give a larger strain for the minimum creep rate. In these alloys the creep deformation takes place very homogeneously and no heterogeneous creep deformation is enhanced even at low stress levels. The minimum creep rates of the Fe-Ni-Co alloys at 700 C are found to be much lower than that of the conventional steel, which is due to fine dispersion strengthening useful even at 700 C in these alloys. It is thus concluded that the Fe-Ni-Co martensite strengthened by Laves phase is very useful to increase the creep resistance at elevated temperatures over 650 C. (orig.)

Effect of Temperature on the Deformation Behavior of B2 Austenite in a Polycrystalline Ni49.9Ti50.1 (at.Percent) Shape Memory Alloy

Science.gov (United States)

Garg, A.; Benafan, O.; Noebe, R. D.; Padula, S. A., II; Clausen, B.; Vogel, S.; Vaidyanathan, R.

2013-01-01

Superelasticity in austenitic B2-NiTi is of great technical interest and has been studied in the past by several researchers [1]. However, investigation of temperature dependent deformation in B2-NiTi is equally important since competing mechanisms of stress-induced martensite (SIM), retained martensite, plastic and deformation twinning can lead to unusual mechanical behaviors. Identification of the role of various mechanisms contributing to the overall deformation response of B2-NiTi is imperative to understanding and maturing SMA-enabled technologies. Thus, the objective of this work was to study the deformation of polycrystalline Ni49.9Ti50.1 (at. %) above A(sub f) (105 C) in the B2 state at temperatures between 165-440 C, and generate a B2 deformation map showing active deformation mechanisms in different temperature-stress regimes.

Nanostructures in a ferritic and an oxide dispersion strengthened steel induced by dynamic plastic deformation

DEFF Research Database (Denmark)

Zhang, Zhenbo

fission and fusion reactors. In this study, two candidate steels for nuclear reactors, namely a ferritic/martensitic steel (modified 9Cr-1Mo steel) and an oxide dispersion strengthened (ODS) ferritic steel (PM2000), were nanostructured by dynamic plastic deformation (DPD). The resulting microstructure...

Reversible magnetic-field-induced martensitic transformation over a wide temperature window in Ni42-xCoxCu8Mn37Ga13 alloys

Science.gov (United States)

Hua, Hui; Wang, Jingmin; Jiang, Chengbao; Xu, Huibin

2018-05-01

Ni42-xCoxCu8Mn37Ga13 (0 ≤ x ≤ 14) alloys are reported to exhibit a magnetostructural transition from weakly-magnetic martensite to ferromagnetic austenite over a rather wide temperature window ranging from 200 K to 380 K. Simultaneously a large magnetization change Δσ of up to 105 Am2 kg-1 is obtained at the martensitic transformation. A reversible magnetic-field-induced martensitic transformation is realized, resulting in a large magnetocaloric effect related to the high magnetic entropy change with a broad working temperature span. This work shows how it is possible to effectively tailor the magnetostructural transition in Ni-Mn-Ga alloys so as to achieve a reversible magnetic-field-induced martensitic transformation and associated functionalities.

Effect of Annealing in Magnetic Field on Ferromagnetic Nanoparticle Formation in Cu-Al-Mn Alloy with Induced Martensite Transformation.

Science.gov (United States)

Titenko, Anatoliy; Demchenko, Lesya

2016-12-01

The paper considers the influence of aging of high-temperature phase on subsequent martensitic transformation in Cu-Al-Mn alloy. The morphology of behavior of martensitic transformation as a result of alloy aging under annealing in a constant magnetic field with different sample orientation relatively to the field direction and without field was studied for direct control of the processes of martensite induction at cooling. Temperature dependences of electrical resistance, magnetic susceptibility, and magnetization, as well as field dependences of magnetization, and phase composition were found. The tendency to the oriented growth of precipitated ferromagnetic phase nanoparticles in a direction of applied field and to an increase of their volume fraction under thermal magnetic treatment of material that favors a reversibility of induced martensitic transformation is observed.

A macroscopic model to simulate the mechanically induced martensitic transformation in metastable austenitic stainless steels

NARCIS (Netherlands)

Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.

2012-01-01

Mechanically induced martensitic transformation and the associated transformation plasticity phenomena in austenitic stainless steels are studied. The mechanisms responsible for the transformation are investigated and put into perspective based on experimental evidence. The stress and strain

Effect of hydrostatic pressure on phase transformations in Kh17N8 steel during deformation

International Nuclear Information System (INIS)

Eshchenko, R.N.; Teplov, V.A.

1984-01-01

The phase composition and structure of Kh17N8 steel strained to different degrees under atmospheric pressure and 1700 MPa are investigated. It has been found that deformation at 1700 MPa causes α and epsilon-martensite formation, the same deformation under atmospheric pressure - only α-martensite formation. The amount of the formed α-martensite is not changed with application of hydrostatic pressure. Electron-microscopic observations have shown that the dispersion of α-martensite formed under pressure is higher than in the absence of pressure; no interconnection in formation of α and epsilon-martensite in samples strained under pressure has been observed

The influence of martensite, bainite and ferrite on the as-quenched constitutive response of simultaneously quenched and deformed boron steel – Experiments and model

International Nuclear Information System (INIS)

Bardelcik, Alexander; Worswick, Michael J.; Wells, Mary A.

2014-01-01

Highlights: • Gleeble tests were conducted to quench and simultaneously deform boron steel. • Different as-quenched vol. fractions of martensite, bainite and ferrite were observed. • Low to int. strain rate tensile tests were conducted on the as-quenched materials. • The presence of ferrite improved the uniform elongation, hardening rate and toughness. • A rate sensitive const. model was developed for varying vol fract. mart/bain/ferrite. - Abstract: This paper examines the relationship between as-formed microstructure and mechanical properties of a hot stamped boron steel used in automotive structural applications. Boron steel sheet metal blanks were austenized and quenched at cooling rates of 30 °C/s, 15 °C/s and 10 °C/s within a Gleeble thermal–mechanical simulator. For each cooling rate condition, the blanks were simultaneously deformed at temperatures of 600 °C and 800 °C. A strain of approximately 0.20 was imposed in the middle of the blanks, from which miniature tensile specimens were extracted. Depending on the cooling rate and deformation temperature imposed on the specimens, some of the as-quenched microstructures consisted of predominantly martensite and bainite, while others consisted of martensite, bainite and ferrite. Optical and SEM metallographraphic techniques were used to quantify the area fractions of the phases present and quasi-static (0.003 s −1 ) uniaxial tests were conducted on the miniature tensile specimens. The results revealed that an area fraction of ferrite greater than 6% led to an increased uniform elongation and an increase in n-value without affecting the strength of the material for equivalent hardness levels. This finding resulted in improved energy absorption due to the presence of ferrite and showed that a material with a predominantly bainitic microstructure containing 16% ferrite (with 257 HV) resulted in a 28% increase in energy absorption when compared to a material condition that was fully bainitic with

Shock wave induced martensitic transformations and morphology changes in Fe-Pd ferromagnetic shape memory alloy thin films

International Nuclear Information System (INIS)

Bischoff, A. J.; Arabi-Hashemi, A.; Ehrhardt, M.; Lorenz, P.; Zimmer, K.; Mayr, S. G.

2016-01-01

Combining experimental methods and classical molecular dynamics (MD) computer simulations, we explore the martensitic transformation in Fe_7_0Pd_3_0 ferromagnetic shape memory alloy thin films induced by laser shock peening. X-ray diffraction and scanning electron microscope measurements at shock wave pressures of up to 2.5 GPa reveal formation of martensitic variants with preferred orientation of the shorter c-axis of the tetragonal unit cell perpendicular to the surface plane. Moreover, consequential merging of growth islands on the film surface is observed. MD simulations unveil the underlying physics that are characterized by an austenite-martensite transformation with a preferential alignment of the c-axis along the propagation direction of the shock wave, resulting in flattening and in-plane expansion of surface features.

Martensitic Transformation in a β-Type Mg-Sc Alloy

Science.gov (United States)

Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Somekawa, Hidetoshi; Koike, Junichi

2018-03-01

Recently, we found that a Mg-Sc alloy with a bcc (β) phase exhibits superelasticity and a shape memory effect at low temperature. In this work, we examined the stress-induced and thermally induced martensitic transformation of the β-type Mg-Sc alloy and investigated the crystal structure of the thermally induced martensite phase based on in situ X-ray diffraction (XRD) measurements. The lattice constants of the martensite phase were calculated to be a = 0.3285 nm, b = 0.5544 nm, and c = 0.5223 nm when we assumed that the martensite phase has an orthorhombic structure (Cmcm). Based on the lattice correspondence between a bcc and an orthorhombic structures such as that in the case of β-Ti shape memory alloys, we estimated the transformation strain of the β Mg-Sc alloy. As a result, the transformation strains along the 001, 011, and 111 directions in the β phase were calculated to be + 5.7, + 8.8, and + 3.3%, respectively.

Martensitic Transformation in a β-Type Mg-Sc Alloy

Science.gov (United States)

Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Somekawa, Hidetoshi; Koike, Junichi

2017-12-01

Recently, we found that a Mg-Sc alloy with a bcc (β) phase exhibits superelasticity and a shape memory effect at low temperature. In this work, we examined the stress-induced and thermally induced martensitic transformation of the β-type Mg-Sc alloy and investigated the crystal structure of the thermally induced martensite phase based on in situ X-ray diffraction (XRD) measurements. The lattice constants of the martensite phase were calculated to be a = 0.3285 nm, b = 0.5544 nm, and c = 0.5223 nm when we assumed that the martensite phase has an orthorhombic structure (Cmcm). Based on the lattice correspondence between a bcc and an orthorhombic structures such as that in the case of β-Ti shape memory alloys, we estimated the transformation strain of the β Mg-Sc alloy. As a result, the transformation strains along the 001, 011, and 111 directions in the β phase were calculated to be + 5.7, + 8.8, and + 3.3%, respectively.

Concerning the problem of the plastic deformation mechanism changeover in neutron-irradiated metals and alloys

International Nuclear Information System (INIS)

Kolesnikov, A.N.; Krasnoselov, V.A.; Prokhorov, V.I.

1982-01-01

With a phenomenological model of plastic deformation instability as a basis, an analysis was made of the neutron irradition effects on the characteristics of strength and plasticity vs. structural parameters and radiation damage morphology. It was demonstrated that the enchanced plasticity in the initial stage of neutron irradiation has to do with the solid solution disintegration. Introduction of indestructible strengthening barriers enhances the stress-resistance of the neck-formation by 1.22 times. The ''big grain'' effect is observable during the deformation channel production only. Both the deformation twinning and deformation-induced martensite transformation raise the plastic flow stability

Effect of microstructure on the fracture toughness of ferrite-martensite-bainite steels

International Nuclear Information System (INIS)

Byun, Thak Sang; Kim, In Sup

1988-01-01

The effect of microstructure on the fracture toughness of ferrite-martensite -bainite steels was investigated with Fe-0.11C-1.64Mn-0.78Si composition. One inch compact tension specimens (1T-CTSs) were machined from hot rolled plates. The microstructure of ferrite-martensite-bainite was introduced to the specimens by the heat treatment of intercritical annealing at 800deg C and isothermal holding at 350deg C. Holding at 350deg C increased volume fraction of bainite, while decreased that of martensite, and refined martensite particles. Single specimen unloading compliance method was used in fracture test to obtain J-resistance (J-R) curve and to determine the fracture toughness(J IC ). Introduction of bainite to the ferrite-martensite steel improved the fracture toughness due to the deformation of bainite which relaxed the stress concentration on the interface of ferrite and martensite. Observation of fracto-graphs through the scanning electron microscope(SEM) identified the fracture mechanism of ferrite-martensite-bainite steels as dimple nucleation and crack growth by decohesion of ferrite matrix and second phase particles and by microvoid coales cence. (Author)

Optical microscope study of the γ(FCC)ε(HC) martensitic transformation of a Fe-16%Mn-9%Cr-5%Si-4%Ni shape memory alloy

International Nuclear Information System (INIS)

Bergeon, N.; Guenin, G.

1995-01-01

The γ(FCC) ε(HC) transformation is studied by light optical microscopy and scanning electron microscopy in a polycrystalline Fe-Mn-Si-Cr-Ni shape memory alloy. Thermal and stress-induced martensites are both studied to point out differences. A color etching method permitted to clearly observe morphological evolutions during the transformation and its reversion. Deformations of a golden microgrid deposed on austenitic samples are observed by SEM during the transformation. This technic has led to point out microscopic differences concerning the two kinds of martensite. SEM results are used to explain light optical microscopy observations. (orig.)

Analysis of the strain induced martensitic transformation in austenitic steel subjected to dynamic perforation

Directory of Open Access Journals (Sweden)

Zaera R.

2012-08-01

Full Text Available An experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is reported. Two target thicknesses are considered, 0.5 and 1.0 mm, and impact velocities range from 35 to 200 m/s. The perforation mechanisms are identified and the effect of the projectile nose-shape on the ability of the target for energy absorption is evaluated. Martensite has been detected in all the impacted samples and the role played by the projectile nose-shape on the transformation is highlighted. A 3D model implemented in ABAQUS/Explicit allowed to simulate the perforation tests. The material is defined through a constitutive description developed by the authors to describe the strain induced martensitic transformation taking place in metastable austenitic steels at high strain rates. The numerical results are compared with the experimental evidence and satisfactory matching is obtained. The numerical model succeeds in describing the perforation mechanisms associated to each projectile-target configuration analysed.

Martensitic cubic → tetragonal transition

International Nuclear Information System (INIS)

Schumann, H.

1983-01-01

Indium-thallium alloys containing 14 to 30% At. Tl have a cubic face-centred beta phase wich changes into a tetragonal face-centred alpha martensite during solidification. The martensite contains twin crystals that are large enough to be seen by means of a light microscope. The phenomenological crystallographic martensite theory was used to calculate Miller's index of the habit plane, the formation of the surface relief, the orientation relations and the critical thickness ratio of the twins. In a beta monocrystal frequently only one of the 24 crystallographic possible habit planes are formed at one end of the sample and migrate through the whole crystal when the temperature drops. Externally applied tension and compression influence in different ways the direction in which the habit plane moves and can even destroy the twinned structure, i.e. they can modify the substructure of the martensite crystal. This induces superelasticity, an effect that has also been described quantitatively. (author)

Influence of pre-deformation, sensitization and oxidation in high temperature water on corrosion resistance of AISI 304 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Lv, Jinlong, E-mail: ljltsinghua@126.com [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Liang, Tongxiang [Beijing Key Laboratory of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Zhongguancun Street, Haidian District, Beijing 100084 (China); State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084 (China); Luo, Hongyun [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Xueyuan Road 37, Beijing 100191 (China)

2016-12-01

Highlights: • The pre-strain accelerated desensitization and sensitization for austenitic stainless steels. • Low temperature sensitization (carbide precipitation) induced α′-martensite. • The sensitization level could affect directly corrosion resistance of the oxide film. - Abstract: The effects of pre-deformation on sensitization of AISI 304 stainless steel were investigated by the double loop electrochemical potentiokinetic reactivation test. The effects of pre-deformation and sensitization on high temperature oxidized film formed in high temperature water were analyzed by a XRD and SEM. The electrochemical impedance spectroscopy at room temperature was used to study corrosion resistance of oxidized film. The point defect density of oxidized film was calculated by Mott–Schottky plots. The results showed that the value of the degree of sensitization first decreased and then slight increased with the increasing of engineering strain. Moreover, low temperature promoted to form sensitization induced “secondary” α′-martensite. The sample with 20% engineering strain had higher impedance value than other samples. The result was supported by further Mott–Schottky experiments. Considering increased α′-martensite with the increasing of strain, the results of the impedance were more consistent with values of the degree of sensitization.

Modulated martensite: why it forms and why it deforms easily

Czech Academy of Sciences Publication Activity Database

Kaufmann, S.; Niemann, R.; Thersleff, T.; Roßler, U.K.; Heczko, Oleg; Buschbeck, J.; Holzapfel, B.; Schultz, L.; Fähler, S.

2011-01-01

Roč. 13, č. 5 (2011), 053029/1-053029/24 ISSN 1367-2630 Grant - others:AVČR(CZ) M100100913 Institutional research plan: CEZ:AV0Z10100520 Keywords : modulated martensite * adaptive phase * Ni-Mn-Ga * magnetic shape memory effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.177, year: 2011

Characterization of long term aged martensitic stainless steels

International Nuclear Information System (INIS)

Tsubota, M.; Hattori, K.; Okada, T.

1992-01-01

Types CA6NM (13Cr), 431 and 630 (17Cr) were aged at 400 degrees C and 350 degrees C for up to 10000 hours, and their hardness change and SCC susceptibility in 288 degrees C water were investigated. Hardness of the alloys increased with aging. Hardness of type 431 aged at 400 degrees C for 10000 hours exceeded 340 in Hv, over which tempered martensitic stainless steels had become susceptible to SCC, and showed high SCC susceptibility. Type 630 had high SCC susceptibility in before and after aged condition, and the hardness in both conditions was more than Hv 340. Therefore, hardness was considered to be a parameter which could describe the SCC susceptibility of martensitic stainless steels. Using activation energy for hardness change 105-125kJ/mol and the critical hardness level Hv=340, the marginal life-time for martensitic stainless steels at 288 degrees C was estimated. Predicted life of type 431 and CA6NM were around 10 5 hours and more than 10 6 hours, respectively. Activation energies obtained for toughness change and hardness change were different. Consequently, it was concluded that at least two factors should be taken into consideration for determining the total life-limit for usage of martensitic stainless steels in the light water reactor environment. The meaning of the existence of critical hardness for SCC susceptibility has been also discussed. Higher than 340 in Hv, yield strength and strain for uniform deformation showed a tendency of saturation. Therefore, it was conjectured that some extreme internal strain level, which may change the plastic deformation manner, is the absolute factor for determining the SCC susceptibility of the alloys in high temperature water

Powder metallurgy and mechanical alloying effects on the formation of thermally induced martensite in an FeMnSiCrNi SMA

Directory of Open Access Journals (Sweden)

Pricop Bogdan

2015-01-01

Full Text Available By ingot metallurgy (IM, melting, alloying and casting, powder metallurgy (PM, using as-blended elemental powders and mechanical alloying (MA of 50 % of particle volume, three types of FeMnSiCrNi shape memory alloy (SMA specimens were fabricated, respectively. After specimen thickness reduction by hot rolling, solution treatments were applied, at 973 and 1273 K, to thermally induce martensite. The resulting specimens were analysed by X-ray diffraction (XRD and scanning electron microscopy (SEM, in order to reveal the presence of ε (hexagonal close-packed, hcp and α’ (body centred cubic, bcc thermally induced martensites. The reversion of thermally induced martensites, to γ (face centred cubic, fcc austenite, during heating, was confirmed by dynamic mechanical analysis (DMA, which emphasized marked increases of storage modulus and obvious internal friction maxima on DMA thermograms. The results proved that the increase of porosity degree, after PM processing, increased internal friction, while MA enhanced crystallinity degree.

Influence of Plastic Deformation on Low-Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low-temperature surface hardening by gaseous nitriding of two commercial stainless steels: EN 1.4369 and AISI 304. The materials were plastically deformed to several levels of equivalent strain by conventional......, reflected-light microscopy, and microhardness testing. The results demonstrate that a case of expanded austenite develops and that the presence of plastic deformation has a significant influence on the morphology of the nitrided case. The presence of strain-induced martensite favors the formation of Cr...

Effect of solute Cu on ductile-to-brittle behavior of martensitic Fe-8% Ni alloy

International Nuclear Information System (INIS)

Junaidi Syarif; Tsuchiyama, Toshihiro; Takaki, Setsuo

2007-01-01

Effect of solute Cu on the ductile-to-brittle (DBT) behaviour of martensitic Fe-8mass%Ni alloy is investigated to understand the effect of solute Cu on mechanical properties of martensitic steel. The DBT behaviours of the Fe-8mass%Ni and the Fe-8mass%Ni-1mass%Cu alloys are almost the same. It is thought to be due to disappearance of the solid solution softening in the martensitic Fe-8mass%Ni-Cu alloys. The solute Cu gives small influence on temperature and strain rate dependences of yield stress and suppressing the twin deformation at lower temperature in the martensitic Fe-8mass%Ni alloy. Therefore, the DBT temperature of the martensitic Fe-8mass%Ni-Cu alloy was not shifted to lower side. (author)

The correlation of local deformation and stress-assisted local phase transformations in MMC foams

Energy Technology Data Exchange (ETDEWEB)

Berek, H., E-mail: harry.berek@ikgb.tu-freiberg.de [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Ballaschk, U.; Aneziris, C.G. [TU Bergakademie Freiberg, Agricolastraße 17, D-09599 Freiberg (Germany); Losch, K.; Schladitz, K. [Fraunhofer ITWM, Fraunhoferplatz 1, D-67663 Kaiserslautern (Germany)

2015-09-15

Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated.

The correlation of local deformation and stress-assisted local phase transformations in MMC foams

International Nuclear Information System (INIS)

Berek, H.; Ballaschk, U.; Aneziris, C.G.; Losch, K.; Schladitz, K.

2015-01-01

Cellular structures are of growing interest for industry, and are of particular importance for lightweight applications. In this paper, a special case of metal matrix composite foams (MMCs) is investigated. The investigated foams are composed of austenitic steel exhibiting transformation induced plasticity (TRIP) and magnesia partially stabilized zirconia (Mg-PSZ). Both components exhibit martensitic phase transformation during deformation, thus generating the potential for improved mechanical properties such as strength, ductility, and energy absorption capability. The aim of these investigations was to show that stress-assisted phase transformations within the ceramic reinforcement correspond to strong local deformation, and to determine whether they can trigger martensitic phase transformations in the steel matrix. To this end, in situ interrupted compression experiments were performed in an X-ray computed tomography device (XCT). By using a recently developed registration algorithm, local deformation could be calculated and regions of interest could be defined. Corresponding cross sections were prepared and used to analyze the local phase composition by electron backscatter diffraction (EBSD). The results show a strong correlation between local deformation and phase transformation. - Graphical abstract: Display Omitted - Highlights: • In situ compressive deformation on MMC foams was performed in an XCT. • Local deformation fields and their gradient amplitudes were estimated. • Cross sections were manufactured containing defined regions of interest. • Local EBSD phase analysis was performed. • Local deformation and local phase transformation are correlated

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels

NARCIS (Netherlands)

Tjahjanto, D.D.; Turteltaub, S.; Suiker, A.S.J.

2007-01-01

The microstructure of multiphase steels assisted by transformation-induced plasticity consists of grains of retained austenite embedded in a ferrite-based matrix. Upon mechanical loading, retained austenite may transform into martensite, as a result of which plastic deformations are induced in the

Crystallographically based model for transformation-induced plasticity in multiphase carbon steels

NARCIS (Netherlands)

Tjahjanto, D.D.; Turteltaub, S.R.; Suiker, A.S.J.

2008-01-01

The microstructure of multiphase steels assisted by transformation-induced plasticity consists of grains of retained austenite embedded in a ferrite-based matrix. Upon mechanical loading, retained austenite may transform into martensite, as a result of which plastic deformations are induced in the

Nanotribological behavior of deep cryogenically treated martensitic stainless steel

Directory of Open Access Journals (Sweden)

Germán Prieto

2017-08-01

Full Text Available Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic–plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally.

Nanotribological behavior of deep cryogenically treated martensitic stainless steel.

Science.gov (United States)

Prieto, Germán; Bakoglidis, Konstantinos D; Tuckart, Walter R; Broitman, Esteban

2017-01-01

Cryogenic treatments are increasingly used to improve the wear resistance of various steel alloys by means of transformation of retained austenite, deformation of virgin martensite and carbide refinement. In this work the nanotribological behavior and mechanical properties at the nano-scale of cryogenically and conventionally treated AISI 420 martensitic stainless steel were evaluated. Conventionally treated specimens were subjected to quenching and annealing, while the deep cryogenically treated samples were quenched, soaked in liquid nitrogen for 2 h and annealed. The elastic-plastic parameters of the materials were assessed by nanoindentation tests under displacement control, while the friction behavior and wear rate were evaluated by a nanoscratch testing methodology that it is used for the first time in steels. It was found that cryogenic treatments increased both hardness and elastic limit of a low-carbon martensitic stainless steel, while its tribological performance was enhanced marginally.

Influence of changing in sign plastic deformation on shape memory effects in titanium nickelide

International Nuclear Information System (INIS)

Belyaev, S.P.; Volkov, A.E.; Evard, M.E.; Leskina, M.L.

2005-01-01

The effects of shape memory, martensite transformation plasticity, and two-way shape memory in titanium nickelide (TiNi) prestrained in an alternating-sign mode have been studied. It was ascertained that the reversible deformation and the temperature-dependent deformation kinetics in the temperature interval of martensite transformation were independent of the degree of prestraining. Based on the results the conclusion is made that an increase in the density of dislocations does not influence essentially the deformation behavior of titanium nickelide in the vicinity of the martensite transformation. The results of computer simulation based on the structural analytical theory are in a satisfactory agreement with the experiment [ru

Ion implantation induced martensite nucleation in SUS301 steel

International Nuclear Information System (INIS)

Kinoshita, Hiroshi; Takahashi, Heishichiro; Gustiono, Dwi; Sakaguchi, Norihito; Shibayama, Tamaki; Watanabe, Seiichi

2007-01-01

Phase transformation behaviors of the austenitic 301 stainless steel was studied under Fe + , Ti + and Ar + ions implantation at room temperature with 100, 200 and 300 keV up to fluence of 1x10 21 ions/m 2 and the microstructures were observed by means of transmission electron microscopy (TEM). The plane and cross-sectional observations of the implanted specimen showed that the induced-phases due to implantation from the γ matrix phase were identified as α' martensite phases with the orientation relationship of (11-bar0) α parallel (111-bar) γ and [111] α parallel [011] γ close to the Kurdjumov-Sachs (K-S). The ion implantation induced phases nucleated near the surface region and the depth position of the nucleation changed depending on the ion accelerating energy and ion species. It was also found that the induced marten sites phases nucleate under the influence of the stress distribution, which is introduced due to the concentration of implanted ions, especially due to the stress gradient caused by the corresponding concentration gradient. (author)

Formation of epsilon martensite by high-pressure torsion in a TRIP steel

International Nuclear Information System (INIS)

Figueiredo, Roberto B.; Sicupira, Felipe L.; Malheiros, Livia Raquel C.; Kawasaki, Megumi; Santos, Dagoberto B.; Langdon, Terence G.

2015-01-01

An Fe–17% Mn–0.06% C–2% Si–3% Al–1% Ni steel exhibiting a phase transformation induced by room temperature deformation was processed by high-pressure torsion (HPT) using a pressure of 6.0 GPa and with the samples subjected to different amounts of torsional straining up to a maximum of 10 turns. A microstructural analysis revealed a phase transformation in the early stages of deformation and a gradual evolution towards a fully-deformed structure. Microhardness measurements showed two stages of hardening with eventual softening at large strains. From X-ray diffraction (XRD) analysis, there is evidence for a reverse martensitic transformation and the stabilization of an h.c.p. epsilon (ε) structure. The formation of an h.c.p. structure takes place in this steel at lower pressures than for pure iron but the results agree with earlier reports of the presence of an ε phase in stainless steel processed by HPT and with the expected reduction in the transition pressure due to the Mn addition

Formation of epsilon martensite by high-pressure torsion in a TRIP steel

Energy Technology Data Exchange (ETDEWEB)

Figueiredo, Roberto B., E-mail: figueiredo-rb@ufmg.br [Department of Materials Engineering and Civil Construction, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Sicupira, Felipe L.; Malheiros, Livia Raquel C. [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Kawasaki, Megumi [Division of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Santos, Dagoberto B. [Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901 (Brazil); Langdon, Terence G. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Departments of Aerospace & Mechanical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-1453 (United States)

2015-02-11

An Fe–17% Mn–0.06% C–2% Si–3% Al–1% Ni steel exhibiting a phase transformation induced by room temperature deformation was processed by high-pressure torsion (HPT) using a pressure of 6.0 GPa and with the samples subjected to different amounts of torsional straining up to a maximum of 10 turns. A microstructural analysis revealed a phase transformation in the early stages of deformation and a gradual evolution towards a fully-deformed structure. Microhardness measurements showed two stages of hardening with eventual softening at large strains. From X-ray diffraction (XRD) analysis, there is evidence for a reverse martensitic transformation and the stabilization of an h.c.p. epsilon (ε) structure. The formation of an h.c.p. structure takes place in this steel at lower pressures than for pure iron but the results agree with earlier reports of the presence of an ε phase in stainless steel processed by HPT and with the expected reduction in the transition pressure due to the Mn addition.

Influence of plastic deformation on low temperature surface hardening of stainless steel by gaseous nitriding

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... analysis, reflected light microscopy and microhardness indentation. The results demonstrate that a case of expanded austenite develops and that, in particular, the presence of strain-induced martensite in the initial (deformed) microstructure has a large influence on the nitrided zone....

Radiation-induced segregation and phase stability in ferritic-martensitic alloy T 91

Energy Technology Data Exchange (ETDEWEB)

Wharry, Janelle P.; Jiao Zhijie; Shankar, Vani [University of Michigan, 2355 Bonisteel Blvd, Ann Arbor, MI 48109-2104 (United States); Busby, Jeremy T. [Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831 (United States); Was, Gary S., E-mail: gsw@umich.edu [University of Michigan, 2355 Bonisteel Blvd, Ann Arbor, MI 48109-2104 (United States)

2011-10-01

Radiation-induced segregation in ferritic-martensitic alloy T 91 was studied to understand the behavior of solutes as a function of dose and temperature. Irradiations were conducted using 2 MeV protons to doses of 1, 3, 7 and 10 dpa at 400 deg. C. Radiation-induced segregation at prior austenite grain boundaries was measured, and various features of the irradiated microstructure were characterized, including grain boundary carbide coverage, the dislocation microstructure, radiation-induced precipitation and irradiation hardening. Results showed that Cr, Ni and Si segregate to prior austenite grain boundaries at low dose, but segregation ceases and redistribution occurs above 3 dpa. Grain boundary carbide coverage mirrors radiation-induced segregation. Irradiation induces formation of Ni-Si-Mn and Cu-rich precipitates that account for the majority of irradiation hardening. Radiation-induced segregation behavior is likely linked to the evolution of the precipitate and dislocation microstructures.

Effects of strain and strain-induced α′-martensite on passive films in AISI 304 austenitic stainless steel

International Nuclear Information System (INIS)

Lv, Jinlong; Luo, Hongyun

2014-01-01

In this paper, the effects of strain and heat treatment on strain-induced α′-martensite of AISI 304 stainless steel tubes were measured by X-ray diffraction. Moreover, the effects of strain and content of α′-martensite on passivated property on the surface of the material in borate buffer solution were evaluated by electrochemical technique. The results showed that the volume fraction of α′-martensite increased gradually with the increase of tensile strain for as-received and solid solution samples. However, α′-martensite in as-received sample was more than that in the solid solution sample. The electrochemical impedance spectroscopy results showed that the solid solution treatment improved corrosion resistance of the steel, especially for samples with small strain. Moreover, acceptor densities were always higher than donor densities for as-received and solid solution samples. With the increase of strain, the increase tendency of acceptor density was more significant than that of donor density. We also found that the total density of the acceptor and donor almost increased linearly with the increase of α′-martensite. The present results indicated that the increased acceptor density might lead to the decreased corrosion resistance of the steel. - Highlights: • The solid solution treatment improved corrosion resistance of the stainless steel. • The deteriorated passivated property after strain could be attributed to the increased acceptor density. • The α′-martensite reduced corrosion resistance of the stainless steel

Cubic martensite in high carbon steel

Science.gov (United States)

Chen, Yulin; Xiao, Wenlong; Jiao, Kun; Ping, Dehai; Xu, Huibin; Zhao, Xinqing; Wang, Yunzhi

2018-05-01

A distinguished structural characteristic of martensite in Fe-C steels is its tetragonality originating from carbon atoms occupying only one set of the three available octahedral interstitial sites in the body-centered-cubic (bcc) Fe lattice. Such a body-centered-tetragonal (bct) structure is believed to be thermodynamically stable because of elastic interactions between the interstitial carbon atoms. For such phase stability, however, there has been a lack of direct experimental evidence despite extensive studies of phase transformations in steels over one century. In this Rapid Communication, we report that the martensite formed in a high carbon Fe-8Ni-1.26C (wt%) steel at room temperature induced by applied stress/strain has actually a bcc rather than a bct crystal structure. This finding not only challenges the existing theories on the stability of bcc vs bct martensite in high carbon steels, but also provides insights into the mechanism for martensitic transformation in ferrous alloys.

Significance of rate of work hardening in tempered martensite embrittlement

International Nuclear Information System (INIS)

Pietikainen, J.

1995-01-01

The main explanations for tempered martensite embrittlement are based on the effects of impurities and cementite precipitation on the prior austenite grain boundaries. There are some studies where the rate of work hardening is proposed as a potential reason for the brittleness. One steel was studied by means of a specially developed precision torsional testing device. The test steel had a high Si and Ni content so ε carbide and Fe 3 C appear in quite different tempering temperature ranges. The M S temperature is low enough so that self tempering does not occur. With the testing device it was possible to obtain the true stress - true strain curves to very high deformations. The minimum toughness was always associated with the minimum of rate of work hardening. The change of deformed steel volume before the loss of mechanical stability is proposed as at least one reason for tempered martensite embrittlement. The reasons for the minimum of the rate of work hardening are considered. (orig.)

Martensitic transformation in zirconia

International Nuclear Information System (INIS)

Deville, Sylvain; Guenin, Gerard; Chevalier, Jerome

2004-01-01

We investigate by atomic force microscopy (AFM) the surface relief resulting from martensitic tetragonal to monoclinic phase transformation induced by low temperature autoclave aging in ceria-stabilized zirconia. AFM appears as a very powerful tool to investigate martensite relief quantitatively and with a great precision. The crystallographic phenomenological theory is used to predict the expected relief induced by the transformation, for the particular case of lattice correspondence ABC1, where tetragonal c axis becomes the monoclinic c axis. A model for variants spatial arrangement for this lattice correspondence is proposed and validated by the experimental observations. An excellent agreement is found between the quantitative calculations outputs and the experimental measurements at nanometer scale yielded by AFM. All the observed features are explained fully quantitatively by the calculations, with discrepancies between calculations and quantitative experimental measurements within the measurements and calculations precision range. In particular, the crystallographic orientation of the transformed grains is determined from the local characteristics of transformation induced relief. It is finally demonstrated that the strain energy is the controlling factor of the surface transformation induced by low temperature autoclave treatments in this material

Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

Directory of Open Access Journals (Sweden)

Wang Lin

2015-01-01

Full Text Available Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.

Constitutive modelling and identification of parameters of the plastic strain-induced martensitic transformation in 316L stainless steel at cryogenic temperatures

CERN Document Server

Garion, C; Sgobba, Stefano

2006-01-01

The present paper is focused on constitutive modelling and identification of parameters of the relevant model of plastic strain- induced martensitic transformation in austenitic stainless steels at low temperatures. The model used to describe the FCCrightward arrow BCC phase transformation in austenitic stainless steels is based on the assumption of linearization of the most intensive part of the transformation curve. The kinetics of phase transformation is described by three parameters: transformation threshold (p/sub xi/), slope (A) and saturation level (xi/sub L/). It is assumed that the phase transformation is driven by the accumulated plastic strain p. In addition, the intensity of plastic deformation is strongly coupled to the phase transformation via the description of mixed kinematic /isotropic linear plastic hardening based on the Mori-Tanaka homogenization. The theory of small strains is applied. Small strain fields, corresponding to phase transformation, are decomposed into the volumic and the shea...

Strain-rate behavior in tension of the tempered martensitic reduced activation steel Eurofer97

Energy Technology Data Exchange (ETDEWEB)

Cadoni, Ezio; Dotta, Matteo; Forni, Daniele [University of Applied Sciences of Southern Switzerland, P.O. Box 105, CH-6952 Canobbio (Switzerland); Spaetig, Philippe, E-mail: philippe.spatig@psi.ch [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, CH-5232 Villigen PSI (Switzerland)

2011-07-31

The tensile properties of the high-chromium tempered martensitic reduced activation steel Eurofer97 were determined from tests carried out over a wide range of strain-rates on cylindrical specimens. The quasi-static tests were performed with a universal electro-mechanical machine, whereas a hydro-pneumatic machine and a JRC-split Hopkinson tensile bar apparatus were used for medium and high strain-rates respectively. This tempered martensitic stainless steel showed significant strain-rate sensitivity. The constitutive behavior was investigated within a framework of dislocations dynamics model using Kock's approach. The parameters of the model were determined and then used to predict the deformation range of the tensile deformation stability. A very good agreement between the experimental results and predictions of the model was found.

Strain-rate behavior in tension of the tempered martensitic reduced activation steel Eurofer97

International Nuclear Information System (INIS)

Cadoni, Ezio; Dotta, Matteo; Forni, Daniele; Spaetig, Philippe

2011-01-01

The tensile properties of the high-chromium tempered martensitic reduced activation steel Eurofer97 were determined from tests carried out over a wide range of strain-rates on cylindrical specimens. The quasi-static tests were performed with a universal electro-mechanical machine, whereas a hydro-pneumatic machine and a JRC-split Hopkinson tensile bar apparatus were used for medium and high strain-rates respectively. This tempered martensitic stainless steel showed significant strain-rate sensitivity. The constitutive behavior was investigated within a framework of dislocations dynamics model using Kock's approach. The parameters of the model were determined and then used to predict the deformation range of the tensile deformation stability. A very good agreement between the experimental results and predictions of the model was found.

Microstructural and crystallographic characteristics of modulated martensite, non-modulated martensite, and pre-martensitic tweed austenite in Ni-Mn-Ga alloys

International Nuclear Information System (INIS)

Zhou, Le; Schneider, Matthew M.; Giri, Anit; Cho, Kyu; Sohn, Yongho

2017-01-01

A combinatorial approach using diffusion couples and TEM analyses was carried out to investigate the composition-dependent martensitic transformation in NiMnGa alloys. The compositions cover a large portion of the off-stoichiometric Ni 2 MnGa compositions and some Mn-rich compositions. Crystallographic variations of the martensitic phase, including non-modulated (NM) martensite, modulated (5M or 7M) martensite, and austenitic phase were identified in the diffusion couples and investigated with respect to their microstructure and crystallography. The 5M and 7M martensitic structures were only found near the interphase boundary between austenite and martensite, while the NM martensitic structures were found mostly away from the interphase boundary. The tetragonality ratio (c/a) for NM martensite generally increases with e/a ratio, but was also dependent on the composition. The habit plane and martensitic microstructure that consists of twinned variants with differing orientations were documented using electron diffraction. The pre-martensitic state was observed in the austenitic phase that was located near the interphase boundary between austenite and martensite, with distinctive tweed microstructure and a strain field originating from the local lattice distortions. The combinatorial approach proves to be efficient and systematic in studying the composition-dependent martensitic transformation in NiMnGa alloys and can be potentially applied to other shape memory alloys.

Cyclic deformation of NiTi shape memory alloys

International Nuclear Information System (INIS)

Liu Yong; Van Humbeeck, J.; Xie Zeliang

1999-01-01

Recently, there is an increasing interest in applying the high damping capacity of shape memory alloys (SMAs). The purpose is to explore the feasibility of those materials for the protection of buildings and other civil constructions as a result of earthquake damages. So far, few experimental results have been reported concerning the mechanical cyclic behaviour of SMAs in their martensitic state (ferroelastic). In the present work, the experimental results on the mechanical behaviour of martensitic NiTi SMAs under tension-compression cyclic deformation up to strains of ±4% are summarized with major attention to the damping capacity, characteristic stresses and strains as a function of deformation cycles. Effect of strain rate, strain amplitude and annealing condition on the martensite damping is summarized. Explanation of the cyclic hardening and cyclic softening phenomenon is proposed based on TEM observations. (orig.)

Effect of Deformation Parameters on Microstructure and Properties During DIFT of X70HD Pipeline Steel

Science.gov (United States)

Wang, Jian; Zhu, Wei; Xiao, Hong; Zhang, Liang-liang; Qin, Hao; Yu, Yue

2018-02-01

Grain refinement is a critical approach to improve the strength of materials without damaging the toughness. The grains of deformation-induced ferrite are considerably smaller than those of proeutectoid ferrite. Grain refinement is crucial to the application of deformation-induced ferrite. The composition of ferrite and bainite or martensite is important in controlling the performance of X70HD pipeline steel, and cooling significantly influences the control of their ratio and grain size. By analyzing the static and dynamic phase-transition points using Gleeble-3800 thermal simulator, thermal simulations were performed through two-stage deformations in the austenite zone. Ferrite transformation rules were studied with thermal simulation tests under different deformation and cooling parameters based on the actual production of cumulative deformation. The influence of deformation parameters on the microstructure transformation was analyzed. Numerous fine-grain deformation-induced ferrites were obtained by regulating various parameters, including deformation temperature, strain rate, cooling rate, final cooling temperature and other parameters. Results of metallographic observation and microtensile testing revealed that the selection of appropriate parameters can refine the grains and improve the performance of the X70HD pipeline steel.

Change of austenite state before martensite transformation and Msub(el) temperature

International Nuclear Information System (INIS)

Sarrak, V.I.; Suvorova, S.O.

1978-01-01

The N31 alloy austenite behaviour in the premartensite temperature range is investigated. To study the austenite state the method of resistance to microplastic deformation sensitive to the structural state of metals is used. The resistance to microplastic deformation was determined by amplitude dependence of internal friction. The Msub(el) temperature is found at which the change of austenite state is observed due to the appearence of elastic nuclei of martensite below the Msub(el) temperature

Evolution of microstructure in stainless martensitic steel for seamless tubing

Science.gov (United States)

Pyshmintsev, I. Yu.; Bityukov, S. M.; Pastukhov, V. I.; Danilov, S. V.; Vedernikova, L. O.; Lobanov, M. L.

2017-12-01

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in the 0.08C-13Cr-3Ni-Mo-V-Nb steel through seamless tube production route: after hot deformation by extrusion; after quenching from various temperatures and subsequent high tempering. It is shown that the martensitic microstructure formed both after hot deformation and after quenching is characterized by the presence of deformation crystallographic texture, which is predetermined by the texture of austenite. The effect of heat treatment on texture, packet refinement, lath width, precipitation of carbides and Charpy impact energy is analyzed.

Martensitic transformation behavior and shape memory properties of Ti-Ni-Pt melt-spun ribbons

International Nuclear Information System (INIS)

Inamura, Tomonari; Takahashi, Yohei; Hosoda, Hideki; Wakashima, Kenji; Nagase, Takeshi; Nakano, Takayoshi; Umakoshi, Yukichi; Miyazaki, Shuichi

2006-01-01

Martensitic transformation behavior and shape memory properties of a Ti 50 Ni 40 Pt 10 (TiNiPt) melt-spun ribbon fabricated by a single roll melt-spinning technique were characterized. The constituent phases of the as-spun ribbon were B2 (parent phase) and B19 (martensite phase) at room temperature. The B2-B19 martensitic transformation temperatures of the as-spun ribbon were 100K higher than those of the bulk-material with the same chemical composition. The martensitic transformation temperatures of the as-spun ribbon were decreased with increasing the temperature of the heat-treatment made after the melt-spinning. The as-spun ribbon and the heat-treated ribbons exhibited shape recovery by heating and/or pseudoelasticity. The martensitic transformation temperatures determined from the temperature dependence of the 0.2% flow stress of the pseudoelastic deformation were in good agreement with those of B2-B19 martensitic transformation determined by DSC. It was confirmed that the observed shape recovery and pseudoelasticity are shape memory effect and superelasticity due to the B2-B19 martensitic transformation. Shape memory effect and superelasticity of melt-spun TiNiPt alloy were found to appear at higher temperatures compared to those of Bulk-material with the same composition. (author)

Microstructural Changes of the Nanostructured Bainitic Steel Induced by Quasi-Static and Dynamic Deformation

Directory of Open Access Journals (Sweden)

Marcisz J.

2017-12-01

Full Text Available Changes in the microstructure of nanostructured bainitic steel induced by quasi-static and dynamic deformation have been shown in the article. The method of deformation and strain rate have important impact on the microstructure changes especially due to strain localization. Microstructure of nanostructured steel Fe-0.6%C-1.9Mn-1.8Si-1.3Cr-0.7Mo consists of nanometer size carbide-free bainite laths and 20-30% volume fraction of retained austenite. Quasi-static and dynamic (strain rate up to 2×102 s−1 compression tests were realized using Gleeble simulator. Dynamic deformation at the strain rate up to 9×103 s−1 was realized by the Split Hopkinson Pressure Bar method (SHPB. Moreover high energy firing tests of plates made of the nanostructured bainitic steel were carried out to produce dynamically deformed material for investigation. Adiabatic shear bands were found as a result of localization of deformation in dynamic compression tests and in firing tests. Microstructure of the bands was examined and hardness changes in the vicinity of the bands were determined. The TEM examination of the ASBs showed the change from the internal shear band structure to the matrix structure to be gradual. This study clearly resolved that the interior (core of the band has an extremely fine grained structure with grain diameter ranging from 100 nm to 200 nm. Martensitic twins were found within the grains. No austenite and carbide reflections were detected in the diffraction patterns taken from the core of the band. Hardness of the core of the ASBs for examined variants of isothermal heat treatment was higher about 300 HV referring to steel matrix hardness.

STUDY OF THE EFFECT OF PRELIMINARY PLASTIC DEFORMATION IN THE PROCESS OF DISSOLUTION DURING TEMPERING OF LOW-CARBON AND BORON-CONTAINING ALLOYS

Directory of Open Access Journals (Sweden)

M. Yu. Filonenko

2009-12-01

Full Text Available In the paper the influence of preliminary deformation on disintegration of martensite in boron-containing and carbonic alloy is explored. It is shown that at the small degree of deformation (7 per cent both in low-carbonic and boron-containing alloys the process of martensite disintegration takes place less intensively. The increase of degree of preliminary deformation in a boron-containing alloy is instrumental in more even distribution of boron-cementite particles appearing as a result of martensite disintegration.

Depth distribution of martensite in xenon implanted stainless steels

International Nuclear Information System (INIS)

Johansen, A.; Johnson, E.; Sarholt-Kristensen, L.; Steenstrup, S.; Hayashi, N.; Sakamoto, I.

1989-01-01

The amount of stress-induced martensite and its distribution in depth in xenon implanted austenitic stainless steel poly- and single crystals have been measured by Rutherford backscattering and channeling analysis, depth selective conversion electron Moessbauer spectroscopy, cross-sectional transmission electron microscopy and x-ray diffraction analysis. In low nickel 17/7, 304 and 316 commercial stainless steels and in 17:13 single crystals the martensitic transformation starts at the surface and develops towards greater depth with increasing xenon fluence. The implanted layer is nearly completely transformed, and the interface between martensite and austenite is rather sharp and well defined. In high nickel 310 commercial stainless steel and 15:19 and 20:19 single crystals, on the other hand, only insignificant amounts of martensite are observed. (orig.)

Microstructural and superficial modification in a Cu-Al-Be shape memory alloy due to superficial severe plastic deformation under sliding wear conditions

Science.gov (United States)

Figueroa, C. G.; Garcia-Castillo, F. N.; Jacobo, V. H.; Cortés-Pérez, J.; Schouwenaars, R.

2017-05-01

Stress induced martensitic transformation in copper-based shape memory alloys has been studied mainly in monocrystals. This limits the use of such results for practical applications as most engineering applications use polycristals. In the present work, a coaxial tribometer developed by the authors was used to characterise the tribological behaviour of polycrystalline Cu-11.5%Al-0.5%Be shape memory alloy in contact with AISI 9840 steel under sliding wear conditions. The surface and microstructure characterization of the worn material was conducted by conventional scanning electron microscopy and atomic force microscopy, while the mechanical properties along the transversal section were measured by means of micro-hardness testing. The tribological behaviour of Cu-Al-Be showed to be optimal under sliding wear conditions since the surface only presented a slight damage consisting in some elongated flakes produced by strong plastic deformation. The combination of the plastically modified surface and the effects of mechanically induced martensitic transformation is well-suited for sliding wear conditions since the modified surface provides the necessary strength to avoid superficial damage while superelasticity associated to martensitic transformation is an additional mechanism which allows absorbing mechanical energy associated to wear phenomena as opposed to conventional ductile alloys where severe plastic deformation affects several tens of micrometres below the surface.

Transformation-induced plasticity in multiphase steels subjected to thermomechanical loading

NARCIS (Netherlands)

Tjahjanto, D.D.; Turteltaub, S.R.; Suiker, A.S.J.; Zwaag, van der S.

2008-01-01

The behaviour of transformation-induced plasticity steels subjected to combined thermomechanical loading is studied at the microscale by means of numerical simulations. The microstructure is composed of an austenitic phase that may deform plastically and/or transform into martensite, and a ferritic

Kinetics of first order phase transformation in metals and alloys. Isothermal evolution in martensite transformation

International Nuclear Information System (INIS)

Iwasaki, Hiroshi; Ohshima, Ken-ichi

2011-01-01

The 11th lecture about microstructures and fluctuation in solids reports on the martensitic phase transformation of alkali metals and alloys. The martensitic transformation is a diffusionless first order phase transformation. Martensitic transformations are classified into two with respect to kinetics, one is isothermal transformation and the other is athermal transformation. The former transformation depends upon both temperature and time, but the latter solely depends on temperature. The former does not have a definite transformation start temperature but occurs after some finite incubation time during isothermal holding. The isothermal martensitic transformation is changed to the athermal one under high magnetic field, and also the reverse transformation occurs under the application of hydrostatic pressure. The former phenomena were observed in Fe-Ni-Mn alloys, Fe-Ni-Cr alloys and also the reverse transformation in Fe-3.1at%Ni-0.5at%Mn alloys. The athermal transformation was observed in Li and Na metals at 73 and 36 K, respectively. A neutron diffraction study has been performed on single crystals of metallic Na. On cooling the virgin sample, the incubation time to transform from the bcc structure to the low-temperature structure (9R structure) is formed to be more than 2h at 38 K, 2 K higher than the transformation temperature of 36 K. The full width of half maximum of the Bragg reflection suddenly increased, due to some deformation introduced by the nucleation of the low-temperature structure. In relation to the deformation, strong extra-diffuse scattering (Huang scattering) was observed around the Bragg reflection in addition to thermal diffuse scattering. The kinetics of the martensitic transformation in In-Tl alloys has been studied by x-ray and neutron diffraction methods. A characteristic incubation time appeared at fixed temperature above Ms, the normal martensitic transformation start temperature. (author)

The role of martensitic transformation on bimodal grain structure in ultrafine grained AISI 304L stainless steel

International Nuclear Information System (INIS)

Sabooni, S.; Karimzadeh, F.; Enayati, M.H.; Ngan, A.H.W.

2015-01-01

In the present study, metastable AISI 304L austenitic stainless steel samples were subjected to different cold rolling reductions from 70% to 93%, followed by annealing at 700 °C for 300 min to form ultrafine grained (UFG) austenite with different grain structures. Transmission electron microscopy (TEM) and nanoindentation were used to characterize the martensitic transformation, in order to relate it to the bimodal distribution of the austenite grain size after subsequent annealing. The results showed that the martensite morphology changed from lath type in the 60% rolled sample to a mixture of lath and dislocation-cell types in the higher rolling reductions. Calculation of the Gibbs free energy change during the reversion treatment showed that the reversion mechanism is shear controlled at the annealing temperature and so the morphology of the reverted austenite is completely dependent on the morphology of the deformation induced martensite. It was found that the austenite had a bimodal grain size distribution in the 80% rolled and annealed state and this is related to the existence of different types of martensite. Increasing the rolling reduction to 93% followed by annealing caused changing of the grain structure to a monomodal like structure, which was mostly covered with small grains of around 300 nm. The existence of bimodal austenite grain size in the 80% rolled and annealed 304L stainless steel led to the improvement of ductility while maintaining a high tensile strength in comparison with the 93% rolled and annealed sample

Surface crack formation on rails at grinding induced martensite white etching layers

DEFF Research Database (Denmark)

Rasmussen, Carsten Jørn; Fæster, Søren; Dhar, Somrita

2017-01-01

The connection between profile grinding of rails, martensite surface layers and crack initiation has been investigated using visual inspection, optical microscopy and 3D X-ray computerized tomography. Newly grinded rails were extracted and found to be covered by a continuous surface layer...... of martensite with varying thickness formed by the grinding process. Worn R350HT and R200 rails were extracted from the Danish rail network as they had transverse bands resembling grinding marks on the running surface. The transverse bands were shown to consist of martensite which had extensive crack formation...... at the martensite/pearlite interface. The cracks in R350HT propagated down into the rail while those in the soft R200 returned to the surface causing only very small shallow spallation. The transverse bands had the same shape, size, orientation, location and periodicity which would be expected from grinding marks...

G-phase precipitation in austenitic stainless steel deformed by high pressure torsion

International Nuclear Information System (INIS)

Shuro, I.; Kuo, H.H.; Sasaki, T.; Hono, K.; Todaka, Y.; Umemoto, M.

2012-01-01

Highlights: ► Using TEM and APT analyses, G-phase precipitation was observed in HPTed SUS304 with no trace of spinodal decomposition. ► G-phase precipitation occurred much shorter time than previous studies probably due to the elimination of prior SD and enhanced diffusion by severe plastic deformation. ► G-phase composition is a function of aging time. ► Tensile tests showed that in SUS304 embrittlement occurs solely due to G-phase precipitation. - Abstract: G phase an intermetallic silicide has been observed in martensite of precipitation hardened stainless steels and in the ferrite of dual (austenite and ferrite) phase stainless steels. In both cases, before G-phase precipitates, the matrix composition changes due to spinodal decomposition and solute partitioning between ferrite and austenite. Thus in the present study, single bcc phase and high Ni content stainless steel, was selected to study G-phase precipitation expecting elimination of the interference from spinodal decomposition and solute partitioning. Fe–18Cr–8Ni (SUS304) austenitic stainless steel samples were deformed at room temperature by high pressure torsion to obtain 100% volume fraction of deformation induced martensite (α′). HPT deformation was chosen due to its ability to induce high strength by grain refinement and also attain 100% α′ at room temperature. After annealing at 400 °C for 500 h, G-phase precipitation was observed in the fully martensitic matrix without spinodal decomposition. Crystallographic analysis of annealed samples using high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) detected a Mn–Ni–Si rich G-phase with fcc crystal structure with lattice parameter of 1.16 nm. The value of lattice parameter corresponds well with previously reported values. Chemical analysis by atom probe tomography (APT) showed G-phase of composition Mn 21 Ni 50 Si 24 Fe 4 Cr. Tensile tests showed that G-phase precipitation leads to

G-phase precipitation in austenitic stainless steel deformed by high pressure torsion

Energy Technology Data Exchange (ETDEWEB)

Shuro, I., E-mail: innoshuro@martens.me.tut.ac.jp [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan); Kuo, H.H. [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan); Sasaki, T.; Hono, K. [National Institute for Materials Sciences, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Todaka, Y.; Umemoto, M. [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan)

2012-08-30

Highlights: Black-Right-Pointing-Pointer Using TEM and APT analyses, G-phase precipitation was observed in HPTed SUS304 with no trace of spinodal decomposition. Black-Right-Pointing-Pointer G-phase precipitation occurred much shorter time than previous studies probably due to the elimination of prior SD and enhanced diffusion by severe plastic deformation. Black-Right-Pointing-Pointer G-phase composition is a function of aging time. Black-Right-Pointing-Pointer Tensile tests showed that in SUS304 embrittlement occurs solely due to G-phase precipitation. - Abstract: G phase an intermetallic silicide has been observed in martensite of precipitation hardened stainless steels and in the ferrite of dual (austenite and ferrite) phase stainless steels. In both cases, before G-phase precipitates, the matrix composition changes due to spinodal decomposition and solute partitioning between ferrite and austenite. Thus in the present study, single bcc phase and high Ni content stainless steel, was selected to study G-phase precipitation expecting elimination of the interference from spinodal decomposition and solute partitioning. Fe-18Cr-8Ni (SUS304) austenitic stainless steel samples were deformed at room temperature by high pressure torsion to obtain 100% volume fraction of deformation induced martensite ({alpha} Prime ). HPT deformation was chosen due to its ability to induce high strength by grain refinement and also attain 100% {alpha} Prime at room temperature. After annealing at 400 Degree-Sign C for 500 h, G-phase precipitation was observed in the fully martensitic matrix without spinodal decomposition. Crystallographic analysis of annealed samples using high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) detected a Mn-Ni-Si rich G-phase with fcc crystal structure with lattice parameter of 1.16 nm. The value of lattice parameter corresponds well with previously reported values. Chemical analysis by atom probe tomography

Microstructural evolution during creep deformation of an 11CrMoVNb ferritic heat resistant steel

Energy Technology Data Exchange (ETDEWEB)

Lee, Kyu-Ho; Park, Dae-Bum [Korea Institute of Science and Technology, Seoul (Korea, Republic of). Materials and Devices Div.; Korea Univ., Seoul (Korea, Republic of). Dept. of Materials Science; Kwun, S.I. [Korea Univ., Seoul (Korea, Republic of). Dept. of Materials Science; Suh, Jin-Yoo; Jung, Woo-Sang [Korea Institute of Science and Technology, Seoul (Korea, Republic of). Materials and Devices Div.

2010-07-01

The effect of creep deformation on the microstructural development of an 11CrMoVNb ferritic heat resistant steel during high temperature creep test is investigated. Coarsening behavior of the precipitates, M{sub 23}C{sub 6} and MX, and growth behavior of martensite laths of crept specimens are carefully observed from both gage and grip parts of the specimens in order to discuss the effect of deformation. Particle coarsening and martensite lath widening are pronounced in the gage part due to the creep deformation. (orig.)

Martensitic transformation and shape memory effect in NiTi alloy covered by chitosan/silver layer

Directory of Open Access Journals (Sweden)

Goryczka Tomasz

2015-01-01

Full Text Available The NiTi shape memory alloy was covered with chitosan/silver layer. Coatings were deposited at room temperature using combination of processing parameters such as deposition voltage and amount of silver in colloidal suspension. Structure of layers was studied by means of X-ray diffraction. Quality of the coatings was evaluated basing on observations done in scanning electron microscopy. Transformation behaviour of coated samples was studied with use of differential scanning calorimeter. The covered sample revealed presence of the reversible martensitic transformation and ability to deformation (in bending mode up to 8%. Forward martensitic transformation, in as-received NiTi alloy and in alloy after layer deposition occurred in two steps B2-R-B19’. After deformation quality of the chitosan/silver layer remained unchanged.

Simulation of the plastic deformation of shape-memory alloys

International Nuclear Information System (INIS)

Likhachev, V.A.; Puschtschajenko, O.V.

1997-01-01

On the basis of the structural analytical theory of durability a mathematical model is developed which describes mechanical properties of shape memory metals. The influence of dislocation glide on martensitic nonelasticity is investigated. Results of numerical modeling show, that within the framework of the model such shape memory phenomena, as pseudo-elasticity in martensite and austenite, deformation cycles (also in a incomplete temperature interval) or the two-way effect can be well described. The two-way effect was simulated assuming inheritence of the effective fields strain in martensite and austenite. (orig.)

Tensile Deformation Temperature Impact on Microstructure and Mechanical Properties of AISI 316LN Austenitic Stainless Steel

Science.gov (United States)

Xiong, Yi; He, Tiantian; Lu, Yan; Ren, Fengzhang; Volinsky, Alex A.; Cao, Wei

2018-03-01

Uniaxial tensile tests were conducted on AISI 316LN austenitic stainless steel from - 40 to 300 °C at a rate of 0.5 mm/min. Microstructure and mechanical properties of the deformed steel were investigated by optical, scanning and transmission electron microscopies, x-ray diffraction, and microhardness testing. The yield strength, ultimate tensile strength, elongation, and microhardness increase with the decrease in the test temperature. The tensile fracture morphology has the dimple rupture feature after low-temperature deformations and turns to a mixture of transgranular fracture and dimple fracture after high-temperature ones. The dominating deformation microstructure evolves from dislocation tangle/slip bands to large deformation twins/slip bands with temperature decrease. The deformation-induced martensite transformation can only be realized at low temperature, and its quantity increases with the decrease in the temperature.

Low temperature surface hardening of stainless steel; the role of plastic deformation

DEFF Research Database (Denmark)

Bottoli, Federico; Jespersen, Freja Nygaard; Hattel, Jesper Henri

2016-01-01

: - plastic deformation of metastable austenitic stainless steels leads to the development of strain-induced martensite, which compromises the uniformity and the homogeneity of the expanded austenite zone. - during low temperature surface engineering composition and stress profiles develop. On numerical......Thermochemical surface engineering by nitriding of austenitic stainless steel transforms the surface zone into expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behavior. As a consequence of the thermochemical surface engineering, huge...

Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

International Nuclear Information System (INIS)

Li Rutao; Zuo Xiurong; Hu Yueyue; Wang Zhenwei; Hu, Dingxu

2011-01-01

In order to satisfy the transportation of the crude oil and gas in severe environmental conditions, a ferrite/martensite dual-phase pipeline steel has been developed. After a forming process and double submerged arc welding, the microstructure of the base metal, heat affected zone and weld metal was characterized using scanning electron microscopy and transmission electron microscopy. The pipe showed good deformability and an excellent combination of high strength and toughness, which is suitable for a pipeline subjected to the progressive and abrupt ground movement. The base metal having a ferrite/martensite dual-phase microstructure exhibited excellent mechanical properties in terms of uniform elongation of 7.5%, yield ratio of 0.78, strain hardening exponent of 0.145, an impact energy of 286 J at - 10 deg. C and a shear area of 98% at 0 deg. C in the drop weight tear test. The tensile strength and impact energy of the weld metal didn't significantly reduce, because of the intragranularly nucleated acicular ferrites microstructure, leading to high strength and toughness in weld metal. The heat affected zone contained complete quenching zone and incomplete quenching zone, which exhibited excellent low temperature toughness of 239 J at - 10 deg. C. - Research Highlights: →The pipe with ferrite/martensite microstructure shows high deformability. →The base metal of the pipe consists of ferrite and martensite. →Heat affected zone shows excellent low temperature toughness. →Weld metal mainly consists of intragranularly nucleated acicular ferrites. →Weld metal shows excellent low temperature toughness and high strength.

A multi-scale model for structure-property relations of materials exhibiting martensite transformation plasticity

NARCIS (Netherlands)

Kouznetsova, V.; Balmachnov, A.; Geers, M.G.D.

2009-01-01

The remarkable mechanical properties of many advanced steels, e.g. metastable austenitic stainless steels, are related to their complex microstructural behaviour, resulting from the interaction between plastic deformation of the phases and the austenite to martensite phase transformation during

Martens-ite

Directory of Open Access Journals (Sweden)

Druce Dunne

2018-05-01

Full Text Available Martensite and martensitic transformations in metals and alloys have been intensively studied for more than a century and many comprehensive and informative reviews have been published. The current review differs insofar as the analysis is performed largely through the prism of detailed studies of the changes in the martensitic transformation in Fe3Pt alloy as a result of austenite ordering. This important alloy is the first ferrous alloy identified as exhibiting thermoelastic transformation and shape memory. The effect of parent phase order on the martensitic transformation offers significant insights into general understanding of the nature of martensitic transformation, particularly the factors contributing to reversible and irreversible transformation. It is concluded that for crystallograhically reversible transformation to occur both strain limiting and strain accommodating factors must be present and that these factors collectively constitute the sufficient condition for reversible martensitic transformation. Although the crystallography of individual plates formed in a given alloy can change with their temperature of formation, this intrinsic variability has not been considered in analyses using phenomenological theory. Significant variability can exist in measured quantities such as habit plane normals and orientation relationships used to test theoretical predictions. Measured lattice parameters, essential data for theoretical calculations, can also differ from the actual parameters existing at the temperature of plate formation.

A macroscopic model to simulate the mechanically induced martensitic transformation in metastable austenitic stainless steels

International Nuclear Information System (INIS)

Perdahcıoğlu, E.S.; Geijselaers, H.J.M.

2012-01-01

Mechanically induced martensitic transformation and the associated transformation plasticity phenomena in austenitic stainless steels are studied. The mechanisms responsible for the transformation are investigated and put into perspective based on experimental evidence. The stress and strain partitioning into the austenite and martensite phases are formulated using a mean-field homogenization approach. At this intermediate length-scale the average stress in the austenite phase is computed and utilized to compute the mechanical driving force resolved in the material. The amount of transformation and the transformation plasticity is derived as a function of the driving force. The mechanical response of the material is obtained by combining the homogenization and the transformation models. The model is verified by mechanical tests under biaxial loading conditions during which different transformation rates are observed. As a final verification of the model, a bending test is used which manifests the stress-state dependency of the transformation.

Deformation behavior of austenitic stainless steel at deep cryogenic temperatures

Science.gov (United States)

Han, Wentuo; Liu, Yuchen; Wan, Farong; Liu, Pingping; Yi, Xiaoou; Zhan, Qian; Morrall, Daniel; Ohnuki, Somei

2018-06-01

The nonmagnetic austenite steels are the jacket materials for low-temperature superconductors of fusion reactors. The present work provides evidences that austenites transform to magnetic martensite when deformation with a high-strain is imposed at 77 K and 4.2 K. The 4.2 K test is characterized by serrated yielding that is related to the specific motion of dislocations and phase transformations. The in-situ transmission electron microscope (TEM) observations in nanoscale reveal that austenites achieve deformation by twinning under low-strain conditions at deep cryogenic temperatures. The generations of twins, martensitic transformations, and serrated yielding are in order of increasing difficulty.

Characterization of the martensite phase formed during hydrogen ion irradiation in austenitic stainless steel

Science.gov (United States)

Jin, Hyung-Ha; Lim, Sangyeob; Kwon, Junhyun

2017-10-01

Microstructural changes in austenitic stainless steel caused by hydrogen ion irradiation were investigated using transmission electron microscopy (TEM). It has been confirmed that the irradiation induced the formation of martensite along the grain boundary; the martensite phase exhibited a crystal orientation relationship with the adjacent austenite phase. The results of this study also indicate that the concentration of Cr in the martensite phase is lower compared to that in the austenite matrix. The TEM results showed the development of asymmetric radiation-induced segregation (RIS) near the grain boundary, which leads to local changes in the chemical composition such as reduction of Cr near the grain boundary. The asymmetric RIS serves as a prerequisite for the formation of the martensite under hydrogen irradiation.

Estimation of the crystallographic strain limit during the reversible β ⇄ α″ martensitic transformation in titanium shape memory alloys

Science.gov (United States)

Zhukova, Yu. S.; Petrzhik, M. I.; Prokoshkin, S. D.

2010-11-01

Three methods are described to calculate the crystallographic strain limit that is determined by the maximum deformation of the crystal lattice in the reversible βbcc ⇄ α″orth martensitic transformation and ensures pseudoelastic deformation accumulation and shape recovery in Ti-Nb-Ta alloys.

In Situ Investigation of the Evolution of Lattice Strain and Stresses in Austenite and Martensite During Quenching and Tempering of Steel

Science.gov (United States)

Villa, M.; Niessen, F.; Somers, M. A. J.

2018-01-01

Energy dispersive synchrotron X-ray diffraction was applied to investigate in situ the evolution of lattice strains and stresses in austenite and martensite during quenching and tempering of a soft martensitic stainless steel. In one experiment, lattice strains in austenite and martensite were measured in situ in the direction perpendicular to the sample surface during an austenitization, quenching, and tempering cycle. In a second experiment, the sin2 ψ method was applied in situ during the austenite-to-martensite transformation to distinguish between macro- and phase-specific micro-stresses and to follow the evolution of these stresses during transformation. Martensite formation evokes compressive stress in austenite that is balanced by tensile stress in martensite. Tempering to 748 K (475 °C) leads to partial relaxation of these stresses. Additionally, data reveal that (elastic) lattice strain in austenite is not hydrostatic but hkl dependent, which is ascribed to plastic deformation of this phase during martensite formation and is considered responsible for anomalous behavior of the 200 γ reflection.

Surface mechanical attrition treatment induced phase transformation behavior in NiTi shape memory alloy

International Nuclear Information System (INIS)

Hu, T.; Wen, C.S.; Lu, J.; Wu, S.L.; Xin, Y.C.; Zhang, W.J.; Chu, C.L.; Chung, J.C.Y.; Yeung, K.W.K.; Kwok, D.T.K.; Chu, Paul K.

2009-01-01

The phase constituents and transformation behavior of the martensite B19' NiTi shape memory alloy after undergoing surface mechanical attrition treatment (SMAT) are investigated. SMAT is found to induce the formation of a parent B2 phase from the martensite B19' in the top surface layer. By removing the surface layer-by-layer, X-ray diffraction reveals that the amount of the B2 phase decreases with depth. Differential scanning calorimetry (DSC) further indicates that the deformed martensite in the sub-surface layer up to 300 μm deep exhibits the martensite stabilization effect. The graded phase structure and transformation behavior in the SMATed NiTi specimen can be attributed to the gradient change in strain with depth.

Isothermal Martensite Formation

DEFF Research Database (Denmark)

Villa, Matteo

Isothermal (i.e. time dependent) martensite formation in steel was first observed in the 40ies of the XXth century and is still treated as an anomaly in the description of martensite formation which is considered as a-thermal (i.e. independent of time). Recently, the clarification of the mechanism...... of lattice strains provided fundamental information on the state of stress in the material and clarified the role of the strain energy on martensite formation. Electron backscatter diffraction revealed that the microstructure of the material and the morphology of martensite were independent on the cooling...... leading to isothermal kinetics acquired new practical relevance because of the identification of isothermal martensite formation as the most likely process responsible for enhanced performances of sub-zero Celsius treated high carbon steel products. In the present work, different iron based alloys...

The strain accommodation in Ti–28Nb–12Ta–5Zr alloy during warm deformation

International Nuclear Information System (INIS)

Farghadany, E.; Zarei-Hanzaki, A.; Abedi, H.R.; Dietrich, D.; Lampke, T.

2014-01-01

The warm deformation behavior of a β-type Ti alloys, composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt, (so called TNTZ alloy), has been investigated in the present work in a warm deformation temperature. A variety of deformation features are characterized in the material microstructure after applied warm deformation scheme. The XRD analysis confirms an enhancement in martensite volume fraction. The electron back scatter diffractometry (EBSD) elucidates that the martensite has been mainly formed by laterally at the vicinity of different types of deformation bands. Both the well-known twining systems in TNTZ series have been occurred during deformation. The micro-shear bands, which are defined as highly concentrated plastic strain regions, are characterized in the deformed microstructure. The micro-shear bands are severely formed in the regions, which accommodate the most amount of applied strain

Stress-induced martensite variant reorientation in magnetic shape memory Ni–Mn–Ga single crystal studied by neutron diffraction

Czech Academy of Sciences Publication Activity Database

Molnár, Peter; Šittner, Petr; Lukáš, Petr; Hannula, S.-P.; Heczko, Oleg

2008-01-01

Roč. 17, č. 3 (2008), 035014/1-035014/4 ISSN 0964-1726 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10480505 Keywords : NiMnGa single crystal * neutron diffraction * stress induced martensite reorientation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.743, year: 2008

Special cases of martensite compatibility: A near single-variant habit-plane and the martensite of nanocrystalline NiTi

Directory of Open Access Journals (Sweden)

Petersmann Manuel

2015-01-01

Full Text Available Lattice parameters measured near the high temperature (~1000°C bcc α to hcp β transformation in an intermetallic Mo-containing γ-TiAl based alloy indicate a middle valued eigenvalue of the corresponding deformation gradient near 1. Habit-planes calculated under the assumption of a simple slip as lattice invariant shear, agree with experimentally determined orientations of the lens like plates recorded via electron backscattering. By contrast, twinning as invariant lattice shear has been investigated in nanocrystalline NiTi. Here the grain size causes the formation mechanism of the martensite to change from a “herring-bone” morphology faciliting a habit-plane between two twinned laminates and the austenite to a single laminate, which in the nonlinear theory formally cannot form a habit-plane with the austenite. Since this might cause high accommodation strains, the effectiveness of stress accommodation of martensite formed in neighboring grains of a polycrystal is investigated. Subsequent numerical microstructural modeling is outlined. The resulting energetically most favorable transformation sequence yields the transformation kinetics.

EBSD and FIB/TEM examination of shape memory effect deformation structures in U-14 at.% Nb

Energy Technology Data Exchange (ETDEWEB)

Clarke, A.J. [Materials Science and Technology Division, Mail Stop G770, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)], E-mail: aclarke@lanl.gov; Field, R.D.; McCabe, R.J.; Cady, C.M.; Hackenberg, R.E.; Thoma, D.J. [Materials Science and Technology Division, Mail Stop G770, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2008-06-15

Detailed examinations of shape memory effect (SME) deformation structures in martensite of U-14 at.% Nb were performed with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). An accommodation strain analysis, which has been previously used to predict SME deformation structures and texture evolution in polycrystalline material, was also performed. Martensite variants and twin relationships observed with EBSD after compressive or tensile deformation were determined to be consistent with those expected from calculated accommodation strains. Focused ion beam (FIB) was used to select twinned regions identified with EBSD for more detailed TEM analysis to verify the presence of these specific twins. The observed SME twinning systems in the martensite agree with previous TEM observations and the predicted {l_brace}1-bar76{r_brace} twinning system was observed experimentally for the first time in U-14 at.% Nb using these complementary techniques.

Mechanical properties of martensitic alloy AISI 422

International Nuclear Information System (INIS)

Huang, F.H.; Hu, W.L.; Hamilton, M.L.

1992-09-01

HT9 is a martensitic stainless steel that has been considered for structural applications in liquid metal reactors (LMRs) as well as in fusion reactors. AISI 422 is a commercially available martensitic stainless steel that closely resembles HT9, and was studied briefly under the auspices of the US LMR program. Previously unpublished tensile, fracture toughness and charpy impact data on AISI 422 were reexamined for potential insights into the consequences of the compositional differences between the two alloys, particularly with respect to current questions concerning the origin of the radiation-induced embrittlement observed in HT9. 8 refs, 8 figs

Shape memory effects, thermal expansion and B19' martensite texture in titanium nickelide

International Nuclear Information System (INIS)

Zel'dovich, V.I.; Sobyanina, G.A.; Rinkevich, O.S.; Gundyrev, V.M.

1996-01-01

The influence of plastic deformation by tension and cold rolling on shape memory effect, reverse shape memory effect, thermal expansion and texture state of martensite in titanium nickelide is under study. The relationship of thermal expansion coefficient to the value of strain during direct and reverse shape memory effect is established

Acoustic emission generated by dislocation mechanisms during the deformation of metals

International Nuclear Information System (INIS)

Heiple, C.R.

1978-01-01

Acoustic emission is a transient elastic wave generated by the rapid release of energy within a material. A wide variety of mechanisms have been proposed as possible sources of acoustic emission. Proposed mechanisms have included crack propagation, precipitate fracture, twin formation, martensite formation, dislocation motion and/or multiplication. This paper is concerned with acoustic emission generated by dislocation mechanisms operating during plastic deformation. Twinning and martensitic phase transformations are excluded even though dislocation motion is involved in the nucleation and growth of twins and the growth of martensite

Acoustic emission generated by dislocation mechanisms during the deformation of metals

Energy Technology Data Exchange (ETDEWEB)

Heiple, C.R.

1978-01-01

Acoustic emission is a transient elastic wave generated by the rapid release of energy within a material. A wide variety of mechanisms have been proposed as possible sources of acoustic emission. Proposed mechanisms have included crack propagation, precipitate fracture, twin formation, martensite formation, dislocation motion and/or multiplication. This paper is concerned with acoustic emission generated by dislocation mechanisms operating during plastic deformation. Twinning and martensitic phase transformations are excluded even though dislocation motion is involved in the nucleation and growth of twins and the growth of martensite.

Quantitative analysis of tensile deformation behavior by in-situ neutron diffraction for ferrite-martensite type dual-phase steels

International Nuclear Information System (INIS)

Morooka, Satoshi; Umezawa, Osamu; Harjo, Stefanus; Hasegawa, Kohei; Toji, Yuki

2012-01-01

The yielding and work-hardening behavior of ferrite-martensite type dual-phase (DP) alloys were clearly analyzed using the in-situ neutron diffraction technique. We successfully established a new method to estimate the stress and strain partitioning between ferrite and martensite phase during loading. Although these phases exhibit the same lattice structure with similar lattice parameters, their lattice strains on (110), (200) and (211) are obviously different from each other under an applied stress. The misfit strains between those phases were clearly accompanied with the phase-scaled internal stream (phase stress). Thus, the martensite phase yielded by higher applied stress than macro-yield stress, which resulted in high work-hardening rate of the DP steel. We also demonstrated that ferrite phase fraction influenced work-hardening behavior. (author)

Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing

Energy Technology Data Exchange (ETDEWEB)

Ghasemi-Nanesa, H; Shirazi, H [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, P.O. Box 14395-731 (Iran, Islamic Republic of); Nili-Ahmadabadi, M, E-mail: sut.caster.81710018@gmail.co, E-mail: nili@ut.ac.i [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, P.O. Box 14395-731 (Iran, Islamic Republic of) and Center of Excellence for High Performance Materials, University of Tehran, P.O. Box 14395-731, Tehran (Iran, Islamic Republic of)

2010-07-01

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was {epsilon} {approx}7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

Mechanical properties of Fe -10Ni -7Mn martensitic steel subjected to severe plastic deformation via cold rolling and wire drawing

Science.gov (United States)

Ghasemi-Nanesa, H.; Nili-Ahmadabadi, M.; Shirazi, H.

2010-07-01

Fe-Ni-Mn martensitic steels are one of the major groups of ultra-high strength steels that have good mechanical properties and ductility in as annealed condition but they suffer from severe inter-granular embitterment after aging. In this paper, the effect of heavy shaped cold rolling and wire drawing on the mechanical properties of Fe-Ni-Mn steel was investigated. This process could provide a large strain deformation in this alloy. The total strain was epsilon ~7. Aging behavior and tensile properties of Fe-10Ni-7Mn were studied after aging at 753 K. The results showed that the ultimate tensile strength and ductility after cold rolling, wire drawing and aging increased up to 2540 MPa and 7.1 %, respectively, while the conventional steels show a premature fracture stress of 830 MPa with about zero ductility after aging.

Effects of thermomechanical process on the microstructure and mechanical properties of a fully martensitic titanium-based biomedical alloy.

Science.gov (United States)

Elmay, W; Prima, F; Gloriant, T; Bolle, B; Zhong, Y; Patoor, E; Laheurte, P

2013-02-01

Thermomechanical treatments have been proved to be an efficient way to improve superelastic properties of metastable β type titanium alloys through several studies. In this paper, this treatment routes, already performed on superelastic alloys, are applied to the Ti-24Nb alloy (at%) consisting of a pure martensite α'' microstructure. By short-time annealing treatments performed on the heavily deformed material, an interesting combination of a large recoverable strain of about 2.5%, a low elastic modulus (35 GPa) and a high strength (900 MPa) was achieved. These properties are shown to be due to a complex microstructure consisting of the precipitation of nanoscale (α+ω) phases in ultra-fine β grains. This microstructure allows a superelastic behavior through stress-induced α'' martensitic transformation. In this study, the microstructures were characterized by X-ray diffraction and transmission electron microscopy and the evolution of the elastic modulus and the strain recovery as a function of the applied strain was investigated through loading-unloading tensile tests. Copyright © 2012 Elsevier Ltd. All rights reserved.

Martensitic transformations in 304 stainless steel after implantation with helium, hydrogen and deuterium

International Nuclear Information System (INIS)

Johnson, E.; Grabaek, L.; Johansen, A.; Sarholt-Kristensen, L.; Hayashi, N.; Sakamoto, I.

1988-01-01

Using conversion electron Moessbauer spectroscopy (CEMS) and glancing angle X-ray diffraction, martensitic transformations have been studied in type 304 austenitic stainless steels implanted with 8 keV helium, hydrogen and deuterium. Furthermore, using CEMS in the energy selective mode (DCEMS), the distribution of martensite in the implantation zone has been analysed as a function of depth. Transformation of the implanted layer occurs after implantation with 10 21 m -2 He + ions while 100 times higher fluence is required for the implanted layer to transform after hydrogen or deuterium implantations. This difference is due to the ability of helium to form high pressure gas bubbles, while implanted hydrogen is continuously lost by back diffusion to the surface. The helium bubbles, which are confined under pressures as high as 60 GPa, will induce extremely high stress levels in the implanted layer, by which the martensitic transformation is directly induced. The fact that a much higher fluence of hydrogen or deuterium is required to induce the transformation, shows that radiation damage plays only a minor role. In this case, the martensitic transformation first occurs when the implanted layer resembles the state of a cathodically charged surface. (orig.)

Phase transformation system of austenitic stainless steels obtained by permanent compressive strain

Energy Technology Data Exchange (ETDEWEB)

Okayasu, Mitsuhiro, E-mail: mitsuhiro.okayasu@utoronto.ca; Tomida, Sai

2017-01-27

In order to understand more completely the formation of strain-induced martensite, phase structures were investigated both before and after plastic deformation, using austenitic stainless steels of various chemical compositions (carbon C=0.007–0.04 mass% and molybdenum Mo=0–2.10 mass%) and varying pre-strain levels (0–30%). Although the stainless steels consisted mainly of γ austenite, two martensite structures were generated following plastic deformation, comprising ε and α′ martensite. The martensitic structures were obtained in the twin deformation and slip bands. The severity of martensite formation (ε and α′) increased with increasing C content. It was found that α′ martensite was formed mainly in austenitic stainless steel lacking Mo, whereas a high Mo content led to a strong ε martensite structure, i.e. a weak α′ martensite. The formation of α′ martensite occurred from γ austenite via ε martensite, and was related to the slip deformation. Molybdenum in austenitic stainless steel had high slip resistance (or weak stress-induced martensite transformation), because of the stacking fault energy of the stainless steel affecting the austenite stability. This resulted in the creation of weak α′ martensite. Models of the martensitic transformations γ (fcc)→ε (hcp)→α′ (bcc) were proposed on both the microscopic and nanoscopic scales. The α′ martensite content of austenitic stainless steel led to high tensile strength; conversely, ε martensite had a weak effect on the mechanical strength. The influence of martensitic formation on the mechanical properties was evaluated quantitatively by statistical analysis.

STUDY OF THE EFFECT OF PRELIMINARY PLASTIC DEFORMATION IN THE PROCESS OF DISSOLUTION DURING TEMPERING OF LOW-CARBON AND BORON-CONTAINING ALLOYS

OpenAIRE

M. Yu. Filonenko; S. B. Piliaieva

2009-01-01

In the paper the influence of preliminary deformation on disintegration of martensite in boron-containing and carbonic alloy is explored. It is shown that at the small degree of deformation (7 per cent) both in low-carbonic and boron-containing alloys the process of martensite disintegration takes place less intensively. The increase of degree of preliminary deformation in a boron-containing alloy is instrumental in more even distribution of boron-cementite particles appearing as a result of ...

Hydrogen-Induced Plastic Deformation in ZnO

Science.gov (United States)

Lukáč, F.; Čížek, J.; Vlček, M.; Procházka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.

In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO micro structure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday's law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogen-induced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.

Deformation mechanisms in austenitic TRIP/TWIP steels at room and elevated temperature investigated by acoustic emission and scanning electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Linderov, M. [Laboratory of Physics of Strength of Materials and Intelligent Diagnostic Systems, Togliatti State University, Togliatti 445667 (Russian Federation); Segel, C.; Weidner, A.; Biermann, H. [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, 09599 Freiberg (Germany); Vinogradov, A., E-mail: vinogradov@tltsu.ru [Laboratory of Physics of Strength of Materials and Intelligent Diagnostic Systems, Togliatti State University, Togliatti 445667 (Russian Federation)

2014-03-01

The modern austenitic stainless TRIP/TWIP steels have an outstanding combination of strength and ductility, depending on their chemical composition and loading conditions. A critical factor, which strongly affects all deformation-induced processes in metastable austenitic steels, is the temperature. To get a better insight into the effect of temperature on the deformation kinetics and transformation processes in high-alloy CrMnNi TRIP/TWIP steels with different austenite stability due to a varied content of Ni (3, 6 and 9 wt%), an acoustic emission (AE) technique was used during uniaxial tension at two different temperatures – ambient and 373 K. The in-situ AE results were paired with detailed SEM investigations using the electron backscattered diffraction (EBSD) technique to identify the deformation-induced phase transformations and mechnical twinning. The cluster analysis of the AE signals has revealed an excellent correlation of AE features with synergistic complexity of deformation mechanisms involved in various combinations: dislocation glide, stacking faults, martensitic phase transformation and twinning.

First interactions between hydrogen and stress-induced reverse transformation of Ni-Ti superelastic alloy

Science.gov (United States)

Yokoyama, Ken'ichi; Hashimoto, Tatsuki; Sakai, Jun'ichi

2017-11-01

The first dynamic interactions between hydrogen and the stress-induced reverse transformation have been investigated by performing an unloading test on a Ni-Ti superelastic alloy subjected to hydrogen charging under a constant applied strain in the elastic deformation region of the martensite phase. Upon unloading the specimen, charged with a small amount of hydrogen, no change in the behaviour of the stress-induced reverse transformation is observed in the stress-strain curve, although the behaviour of the stress-induced martensite transformation changes. With increasing amount of hydrogen charging, the critical stress for the reverse transformation markedly decreases. Eventually, for a larger amount of hydrogen charging, the reverse transformation does not occur, i.e. there is no recovery of the superelastic strain. The residual martensite phase on the side surface of the unloaded specimen is confirmed by X-ray diffraction. Upon training before the unloading test, the properties of the reverse transformation slightly recover after ageing in air at room temperature. The present study indicates that to change the behaviour of the reverse transformation a larger amount of hydrogen than that for the martensite transformation is necessary. In addition, it is likely that a substantial amount of hydrogen in solid solution more strongly suppresses the reverse transformation than hydrogen trapped at defects, thereby stabilising the martensite phase.

Strength of initially virgin martensites at - 196 °C after aging and tempering

Science.gov (United States)

Eldis, George T.; Cohen, Morris

1983-06-01

The compressive strength at -196°C of martensites in Fe-0.26 pct C-24 pct Ni, Fe-0.4 pct C-21 pct Ni, and Fe-0.4 pct C-18 pct Ni-3 pct Mo alloys, all with subzero M temperatures, has been determined in the virgin condition and after one hour at temperatures from -80 to +400 °C. The effects of ausforming (20 pct reduction in area of the austenite by swaging at room temperature prior to the martensitic transformation) were also investigated. For the unausformed martensites, aging at temperatures up to 0 °C results in relatively small increases in strength. Above 0 °C, the age hardening increment increases rapidly, reaching a maximum at 100 °C. Above 100 °C, the strength decreases continuously with increasing tempering temperature except for the molybdenum-containing alloy, which exhibits secondary hardening on tempering at 400 °C. For the ausformed martensites, the response to aging at subzero temperatures is greater than for unausformed material. Strength again passes through a maximum on aging at 100 °C. However, on tempering just above 100 °C, the ausformed materials show a slower rate of softening than the unausformed martensites. The strengthening produced by the ausforming treatment is largest for the Fe-0.4 pct C-18 pct Ni-3 pct Mo alloy, but there is no evidence of carbide precipitation in the deformed austenite to a°Count for this effect of molybdenum.

Evaluation of stress-induced martensite phase in ferromagnetic shape memory alloy Fe-30.2at%Pd by non-destructive Barkhausen noise

Science.gov (United States)

Furuya, Yasubumi; Okazaki, Teiko; Ueno, Takasi; Spearing, Mark; Wutting, Manfred

2005-05-01

Barkhausen noise (BHN) method seems a useful tecnique to non-destructive evaluation of martensite phase transformation of ferromagnetic shape memory alloy, which is used as the filler of our proposing "Smart Composite Board". The concept of design for "Smart Composite Board" which can combine the non-destructive magnetic inspection and shape recovery function in the material itself was formerly proposed. In the present study, we survey the possibility of Barkhausen noise (BHN) method to detect the transformation of microscopic martensite phase caused by stress-loading in Fe-30.2at%Pd thin foil, which has a stable austenite phase (fcc structure) at room temperature. The BHN voltage was measured at loading stress up to 100 MPa in temperature range of 300K to 373K. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. A phase transformation caused by loading stress were analyzed also by X-ray diffraction. The signals of BHN are analyzed by the time of magnetization and the noise frequency. BHN caused by grain boundaries appears in the lower frequency range (1kHz-3kHz) and BHN by martensite twin in the higher frequency range (8kHz-10kHz). The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy.

Moessbauer and TEM study of martensitic transformations in ion implanted 17/7 stainless steel

International Nuclear Information System (INIS)

Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Graabaek, L.

1986-01-01

It has earlier been shown that implantation of antimony into austenitic stainless steels induces martensitic phase transformations γ (fcc)→α (bcc). In the present work we have investigated which mechanisms are responsible for the transformation. Samples of 17/7 steels were implanted with noble gases (Kr, Ar) or the stainless steel constituent elements (Fe, Ni, Cr). The energies were selected to give ranges ∝40 nm. The phases present after implantation and the microstructures of the implanted samples were studied by CEMS and TEM respectively. A martensitic (α) phase was found to form after implantation both with Ni, Fe and Cr, in spite of the fact that these elements have opposite tendencies for stabilization of the austenite (γ) phase. The efficiency of martensite formation is therefore mainly related to stress relief associated with secondary radiation damage. This was substantiated from the noble gas implantations, where the highest degree of transformation was observed for fluences where bubble formation occurs. The CEMS analyses show that the transformation efficiency in such cases is nearly 100%. The hyperfine parameters of the implantation induced α phase are similar to those from conventionally induced martensites. (orig.)

The difference in thermal and mechanical stabilities of austenite between carbon- and nitrogen-added metastable austenitic stainless steels

International Nuclear Information System (INIS)

Masumura, Takuro; Nakada, Nobuo; Tsuchiyama, Toshihiro; Takaki, Setsuo; Koyano, Tamotsu; Adachi, Kazuhiko

2015-01-01

In order to evaluate the effects of carbon and nitrogen addition on the stability of austenite, athermal and deformation-induced α′-martensitic transformation behaviors were investigated using type 304-metastable austenitic stainless steels containing 0.1 mass% carbon or nitrogen. The difference in the development of the deformation microstructure in particular is discussed in terms of the stacking-fault energy (SFE). Since carbon-added steel has a lower SFE than that of nitrogen-added steel, deformation twins and ε-martensite were preferentially formed in the carbon-added steel, whereas a dislocation cell structure developed in the nitrogen-added steel. Crystallographic analysis using the electron backscatter diffraction method revealed that the difference in the deformation microstructure has a significant influence on the growth behavior of deformation-induced α′-martensite, that is, the interface of the deformation twins and ε-martensite suppresses the growth of α′-martensite, whereas dislocation cell boundaries are not effective. As a result, the mechanical stability of carbon-added steel is slightly higher than that of nitrogen-added steel, although the thermal stabilization effect of carbon is much lower than that of nitrogen

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.

Depth distribution analysis of Martensitic transformations in Xe implanted austenitic stainless steel

DEFF Research Database (Denmark)

Johnson, E.; Gerritsen, E.; Chechenin, N.G.

1989-01-01

In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...... electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1 × 1020 m−2. The thickness of the transformed layer increases with fluence to ≈ 150 nm at 1 × 10 21 m−2, which far exceeds the range plus straggling...

Convoluted dislocation loops induced by helium irradiation in reduced-activation martensitic steel and their impact on mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, Canada K7L 3N6 (Canada); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wen, Yongming [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

2014-06-01

Helium irradiation induced dislocation loops in reduced-activation martensitic steels were investigated using transmission electron microscopy. The specimens were irradiated with 100 keV helium ions to 0.8 dpa at 350 °C. Unexpectedly, very large dislocation loops were found, significantly larger than that induced by other types of irradiations under the same dose. Moreover, the large loops were convoluted and formed interesting flower-like shape. The large loops were determined as interstitial type. Loops with the Burgers vectors of b=〈100〉 were only observed. Furthermore, irradiation induced hardening caused by these large loops was observed using the nano-indentation technique.

Surface severe plastic deformation of AISI 304 via conventional shot peening, severe shot peening and repeening

Energy Technology Data Exchange (ETDEWEB)

Unal, Okan, E-mail: unalokan78@gmail.com [Mechanical Engineering Department, Bartın University, Bartın 74100 (Turkey); Varol, Remzi [Mechanical Engineering Department, Suleyman Demirel University, Isparta 32200 (Turkey)

2015-10-01

Highlights: • CSP and SSP treatments transform austenite to metastable martensite structure. • Nanograin layer thickness after CSP and SSP is 8 μm and 22 μm, respectively. • Shot peening leads to carbon segregation from coarse to nano grain layer. • Repeening is an effective way to reduce surface roughness. - Abstract: Air blast conventional shot peening (CSP), severe shot peening (SSP) and repeening (RP) as a severe plastic deformation applications on AISI 304 austenitic stainless steel is addressed. Shot peened specimens are investigated based on optical, FESEM and digital microscope. The investigations present the austenite transformation to metastable martensite via mechanical twinning due to plastic deformation with high strain rates. It is found that SSP induces thicker nanograin layer with compared to CSP. In XRD studies, the austenite peaks broaden by means of severe shot peening and FWHM increase reveals the grain size reduction below 25 nm regimes on the surface. In EDAX line analysis of CSP specimen, carbon content increase has been detected from deformed layer through the nanocrystalline layer then the content reduces. The carbon segregation takes place due to the energy level distinction between dislocations and Fe−C bonds. 3d contour digital microscope studies and roughness investigations reveal that SSP has deleterious side effect on the surface roughness and surface flatness. However, RP is an effective way to reduce the surface roughness to reasonable values.

Effect of structure evolution induced by ultrasonic peening on the corrosion behavior of AISI-321 stainless steel

International Nuclear Information System (INIS)

Mordyuk, B.N.; Prokopenko, G.I.; Vasylyev, M.A.; Iefimov, M.O.

2007-01-01

A nanocrystalline surface layer was produced on an AISI-321 stainless steel by severe plastic deformation via ultrasonic peening (UP). The microstructural evolution of the surface layer was characterized by means of X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The volume fraction of strain-induced α-martensite as a function of the effective strain (e-bar) was evaluated quantitatively using XRD and magnetic measurements. Considering the e-bar magnitudes and the TEM data obtained, it is concluded that a grain refinement of austenitic structure passes ahead of the α-martensite formation, particularly in the top surface layer. The nanocrystalline austenitic grain structure (mean grain size∼15nm) was observed at e-bar=0.45, while the startup of the strain-induced martensitic transformation was revealed at the strain extent of 0.62. The nanostructured surface layer formed after straining to e-bar=0.8 already contains mainly the martensite nanograins characterized by an average size of about 10nm. Grain size increased gradually up to 60nm within the layer containing both austenite and martensite phases at a depth of about 30μm from the treated surface. Both the microhardness behavior of the stainless steel surface and its corrosion performance in 3.5% NaCl solution can be enhanced by the UP. They are shown to be in correlation with: (i) the grain refinement process and (ii) the increase in the volume fraction of strain-induced α-martensite

The morphology of lath martensite: a new perspective

Directory of Open Access Journals (Sweden)

Koumatos Konstantinos

2015-01-01

Full Text Available A mathematical framework is proposed to predict the features of the (5 5 7 lath transformation in low-carbon steels based on energy minimisation. This theory generates a one-parameter family of possible habit plane normals and a selection mechanism then identifies the (5 5 7 normals as those arising from a deformation with small atomic movement and maximal compatibility. While the calculations bear some resemblance to those of double shear theories, the assumptions and conclusions are different. Interestingly, the predicted microstructure morphology resembles that of plate martensite, in the sense that a type of twinning mechanism is involved.

Transition from many domain to single domain martensite morphology in small-scale shape memory alloys

International Nuclear Information System (INIS)

Ueland, Stian M.; Schuh, Christopher A.

2013-01-01

The morphology of the martensitic transformation during a superelastic cycle is studied by in situ scanning electron microscopy deformation experiments in microwires of Cu–Zn–Al. The diameters of the wires studied (21–136 μm) span the range in which significant size effects upon transformation hysteresis have been observed. In larger wires the transformation is accommodated by the continual nucleation of many new martensite plates that grow and eventually coalesce with their neighbors. In small wires a single martensite plate nucleates at the start of transformation and then proceeds to grow in a monolithic fashion; the wire transforms by smooth axial propagation of a single interface. The transition from many domain to single domain transformation is gradual with wire diameter, and is based upon scaling of the domain density with sample size. We attribute it to a crossover from bulk to surface obstacle control of transformation front propagation. This observation also sheds light on reported size effects in energy dissipation in shape memory alloys

Fine grained 304 ASS processed by a severe plastic deformation and subsequent annealing; microstructure and mechanical properties evaluation

Science.gov (United States)

Salout, Shima Ahmadzadeh; Shirazi, Hasan; Nili-Ahmadabadi, Mahmoud

2018-01-01

The current research is an attempt to study the effect of a novel severe plastic deformation technique so called "repetitive corrugation and straightening by rolling" (RCSR) and subsequent annealing on the microstructure and mechanical properties of AISI type 304 austenitic stainless steel. In this study, RCSR process was carried out at 200 °C on the 304 austenitic stainless steel (above Md30 temperature that is about 50 °C for this stainless steel) in order to avoid the formation of martensite phase when a high density of dislocations was introduced into the austenite phase and also high density of mechanical twins was induced in the deformed 304 austenitic stainless steel. Because of relationship between deformation temperature, stacking fault energy (SFE) and mechanisms of deformation. Thereafter subsequently, annealing treatment was applied into deformed structure in order to refine the microstructure of 304 stainless s teel. The specimens were examined by means of optical microscopy (OM), scanning electron microscopy (SEM), tensile and micro-hardness tests. The results indicate that by increasing the cycles of RCSR process (increasing applied strain), further mechanical twins are induced, the hardness and in particular, the yield stress of specimens have been increased.

On the effectiveness of surface severe plastic deformation by shot peening at cryogenic temperature

Science.gov (United States)

Novelli, M.; Fundenberger, J.-J.; Bocher, P.; Grosdidier, T.

2016-12-01

The effect of cryogenic temperature (CT) on the graded microstructures obtained by severe shot peening using surface mechanical attrition treatment (SMAT) was investigated for two austenitic steels that used different mechanisms for assisting plastic deformation. For the metastable 304L steel, the depth of the hardened region increases because CT promotes the formation of strain induced martensite. Comparatively, for the 310S steel that remained austenitic, the size of the subsurface affected region decreases because of the improved strength of the material at CT but the fine twinned nanostructures results in significant top surface hardening.

Model of the Evolution of Deformation Defects and Irreversible Strain at Thermal Cycling of Stressed TiNi Alloy Specimen

Directory of Open Access Journals (Sweden)

Volkov Aleksandr E.

2015-01-01

Full Text Available This microstructural model deals with simulation both of the reversible and irreversible deformation of a shape memory alloy (SMA. The martensitic transformation and the irreversible deformation due to the plastic accommodation of martensite are considered on the microscopic level. The irreversible deformation is described from the standpoint of the plastic flow theory. Isotropic hardening and kinematic hardening are taken into account and are related to the densities of scattered and oriented deformation defects. It is supposed that the phase transformation and the micro plastic deformation are caused by the generalized thermodynamic forces, which are the derivatives of the Gibbs’ potential of the two-phase body. In terms of these forces conditions for the phase transformation and for the micro plastic deformation on the micro level are formulated. The macro deformation of the representative volume of the polycrystal is calculated by averaging of the micro strains related to the evolution of the martensite Bain’s variants in each grain comprising this volume. The proposed model allowed simulating the evolution of the reversible and of the irreversible strains of a stressed SMA specimen under thermal cycles. The results show a good qualitative agreement with available experimental data. Specifically, it is shown that the model can describe a rather big irreversible strain in the first thermocycle and its fast decrease with the number of cycles.

Analysis of the non-isothermal austenite-martensite transformation in 13% Cr-type martensitic stainless steels

International Nuclear Information System (INIS)

Garcia-De-Andris, C.; Alvarez, L.F.

1996-01-01

In martensitic stainless steels, as in other alloyed containing carbide-forming elements, the carbide dissolution and precipitation processes that take place during heat treatment can cause modifications to the chemical composition of the austenite phase of these steels. The chemical composition of this phase is a fundamental factor for the evolution of the martensitic transformation. As a result of their influence on the dissolution and precipitation processes, the parameters of the quenching heat treatment exert a strong influence on the behavior of the martensitic transformation in these steels. In the present study, the effect of the heating temperature and the cooling rate on the martensitic transformation in two 13% Cr-type martensitic stainless steels with different carbon contents were properly evaluated. (author)

Phase Transformation of Metastable Austenite in Steel during Nano indentation

International Nuclear Information System (INIS)

Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

2013-01-01

These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

Phase Transformation of Metastable Austenite in Steel during Nano indentation

Energy Technology Data Exchange (ETDEWEB)

Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

2013-05-15

These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high strain rate loading

OpenAIRE

Wang Lin; Wang Yangwei; Xu Xin; Liu Chengze

2015-01-01

Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy...

Understanding the effect of uniaxial tensile strain on the early stages of sensitization in AISI 304 austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Chowdhury, P.S., E-mail: psc0126@gmail.com [Techno India Agartala, Maheshkhola, Agartala, West Tripura PIN – 799004 (India); Guchhait, S.K.; Mitra, P.K. [Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700032 (India); Mukherjee, P.; Gayathri, N. [Variable Energy Cyclotron Centre (VECC), 1/AF Bidhan Nagar, Kolkata 700064 (India); Mitra, M.K. [Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700032 (India)

2015-04-01

In the present study, an attempt has been made to understand the effect of different competing mechanisms controlling the overall degree of sensitization (DOS) of deformed austenitic stainless steel at the early stage of sensitization. The Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) studies were performed to characterize the Degree of Sensitization (DOS) as a function of both pre-defined strain and sensitization temperature. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to explain the phenomena qualitatively. A non monotonous behaviour in the variation of DOS has been observed with deformation and sensitization temperature. The presence of Deformation Induced Martensites (DIM) and their transformation into tempered martensites (α + M{sub 23}C{sub 6}) at higher temperatures was found to play major roles in controlling the overall sensitization and desensitization processes. - Highlights: • Interplay of various dynamic processes (four) in the early sensitization. • Deformation induced martensite (α′) playing major role at low temperature. • α (Tempered martensite) induced processes plays a vital role at higher temperatures. • Results in non monotonous variation in degree of sensitisation (DOS)

Development of a stress-induced martensitic transformation criterion for a Cu–Al–Be polycrystalline shape memory alloy undergoing uniaxial tension

International Nuclear Information System (INIS)

García-Castillo, F.N.; Cortés-Pérez, J.; Amigó, V.; Sánchez-Arévalo, F.M.; Lara-Rodríguez, G.A.

2015-01-01

This study presents a criterion for predicting the martensitic variants (MVs) that appear during the stress-induced martensitic transformation (SIMT) in a polycrystalline sample of Cu–11.5% wt. Al–0.5% wt. Be under simple tension. Our criterion is based on crystallographic parameters, such as the crystal orientation and Schmid factor (SF). The displacement vector fields (DVFs) were obtained in the observation system by a mathematical model and were used to distort the boundary of a set of grains. From the DVF, the strain tensor for each grain was obtained, and the strain ratio (SR) in the observation system was calculated. Electron backscattering diffraction (EBSD) measurements were performed to determine the crystal orientation of the grains. The inverse SF was used to determine the in-plane stress transformation diagrams (STDs) for each studied grain. The combination of a balance criterion (BC) and STD provided a criterion that allowed us to predict the possible order of stress-induced MVs formed as a function of the crystal orientation and thermomechanical parameters of the shape memory alloy (SMA) with higher accuracy than when using the criteria separately. To validate our criteria, we tested other researchers’ published results. Our results were in agreement and were capable of predicting the stress-induced MVs in a polycrystalline SMA

The effects of strain-induced martensitic transformation and temperature on impact fatigue crack propagation behavior of SUS 304 at low temperature

International Nuclear Information System (INIS)

Murakami, Ri-ichi; Akizono, Koichi; Kusukawa, Kazuhiro.

1988-01-01

The fatigue crack propagation behavior in fatigue impact at room temperature and 103 K was investigated by means of fracture mechanics, X-ray diffraction analysis and fractography for an austenitic stainless steel, SUS 304. The crack growth rate in fatigue impact decreased with decreasing temperature. The crack growth rate at room temperature was scarcely influenced by the microstructure, while at low temperature it was markedly influenced by the microstructure. The effects of microstructure and temperature on the crack growth rate were closely related to the strain-induced martensitic transformation. The martensitic transformation was influenced by the microstructure, the temperature, the fracture morphology and the stress intensity level and resulted in a decrease in crack growth rate with increasing crack opening level. (author)

Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Stress-induced martensitic transformations in a Cu-Al-Ni shape memory alloy studied by in situ transmission electron microscopy

Czech Academy of Sciences Publication Activity Database

Zárubová, Niva; Gemperlová, Juliana; Gärtnerová, Viera; Gemperle, Antonín

481-482, č. 5 (2008), s. 457-461 ISSN 0921-5093 R&D Projects: GA ČR GA202/04/2016; GA AV ČR(CZ) IAA200100627 Institutional research plan: CEZ:AV0Z10100520 Keywords : in situ TEM straining * CuAlNi shape memory alloy * stress -induced formation of martensite Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.806, year: 2008

The influence of the martensitic transformation on the fatigue of an AISI type 316 metastable stainless steel

International Nuclear Information System (INIS)

Pacheco, D.J; Sousa e Silva, A.S. de; Monteiro, S.N.

The influence of the martensitic transformation on the process of pulse tension fatigue of a AISI type 316 metastable stainless steel was studied at 25 0 and 196 0 c. The fatigue tests were performed on annealed and cold worked specimens in order to separate the effects of static transformation, dynamic transformation and work hardening. The fatigue limits obtained from the corresponding Wohler curves were compared for the different test conditions. The results showed that the fatigue is not affected by the dynamically induced martensite. On the other hand the static martensite, previously induced, appears to decrease the resistance to fatigue. The reasons for these effects are discussed. (Author) [pt

Influence of the Martensitic Transformation on the Microscale Plastic Strain Heterogeneities in a Duplex Stainless Steel

Science.gov (United States)

Lechartier, Audrey; Martin, Guilhem; Comby, Solène; Roussel-Dherbey, Francine; Deschamps, Alexis; Mantel, Marc; Meyer, Nicolas; Verdier, Marc; Veron, Muriel

2017-01-01

The influence of the martensitic transformation on microscale plastic strain heterogeneity of a duplex stainless steel has been investigated. Microscale strain heterogeneities were measured by digital image correlation during an in situ tensile test within the SEM. The martensitic transformation was monitored in situ during tensile testing by high-energy synchrotron X-ray diffraction. A clear correlation is shown between the plasticity-induced transformation of austenite to martensite and the development of plastic strain heterogeneities at the phase level.

Microscopic residual stress evolution during deformation process of an Fe---Mn---Si---Cr shape memory alloy investigated using white X-ray microbeam diffraction

International Nuclear Information System (INIS)

Kwon, E.P.; Sato, S.; Fujieda, S.; Shinoda, K.; Kajiwara, K.; Sato, M.; Suzuki, S.

2013-01-01

Microscopic residual stress evolution in different austenite (γ) grains during shape memory process in an Fe---Mn---Si---Cr alloy was investigated using the white X-ray microbeam diffraction technique. The use of high-energy white X-ray microbeam with small beam size allowed us to measure the microscopic residual stress in coarse γ grains with specific orientation. After tensile deformation large compressive residual stress was evolved in γ grains due to the formation of stress-induced ε martensite, but upon recovery heating it almost disappeared as a result of reverse transformation of martensite. The magnitude of compressive residual stress was higher in grains with orientations close to 〈144〉 and 〈233〉 orientations than in a grain with near 〈001〉 orientation. Analysis of the microstructure of each grain using electron backscattering diffraction suggested that the difference in the magnitude of compressive residual stress could be attributed to different martensitic transformation characteristics in the grains

Step-wise stimulated martensitic transformations

International Nuclear Information System (INIS)

Airoldi, G.; Riva, G.

1991-01-01

NiTi alloys, widely known both for their shape memory properties and for unusual pseudoelastic behaviour, are now on the forefront attention for step-wise induced memory processes, thermal or stress stimulated. Literature results related to step-wise stimulated martensite (direct transformation) are examined and contrasted with step-wise thermal stimulated parent phase (reverse transformation). Hypothesis are given to explain the key characters of both transformations, a thermodynamic model from first principles being till now lacking

A 3D finite-strain-based constitutive model for shape memory alloys accounting for thermomechanical coupling and martensite reorientation

Science.gov (United States)

Wang, Jun; Moumni, Ziad; Zhang, Weihong; Xu, Yingjie; Zaki, Wael

2017-06-01

The paper presents a finite-strain constitutive model for shape memory alloys (SMAs) that accounts for thermomechanical coupling and martensite reorientation. The finite-strain formulation is based on a two-tier, multiplicative decomposition of the deformation gradient into thermal, elastic, and inelastic parts, where the inelastic deformation is further split into phase transformation and martensite reorientation components. A time-discrete formulation of the constitutive equations is proposed and a numerical integration algorithm is presented featuring proper symmetrization of the tensor variables and explicit formulation of the material and spatial tangent operators involved. The algorithm is used for finite element analysis of SMA components subjected to various loading conditions, including uniaxial, non-proportional, isothermal and adiabatic loading cases. The analysis is carried out using the FEA software Abaqus by means of a user-defined material subroutine, which is then utilized to simulate a SMA archwire undergoing large strains and rotations.

The Formation of Martensitic Austenite During Nitridation of Martensitic and Duplex Stainless Steels

Science.gov (United States)

Zangiabadi, Amirali; Dalton, John C.; Wang, Danqi; Ernst, Frank; Heuer, Arthur H.

2017-01-01

Isothermal martensite/ferrite-to-austenite phase transformations have been observed after low-temperature nitridation in the martensite and δ-ferrite phases in 15-5 PH (precipitation hardening), 17-7 PH, and 2205 (duplex) stainless steels. These transformations, in the region with nitrogen concentrations of 8 to 16 at. pct, are consistent with the notion that nitrogen is a strong austenite stabilizer and substitutional diffusion is effectively frozen at the paraequilibrium temperatures of our experiments. Our microstructural and diffraction analyses provide conclusive evidence for the martensitic nature of these phase transformations.

Energy landscape for martensitic phase transformation in shape memory NiTi

International Nuclear Information System (INIS)

Kibey, S.; Sehitoglu, H.; Johnson, D.D.

2009-01-01

First-principles calculations are presented for parent B2 phase and martensitic B19 and B19' phases in NiTi. The results indicate that both B19 and B19' are energetically more stable than the parent B2 phase. By means of ab initio density functional theory, the complete distortion-shuffle energy landscape associated with B2 → B19 transformation in NiTi is then determined. In addition to accounting for the Bain-type deformation through the Cauchy-Born rule, the study explicitly accounts for the shuffle displacements experienced by the internal ions in NiTi. The energy landscape allows the energy barrier associated with the B2 → B19 transformation pathway to be identified. The results indicate that a barrier of 0.48 mRyd atom -1 (relative to the B2 phase) must be overcome to transform the parent B2 NiTi to orthorhombic B19 martensite

Study of martensitic transformation in stainless steel by CEMS and RBS channeling

International Nuclear Information System (INIS)

Hayashi, N.; Sakamoto, I.; Tanoue, H.

1993-01-01

The effect of Xe ion irradiation in a single crystal of 17/13 stainless steel has been studied, using RBS channeling techniques and conversion electron Moessbauer spectroscopy (CEMS). 300 keV Xe ions were used to induce martensitic transformation in the austentic steel. A dynamic behavior of the transformation was observed as functions of the fluence and depth dependence. The martensite appears abruptly at a critical fluence, in contrast with polycrystalline 17/7 stainless steel. (orig.)

Micromechanics of transformation-induced plasticity and variant coalescence

International Nuclear Information System (INIS)

Marketz, F.; Fischer, F.D.; University for Mining and Metallurgy, Leoben; Tanaka, K.

1996-01-01

Quantitative micromechanics descriptions of both transformation-induced plasticity (TRIP) associated with the martensitic transformation in an Fe-Ni alloy and of variant coalescence in a Cu-Al-Ni shape memory alloy are presented. The macroscopic deformation behavior of a polycrystalline aggregate as a result of the rearrangements within the crystallites is modelled with the help of a finite element based periodic microfield approach. In the case of TRIP the parent→martensite transformation is described by microscale thermodynamic and kinetic equations taking into account internal stress states. The simulation of a classical experiment on TRIP allows to quantify the Magee-effect and the Greenwood-Johnson effect. Furthermore, the development of the martensitic microstructure is studied with respect to the stress-assisted transformation of preferred variants. In the case of variant coalescence the strain energy due to internal stress states has an important influence on the mechanical behavior. Formulating the reorientation process on the size scale of self-accommodating plate groups in terms of the mobility of the boundaries between martensitic variants the macroscopic behavior in uniaxial tension is predicted by an incremental modelling procedure. Furthermore, influence of energy dissipation on the overall behavior is quantified. (orig.)

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.

Micromechanical analysis of martensite distribution on strain localization in dual phase steels by scanning electron microscopy and crystal plasticity simulation

Energy Technology Data Exchange (ETDEWEB)

Jafari, M. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Ziaei-Rad, S., E-mail: szrad@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Saeidi, N. [Department of Materials Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Jamshidian, M. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

2016-07-18

The morphology and distribution of the dispersed martensite islands in the ferrite matrix plays a key role in the formation of shear bands in dual phase steels. In this study, we investigate the relationship between the martensite dispersion and the strain localization regions due to the formation of shear bands in fine-grained DP 780 steel, employing experimental observations as well as numerical simulations. SEM studies of the deformed microstructure showed that voids nucleated at ferrite-martensite interface within larger ferrite grains and regions with low local martensite fraction. The experimental results were precisely analyzed by finite element simulations based on the theory of crystal plasticity. A parametric study was then performed to obtain a deeper insight in to the effect of martensite dispersion on the strain localization of the neighboring ferrite. Crystal plasticity simulation results revealed that in a more regular structure compared to a random structure, a greater region of the ferrite phase contributes to accommodate plasticity. In addition, these regions limit the formation of main shear bands by creating barriers against stress concentration regions, results in lower growth and interaction of stress concentration regions with each others.

Finite Element Calculation of Local Variation in the Driving Force for Austenite to Martensite Transformation

International Nuclear Information System (INIS)

Datta, K.; Geijselaers, H. J. M.; Huetink, J.; Post, J.; Dinsdale, A.

2007-01-01

The mechanics and thermodynamics of strain induced martensitic transformation are coupled for a metastable alloy steel and implemented in FE models of forming processes. The basic formulations are based on a fifty year old treaty by Patel and Cohen. The variation in Gibbs energy due to local variation in strain, strain rate, temperature and state of stress of a forming part is calculated by FE codes. The local variation in Gibbs energy gives a probabilistic image of the potential sites for strain induced martensitic transformations

Texture, morphology and deformation mechanisms in β-transformed Zircaloy-4

International Nuclear Information System (INIS)

Ciurchea, D.; Furtuna, I.; Todica, M.; Roth, M.

1996-01-01

The morphology of the β(bcc) transformed Zircaloy-4 may be treated as a lenticular-twinned martensite. The texture is a consequence of the degeneration of the left angle 0001 right angle α , left angle 1010 right angle α and left angle 1011 right angle α directions into left angle 110 right angle β directions. The crystallographic mechanisms implied in the accommodation of the microscopic Bain strain are (1010) left angle 1120 right angle prism slip, (1012) left angle 101 1 right angle twinning and (1011) left angle 1012 right angle twinning. This degeneration explains the 'parallel plate' and 'basketweave' morphologies observed by microscopy and the texture of the β transformed tube. The macroscopic Bain strain was calculated and agrees with the dimensional measurements. The deformation mechanisms of β transformed Zircaloy-4 are identified from the new texture and from deformation experiments as twinning and interplatelet glide. The interplatelet glide induces a fragile character of fracture in the 'parallel plate' morphology. (orig.)

Effects of deformation and boron on microstructure and continuous cooling transformation in low carbon HSLA steels

Energy Technology Data Exchange (ETDEWEB)

Jun, H.J. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kang, J.S. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Seo, D.H. [Technical Research Laboratories, POSCO, Pohang 545-090 (Korea, Republic of); Kang, K.B. [Technical Research Laboratories, POSCO, Pohang 545-090 (Korea, Republic of); Park, C.G. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)]. E-mail: cgpark@postech.ac.kr

2006-04-25

The continuous-cooling-transformation (CCT) diagram and continuous cooled microstructure were investigated for low carbon (0.05 wt.% C) high strength low alloy steels with/without boron. Microstructures observed in continuous cooled specimens were composed of pearlite, quasi-polygonal ferrite, granular bainite, acicular ferrite, bainitic ferrite, lower bainite, and martensite depending on cooling rate and transformation temperature. A rapid cooling rate depressed the formation of pearlite and quasi-polygonal ferrite, which resulted in higher hardness. However, hot deformation slightly increased transformation start temperature, and promoted the formation of pearlite and quasi-polygonal ferrite. Hot deformation also strongly promoted the acicular ferrite formation which did not form under non-deformation conditions. Small boron addition effectively reduced the formation of pearlite and quasi-polygonal ferrite and broadened the cooling rate region for bainitic ferrite and martensite.

Microscale-calibrated modeling of the deformation response of dual-phase steels

International Nuclear Information System (INIS)

Chen, Peng; Ghassemi-Armaki, Hassan; Kumar, Sharvan; Bower, Allan; Bhat, Shrikant; Sadagopan, Sriram

2014-01-01

A combination of micropillar compression tests and microstructure-based numerical simulations were used to determine the flow strength and strain rate partitioning in uniaxial tension in two commercial low-carbon dual-phase sheet steels, DP980 (0.09% C–2.15% Mn–0.60% Si (wt.%)) and DF140T (0.15% C–1.45% Mn–0.30% Si (wt.%)). The two steels have different microstructures, with the martensite volume fraction in DP980 being ∼60%, compared to ∼40% in DF140T. Nevertheless, they exhibit similar uniaxial stress–strain behavior. To determine the microstructural origin of this behavior, micropillar compression specimens from ferrite and martensitic phases in both steels were deformed in uniaxial compression to obtain their individual response. A microstructure-based crystal plasticity model that accounts for non-Schmid behavior in the ferrite phase and contains a detailed description of the hierarchical microstructure of martensite was developed and material parameters were determined by fitting model predictions to the micropillar compression data. The crystal plasticity model was then used to predict the flow stress and strain rate partitioning during uniaxial tensile deformation of the two steels. The ferrite phase in the two steels was found to have similar flow strength. In contrast, the flow stress of martensite in DF140T was found to be approximately twice that in DP980. This strength difference is offset by the difference in martensite volume fraction in the two steels, resulting in nearly identical uniaxial tensile behavior. The strain rate partitioning and interfacial stress distributions in the two steels differ significantly, however, and have important implications on their tensile ductility

Work Hardening, Dislocation Structure, and Load Partitioning in Lath Martensite Determined by In Situ Neutron Diffraction Line Profile Analysis

Science.gov (United States)

Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Gong, Wu; Aizawa, Kazuya; Tichy, Geza; Shi, Zengmin; Ungár, Tamas

2017-09-01

A lath martensite steel containing 0.22 mass pct carbon was analyzed in situ during tensile deformation by high-resolution time-of-flight neutron diffraction to clarify the large work-hardening behavior at the beginning of plastic deformation. The diffraction peaks in plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in two lath packets: soft packet, where the dislocation glides are favorable, and hard packet, where they are unfavorable. The dislocation density was as high as 1015 m-2 in the as-heat-treated state. During tensile straining, the load and dislocation density became different between the two lath packets. The dislocation character and arrangement varied in the hard packet but hardly changed in the soft packet. In the hard packet, dislocations that were mainly screw-type in the as-heat-treated state became primarily edge-type and rearranged towards a dipole character related to constructing cell walls. The hard packet played an important role in the work hardening in martensite, which could be understood by considering the increase in dislocation density along with the change in dislocation arrangement.

A study of local deformation and damage of dual phase steel

International Nuclear Information System (INIS)

Sirinakorn, T.; Wongwises, S.; Uthaisangsuk, V.

2014-01-01

Highlights: • Crack initiation in DP microstructure was investigated using 2D RVE simulation. • The GTN damage model was used to describe void evolution in ferrite and interphase. • Predicted damage at triple junctions agreed with observed crack initiation sites. • RVE with GNDs zone showed damages took place at earlier deformation state. • Overall loading condition exhibited significant effect on damage evolution rate. - Abstract: Deformation and fracture behavior of Dual Phase (DP) high strength steel were investigated by means of a microstructure based Finite Element (FE) modeling. Representative Volume Elements (RVEs) were applied to consider effects of various microstructure constituents and characteristics. Individual stress–strain curves were provided for ferrite, martensite as well as transformation induced Geometrically Necessary Dislocations (GNDs) taking into account in the RVEs. Principally, the GNDs occurred around phase boundaries during quenching process due to the austenite–martensite transformation. Flow behaviors of individual phases were defined on the basis of dislocation theory and partitioning of local chemical composition. Then, flow curves of the examined DP steel were predicted. Furthermore, the Gurson–Tvergaard–Needleman (GTN) model was used to represent ductile damage evolution in the microstructure. Occurrences of void initiation were characterized and damage parameters for RVE simulations were hence identified. Finally, influences of the GNDs, local stress and strain distributions and interactions between phases on predicted crack initiation in the DP microstructure were discussed and correlated with experimental results

Materials model for describing the austenite-martensite phase transformation considering transformation-induced plasticity; Ein Materialmodell zur Beschreibung der Austenit-Martensit Phasentransformation unter Beruecksichtigung der transformationsinduzierten Plastizitaet

Energy Technology Data Exchange (ETDEWEB)

Oberste-Brandenburg, C.

1999-06-01

In this thesis, a model to describe the austenite martensite transformation was developed. The transformation induced plasticity (TRIP) was taken into consideration. The model can be used to design complex structures. A local examination of the energy and entropy balance at the phase boundary serves as the starting point for the identification of the thermodynamical driving force and the thermodynamic flow. For both, a tensorial description is necessary for a general nonhydrostatically stressed solid. In the second part, a material law for the description of TRIP-Steels was developed based on the values derived in the first part. The different mechanical behavior of the phases, especially the differing yield stresses, was taken into account. The model developed was implemented into the finite element program MARC. Simulations of the material and the structural behavior were performed. The experimentally observed strong dependence of the transformation kinetics on the yield stress of the austenite and the dependence of the orientation of the martensite inclusion on the stress state could be verified. (orig.) [German] Im Rahmen dieser Arbeit wurde ein Materialmodell zur Beschreibung der Austenit-Martensit Phasenumwandlung unter Beruecksichtigung der transformationsinduzierten Plastizitaet (TRIP) entwickelt. Das Modell ist zur Berechnung ausgedehnter Strukturen einsetzbar. Eine lokale Betrachtung der Energie- und Entropiebilanz an der Phasengrenze bildet den Ausgangspunkt zur Identifikation der thermodynamischen Kraft und des thermodynamischen Flusses bei Beschreibung der Transformationskinetik. Fuer beide Groessen muss fuer den allgemein nichthydrostatischen Spannungszustand eine tensorielle Beschreibung verwendet werden. Im zweiten Teil der Arbeit bilden diese Groessen die Basis zur Entwicklung eines Stoffgesetzes zur Beschreibung des TRIP-Phaenomens. Es wird das unterschiedliche mechanische Verhalten der Phasen, insbesondere die stark unterschiedlichen

Strčess-induced martensitic transformation in Cu-Al-Zn-Mn polycrystal investigated by two in -situ neutron diffraction techniques

Czech Academy of Sciences Publication Activity Database

Šittner, Petr; Lukáš, Petr; Neov, Dimitar; Daymond, M. R.; Novák, Václav; Swallowe, G. M.

2002-01-01

Roč. 324, - (2002), s. 225-234 ISSN 0921-5093 R&D Projects: GA MŠk ME 186; GA ČR GV202/97/K038; GA AV ČR IAA1010909 Institutional research plan: CEZ:AV0Z1010914 Keywords : Stress-induced martensitic transformation * Cu-Al-Zn-Mn polycrystal * neutron diffraction technique Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.107, year: 2002

Investigation of route to martensitic transition in Ni-Mn-In shape memory alloys

Science.gov (United States)

Nevgi, R.; Priolkar, K. R.; Righi, L.

2018-04-01

The temperature dependent x-ray diffraction and magnetization measurements on the off stoichiometric Ni2Mn1+xIn1-x alloys have confirmed the appearance of martensite at critical Mn concentration of x=0.35. The high temperature phase of all the alloys have cubic L21 structure with the lattice constant steadily decreasing with increase in Mn concentration. Martensitic transition begins to appear in Ni2Mn1.35In0.65 at about 197K and the structure seems to adopt two phases including the major cubic along with the modulated monoclinic phase. This has been explained on the basis of number of Mn-Ni-Mn hybridized pairs that are responsible for inducing martensitic transition.

Corrosion resistance of Ultra-Low-Carbon 19% Cr-11% Ni stainless steel for nuclear fuel reprocessing plants in nitric acid

International Nuclear Information System (INIS)

Ariga, Tamako; Takagi, Yoshio; Inazumi, Toru; Masamura, Katsumi; Sukekawa, M.

1995-01-01

An Ultra-Low-Carbon 19% Cr-11% Ni Stainless Steels used in nuclear fuel reprocessing plants where highly corrosion resistance in nitric acid is required has been developed. This steel has optimized the chemistry composition to decrease inclusions and deformation-induced martensitic transformation. The formation of deformation-induced martensite has the potential danger of accelerating corrosion in nitric acid. In this paper, effects of cold reduction and martensitic transformation on corrosion resistance of Ultra-Low-Carbon Stainless Steels in nitric acid are discussed. The developed steel showed excellent corrosion resistance during long-term exposure to nitric acid. (author)

Effect of cold deformation on latent energy value and high-temperature mechanical properties of 12Cr18Ni10Ti steel

International Nuclear Information System (INIS)

Maksimkin, O.P.; Shiganakov, Sh.B.; Gusev, M.N.

1997-01-01

Energetic and magnetic characteristics and also the high-temperature mechanical properties depending on the preliminary cold deformation of 12Cr18Ni10Ti steel are presented. It is shown that the value of storage energy in the steel has being grown with increase of the deformation. The rate of its growth has been increased after beginning of martensitic γ→α'- transformation when value of comparative storage energy at first decreased and then has been stay practically constant. Level of mechanical properties of the steel at 1073 K has been determined not only by value of cold deformation but and structural reconstruction corresponding to deformations 35-45% and accompanying with α'-phase martensite formation and change of energy accumulating rate. Preliminary cold deformation (40-60 %) does not improve high- temperature plasticity of steel samples implanted by helium. refs. 7, figs. 2

Insight into the Effects of Reinforcement Shape on Achieving Continuous Martensite Transformation in Phase Transforming Matrix Composites

Science.gov (United States)

Zhang, Xudong; Ren, Junqiang; Wang, Xiaofei; Zong, Hongxiang; Cui, Lishan; Ding, Xiangdong

2017-12-01

A continuous martensite transformation is indispensable for achieving large linear superelasticity and low modulus in phase transforming metal-based composites. However, determining how to accurately condition the residual martensite in a shape memory alloy matrix though the reinforcement shape to achieve continuous martensite transformation has been a challenge. Here, we take the finite element method to perform a comparative study of the effects of nanoinclusion shape on the interaction and martensite phase transformation in this new composite. Two typical samples are compared: one reinforced by metallic nanowires and the other by nanoparticles. We find that the residual martensite within the shape memory alloy matrix after a pretreatment can be tailored by the reinforcement shape. In particular, our results show that the shape memory alloy matrix can retain enough residual martensite phases to achieve continuous martensite transformation in the subsequent loading when the aspect ratio of nanoreinforcement is larger than 20. In contrast, the composites reinforced with spherical or low aspect ratio reinforcement show a typical nonlinear superelasticity as a result of a low stress transfer-induced discontinuous martensite transformation within the shape memory alloy matrix.

Effect of the bainitic and martensitic microstructures on the hardening and embrittlement under neutron irradiation of a reactor pressure vessel steel

Energy Technology Data Exchange (ETDEWEB)

Marini, B., E-mail: bernard.marini@cea.fr [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SRMA, F-91191 Gif-sur Yvette (France); Averty, X. [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SEMI (now DEN/DANS/DM2S/SEMT), F-91191 Gif-sur Yvette (France); Wident, P.; Forget, P.; Barcelo, F. [Commissariat à l' Energie Atomique et aux Energies Alternatives, DEN/DANS/DMN/SRMA, F-91191 Gif-sur Yvette (France)

2015-10-15

The hardening and the embrittlement under neutron irradiation of an A508 type RPV steel considering three different microstructures (bainite, bainite-martensite and martensite)have been investigated These microstructures were obtained by quenching after autenitization at 1100 °C. The irradiation induced hardening appears to depend on microstructure and is correlated to the yield stress before irradiation. The irradiation induced embrittlement shows a more complex dependence. Martensite bearing microstructures are more sensitive to non hardening embrittlement than pure bainite. This enhanced sensitivity is associated with the development of intergranular brittle facture after irradiation; the pure martensite being more affected than the bainite-martensite. It is of interest to note that this mixed microstructure appears to be more embrittled than the pure bainitic or martensitic phases in terms of temperature transition shift. This behaviour which could emerge from the synergy of the embrittlement mechanisms of the two phases needs further investigations. However, the role of microstructure on brittle intergranular fracture development appears to be qualitatively similar under neutron irradiation and thermal ageing.

Effects on the martensitic transformations and the microstructure of CuAlNi single crystals after ageing at 473 K

Energy Technology Data Exchange (ETDEWEB)

Araujo, V.E.A., E-mail: aaraujo@citedef.gob.ar [Departamento de Investigaciones en Sólidos, CITEDEF, UNIDEF (MINDEF-CONICET), J.B. de La Salle 4397, (1603) Villa Martelli, Buenos Aires (Argentina); Gastien, R. [Departamento de Investigaciones en Sólidos, CITEDEF, UNIDEF (MINDEF-CONICET), J.B. de La Salle 4397, (1603) Villa Martelli, Buenos Aires (Argentina); Zelaya, E. [División Física de Metales, Centro Atómico Bariloche–CNEA, S.C. Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Beiroa, J.I.; Corro, I. [Departamento de Investigaciones en Sólidos, CITEDEF, UNIDEF (MINDEF-CONICET), J.B. de La Salle 4397, (1603) Villa Martelli, Buenos Aires (Argentina); Sade, M. [División Física de Metales, Centro Atómico Bariloche–CNEA, S.C. Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo (Argentina); Lovey, F.C. [División Física de Metales, Centro Atómico Bariloche–CNEA, S.C. Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo (Argentina)

2015-08-25

Highlights: • Thermally induced martensitic transformations are studied after ageing at 473 K. • β ↔ β′ stress induced martensitic transformations were analysed after ageing at 473 K. • Pseudoelastic cycling was studied after ageing at 473 K. • Microstructure before and after ageing at 473 K was analysed using TEM. • Effect of γ precipitates and ordering processes is discussed. - Abstract: Isothermal treatments at 473 K were performed in CuAlNi single crystals to study their effects on the main properties of this shape memory material. Both the stress and thermally induced martensitic transformations were monitored after these ageing treatments. An increase of the critical transformation temperature was detected and the type of induced martensite changed from γ′ into β′ after a long enough ageing time. Pseudoelastic cycling was studied after thermal ageing; mechanical behaviour evolved on cycling and a repetitive behaviour was obtained after a small number of cycles. Changes in microstructure were analysed in the β phase by transmission electron microscopy which allowed observing the morphology and distribution of γ precipitates. The changes obtained in shape memory properties were discussed considering the atomic ordering evolution and characteristics of the precipitates.

Relationship between thermomechanical treatment, microstructure and α' martensite in stainless Fe-based shape memory alloys

International Nuclear Information System (INIS)

Otubo, J.; Mei, P.R.; Shinohara, A.H.; Suzuki, C.K.

1999-01-01

This work presents some preliminary results relating training treatment, training temperature and the formation of α' martensite to the shape recovery effect of stainless shape memory alloys. For the composition tested, the sample shows some mechanical memory (constant tensile stress at 4% strain and constant yield stress throughout the training cycles) with a very good shape recovery (95% after 4% tensile strain) at a training temperature of 873 K. Its residual strain is related to the generation of perfect dislocations only. For the sample trained at 723 K, the residual strain could be attributed to incomplete reversion of stress-induced ε martensite, in part due to the blocking effect of α' martensite and also to the generation of perfect dislocations. The influence of α' martensite on shape recovery is relative and is dependent on training temperature, and the preferential growth of α' martensite is shown to occur for large grain size. (orig.)

In Situ Neutron Diffraction Analyzing Stress-Induced Phase Transformation and Martensite Elasticity in [001]-Oriented Co49Ni21Ga30 Shape Memory Alloy Single Crystals

Science.gov (United States)

Reul, A.; Lauhoff, C.; Krooß, P.; Gutmann, M. J.; Kadletz, P. M.; Chumlyakov, Y. I.; Niendorf, T.; Schmahl, W. W.

2018-02-01

Recent studies demonstrated excellent pseudoelastic behavior and cyclic stability under compressive loads in [001]-oriented Co-Ni-Ga high-temperature shape memory alloys (HT-SMAs). A narrow stress hysteresis was related to suppression of detwinning at RT and low defect formation during phase transformation due to the absence of a favorable slip system. Eventually, this behavior makes Co-Ni-Ga HT-SMAs promising candidates for several industrial applications. However, deformation behavior of Co-Ni-Ga has only been studied in the range of theoretical transformation strain in depth so far. Thus, the current study focuses not only on the activity of elementary deformation mechanisms in the pseudoelastic regime up to maximum theoretical transformation strains but far beyond. It is shown that the martensite phase is able to withstand about 5% elastic strain, which significantly increases the overall deformation capability of this alloy system. In situ neutron diffraction experiments were carried out using a newly installed testing setup on Co-Ni-Ga single crystals in order to reveal the nature of the stress-strain response seen in the deformation curves up to 10% macroscopic strain.

Martensite transformation in antimony implanted stainless steel

International Nuclear Information System (INIS)

Johnson, E.; Littmark, U.; Johansen, A.; Christodoulides, C.

1981-01-01

The authors have used Rutherford backscattering analysis (RBS) and transmission electron microscopy (TEM) and diffraction to investigate austenitic stainless steel crystals implanted at room temperature with 80 keV Sb + ions to a fluence of 5 x 10 20 ions/m 2 , thus providing implantation with a heavy group V element. RBS channeling spectra from implanted crystals show a damage peak which approaches the height of the random level and therefore indicates a very high degree of disorder in the implanted layers. The distribution of the disorder extends to a depth 3-5 times the depth of the primary radiation damage. The Sb peaks under channeling as well as random conditions are indistinguishable, confirming that substitutionality during implantation is negligible. To establish the nature of the disorder which cannot be assessed from the RBS analysis alone, and in particular to assess whether an amorphous alloy is formed in the implanted layer as indicated from the RBS spectra, samples implanted under similar conditions were investigated in the TEM. Significant extra spots in the patterns can be ascribed to the presence of a radiation induced b.c.c. phase of martensitic origin. The result that a significant amount of martensite can be induced by antimony implantation seems to indicate that the main driving force for the transition is due to damage induced stress concentrations. (Auth.)

Microstructural stability of fast reactor irradiated 10 to 12% Cr ferritic-martensitic stainless steels

International Nuclear Information System (INIS)

Little, E.A.; Stoter, L.P.

1982-01-01

The strength and microstructural stability of three 10 to 12% Cr ferritic-martensitic stainless steels have been characterized following fast reactor irradiation to damage levels of 30 displacements per atom (dpa) at temperatures in the range 380 to 615 0 C. Irradiation results in either increases or decreases in room temperature hardness depending on the irradiation temperature. These strength changes can be qualitatively rationalized in terms of the combined effects of irradiation-induced interstitial dislocation loop formation and recovery of the dislocation networks comprising the initial tempered martensite structures. Precipitate evolution in the irradiated steels is associated with the nonequilibrium segregation of the elements nickel, silicon, molybdenum, chromium and phosphorus, brought about by solute-point defect interactions. The principal irradiation-induced precipitates identified are M 6 X, intermetallic chi and sigma phases and also α' (Cr-rich ferrite). The implications of the observed microstructural changes on the selection of martensitic stainless steels for fast reactor wrapper applications are briefly considered

The Relevant Role of Dislocations in the Martensitic Transformations in Cu-Al-Ni Single Crystals

Science.gov (United States)

Gastien, R.; Sade, M.; Lovey, F. C.

2018-03-01

The interaction between dislocations and martensitic transformations in Cu-Al-Ni alloys is shortly reviewed. Results from many researchers are critically analyzed towards a clear interpretation of the relevant role played by dislocations on the properties of shape memory alloys in Cu-based alloys. Both thermally and stress-induced transformations are considered and focus is paid on two types of transitions, the β→β' and the formation of a mixture of martensites: β→β' + γ'. After cycling in the range where both martensites are formed, the twinned γ' phase is inhibited and cycling evolves into the formation of only β'. A model which considers the difference in energy of each γ' twin variant due to the introduced dislocations quantitatively explains the inhibition of γ' in both thermally and stress-induced cycling. The type of dislocations which are mainly introduced, mixed with Burgers vector belonging to the basal plane of the β' martensite, enables also to explain the unmodified mechanical behavior during β→β' cycling. The reported behavior shows interesting advantages of Cu-Al-Ni single crystals if mechanical properties are comparatively considered with those in other Cu-based alloys.

Martensite phase reversion-induced nano/ ultrafine grained AISI 304L stainless steel with magnificent mechanical properties

Directory of Open Access Journals (Sweden)

Mohammad Shirdel

2015-06-01

Full Text Available Austenitic stainless steels are extensively used in various applications requiring good corrosion resistance and formability. In the current study, the formation of nano/ ultrafine grained austenitic microstructure in a microalloyed AISI 304L stainless steel was investigated by the advanced thermomechanical process of reversion of strain-induced martensite. For this purpose, samples were subjected to heavy cold rolling to produce a nearly complete martensitic structure. Subsequently, a wide range of annealing temperatures (600 to 800°C and times (1 to 240 min were employed to assess the reversion behavior and to find the best annealing condition for the production of the nano/ultrafine grained austenitic microstructure. Microstructural characterizations have been performed using X-ray diffraction (XRD, scanning electron microscopy (SEM, and magnetic measurement, whereas the mechanical properties were assessed by tensile and hardness tests. After thermomechanical treatment, a very fine austenitic structure was obtained, which was composed of nano sized grains of ~ 85 nm in an ultrafine grained matrix with an average grain size of 480 nm. This microstructure exhibited superior mechanical properties: high tensile strength of about 1280 MPa with a desirable elongation of about 41%, which can pave the way for the application of these sheets in the automotive industry.

Reliability/unreliability of mixture rule in a low alloy ferrite–martensite dual phase steel

International Nuclear Information System (INIS)

Fereiduni, E.; Ghasemi Banadkouki, S.S.

2013-01-01

consequence of more constraints induced in the ferrite grains during martensitic phase transformation. The higher martensite volume fraction in the vicinity of thinner continuous grain boundary ferrite networks has been associated with the harder ferrite formation

Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

Energy Technology Data Exchange (ETDEWEB)

Oliveira, J.P., E-mail: jp.oliveira@campus.fct.unl.pt [CENIMAT/i3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Braz Fernandes, F.M. [CENIMAT/i3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Miranda, R.M. [UNIDEMI, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (Portugal); Schell, N. [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, D-21502 Geesthacht (Germany); Ocaña, J.L. [Centro Láser UPM, Universidad Politécnica de Madrid, Edificio “La Arboleda”, Ctra. Valencia, km 7,300, Campus Sur UPM, 28031 Madrid (Spain)

2016-09-15

Although laser welding is probably the most used joining technique for NiTi shape memory alloys there is still a lack of understanding about the effects of laser welding parameters on the microstructural induced changes: in both the heat affected and fusion zones martensite may be present, while the base material is fully austenitic. Synchrotron X-ray diffraction was used for fine probing laser welded NiTi joints. Through Rietveld refinement the martensite and austenite phase fractions were determined and it was observed that the martensite content increases towards the weld centreline. This is related to a change of the local transformation temperatures on these regions, which occurs due to compositional variation in those regions. The martensite phase fraction in the thermally affected regions may have significant implications on functional properties on these joints. - Highlights: •Synchrotron X-ray diffraction was used for fine probing of the microstructure in laser welded NiTi joints. •Rietveld refinement allowed to determine the content of martensite along the heat affected and fusion zones. •The martensite content increases from the base material towards the weld centreline.

Cyclic deformation behavior of steels and light-metal alloys

International Nuclear Information System (INIS)

Walther, Frank; Eifler, Dietmar

2007-01-01

The detailed knowledge of the cyclic deformation behavior of metallic materials is an essential condition for the comprehensive understanding of fatigue mechanisms and a reliable lifetime calculation of cyclically loaded specimens and components. Various steels and light-metal alloys were investigated under stress and strain control on servohydraulic testing systems. In addition to mechanical stress-strain hysteresis measurements, the changes of the specimen temperature and the electrical resistance due to plastic deformation processes were measured. The plasticity-induced martensite formation in metastable austenitic steels was detected in situ with a ferritescope sensor. As advanced magnetic measuring technique giant-magneto-resistance sensors in combination with an universal eddy-current equipment were used for the on-line monitoring of fatigue processes. Due to their direct dependence on microstructural changes, all physical values show a clear interaction with the actual fatigue state. The results of the plastic strain, thermometric, electric and magnetic measuring techniques were presented versus the number of cycles as well as in Morrow and Coffin-Manson plots. The microstructures were characterized by scanning electron microscopy

Cyclic deformation behavior of steels and light-metal alloys

Energy Technology Data Exchange (ETDEWEB)

Walther, Frank [University of Kaiserslautern, Institute of Materials Science and Engineering, P.O. Box 3049, D-67653 Kaiserslautern (Germany)], E-mail: walther@mv.uni-kl.de; Eifler, Dietmar [University of Kaiserslautern, Institute of Materials Science and Engineering, P.O. Box 3049, D-67653 Kaiserslautern (Germany)

2007-11-15

The detailed knowledge of the cyclic deformation behavior of metallic materials is an essential condition for the comprehensive understanding of fatigue mechanisms and a reliable lifetime calculation of cyclically loaded specimens and components. Various steels and light-metal alloys were investigated under stress and strain control on servohydraulic testing systems. In addition to mechanical stress-strain hysteresis measurements, the changes of the specimen temperature and the electrical resistance due to plastic deformation processes were measured. The plasticity-induced martensite formation in metastable austenitic steels was detected in situ with a ferritescope sensor. As advanced magnetic measuring technique giant-magneto-resistance sensors in combination with an universal eddy-current equipment were used for the on-line monitoring of fatigue processes. Due to their direct dependence on microstructural changes, all physical values show a clear interaction with the actual fatigue state. The results of the plastic strain, thermometric, electric and magnetic measuring techniques were presented versus the number of cycles as well as in Morrow and Coffin-Manson plots. The microstructures were characterized by scanning electron microscopy.

Kinetics of the deformation induced memory effect in polyamide-6

NARCIS (Netherlands)

Drongelen, van M.; Stroeks, A.A.M.; Peters, G.W.M.

2015-01-01

Nascent polyamide-6 shows a peculiar and irreversible effect; the quiescent crystallization kinetics on cooling are accelerated upon deformation in the melt, even after full relaxation of the melt. This phenomenon, known as the orientation (or better, deformation) induced memory effect of polyamide

Deformation-induced crystallographic-preferred orientation of hcp-iron: An experimental study using a deformation-DIA apparatus

Science.gov (United States)

Nishihara, Yu; Ohuchi, Tomohiro; Kawazoe, Takaaki; Seto, Yusuke; Maruyama, Genta; Higo, Yuji; Funakoshi, Ken-ichi; Tange, Yoshinori; Irifune, Tetsuo

2018-05-01

Shear and uniaxial deformation experiments on hexagonal close-packed iron (hcp-Fe) was conducted using a deformation-DIA apparatus at a pressure of 13-17 GPa and a temperature of 723 K to determine its deformation-induced crystallographic-preferred orientation (CPO). Development of the CPO in the deforming sample is determined in-situ based on two-dimensional X-ray diffraction using monochromatic synchrotron X-rays. In the shear deformation geometry, the and axes gradually align to be sub-parallel to the shear plane normal and shear direction, respectively, from the initial random texture. In the uniaxial compression and tensile geometry, the and axes, respectively, gradually align along the direction of the uniaxial deformation axis. These results suggest that basal slip (0001) is the dominant slip system in hcp-Fe under the studied deformation conditions. The P-wave anisotropy for a shear deformed sample was calculated using elastic constants at the inner core condition by recent ab-initio calculations. Strength of the calculated anisotropy was comparable to or higher than axisymmetric anisotropy in Earth's inner core.

Gaseous surface hardening of martensitic stainless steels

DEFF Research Database (Denmark)

Tibollo, Chiara; Villa, Matteo; Christiansen, Thomas L.

The present work addresses heat and surface treatments of martensitic stainless steel EN 1.4028. Different combinations of heat treatments and surface treatments were performed: conventional austenitisation, cryogenic treatment and in particular high temperature solution nitriding (HTSN) and low...... that cubic lath martensite in conventionally austenitised EN 1.4028 dissolves nitrogen and develops expanded martensite (ferrite) during LTSH. HTSN leads to a microstructure of tetragonal plate martensite and retained austenite. The content of retained austenite can be reduced by a cryo...

Orientation relationship in Eurofer martensitic steels

International Nuclear Information System (INIS)

Barcelo, F.; De Carlan, Y.; Bechade, J.L.; Fournier, B.

2009-01-01

Both TEM and SEM/EBSD orientation measurements are carried out on a Eurofer97 martensitic steel. The influence of the prior austenitic grain size is studied using dedicated heat treatments. The intra laths misorientation is estimated by TEM. SEM/EBSD orientation mapping enable to study the actual orientation relationship (OR) between the parent austenitic phase and the martensitic phase. Neither the Nishiyama-Wasserman nor the Kurdjumov-Sachs OR is able to account for both the misorientation angle distributions, the pole figure and the misorientation axes measured. The mixed OR recently proposed by Gourgues et al. (Electron backscattering diffraction study of acicular ferrite, bainite, and martensite steel microstructures, Mater. Sci. Tech. 16 (2000), p. 26-40.) and Sonderegger et al. (Martensite laths in creep resistant martensitic 9-12% Cr steels - Calculation and measurement of misorientations, Mater. Characterization (2006), in Press.) seems to be able to account for most of these results. Based on this OR, a new angular criterion is proposed to detect blocks of laths. (authors)

Influence of preliminary deformation and phase strengthening on γ reversible α transformation kinetics in cerium under pressure

International Nuclear Information System (INIS)

Larionov, L.V.; Livshits, L.D.; Peresada, G.I.; AN SSSR, Moscow. Inst. Fiziki Zemli)

1985-01-01

Using the methods of piezo- and resistometry the influence of preliminary plastic deformation, phase transformation induced strengthening and heat treatment on kinetics of γ reversible α transformation in cerium is studied. It is shown, that the used methods of preliminary treatment of sample material do not change pressure value of γ → α and α →γ transformation initiation and do not affect hysteresis value, but affect considerably its kinetics. Preliminary plastic deformation and structural strengthening increase the average formation rate of a new phase. According to the data of tensile tests, structural strengthening, apprearing as a result of one cycle of γ → α → γ transformation, increases cerium strength characteristics 6y 30-50% with simultaneous decrease in plasticity. Metallographic studies confirm martensitic character of γ → α → γ transformations in cerium

A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

Energy Technology Data Exchange (ETDEWEB)

Byun, Thak Sang, E-mail: thaksang.byun@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Hoelzer, David T. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kim, Jeoung Han [Hanbat National University, Daejeon 305-719 (Korea, Republic of); Maloy, Stuart A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2017-02-15

The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The K{sub JQ} versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

Transformation kinetics of selected steel grades after plastic deformation

Directory of Open Access Journals (Sweden)

R. Kawulok

2016-07-01

Full Text Available The aim of this article was to assess the impact of previous plastic deformation on the kinetics of transformations of four selected steels. The research was conducted with use of the universal plastometer GLEEBLE 3800, when Continuous Cooling Transformation (CCT and Deformation Continuous Cooling Transformation (DCCT diagrams of selected steels were constructed on the basis of dilatometric tests. The research confirmed that the strain accelerates the particularly the transformations controlled by diffusion. Bainitic transformation was accelerated in three of the four steels. In the case of martensitic transformation the effect of the previous deformation was relatively small, but with clearly discernible trend.

CEMS of Sb+ implanted stainless steels

International Nuclear Information System (INIS)

Roy-Poulsen, H.; Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Hayashi, H.

1986-01-01

Martensitic transformations have been analyzed in a series of antimony implanted austenitic stainless steels using CEMS. The implanted samples contain about 70 vol% martensite, which is considerably more than can be formed conventionally by plastic deformation of cooling below the martensite start temperature. CEM spectra from implantation induced martensite and from martensite formed in conventional processes are virtually identical. In both cases the hyperfine field is ∼ 25T. (Auth.)

CEMS of Sb+ implanted stainless steels

International Nuclear Information System (INIS)

Roy-Poulsen, H.; Copenhagen Univ.; Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Hayashi, H.

1985-01-01

Martensitic transformations have been analyzed in a series of antimony implanted austenitic stainless steels using CEMS. The implanted samples contain about 70 vol% martensite, which is considerably more than can be formed conventionally by plastic deformation or cooling below the martensite start temperature. CEM spectra from implantation induced martensite and from martensite formed in conventional processes are virtually identical. In both cases the hyperfine field is ∝25 T. (orig.)

In-situ investigation of strain-induced martensitic transformation kinetics in an austenitic stainless steel by inductive measurements

NARCIS (Netherlands)

Alonso de Celada Casero, C.; Kooiker, Harm; Groen, Manso; Post, J; San Martin, D

2017-01-01

An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ) to martensite (α′) phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite

Microstructure Evolution and Mechanical Behavior of a Hot-Rolled High-Manganese Dual-Phase Transformation-Induced Plasticity/Twinning-Induced Plasticity Steel

Science.gov (United States)

Fu, Liming; Shan, Mokun; Zhang, Daoda; Wang, Huanrong; Wang, Wei; Shan, Aidang

2017-05-01

The microstructures and deformation behavior were studied in a high-temperature annealed high-manganese dual-phase (28 vol pct δ-ferrite and 72 vol pct γ-austenite) transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steel. The results showed that the steel exhibits a special Lüders-like yielding phenomenon at room temperature (RT) and 348 K (75 °C), while it shows continuous yielding at 423 K, 573 K and 673 K (150 °C, 300 °C and 400 °C) deformation. A significant TRIP effect takes place during Lüders-like deformation at RT and 348 K (75 °C) temperatures. Semiquantitative analysis of the TRIP effect on the Lüders-like yield phenomenon proves that a softening effect of the strain energy consumption of strain-induced transformation is mainly responsible for this Lüders-like phenomenon. The TWIP mechanism dominates the 423 K (150 °C) deformation process, while the dislocation glide controls the plasticity at 573 K (300 °C) deformation. The delta-ferrite, as a hard phase in annealed dual-phase steel, greatly affects the mechanical stability of austenite due to the heterogeneous strain distribution between the two phases during deformation. A delta-ferrite-aided TRIP effect, i.e., martensite transformation induced by localized strain concentration of the hard delta-ferrite, is proposed to explain this kind of Lüders-like phenomenon. Moreover, the tensile curve at RT exhibits an upward curved behavior in the middle deformation stage, which is principally attributed to the deformation twinning of austenite retained after Lüders-like deformation. The combination of the TRIP effect during Lüders-like deformation and the subsequent TWIP effect greatly enhances the ductility in this annealed high-manganese dual-phase TRIP/TWIP steel.

Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

International Nuclear Information System (INIS)

L’vov, Victor A; Kosogor, Anna; Barandiaran, Jose M; Chernenko, Volodymyr A

2015-01-01

An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect. (paper)

Main factors causing intergranular and quasi-cleavage fractures at hydrogen-induced cracking in tempered martensitic steels

Science.gov (United States)

Kurokawa, Ami; Doshida, Tomoki; Hagihara, Yukito; Suzuki, Hiroshi; Takai, Kenichi

2018-05-01

Though intergranular (IG) and quasi-cleavage (QC) fractures have been widely recognized as typical fracture modes of the hydrogen-induced cracking in high-strength steels, the main factor has been unclarified yet. In the present study, the hydrogen content dependence on the main factor causing hydrogen-induced cracking has been examined through the fracture mode transition from QC to IG at the crack initiation site in the tempered martensitic steels. Two kinds of tempered martensitic steels were prepared to change the cohesive force due to the different precipitation states of Fe3C on the prior γ grain boundaries. A high amount of Si (H-Si) steel has a small amount of Fe3C on the prior austenite grain boundaries. Whereas, a low amount of Si (L-Si) steel has a large amount of Fe3C sheets on the grain boundaries. The fracture modes and initiations were observed using FE-SEM (Field Emission-Scanning Electron Microscope). The crack initiation sites of the H-Si steel were QC fracture at the notch tip under various hydrogen contents. While the crack initiation of the L-Si steel change from QC fracture at the notch tip to QC and IG fractures from approximately 10 µm ahead of the notch tip as increasing in hydrogen content. For L-Si steels, two possibilities are considered that the QC or IG fracture occurred firstly, or the QC and IG fractures occurred simultaneously. Furthermore, the principal stress and equivalent plastic strain distributions near the notch tip were calculated with FEM (Finite Element Method) analysis. The plastic strain was the maximum at the notch tip and the principle stress was the maximum at approximately 10 µm from the notch tip. The position of the initiation of QC and IG fracture observed using FE-SEM corresponds to the position of maximum strain and stress obtained with FEM, respectively. These findings indicate that the main factors causing hydrogen-induced cracking are different between QC and IG fractures.

Reversed austenite for enhancing ductility of martensitic stainless steel

Science.gov (United States)

Dieck, S.; Rosemann, P.; Kromm, A.; Halle, T.

2017-03-01

The novel heat treatment concept, “quenching and partitioning” (Q&P) has been developed for high strength steels with enhanced formability. This heat treatment involves quenching of austenite to a temperature between martensite start and finish, to receive a several amount of retained austenite. During the subsequent annealing treatment, the so called partitioning, the retained austenite is stabilized due to carbon diffusion, which results in enhanced formability and strength regarding strain induced austenite to martensite transformation. In this study a Q&P heat treatment was applied to a Fe-0.45C-0.65Mn-0.34Si-13.95Cr stainless martensite. Thereby the initial quench end temperature and the partitioning time were varied to characterize their influence on microstructural evolution. The microstructural changes were analysed by dilatometer measurements, X-ray diffraction and scanning electron microscopy, including electron back-scatter diffraction. Compression testing was made to examine the mechanical behaviour. It was found that an increasing partitioning time up to 30 min leads to an enhanced formability without loss in strength due to a higher amount of stabilized retained and reversed austenite as well as precipitation hardening.

Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

Science.gov (United States)

Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

1994-09-01

The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement.

Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

International Nuclear Information System (INIS)

Hasegawa, Akira; Shiraishi, Haruki; Matsui, Hideki; Abe, Katsunori

1994-01-01

The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement. ((orig.))

Martensite shear phase reversion-induced nanograined/ultrafine-grained Fe-16Cr-10Ni alloy: The effect of interstitial alloying elements and degree of austenite stability on phase reversion

Energy Technology Data Exchange (ETDEWEB)

Misra, R.D.K., E-mail: dmisra@louisiana.edu [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Zhang, Z.; Venkatasurya, P.K.C. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Madison Hall Room 217, P.O. Box 44130, Lafayette, LA 70504-1430 (United States); Somani, M.C.; Karjalainen, L.P. [Department of Mechanical Engineering, University of Oulu, P.O. Box 4200, Oulu 90014 (Finland)

2010-11-15

Research highlights: {yields} Development of a novel process involving phase-reversion annealing process. {yields} Austensite stability strongly influences development of nanograined structure. {yields} Interstitial elements influence microstructural evolution during annealing. - Abstract: We describe here an electron microscopy study of microstructural evolution associated with martensitic shear phase reversion-induced nanograined/ultrafine-grained (NG/UFG) structure in an experimental Fe-16Cr-10Ni alloy with very low interstitial content. The primary objective is to understand and obtain fundamental insights on the influence of degree of austenite stability (Fe-16Cr-10Ni, 301LN, and 301 have different austenite stability index) and interstitial elements (carbon and nitrogen) in terms of phase reversion process, microstructural evolution during reversion annealing, and temperature-time annealing sequence. A relative comparison of Fe-16Cr-10Ni alloy with 301LN and 301 austenitic stainless steels indicated that phase reversion in Fe-16Cr-10Ni occurred by shear mechanism, which is similar to that observed for 301, but is different from the diffusional mechanism in 301LN steel. While the phase reversion in the experimental Fe-16Cr-10Ni alloy and 301 austenitic stainless steel occurred by shear mechanism, there were fundamental differences between these two alloys. The reversed strain-free austenite grains in Fe-16Cr-10Ni alloy were characterized by nearly same crystallographic orientation, where as in 301 steel there was evidence of break-up of martensite laths during reversion annealing resulting in several regions of misoriented austenite grains in 301 steel. Furthermore, a higher phase reversion annealing temperature range (800-900 deg. C) was required to obtain a fully NG/UFG structure of grain size 200-600 nm. The difference in the phase reversion and the temperature-time sequence in the three stages is explained in terms of Gibbs free energy change that

Theory and Model for Martensitic Transformations

DEFF Research Database (Denmark)

Lindgård, Per-Anker; Mouritsen, Ole G.

1986-01-01

Martensitic transformations are shown to be driven by the interplay between two fluctuating strain components. No soft mode is needed, but a central peak occurs representing the dynamics of strain clusters. A two-dimensional magnetic-analog model with the martensitic-transition symmetry is constr......Martensitic transformations are shown to be driven by the interplay between two fluctuating strain components. No soft mode is needed, but a central peak occurs representing the dynamics of strain clusters. A two-dimensional magnetic-analog model with the martensitic-transition symmetry...... is constructed and analyzed by computer simulation and by a theory which accounts for correlation effects. Dramatic precursor effects at the first-order transition are demonstrated. The model is also of relevance for surface reconstruction transitions....

Atomic scale characterization of white etching area and its adjacent matrix in a martensitic 100Cr6 bearing steel

Energy Technology Data Exchange (ETDEWEB)

Li, Y.J., E-mail: y.li@mpie.de [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf D-40237 (Germany); Center for Interface-Dominated High Performance Materials, Ruhr-Universität Bochum, Bochum 44780 (Germany); Herbig, M.; Goto, S. [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf D-40237 (Germany); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf D-40237 (Germany)

2017-01-15

Atom probe tomography was employed to characterize the microstructure and C distribution in the white etching area (WEA) of a martensitic 100Cr6 bearing steel subjected to rolling contact fatigue. Different from its surrounding matrix where a plate-like martensitic structure prevails, the WEA exhibits equiaxed grains with a uniform grain size of about 10 nm. Significant C grain boundary enrichment (>7.5at.%) and an overall higher C concentration than the nominal value are observed in the WEA. These results suggest that the formation of WEA results from severe local plastic deformation that causes dissolution of carbides and the redistribution of C. - Highlights: •APT has been applied to characterize the microstructure of white etching area (WEA). •Quantitative analyses of C distribution indicate that carbides are dissolved on the WEA. •WEA contains equiaxed grains with a uniform grain size of 10 nm. •C segregation at grain boundaries stabilizes the nanosized grain structure. •Formation of WEA is explained by severe local plastic deformation introduced by cyclic contact loading.

Effect of hot rolling on the structure and the mechanical properties of nitrogen-bearing austenitic-martensitic 14Kh15AN4M steel

Science.gov (United States)

Bannykh, O. A.; Betsofen, S. Ya.; Lukin, E. I.; Blinov, V. M.; Voznesenskaya, N. M.; Tonysheva, O. A.; Blinov, E. V.

2016-04-01

The effect of the rolling temperature and strain on the structure and the properties of corrosionresistant austenitic-martensitic 14Kh15AN4M steel is studied. The steel is shown to exhibit high ductility: upon rolling in the temperature range 700-1100°C at a reduction per pass up to 80%, wedge steel specimens are uniformly deformed along and across the rolling direction without cracking and other surface defects. Subsequent cold treatment and low-temperature tempering ensure a high hardness of the steel (50-56 HRC). Austenite mainly contributes to the hardening upon rolling in the temperature range 700-800°C at a reduction of 50-70%, and martensite makes the main contribution at higher temperatures and lower strains. Texture does not form under the chosen deformation conditions, which indicates dynamic recrystallization with the nucleation and growth of grains having no preferential orientation.

Irradiation effects on tensile ductility and dynamic toughness of ferritic-martensitic 7-12 Cr steels

International Nuclear Information System (INIS)

Preininger, D.

2006-01-01

The superimposed effect of irradiation-induced hardening by small defects (clusters, dislocation loops) and chromium-rich - precipitate formations on tensile ductility and Charpy-impact behaviour of various ferritic-martensitic (7-13)CrWVTa(Ti)-RAFM steels have been examined by micro-mechanical deformation and ductile/dynamic fracture models. Analytical relations have been deduced describing irradiation-induced changes of uniform ductility and fracture strain as well as ductile-to-brittle transition temperature DBTT and ductile upper shelf energy USE observed from impact tests. The models apply work-hardening with competitive action of relevant dislocation multiplication and annihilation reactions. The impact model takes into account stress intensity with local plasticity and fracture within the damage zone of main crack. Especially, the influences of radiation-induced changes in ductile and dynamic fracture stresses have been considered together with effects from strain rate sensitivity of strength, precipitate morphology as mean size dp and volume fraction fv as well as deformation temperature and strain rate. For these, particularly the correlation between tensile ductility and impact properties have been examined. Strengthening by clusters and loops generally reduces uniform ductility, and more stronger fracture strain as well as ductile upper shelf energy USE and additionally increases DBTT for constant fracture stresses. A superimposed precipitation hardening by formation of 3-6 nm, f v 6 nm, which clear above the sharable limit of coherent precipitates increases with increasing fraction fv and but strongly reduces with increasing matrix strength due to full martensitic structure, higher C, N alloying contents and pronounced hardening by irradiation-induced cluster and loop formations. A combined increase of fracture stresses due to irradiation-induced changes of the grain boundary structure diminishes the strength-induced increase in DBTT and more stronger

Tuning martensitic transformation, large magnetoresistance and strain in Ni50-xFexMn36Sn14 Heusler alloys

Science.gov (United States)

Liao, Pan; Jing, Chao; Zheng, Dong; Li, Zhe; Kang, Baojuan; Deng, Dongmei; Cao, Shixun; Lu, Bo; Zhang, Jincang

2015-09-01

We have investigated the martensitic transformation, exchange bias, magnetoresistance (MR) and strain in Ni50-xFexMn36Sn14 (x=1, 2, 3, 4) Heusler alloys. With the increase of Fe content, the austenite phase could be stabilized with L21 structure and hence the martensitic transition shifts to a lower temperature and finally disappears. This behavior can be understood by the weakening of Ni-Mn hybridization to suppress AFM interactions and enhancement of Fe-Fe ferromagnetic exchange interactions. The same reason can account for the slight decrease of exchange bias field (HEB) with the increase of the Fe content from x=1 to 2 and the disappearance of HEB for x=3. We observed MR effect for x=3, and a maximum MR value of -52% was achieved, which can be explained by the change in the electronic structure during martensitic transformation induced by the magnetic field. In addition, a large strain of 0.207% in Ni49Fe1Mn36Sn14 was observed due to the changes of lattice parameters during the martensitic transformation induced by temperature.

Tuning avalanche criticality: acoustic emission during the martensitic transformation of a compressed Ni-Mn-Ga single crystal

Czech Academy of Sciences Publication Activity Database

Niemann, R.; Baró, J.; Heczko, Oleg; Schultz, L.; Fähler, S.; Vives, E.; Mañosa, L.; Planes, A.

2012-01-01

Roč. 86, č. 21 (2012), "214101-1"-"214101-6" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP107/11/0391 Institutional research plan: CEZ:AV0Z10100520 Keywords : stress -induced martensitic transformation * Ni-Mn-Ga * magnetic shape memory alloy * ferromagnetic martensite * acoustic emission during transformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.767, year: 2012

Modeling of the Austenite-Martensite Transformation in Stainless and TRIP Steels

NARCIS (Netherlands)

Geijselaers, Hubertus J.M.; Hilkhuijsen, P.; Bor, Teunis Cornelis; Perdahcioglu, Emin Semih; van den Boogaard, Antonius H.; Zhang, S.-H.; Liu, X.-H.; Gheng, M.; Li, J.

2013-01-01

The transformation of austenite to martensite is a dominant factor in the description of the constitutive behavior during forming of TRIP assisted steels. To predict this transformation different models are currently available. In this paper the transformation is regarded as a stress induced process

Transformation induced plasticity in maraging steel: an experimental study

International Nuclear Information System (INIS)

Nagayama, K.; Kitajima, Y.; Kigami, S.; Tanaka, K.

2000-01-01

The deformation behavior of a maraging TRIP (transformation induced plasticity) steel (MAVAL X12) is studied experimentally under a constant load. The existence of the back stress in the axial direction is directly proved by investigating the dilatation curves. Martensite-start lines are given under tensile, compressive and shear stresses. The evolution of TRIP strain and the maximum TRIP strain are determined. The alloy response during isothermal tensile test is explained in terms of influences both by the composite and transformation. (orig.)

Magnetic interactions in martensitic Ni-Mn based Heusler systems

Energy Technology Data Exchange (ETDEWEB)

Aksoy, Seda

2010-04-22

In this work, magnetic, magnetocaloric and structural properties are investigated in Ni-Mn-based martensitic Heusler alloys with the aim to tailor these properties as well as to understand in detail the magnetic interactions in the various crystallographic states of these alloys. We choose Ni{sub 50}Mn{sub 34}In{sub 16} as a prototype which undergoes a martensitic transformation and exhibits field-induced strain and the inverse magnetocaloric effect. Using the structural phase diagram of martensitic Ni-Mn-based Heusler alloys, we substitute gallium and tin for indium to carry these effects systematically closer to room temperature by shifting the martensitic transformation. A magneto-calorimeter is designed and built to measure adiabatically the magnetocaloric effect in these alloys. The temperature dependence of strain under an external magnetic field is studied in Ni{sub 50}Mn{sub 50-x}Z{sub x} (Z: Ga, Sn, In and Sb) and Ni{sub 50}Mn{sub 34}In{sub 16-x}Z{sub x} (Z: Ga and Sn). An argument based on the effect of the applied magnetic field on martensite nucleation is adopted to extract information on the direction of the magnetization easy axis in the martensitic unit cell in Heusler alloys. Parallel to these studies, the structure in the presence of an external field is also studied by powder neutron diffraction. It is demonstrated that martensite nucleation is influenced by cooling the sample under a magnetic field such that the austenite phase is arrested within the martensitic state. The magnetic interactions in Ni{sub 50}Mn{sub 37}Sn{sub 13} and Ni{sub 50}Mn{sub 40}Sb{sub 10} are characterized by using neutron polarization analysis. Below the martensitic transformation temperature, M{sub s}, an antiferromagnetically correlated state is found. Ferromagnetic resonance experiments are carried out on Ni{sub 50}Mn{sub 37}Sn{sub 13} and Ni{sub 50}Mn{sub 34}In{sub 16} to gain more detailed information on the nature of the magnetic interactions. The experimental

Novel ferrite–austenite duplex lightweight steel with 77% ductility by transformation induced plasticity and twinning induced plasticity mechanisms

International Nuclear Information System (INIS)

Sohn, Seok Su; Choi, Kayoung; Kwak, Jai-Hyun; Kim, Nack J.; Lee, Sunghak

2014-01-01

The need for lightweight materials has been an important issue in automotive industries to reduce greenhouse gas emission and to improve fuel efficiency. In addition, automotive steels require an excellent combination of strength and ductility to sustain automotive structures and to achieve complex shapes, but the traditional approach to obtain a reduction in weight from down-gauged steels with high strength has many limitations. Here, we present a new ferrite–austenite duplex lightweight steel containing a low-density element, Al; this steel exhibits tensile elongation up to 77% as well as high tensile strength (734 MPa). The enhanced properties are attributed to the simultaneous formation of deformation-induced martensites and deformation twins and the additional plasticity due to deformation twinning in austenite grains having optimal mechanical stability. The present work gives a promise for automotive applications requiring excellent properties as well as reduced specific weight

The important role of martensite laths to fracture toughness for the ductile fracture controlled by the strain in EA4T axle steel

International Nuclear Information System (INIS)

Liang, Yilong; Long, Shaolei; Xu, Pingwei; Lu, Yemao; Jiang, Yun; Liang, Yu; Yang, Ming

2017-01-01

The Hall-Petch relationship was used to investigate the role of martensite lath on fracture toughness (K IC ) during ductile fracture in a low-carbon EA4T axle steel. The hierarchical structures of lath martensite was clarified by means of optical microscope (OM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). Firstly, in such hierarchical structures, packet size (d p ) and block size (d b ) increase significantly with the size of prior austenite (d r ), while the martensite lath width (d l ) decreases. Subsequently, K IC was measured and follows the Hall-Petch relationship with d l . It depends on the rotation, bending and direct shear during crack propagation of laths, confirmed by EBSD. Besides, fracture toughness (K IC ) is proportional to a parameter ε v , the matrix strain, which is related to the plastic deformation of laths. Therefore, the martensite lath in hierarchical structures is the effective control unit of K IC during ductile fracture controlled by the strain.

The important role of martensite laths to fracture toughness for the ductile fracture controlled by the strain in EA4T axle steel

Energy Technology Data Exchange (ETDEWEB)

Liang, Yilong, E-mail: liangyilong@126.com [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Long, Shaolei; Xu, Pingwei; Lu, Yemao [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Jiang, Yun [Guizhou key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China); Liang, Yu; Yang, Ming [College of Materials Science and Metallurgical Engineering, Guizhou University (China); Guizhou key Laboratory for Mechanical Behavior and Microstructure of Materials (China); National & Local Joint Engineering Laboratory for High-performance Metal Structure Material and Advanced Manufacturing Technology (China)

2017-05-17

The Hall-Petch relationship was used to investigate the role of martensite lath on fracture toughness (K{sub IC}) during ductile fracture in a low-carbon EA4T axle steel. The hierarchical structures of lath martensite was clarified by means of optical microscope (OM), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). Firstly, in such hierarchical structures, packet size (d{sub p}) and block size (d{sub b}) increase significantly with the size of prior austenite (d{sub r}), while the martensite lath width (d{sub l}) decreases. Subsequently, K{sub IC} was measured and follows the Hall-Petch relationship with d{sub l}. It depends on the rotation, bending and direct shear during crack propagation of laths, confirmed by EBSD. Besides, fracture toughness (K{sub IC}) is proportional to a parameter ε{sub v}, the matrix strain, which is related to the plastic deformation of laths. Therefore, the martensite lath in hierarchical structures is the effective control unit of K{sub IC} during ductile fracture controlled by the strain.

Crystallographic theory of the martensitic transformation

Directory of Open Access Journals (Sweden)

Edwar A. Torres-López

2014-08-01

Full Text Available The martensitic transformation is one of the most researched topics in the materials science during the 20th century. The second half of this century was mainly remembered by the development of several theories related with the kinetics of phase transformation, the mechanisms involved in the nucleation phenomenon, and the way as the crystallographic change is produced. In this paper are described the fundamental concepts that are defined in the crystallographic framework of the martensitic transformation. The study is focused on the application of the most outstanding crystallographic models: the Bain; the Wechsler, Lieberman & Read; and the Bowles & Mackenzie. The topic is presented based upon the particular features of the martensitic transformation, such as its non-diffusional character, type of interface between parent (austenite and product (martensite phases, the formation of substructural defects, and the shape change; all of these features are mathematically described by equations aimed to predict how the transformation will take place rather than to explain the actual movement of the atoms within the structure. This mathematical development is known as the Phenomenological Theory of Martensite Crystallography (PTMC.

Estimation of the kinetics of martensitic transformation in austenitic stainless steels by conventional and novel approaches

Energy Technology Data Exchange (ETDEWEB)

Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

2015-01-29

A comparative study was carried out on the kinetics of the martensitic transformation in a 304L stainless steel during cold rolling by conventional and novel approaches. The phase analysis based on X-ray diffraction patterns and metallography and also magnetic measurements based on ferritescope readings were utilized to elucidate the kinetics of the martensitic transformation. A straightforward magnetic measurement approach for evaluating the amount of strain-induced martensite in metastable austenitic stainless steels has been introduced in this study. This technique collects the data throughout the bulk of the material to give a realistic estimate of the amount of ferromagnetic martensite. This is an advantage over the surface collecting methods such as ferritescope readings, which overestimates the amount of martensite due to its inhomogeneous distribution through the thickness based on the frictional effects between the rolls and the specimen surface. The proposed approach can be applied in various designs for static/continuous magnetic measurement of bulk materials that is advantageous compared with the conventional vibrating sample magnetometer technique which is useful for static measurement of bulk materials with specific shapes. Moreover, in analogy to ferritescope, the output data of the developed device is directly related to the amount of martensite.

Estimation of the kinetics of martensitic transformation in austenitic stainless steels by conventional and novel approaches

International Nuclear Information System (INIS)

Shirdel, M.; Mirzadeh, H.; Parsa, M.H.

2015-01-01

A comparative study was carried out on the kinetics of the martensitic transformation in a 304L stainless steel during cold rolling by conventional and novel approaches. The phase analysis based on X-ray diffraction patterns and metallography and also magnetic measurements based on ferritescope readings were utilized to elucidate the kinetics of the martensitic transformation. A straightforward magnetic measurement approach for evaluating the amount of strain-induced martensite in metastable austenitic stainless steels has been introduced in this study. This technique collects the data throughout the bulk of the material to give a realistic estimate of the amount of ferromagnetic martensite. This is an advantage over the surface collecting methods such as ferritescope readings, which overestimates the amount of martensite due to its inhomogeneous distribution through the thickness based on the frictional effects between the rolls and the specimen surface. The proposed approach can be applied in various designs for static/continuous magnetic measurement of bulk materials that is advantageous compared with the conventional vibrating sample magnetometer technique which is useful for static measurement of bulk materials with specific shapes. Moreover, in analogy to ferritescope, the output data of the developed device is directly related to the amount of martensite

Formation process of lamella structures by deformation in an Fe-Mn-Si-Cr-Ni shape memory alloy

International Nuclear Information System (INIS)

Kikuchi, T.; Kajiwara, S.; Tomota, Y.

1995-01-01

For Fe-Mn-Si-Cr-Ni shape memory alloys, it was previously found by HREM study that the formation of the nanometric lamella structures consisting of f.c.c. and h.c.p. phase is very important to exhibit good shape memory effect. In the present work, the formation process of such lamella structures has been studied in detail. The results are as follows. The transformation is initiated by random formation of extremely thin martensite plates with 1-2 nm width and then these plates are clustered and some of them coalesce to form thicker martensite plates with increasing deformation. The clustered regions are 400-600 nm wide and will correspond to the above mentioned lamella structures. These clustered regions are considered also to correspond to the thinnest martensite plate observable with optical microscope. In the optical microscopic scale, the thin martenite plates with the smallest width are formed rather uniformly in an austenite grain, and with further increasing deformation, they are clustered and coalesce into thicker plates with 3-8 μm width. (orig.)

AC electric field induced droplet deformation in a microfluidic T-junction.

Science.gov (United States)

Xi, Heng-Dong; Guo, Wei; Leniart, Michael; Chong, Zhuang Zhi; Tan, Say Hwa

2016-08-02

We present for the first time an experimental study on the droplet deformation induced by an AC electric field in droplet-based microfluidics. It is found that the deformation of the droplets becomes stronger with increasing electric field intensity and frequency. The measured electric field intensity dependence of the droplet deformation is consistent with an early theoretical prediction for stationary droplets. We also proposed a simple equivalent circuit model to account for the frequency dependence of the droplet deformation. The model well explains our experimental observations. In addition, we found that the droplets can be deformed repeatedly by applying an amplitude modulation (AM) signal.

Effect of indentation temperature on nickel-titanium indentation-induced two-way shape-memory surfaces

International Nuclear Information System (INIS)

Brinckmann, Stephan A.; Frensemeier, Mareike; Laursen, Christopher M.; Maier, Hans J.; Britz, Dominik; Schneider, Andreas S.; Mücklich, Frank; Frick, Carl P.

2016-01-01

This study investigated the effect of temperature on indentation-induced one-way and two-way shape memory properties in Ti-50.3 at% Ni alloy. Indentation temperatures ranged from below the martensite finish temperature (M f ) to above the austenite finish temperature (A f ) with the explicit intent of varying the indented phase. Samples used in the study were characterized by differential scanning calorimetry and transmission electron microscopy (TEM). The topographical behavior of the shape memory effect was investigated through Vickers indentation and laser scanning 3D confocal measurements. The magnitudes of deformation recovery associated with the one-way and two-way shape-memory effect (OWSME, TWSME) decreased with increasing indentation temperatures, which is a reflection of the decreasing volume of material experiencing martensitic reorientation during indentation. Indented and subsequently planarized samples exhibited TWSME protrusions when thermally cycled. Laser scanning measurements were used to characterize the height of the protrusions as increasing depths of material were polished away, which provided insight into the overall affected volume beneath the indent. As indentation temperatures increased, both the height of the protrusions, and consequently the polish depth necessary to completely remove the effect, decreased. TEM investigations revealed that directly underneath a nanoindent the microstructure was very fine due to the high-strain deformation; this was contrasted with a much coarser grain size in the undeformed bulk material. Overall these results strongly imply that the deformation recovery associated with the OWSME and TWSME can be maximized by indenting at temperatures at M f or below because the volume of deformed microstructure beneath the indent is maximized. This finding has important practical value for any potential application that utilizes indentation-induced phase transformation deformation recovery in NiTi.

Effect of indentation temperature on nickel-titanium indentation-induced two-way shape-memory surfaces

Energy Technology Data Exchange (ETDEWEB)

Brinckmann, Stephan A. [University of Wyoming, Mechanical Engineering Department, Laramie (United States); Frensemeier, Mareike [INM - Leibniz Institute for New Materials, Saarbrücken (Germany); Laursen, Christopher M. [University of Wyoming, Mechanical Engineering Department, Laramie (United States); Maier, Hans J. [Leibniz Universität Hannover, Institut für Werkstoffkunde (Materials Science), Garbsen (Germany); Britz, Dominik [Saarland University, Department of Materials Science and Engineering, Saarbrücken (Germany); Schneider, Andreas S. [AG der Dillinger Hüttenwerke, Department for Research, Development and Plate-Design, Dillingen (Germany); Mücklich, Frank [Saarland University, Department of Materials Science and Engineering, Saarbrücken (Germany); Frick, Carl P., E-mail: cfrick@uwyo.edu [University of Wyoming, Mechanical Engineering Department, Laramie (United States)

2016-10-15

This study investigated the effect of temperature on indentation-induced one-way and two-way shape memory properties in Ti-50.3 at% Ni alloy. Indentation temperatures ranged from below the martensite finish temperature (M{sub f}) to above the austenite finish temperature (A{sub f}) with the explicit intent of varying the indented phase. Samples used in the study were characterized by differential scanning calorimetry and transmission electron microscopy (TEM). The topographical behavior of the shape memory effect was investigated through Vickers indentation and laser scanning 3D confocal measurements. The magnitudes of deformation recovery associated with the one-way and two-way shape-memory effect (OWSME, TWSME) decreased with increasing indentation temperatures, which is a reflection of the decreasing volume of material experiencing martensitic reorientation during indentation. Indented and subsequently planarized samples exhibited TWSME protrusions when thermally cycled. Laser scanning measurements were used to characterize the height of the protrusions as increasing depths of material were polished away, which provided insight into the overall affected volume beneath the indent. As indentation temperatures increased, both the height of the protrusions, and consequently the polish depth necessary to completely remove the effect, decreased. TEM investigations revealed that directly underneath a nanoindent the microstructure was very fine due to the high-strain deformation; this was contrasted with a much coarser grain size in the undeformed bulk material. Overall these results strongly imply that the deformation recovery associated with the OWSME and TWSME can be maximized by indenting at temperatures at M{sub f} or below because the volume of deformed microstructure beneath the indent is maximized. This finding has important practical value for any potential application that utilizes indentation-induced phase transformation deformation recovery in NiTi.

Martensitic transformation in an intergranular corrosion area of austenitic stainless steel during thermal cycling

International Nuclear Information System (INIS)

La Fontaine, Alexandre; Yen, Hung-Wei; Trimby, Patrick; Moody, Steven; Miller, Sarah; Chensee, Martin; Ringer, Simon; Cairney, Julie

2014-01-01

An oxidation-assisted martensitic phase transformation was observed in an austenitic stainless steel after thermal cycling up to 970 °C in air in a solar thermal steam reformer. The intergranular corrosion areas were investigated by electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). The structural-and-chemical maps revealed that within intergranular corrosion areas this martensitic transformation primarily occurs in oxidation-induced chromium-depleted zones, rather than due to only sensitization. This displacive transformation may also play a significant role in the rate at which intergranular corrosion takes place

EARTHQUAKE-INDUCED DEFORMATION STRUCTURES AND RELATED TO EARTHQUAKE MAGNITUDES

Directory of Open Access Journals (Sweden)

Savaş TOPAL

2003-02-01

Full Text Available Earthquake-induced deformation structures which are called seismites may helpful to clasify the paleoseismic history of a location and to estimate the magnitudes of the potention earthquakes in the future. In this paper, seismites were investigated according to the types formed in deep and shallow lake sediments. Seismites are observed forms of sand dikes, introduced and fractured gravels and pillow structures in shallow lakes and pseudonodules, mushroom-like silts protruding laminites, mixed layers, disturbed varved lamination and loop bedding in deep lake sediments. Earthquake-induced deformation structures, by benefiting from previous studies, were ordered according to their formations and earthquake magnitudes. In this order, the lowest eartquake's record is loop bedding and the highest one is introduced and fractured gravels in lacustrine deposits.

''Some features of γ-ε martensitic transformation and shape memory effect in Fe-Mn-Si based alloys''

International Nuclear Information System (INIS)

Gulyaev, A.A.

1995-01-01

In the present paper several important aspects concerning the shape memory behavior of the ε-martensite in the cost-saving Fe-Mn-Si-based alloys and its application are reported. Some kinetic features of the γ-ε martensitic transformation are discussed. The effects of the composition, volume change induced by the transformation, strength of austenite, temperature of pre strain on the shape memory effect have been investigated. (orig.)

The Potential of Self-Tempered Martensite and Bainite in Improving the Fatigue Strength of Thermomechanically Processed Steels

Directory of Open Access Journals (Sweden)

Krupp Ulrich

2018-01-01

Full Text Available In contrast to a two-stage hardening and tempering process, the definition of optimized cooling routes after hot working of low-alloy Cr steel allows the adjustments of high-strength microstructures with a sufficient degree of ductility at the same time without any additional heat-treatment. While compressed air cooling after hot forging of micro-alloyed steel grades leads to the formation of lower bainite with finedispersed cementite platelets, quenching by water spray down to the martensite start temperature results in the formation of martensite, that is self-tempered during the subsequent slow-cooling in air. The precipitation of nano-sized cementite precipitates result in superior mechanical properties with respect to impact and tensile testing. Cyclic deformation and crack propagation tests being carried out using resonance testing (100Hz and ultrasonic fatigue testing (20kHz systems revealed a pronounced increase in fatigue strength by about 150MPa of the self-tempered martensite condition as compared to the bainitic modification. For the latter one, a steady decrease of the fatigue strength is observed rather than the existence of a real fatigue limit.

Computer simulation of martensitic transformations in idealized systems

International Nuclear Information System (INIS)

Chen, S.H.R.

1979-06-01

Very little theoretical work on the development of the martensitic transformation and the characteristics of the resulting microstructure exists. This thesis advances the theory of the martensite transformation by constructing a computer model of a martensitic transformation in an idealized system. The model has its source in the general observation that the characteristics of martensitic transformations in solids are largely determined by accomodating the strain associated with the martensitic distortion of the crystal lattice. A review and adaptation of prior theoretical work leads to the development of a theory which allows the straightforward computation of the elastic energy associated with an arbitrary distribution of defects in an elastically anisotropic body under the assumption that the body has uniform elastic constants and that anharmonic effects may be neglected. Equations are cast in which the energy is written as a simple sum of binary interactions in which the defects influence one another according to an elastic potential whose form can be calculated. At the time that the energetic equations take a simple form the kinematics of the process involving the appearance of elastic inclusions are also known to be simple. The martiensitic transformation is modeled as a transformation which occurs through the sequential formation of individual martensitic elements, each carries the elementary transformation strain. Statistical equations developed govern the selection of the transformation path, or sequence that elementary martensite particles appear in the model, and specifies the kinetics of transformation.A useful representative path is defined as the minimum energy path. The model is used for the detailed simulation of a martensitic transformation in a pseudo two-dimensional system. Virtually all interesting qualitative aspects of the developing martensitic transformation are shown to be inherently present within it

Development of a new ultrafine grained dual phase steel and examination of the effect of grain size on tensile deformation behavior

Energy Technology Data Exchange (ETDEWEB)

Saeidi, N., E-mail: navidsae@gmail.com; Ashrafizadeh, F.; Niroumand, B.

2014-04-01

Ultrafine grained dual phase (DP) steels are among the newest grades of DP steels that incorporate the uniform distribution of fine martensite particles (in the order of 1–2 μm) within a ferrite matrix. These new grades of steels have been developed in response to the world's demand for decreasing the fuel consumption in automobiles by increasing the strength to weight ratio. In the present research, a new kind of ultrafine grained DP (UFG-DP) steel with an average grain size of about 2 μm as well as a coarse grained DP (CG-DP) steel with an average grain size of about 5.4 μm was produced by consecutive intercritical annealing and cold rolling of low carbon AISI 8620 steel. The martensite volume fraction for both microstructures was the same and about 50 percent. Scanning electron microscopy (SEM) microstructural examination and room temperature tensile deformation analyses were performed on both UFG-DP and CG-DP steels and their deformation behavior in terms of strength, elongation and strain hardening was studied and compared. Room-temperature uniaxial tensile tests revealed that for a given martensite volume fraction, yield and tensile strengths were not very sensitive to martensite morphology. However, uniform and total elongation values were noticeably affected by refining martensite particles. The higher plasticity of fine martensite particles as well as the more uniform strain distribution within the UFG-DP microstructure resulted in higher strain hardenability and, finally, the higher ductility of the UFG-DP steel.

Isothermal martensite formation at sub-zero temperatures

DEFF Research Database (Denmark)

Stojko, Allan; Hansen, Mikkel Fougt; Slycke, Jan

2010-01-01

austenitized and quenched in oil and thereafter investigated with vibrating sample agnetometry, which allows a quantitative assessment of the fraction of retained austenite as a function of the subzero temperature and time. Isothermal martensite formation was observed on interrupting the continuous cooling (5...... with a continuation of the martensitic transformation. On prolonged isothermal holding a volume reduction was observed for AISI 52100, but not for AISI 1070. A mechanism is proposed that explains the occurrence of isothermal martensite formation....

Modelling of liquid sodium induced crack propagation in T91 martensitic steel: Competition with ductile fracture

Energy Technology Data Exchange (ETDEWEB)

Hemery, Samuel [Institut PPRIME, CNRS, Université de Poitiers, ISAE ENSMA, UPR 3346, Téléport 2, 1 Avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Berdin, Clotilde, E-mail: clotilde.berdin@u-psud.fr [Univ Paris-Sud, SP2M-ICMMO, CNRS UMR 8182, F-91405 Orsay Cedex (France); Auger, Thierry; Bourhi, Mariem [Ecole Centrale-Supelec, MSSMat CNRS UMR 8579, F-92295 Chatenay Malabry Cedex (France)

2016-12-01

Liquid metal embrittlement (LME) of T91 steel is numerically modeled by the finite element method to analyse experimental results in an axisymmetric notched geometry. The behavior of the material is identified from tensile tests then a crack with a constant crack velocity is introduced using the node release technique in order to simulate the brittle crack induced by LME. A good agreement between the simulated and the experimental macroscopic behavior is found: this suggests that the assumption of a constant crack velocity is correct. Mechanical fields during the embrittlement process are then extracted from the results of the finite element model. An analysis of the crack initiation and propagation stages: the ductile fracture probably breaks off the LME induced brittle fracture. - Highlights: • T91 martensitic steel is embrittled by liquid sodium depending on the loading rate at 573 K. • The mechanical behavior is modeled by a von Mises elastic-plastic law. • The LME induced crack propagates at a constant velocity. • The mechanical state at the crack tip does not explain a brittle crack arrest. • The occurrence of the ductile fracture breaks off the brittle fracture.

Martensitic transformation and residual stresses after thermomechanical treatment of heat treatable steel 42CrMo4 (SAE 4140)

Energy Technology Data Exchange (ETDEWEB)

Weise, A. [Technische Univ. Chemnitz-Zwickau, Chemnitz (Germany). Fakultaet fuer Maschinenbau und Verfahrenstechnik; Fritsche, G. [Technische Univ. Chemnitz-Zwickau, Chemnitz (Germany). Fakultaet fuer Maschinenbau und Verfahrenstechnik

1996-01-01

The influence of thermomechanical deformation on the residual stresses caused by quenching in bar shaped specimens of heat treatable steel 42CrMo4 has been investigated using a mechanical method for determining the distribution of residual stresses of the first kind. The results obtained show that the residual stress distribution after quenching is affected by the strengthening and softening of the austenite as a result of deformation and recrystallization and the modified transformation behaviour in martensite stage. An attempt is made to discuss qualitatively the influence of these changes on the generation of residual stresses as compared to results obtained after conventional hardening. (orig.).

Martensitic transformation and residual stresses after thermomechanical treatment of heat treatable steel 42CrMo4 (SAE 4140)

International Nuclear Information System (INIS)

Weise, A.; Fritsche, G.

1996-01-01

The influence of thermomechanical deformation on the residual stresses caused by quenching in bar shaped specimens of heat treatable steel 42CrMo4 has been investigated using a mechanical method for determining the distribution of residual stresses of the first kind. The results obtained show that the residual stress distribution after quenching is affected by the strengthening and softening of the austenite as a result of deformation and recrystallization and the modified transformation behaviour in martensite stage. An attempt is made to discuss qualitatively the influence of these changes on the generation of residual stresses as compared to results obtained after conventional hardening. (orig.)

Effects of annealing and deforming temperature on microstructure and deformation characteristics of Ti-Ni-V shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

He Zhirong, E-mail: hezhirong01@163.com [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China); Liu Manqian [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China)

2012-07-25

Highlights: Black-Right-Pointing-Pointer The deformation behaviors of annealed Ti-50.8Ni-0.5V shape memory alloy (SMA) were given. Black-Right-Pointing-Pointer The effect of annealing temperature on microstructure and deformation characteristics of Ti-50.8Ni-0.5V SMA was shown. Black-Right-Pointing-Pointer The effect of deforming temperature on deformation characteristics of Ti-50.8Ni-0.5V SMA was given. - Abstract: Effects of annealing temperature T{sub an} and deforming temperature T{sub d} on microstructure and deformation characteristics of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing T{sub an}, the microstructure of Ti-50.8Ni-0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 Degree-Sign C; the critical stress for stress-induced martensite {sigma}{sub M} of the alloy decreases first and then increases, and the minimum value 382 MPa is got at T{sub an} = 450 Degree-Sign C; the residual strain {epsilon}{sub R} first increases, then decreases, and then increases, and its maximum value 2.5% is reached at T{sub an} = 450 Degree-Sign C. With increasing T{sub d}, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME {yields} SE transformation temperature was affected by T{sub an}; the {sigma}{sub M} of the alloy increases linearly; the {epsilon}{sub R} of the alloy annealed at 350-600 Degree-Sign C decreases first and then tends to constant, while that of the alloy annealed at 650 Degree-Sign C and 700 Degree-Sign C decreases first and then increases. To get an excellent SE at room temperature for Ti-50.8Ni-0.5V alloy, T{sub an} should be 500-600 Degree-Sign C.

Characterization of Transformation-Induced Defects in Nickel Titanium Shape Memory Alloys

Science.gov (United States)

Bowers, Matthew L.

Shape memory alloys have remarkable strain recovery properties that make them ideal candidates for many applications that include devices in the automotive, aerospace, medical, and MEMS industries. Although these materials are widely used today, their performance is hindered by poor dimensional stability resulting from cyclic degradation of the martensitic transformation behavior. This functional fatigue results in decreased work output and cyclic accumulation of permanent strain. To date, few studies have taken a fundamental approach to investigating the interaction between plasticity and martensite growth and propagation, which is vitally important to mitigating functional fatigue in future alloy development. The current work focuses on understanding the interplay of these deformation mechanisms in NiTi-based shape memory alloys under a variety of different thermomechanical test conditions. Micron-scale compression testing of NiTi shape memory alloy single crystals is undertaken in an effort to probe the mechanism of austenite dislocation generation. Mechanical testing is paired with post mortem defect analysis via diffraction contrast scanning transmission electron microscopy (STEM). Accompanied by micromechanics-based modeling of local stresses surrounding a martensite plate, these results demonstrate that the previously existing martensite and resulting austenite dislocation substructure are intimately related. A mechanism of transformation-induced dislocation generation is described in detail. A study of pure and load-biased thermal cycling of bulk polycrystalline NiTi is done for comparison of the transformation behavior and resultant defects to the stress-induced case. Post mortem and in situ STEM characterization demonstrate unique defect configurations in this test mode and STEM-based orientation mapping reveals local crystal rotation with increasing thermal cycles. Changes in both martensite and austenite microstructures are explored. The results for

FE calculations on a three stage metal forming process of Sandvik Nanoflex

NARCIS (Netherlands)

Voncken, R.M.J.; Sluis, van der O.; Post, J.; Huetink, J.; Ghosh, S.; Castro, J.C.; Lee, J.K.

2004-01-01

Sandvik Nanoflex™ combines good corrosion resistance with high strength. This steel has good deformability in austenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-induced transformation into martensite takes place. After deformation,

FE calculations on a three stage metal forming process of Sandvik Nanoflex

NARCIS (Netherlands)

Voncken, R.M.J.; van der Sluis, O.; Post, J.; Huetink, Han

2004-01-01

Sandvik NanoflexTM combines good corrosion resistance with high strength. This steel has good deformability in austenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-induced transformation into martensite takes place. After deformation,

Irradiation deformation due to SIPA induced dislocation anisotropy

International Nuclear Information System (INIS)

Woo, CH.

1980-02-01

A contribution to irradiation deformation resulting from the stress-induced preferred adsorption (SIPA) effect is considered. SIPA causes a variation of the growth rates of irradiation-generated dislocation loops, according to the alignment of their Burgers vectors with respect to the applied stress. A prolinged period under an applied stress then creates an anisotropic dislocation structure in which the majority of dislocations have their Burgers vectors in alignment with the stress. In the presence of 'neutral' sinks, the resulting anisotropic dislocation structure causes plastic deformation similar to the way in which irradiation growth occurs in zirconium. This mechanism is called SIPA-induced growth (SIG). We have shown that SIG is very significant in comparison to SIPA, except when little or no loop growth has occurred during the period the stress is applied. This report contains the detailed formulation and derivation of the formulae for the evaluation of the contribution due to SIG. (auth)

The Mechanism of High Ductility for Novel High-Carbon Quenching-Partitioning-Tempering Martensitic Steel

Science.gov (United States)

Qin, Shengwei; Liu, Yu; Hao, Qingguo; Wang, Ying; Chen, Nailu; Zuo, Xunwei; Rong, Yonghua

2015-09-01

In this article, a novel quenching-partitioning-tempering (Q-P-T) process was applied to treat Fe-0.6C-1.5Mn-1.5Si-0.6Cr-0.05Nb hot-rolled high-carbon steel and the microstructures including retained austenite fraction and the average dislocation densities in both martensite and retained austenite were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, respectively. The Q-P-T steel exhibits high strength (1950 MPa) and elongation (12.4 pct). Comparing with the steel treated by traditional quenching and tempering (Q&T) process, the mechanism of high ductility for high-carbon Q-P-T steel is revealed as follows. Much more retained austenite existing in Q-P-T steel than in Q&T one remarkably enhances the ductility by the following two effects: the dislocation absorption by retained austenite effect and the transformation-induced plasticity effect. Besides, lower dislocation density in martensite matrix produced by Q-P-T process plays an important role in the improvement of ductility. However, some thin plates of twin-type martensite embedded in dislocation-type martensite matrix in high-carbon Q-P-T steel affect the further improvement of ductility.

Alloying effect on martensite transformation in stainless steels

International Nuclear Information System (INIS)

Gulyaev, A.P.; Shlyamnev, A.P.; Sorokina, N.A.

1975-01-01

The effect of cobalt, nickel, molybdenum on the martensite transformation kinetics in stainless steels containing 9 to 13% Cr has been studied. Cobalt in Fe-Cr base alloys decreases the temperature of the Msub(in) and Msub(fin) points without a considerable decrease of the martensite phase amount after the transformation. Nickel reduces the martensite transformation temperature range, the nickel effect being enhanced in the presence of cobalt, which is characterized by a change of the linear dependence Msub(in)=f(%Ni) for a quadratic one. Molybdenum decreases the temperature of the Msub(in) and Msub(fin) points intensively, thus, substantially increasing the residual austenite amount. In the steels investigated Ni and Co decrease, whereas Mo increases, to some extent, the temperature of the reverse a-γ-transformation. The reduction of chromium content from 13 to 9% stimulates the martensite transformation initiation, that is why, in alloys containing 9% Cr, the increase in the contents of Ni, Co., Mo with the martensite structure maintained is possible. A further alloying of steel containing 13% Cr with these elements is rather limited due to the inhibition of the martensite transformation

Driving higher magnetic field sensitivity of the martensitic transformation in MnCoGe ferromagnet

Science.gov (United States)

Ma, S. C.; Ge, Q.; Hu, Y. F.; Wang, L.; Liu, K.; Jiang, Q. Z.; Wang, D. H.; Hu, C. C.; Huang, H. B.; Cao, G. P.; Zhong, Z. C.; Du, Y. W.

2017-11-01

The sharp metamagnetic martensitic transformation (MMT) triggered by a low critical field plays a pivotal role in magnetoresponsive effects for ferromagnetic shape memory alloys (FSMAs). Here, a sharper magnetic-field-induced metamagnetic martensitic transformation (MFIMMT) is realized in Mn1-xCo1+xGe systems with a giant magnetocaloric effect around room temperature, which represents the lowest magnetic driving and completion fields as well as the largest magnetization difference around MFIMMT reported heretofore in MnCoGe-based FSMAs. More interestingly, a reversible MFIMMT with field cycling is observed in the Mn0.965Co0.035Ge compound. These results indicate that the consensus would be broken that the magnetic field is difficult to trigger the MMT for MnCoGe-based systems. The origin of a higher degree of sensitivity of martensitic transformation to the magnetic field is discussed based on the X-ray absorption spectroscopic results.

Diffuse scattering as an indicator for martensitic variant selection

International Nuclear Information System (INIS)

Gao, Lei; Ding, Xiangdong; Zong, Hongxiang; Lookman, Turab; Sun, Jun; Ren, Xiaobing; Saxena, Avadh

2014-01-01

Diffuse scattering is an important precursor phenomenon prior to the martensitic transformation (MT). It is related to the correlated atomic position fluctuations prior to the MT and can provide important hints of the transformation mechanism. However, the role of this precursor phenomenon in the MT is not clear so far. Here we study the evolution of diffraction patterns prior to temperature- and stress-induced MTs and consider the evolution of atomic configurations during the whole MT process, using molecular dynamics simulations on a generic body-centered cubic–hexagonal close-packed transformation as an example. Our results show that, although the diffuse scattering changes with external fields, there exists a general relationship between the transformation pathways, the diffuse scattering streaks and the martensitic products. Two preferred transformation pathways with opposite shuffle directions lead to a single specific diffuse scattering streak prior to the MT and form one pair of anti-variants after the MT. Thus the distribution of diffuse scattering acts as an indicator of the selection of martensitic variants. In addition, we find that the applied stress can change the shear order parameter of the phase transformation, and subsequently determines the preferred transformation pathways and the distribution of diffuse scattering streaks. This work establishes a relationship between the transformation mechanism, the precursor phenomenon and the products after the MT under the influence of external fields

Nanostructures by Severe Plastic Deformation of Steels: Advantages and Problems

Directory of Open Access Journals (Sweden)

Dobatkin, S. V.

2006-01-01

Full Text Available The aim of this paper is to consider the features of structure evolution during severe plastic deformation (SPD of steels and its influence on mechanical properties. The investigation have been carried out mainly on low carbon steels as well as on austenitic stainless steels after SPD by torsion under high pressure (HPT and equal channel angular (ECA pressing. Structure formation dependencies on temperature deformation conditions, strain degree, chemical composition, initial state and pressure are considered. The role of phase transformations for additional grain refinement, namely, martensitic transformation, precipitation of carbide particles during SPD and heating is underlined.

Detailed analysis of surface asperity deformation mechanism in diffusion bonding of steel hollow structural components

Energy Technology Data Exchange (ETDEWEB)

Zhang, C. [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Laboratoire de Mecanique des Contacts et des Structures (LaMCoS), INSA Lyon, 20 Avenue des Sciences, F-69621 Villeurbanne Cedex (France); Li, H. [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Li, M.Q., E-mail: zc9997242256@126.com [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China)

2016-05-15

Graphical abstract: This study focused on the detailed analysis of surface asperity deformation mechanism in diffusion bonding of steel hollow structural component. A special surface with regular patterns was processed to be joined so as to observe the extent of surface asperity deformation under different applied bonding pressures. Fracture surface characteristic combined with surface roughness profiles distinctly revealed the enhanced surface asperity deformation as the applied pressure increases. The influence of surface asperity deformation mechanism on joint formation was analyzed: (a) surface asperity deformation not only directly expanded the interfacial contact areas, but also released deformation heat and caused defects, indirectly accelerating atomic diffusion, then benefits to void shrinkage; (b) surface asperity deformation readily introduced stored energy difference between two opposite sides of interface grain boundary, resulting in strain induced interface grain boundary migration. In addition, the influence of void on interface grain boundary migration was analyzed in detail. - Highlights: • A high quality hollow structural component has been fabricated by diffusion bonding. • Surface asperity deformation not only expands the interfacial contact areas, but also causes deformation heat and defects to improve the atomic diffusion. • Surface asperity deformation introduces the stored energy difference between the two opposite sides of interface grain boundary, leading to strain induced interface grain boundary migration. • The void exerts a dragging force on the interface grain boundary to retard or stop interface grain boundary migration. - Abstract: This study focused on the detailed analysis of surface asperity deformation mechanism in similar diffusion bonding as well as on the fabrication of high quality martensitic stainless steel hollow structural components. A special surface with regular patterns was processed to be joined so as to

Neutron diffraction study of stress-induced martensitic transformation and variant change in Fe-Pd shape memory alloy

International Nuclear Information System (INIS)

Oliver, E.C.; Mori, T.; Daymond, M.R.; Withers, P.J.

2003-01-01

Neutron diffraction spectra were recorded during tensile testing of Fe-30.5 at.% Pd shape memory alloy at temperatures above M s and below M f . Peak intensity changes indicate that the application of tensile stress to initially fully austenitic material results in the preferential martensitic transformation of grains oriented with austenite parallel to the tensile axis. Tensile stress applied to initially fully martensitic material causes the greatest extent of reorientation in those variants oriented with martensite lying parallel to the tensile axis. These results are interpreted using a simple elasticity-based theory. Additionally, diffraction peak shifts provide information on the development of lattice strain in differently oriented grain families during loading. This indicates that above M s the alloy exhibits high single crystal elastic anisotropy. Below M f the apparent stiffnesses of different grain families suggest that axially compressive internal stresses develop in those grain families in which most variant reorientation occurs. These stresses act to reverse the variant changes upon subsequent unloading

Cryogenic deformation microstructures of 32Mn-7Cr-1Mo-0.3N austenitic steels

International Nuclear Information System (INIS)

Fu Ruidong; Qiu Liang; Wang Tiansheng; Wang Cunyu; Zheng Yangzeng

2005-01-01

The cryogenic deformation microstructures of impact and tensile specimens of 32Mn-7Cr-1Mo-0.3N austenitic steel were investigated using light microscopy and transmission electron microscopy. The results show that the deformation microstructures of the impact specimens are mainly composed of stacking faults, network dislocation, slip bands, and a few mechanical twins and ε-martensite. These microstructures cross with each other in a crystal angle. The deformation microstructures of the tensile specimens consist only of massive slip bands, in which a few mechanical twins and ε-martenite are located. Because of the larger plastic deformation the slip band traces become bent. All the deformation microstructures are formed on the {111} planes and along the orientation

The evolution of internal stress and dislocation during tensile deformation in a 9Cr ferritic/martensitic (F/M) ODS steel investigated by high-energy X-rays

International Nuclear Information System (INIS)

Zhang, Guangming; Zhou, Zhangjian; Mo, Kun; Miao, Yinbin; Liu, Xiang; Almer, Jonathan; Stubbins, James F.

2015-01-01

An application of high-energy wide angle synchrotron X-ray diffraction to investigate the tensile deformation of 9Cr ferritic/martensitic (F/M) ODS steel is presented. With tensile loading and in-situ X-ray exposure, the lattice strain development of matrix was determined. The lattice strain was found to decrease with increasing temperature, and the difference in Young's modulus of six different reflections at different temperatures reveals the temperature dependence of elastic anisotropy. The mean internal stress was calculated and compared with the applied stress, showing that the strengthening factor increased with increasing temperature, indicating that the oxide nanoparticles have a good strengthening impact at high temperature. The dislocation density and character were also measured during tensile deformation. The dislocation density decreased with increasing of temperature due to the greater mobility of dislocation at high temperature. The dislocation character was determined by best-fit methods for different dislocation average contrasts with various levels of uncertainty. The results shows edge type dislocations dominate the plastic strain at room temperature (RT) and 300 °C, while the screw type dislocations dominate at 600 °C. The dominance of edge character in 9Cr F/M ODS steels at RT and 300 °C is likely due to the pinning effect of nanoparticles for higher mobile edge dislocations when compared with screw dislocations, while the stronger screw type of dislocation structure at 600 °C may be explained by the activated cross slip of screw segments. - Highlights: • The tensile deformation of 9Cr ODS steel was studied by synchrotron irradiation. • The evolution of internal mean stress was calculated. • The evolution of dislocation character was determined by best-fit method. • Edge type dominates plasticity at RT and 300 °C, while screw type dominates at 600 °C.

The evolution of internal stress and dislocation during tensile deformation in a 9Cr ferritic/martensitic (F/M) ODS steel investigated by high-energy X-rays

Energy Technology Data Exchange (ETDEWEB)

Zhang, Guangming [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States); Zhou, Zhangjian, E-mail: zhouzhj@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, Beijing, Beijing 100083 (China); Mo, Kun [Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Miao, Yinbin; Liu, Xiang [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States); Almer, Jonathan [X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Stubbins, James F. [Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, IL 61801 (United States)

2015-12-15

An application of high-energy wide angle synchrotron X-ray diffraction to investigate the tensile deformation of 9Cr ferritic/martensitic (F/M) ODS steel is presented. With tensile loading and in-situ X-ray exposure, the lattice strain development of matrix was determined. The lattice strain was found to decrease with increasing temperature, and the difference in Young's modulus of six different reflections at different temperatures reveals the temperature dependence of elastic anisotropy. The mean internal stress was calculated and compared with the applied stress, showing that the strengthening factor increased with increasing temperature, indicating that the oxide nanoparticles have a good strengthening impact at high temperature. The dislocation density and character were also measured during tensile deformation. The dislocation density decreased with increasing of temperature due to the greater mobility of dislocation at high temperature. The dislocation character was determined by best-fit methods for different dislocation average contrasts with various levels of uncertainty. The results shows edge type dislocations dominate the plastic strain at room temperature (RT) and 300 °C, while the screw type dislocations dominate at 600 °C. The dominance of edge character in 9Cr F/M ODS steels at RT and 300 °C is likely due to the pinning effect of nanoparticles for higher mobile edge dislocations when compared with screw dislocations, while the stronger screw type of dislocation structure at 600 °C may be explained by the activated cross slip of screw segments. - Highlights: • The tensile deformation of 9Cr ODS steel was studied by synchrotron irradiation. • The evolution of internal mean stress was calculated. • The evolution of dislocation character was determined by best-fit method. • Edge type dominates plasticity at RT and 300 °C, while screw type dominates at 600 °C.

Lattice defect inheritance during γ-α-γ transformation in steel having no ''reverse'' (martensite) transition during austenization

International Nuclear Information System (INIS)

Bernshtejn, M.L.; Zajmovskij, V.A.; Kozlova, A.G.; Kolupaeva, T.L.

1979-01-01

An investigation was carried out, using an electron microscope technique, of the substructure of austenite in the 120Kh3G steel. It was shown that the austenite substructure, resulting from high-temperature mechanical working, is inherited on deep cooling by the low-temperature phase (martensite), and in subsequent heating is again inherited by austenite. If the disintegration of the hot-deformed austenite takes place in the pearlite phase, reheating gives rise to an austenite free from the substructure

The evolution of internal stress and dislocation during tensile deformation in a 9Cr ferritic/martensitic (F/M) ODS steel investigated by high-energy X-rays

Energy Technology Data Exchange (ETDEWEB)

Zhang, Guangming; Zhou, Zhangjian; Mo, Kun; Miao, Yinbin; Liu, Xiang; Almer, Jonathan; Stubbins, James F.

2015-12-01

An application of high-energy wide angle synchrotron X-ray diffraction to investigate the tensile deformation of 9Cr ferritic/martensitic (F/M) ODS steel is presented. With tensile loading and in-situ Xray exposure, the lattice strain development of matrix was determined. The lattice strain was found to decrease with increasing temperature, and the difference in Young's modulus of six different reflections at different temperatures reveals the temperature dependence of elastic anisotropy. The mean internal stress was calculated and compared with the applied stress, showing that the strengthening factor increased with increasing temperature, indicating that the oxide nanoparticles have a good strengthening impact at high temperature. The dislocation density and character were also measured during tensile deformation. The dislocation density decreased with increasing of temperature due to the greater mobility of dislocation at high temperature. The dislocation character was determined by best-fit methods for different dislocation average contrasts with various levels of uncertainty. The results shows edge type dislocations dominate the plastic strain at room temperature (RT) and 300 C, while the screw type dislocations dominate at 600 C. The dominance of edge character in 9Cr F/M ODS steels at RT and 300 C is likely due to the pinning effect of nanoparticles for higher mobile edge dislocations when compared with screw dislocations, while the stronger screw type of dislocation structure at 600 C may be explained by the activated cross slip of screw segments.

Static Recrystallization Behavior of Z12CN13 Martensite Stainless Steel

Science.gov (United States)

Luo, Min; Zhou, Bing; Li, Rong-bin; Xu, Chun; Guo, Yan-hui

2017-09-01

In order to increase the hot workability and provide proper hot forming parameters of forging Z12CN13 martensite stainless steel for the simulation and production, the static recrystallization behavior has been studied by double-pass hot compression tests. The effects of deformation temperature, strain rate and inter-pass time on the static recrystallization fraction by the 2% offset method are extensively studied. The results indicate that increasing the inter-pass time and the deformation temperature as well as strain rate appropriately can increase the fraction of static recrystallization. At the temperature of 1050-1150 °C, inter-pass time of 30-100 s and strain rate of 0.1-5 s-1, the static recrystallization behavior is obvious. In addition, the kinetics of static recrystallization behavior of Z12CN13 steel has been established and the activation energy of static recrystallization is 173.030 kJ/mol. The substructure and precipitates have been studied by TEM. The results reveal that the nucleation mode is bulging at grain boundary. Undissolved precipitates such as MoNi3 and Fe3C have a retarding effect on the recrystallization kinetics. The effect is weaker than the accelerating effect of deformation temperature.

Martensitic phase transformation in shape-memory alloys

International Nuclear Information System (INIS)

Golestaneh, A.A.

1979-01-01

Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M → P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M → P → M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface

X-ray diffraction study of thermally and stress-induced phase transformations in single crystalline Ni-Mn-Ga alloys

International Nuclear Information System (INIS)

Martynov, V.V.

1995-01-01

Using in-situ single crystal X-ray diffraction methods, thermally- and stress-induced crystal structure evolution was investigated in two Ni-Mn-Ga Heusler-type alloys. For the 51at.%Ni-24at.%Mn-25at.%Ga alloy it was found that application of external stress in a temperature range ∼20 C above the M s at first causes intensity changes of X-ray diffuse scattering peaks in β-phase. Further stressing results in stress-induced phase transformations and under the appropriate conditions three successive martensitic transformations (one is parent-to-martensite and two are martensite-to-martensite transformations) can be stress induced. Of these only the parent-to-martensite transformation can be thermally-induced. Two successive structural transformations (thermally-induced parent-to-martensite and stress-induced martensite-to-martensite transformations) were found in 52at.%Ni-25at.%Mn-23at.%Ga alloy. Crystal structure, lattice parameters, type of modulation, and the length of modulation period for all martensites were identified. (orig.)

Influence on SME and microstructure in FeMnSiCrNi SMA for strengthening of austenite matrix

International Nuclear Information System (INIS)

Gu, N.; Lin, C.; Song, X.; Peng, H.; Yin, F.

2000-01-01

Influences of solution- and deformation-strengthening on SME and the microstructures of FeMnSiCrNi SMA were researched. SME and the training effect were both obviously improved when 0.3%C added into the alloy. It was observed that some thermo-induced martensites, distributing disorderly in the matrix, formed in the alloy without carbon, while in the alloy with carbon, more stress-induced martensites, distributing orderly in the matrix, were found, thus resulting in the better SME. As far as the treatment methods were concerned, one time deformation-strengthening could be better than training many times. The ε-martensites in the strengthened alloy appeared larger in amount, short plate in shape and distributed with nearly the same orientation, which is closely related to the better SME. (orig.)

Wear resistance and structural changes in nitrogen-containing high-chromium martensitic steels under conditions of abrasive wear and sliding friction

International Nuclear Information System (INIS)

Makarov, A.V.; Korshunov, L.G.; Schastlivtsev, V.M.; Chernenko, N.L.

1998-01-01

Martensitic nitrogen-containing steels Kh17N2A0.14, Kh13A0.14, Kh14G4A0.22 as well as steel 20Kh13 were studied for their wear resistance under conditions of friction and abrasion. Metallography, X ray diffraction analysis and electron microscopy were used to investigate the structural changes taking place in a thin surface layer on wearing. It is shown that an increase of nitrogen content of 0.14 to 0.22% promotes an enhancement of steel resistance to abrasive and adhesive wear, especially after tempering in the range of 500-550 deg C. Typically, the nitrogen-containing steels exhibit lower resistance to various types of wear in comparison with the steels with high-carbon martensite due to their lower deformability under conditions of friction loading

Microstructure of laser cladded martensitic stainless steel

CSIR Research Space (South Africa)

Van Rooyen, C

2006-08-01

Full Text Available and martensite with 10% ferrite for Material B. Table 7 - Proposed martensitic stainless steel alloys for laser cladding Material C* Cr Ni Mn Si Mo Co Ms (ºC)* Cr eq Ni eq Material A 0.4 13 - 1 0.5 2.5 5.5 120 16.5 12.5 Material B 0.2 15 2 1 0.7 2.5 5.5 117... dilution, low heat input, less distortion, increased mechanical and corrosion properties excellent repeatability and control of process parameters. Solidification of laser cladded martensitic stainless steel is primarily austenitic. Microstructures...

The basic elementary particles as martensitic nucleus

International Nuclear Information System (INIS)

Aguinaco-Bravo, V. J.; Onoro, J.

1999-01-01

The martensitic transformation is a diffusional structural change that produces an important modification of the microstructure and properties of materials. In this paper we propose how the martensitic phase is nucleated from a basic elementary particle (bep). The bep is formed in several stages. Vacancies, divacancies, etc. are formed at high temperature, which collapse into prismatic dislocation loops during the cooling process. We define a bep as a dislocation loop reaching a critical radius and fulfilling certain elastic energy conditions. A martensitic nucleus is a bep that coincides crystallographically with the habit plane of the matrix. (Author) 16 refs

Characterization of martensitic transformations using acoustic emission

International Nuclear Information System (INIS)

Tatro, C.A.

1984-01-01

Acoustic emission (AE) is a highly sensitive technique which can reveal changes in materials not detectable by other means. The goal of this project was to obtain basic information on the AE response to martensitic transformation in steel. This information will enable the use of AE for improved quality assurance testing of rough-cut component blanks and semifinished parts. The AE response was measured as a function of temperature in four steels undergoing martensitic transformation, and the AE response was compared with martensitic start temperature M/sub s/ and finish temperature M/sub f/ obtained by other methods. As measured by AE activity, M/sub s/ occurred as much as 26 0 C higher than previously reported using less sensitive measurement techniques. It was also found that 10 to 30% of an alloy of Fe-0.2% C-27% Ni transformed to martensite during one AE burst. These results show that AE can be used to study transformations both inside and outside the classical M/sub s/-M/sub f/ ranges. The findings will help to achieve the goal of using AE for quality assurance testing, and will add to the knowledge of the basic materials science of martensitic transformations

Non-Newtonian Flow-Induced Deformation From Pressurized Cavities in Absorbing Porous Tissues

Science.gov (United States)

Ahmed, Aftab; Siddique, Javed

2017-11-01

We investigate the behavior of a spherical cavity in a soft biological tissue modeled as a deformable porous material during an injection of non-Newtonian fluid that follows a power law model. Fluid flows into the neighboring tissue due to high cavity pressure where it is absorbed by capillaries and lymphatics at a rate proportional to the local pressure. Power law fluid pressure and displacement of solid in the tissue are computed as function of radial distance and time. Numerical solutions indicate that shear thickening fluids exhibit less fluid pressure and induce small solid deformation as compared to shear thinning fluids. The absorption in the biological tissue increases as a consequence of flow induced deformation for power law fluids. In most cases non-Newtonian results are compared with viscous fluid case to magnify the differences.

Isothermal martensitic transformation as an internal-stress-increasing process

International Nuclear Information System (INIS)

Liu, Y.; Xie, Z.L.; Haenninen, H.; Humbeeck, J. van; Pietikaeinen, J.

1995-01-01

Based on the results that the magnitude of the stabilization of retained austenite increases with increasing the amount of martensite transformed, it has been assumed that the martensitic transformation is accompanied with an increase in internal resisting stress which subsequently results in the stabilization of retained austenite. By simplifying this internal resisting stress to be a type of hydrostatic compressive stress acting on retained austenite due to surrounding martensite plates, a thermodynamical analysis for an isothermal martensitic transformation under applied hydrostatic pressure has been performed. The calculated results, to some extent, show a good agreement with the experimental data. (orig.)

Observation of the two-way shape memory effect in an atomistic model of martensitic transformation

Directory of Open Access Journals (Sweden)

Eduardo Jagla

2017-05-01

Full Text Available We study a system of classical particles in two dimensions interacting through an isotropic pair potential that displays a martensitic phase transition between a triangular and a rhomboidal structure upon the change of a single parameter. Previously it was shown that this potential is able to reproduce the shape memory effect and super-elasticity, among other well known features of the phenomenology of martensites. Here we extend those previous studies and describe the development of the more subtle two-way shape memory effect. We show that in a poly-crystalline sample, the effect is mostly due to the existence of retained martensite within the austenite phase. We also study the case of a single crystal sample where the effect is associated to particular orientations of the dislocations, either induced by training or by an ad hoc construction of a starting sample.

Predictive modeling of interfacial damage in substructured steels: application to martensitic microstructures

International Nuclear Information System (INIS)

Maresca, F; Kouznetsova, V G; Geers, M G D

2016-01-01

Metallic composite phases, like martensite present in conventional steels and new generation high strength steels exhibit microscale, locally lamellar microstructures characterized by alternating layers of phases or crystallographic variants. The layers can be sub-micron down to a few nanometers thick, and they are often characterized by high contrasts in plastic properties. As a consequence, fracture in these lamellar microstructures generally occurs along the layer interfaces or within one of the layers, typically parallel to the interface. This paper presents a computational framework that addresses the lamellar nature of these microstructures, by homogenizing the plastic deformation at the mesoscale by using the microscale response of the laminates. Failure is accounted for by introducing a family of damaging planes that are parallel to the layer interface. Mode I, mode II and mixed-mode opening are incorporated. The planes along which failure occurs are captured using a smeared damage approach. Coupling of damage with isotropic or anisotropic plasticity models, like crystal plasticity, is straightforward. The damaging planes and directions do not need to correspond to crystalline slip planes, and normal opening is also included. Focus is given on rate-dependent formulations of plasticity and damage, i.e. converged results can be obtained without further regularization techniques. The validation of the model using experimental observations in martensite-austenite lamellar microstructures in steels reveals that the model correctly predicts the main features of the onset of failure, e.g. the necking point, the failure initiation region and the failure mode. Finally, based on the qualitative results obtained, some material design guidelines are provided for martensitic and multi-phase steels. (paper)

Nonlinear Model of Pseudoelastic Shape Memory Alloy Damper Considering Residual Martensite Strain Effect

Directory of Open Access Journals (Sweden)

Y. M. Parulekar

2012-01-01

Full Text Available Recently, there has been increasing interest in using superelastic shape memory alloys for applications in seismic resistant-design. Shape memory alloys (SMAs have a unique property by which they can recover their original shape after experiencing large strains up to 8% either by heating (shape memory effect or removing stress (pseudoelastic effect. Many simplified shape memory alloy models are suggested in the past literature for capturing the pseudoelastic response of SMAs in passive vibration control of structures. Most of these models do not consider the cyclic effects of SMA's and resulting residual martensite deformation. Therefore, a suitable constitutive model of shape memory alloy damper which represents the nonlinear hysterical dynamic system appropriately is essential. In this paper a multilinear hysteretic model incorporating residual martensite strain effect of pseudoelastic shape memory alloy damper is developed and experimentally validated using SMA wire, based damper device. A sensitivity analysis is done using the proposed model along with three other simplified SMA models. The models are implemented on a steel frame representing an SDOF system and the comparison of seismic response of structure with all the models is made in the numerical study.

Effect of Ni4Ti3 precipitation on martensitic transformation in Ti-Ni

International Nuclear Information System (INIS)

Zhou, N.; Shen, C.; Wagner, M.F.-X.; Eggeler, G.; Mills, M.J.; Wang, Y.

2010-01-01

Precipitation of Ni 4 Ti 3 plays a critical role in determining the martensitic transformation path and temperature in Ni-Ti shape memory alloys. In this study, the equilibrium shape of a coherent Ni 4 Ti 3 precipitate and the concentration and stress fields around it are determined quantitatively using the phase field method. Most recent experimental data on lattice parameters, elastic constants, precipitate-matrix orientation relationship and thermodynamic database are used as model inputs. The effects of the concentration and stress fields on subsequent martensitic transformations are analyzed through interaction energy between a nucleating martensitic particle and the existing microstructure. Results indicate that R-phase formation prior to B19' phase could be attributed to both direct elastic interaction and stress-induced spatial variation in concentration near Ni 4 Ti 3 precipitates. The preferred nucleation sites for the R-phase are close to the broad side of the lenticular-shaped Ni 4 Ti 3 precipitates, where tension normal to the habit plane is highest, and Ni concentration is lowest.

Development of TRIP-Aided Lean Duplex Stainless Steel by Twin-Roll Strip Casting and Its Deformation Mechanism

Science.gov (United States)

Zhao, Yan; Zhang, Weina; Liu, Xin; Liu, Zhenyu; Wang, Guodong

2016-12-01

In the present work, twin-roll strip casting was carried out to fabricate thin strip of a Mn-N alloyed lean duplex stainless steel with the composition of Fe-19Cr-6Mn-0.4N, in which internal pore defects had been effectively avoided as compared to conventional cast ingots. The solidification structure observed by optical microscope indicated that fine Widmannstatten structure and coarse-equiaxed crystals had been formed in the surface and center, respectively, with no columnar crystal structures through the surface to center of the cast strip. By applying hot rolling and cold rolling, thin sheets with the thickness of 0.5 mm were fabricated from the cast strips, and no edge cracks were formed during the rolling processes. With an annealing treatment at 1323 K (1050 °C) for 5 minutes after cold rolling, the volume fractions of ferrite and austenite were measured to be approximately equal, and the distribution of alloying elements in the strip was further homogenized. The cold-rolled and annealed sheet exhibited an excellent combination of strength and ductility, with the ultimate tensile strength and elongation having been measured to be 1000 MPa and 65 pct, respectively. The microstructural evolution during deformation was investigated by XRD, EBSD, and TEM, indicating that ferrite and austenite had different deformation mechanisms. The deformation of ferrite phase was dominated by dislocation slipping, and the deformation of austenite phase was mainly controlled by martensitic transformation in the sequence of γ→ ɛ-martensite→ α'-martensite, leading to the improvement of strength and plasticity by the so-called transformation-induced plasticity (TRIP) effect. By contrast, lean duplex stainless steels of Fe-21Cr-6Mn-0.5N and Fe-23Cr-7Mn-0.6N fabricated by twin-roll strip casting did not show TRIP effects and exhibited lower strength and elongation as compared to Fe-19Cr-6Mn-0.4N.

Cyclic softening as a parameter for prediction of remnant creep rupture life of a Indian reduced activation ferritic–martensitic (IN-RAFM) steel subjected to fatigue exposures

Energy Technology Data Exchange (ETDEWEB)

Sarkar, Aritra, E-mail: aritra@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Vijayanand, V.D.; Shankar, Vani; Parameswaran, P.; Sandhya, R.; Laha, K.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Rajendrakumar, E. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India)

2014-12-15

Sequential fatigue-creep tests were conducted on Indian reduced activation ferritic–martensitic steel at 823 K leading to sharp decrease in residual creep life with increase in prior fatigue exposures. Extensive recovery of martensitic-lath structure taking place during fatigue deformation, manifested as cyclic softening in the cyclic stress response, shortens the residual creep life. Based on the experimental results, cyclic softening occurring during fatigue stage can be correlated with residual creep life, evolving in an empirical model which predicts residual creep life as a function of cyclic softening. Predicted creep lives for specimens pre-cycled at various strain amplitudes are explained on the basis of mechanism of cyclic softening.

Microstructure-Sensitive Modeling of High Cycle Fatigue (Preprint)

Science.gov (United States)

2009-03-01

liquid nitrogen bath to obtain complete martensitic transformation at the surface. This is followed by tempering at 500°C for 1.5 hours to achieve...microstructure of martensite [38-42] and the scales over which process-induced strengthening effects are realized in components, it is quite challenging to...Deformation and fracture in martensitic carbon steels tempered at low temperatures. Metallurgical and Materials Transactions A: Physical Metallurgy and

Plasticity-induced martensitic transformation in austenitic stainless steels SUS 304 and SUS 316 L at room and liquid nitrogen temperatures. Quantitative measurement using X-ray diffraction method

International Nuclear Information System (INIS)

Iwasaki, Yoshifumi; Nakasone, Yuji; Shimizu, Tetsu; Kobayashi, Noboru

2006-01-01

The present study investigates plasticity-induced martensitic transformation in two types of austenitic stainless steels SUS 304 and 316 L subjected to uniform tensile stresses at room and liquid nitrogen temperatures. The X-ray diffraction method was used in order to measure volume fractions of transformed α' and ε' martensitic phases and to obtain the dependence of the volume fractions of these phases on the applied strain level ε. The difficulty in the measurement of the martensitic phases by the X-ray diffraction method caused by the preferred orientation which had been introduced during the rolling process and during the tensile tests was overcome by the help of Arnell's Method. Two types of target materials, i.e. Cu and Mo for the X-ray source were used to verify the accuracy and reproducibility of the present X-ray diffraction analyses. The results were also compared with those obtained by the saturation magnetization method using VSM, or vibrating-sample magnetometer reported elsewhere. It was revealed that α' was transformed in SUS 304 both at 297 and 77 K whereas in SUS 316L only at 77 K. Another type of martensitic phase, i.e., ε was transformed in the both steels only at 77 K. Almost the same values of the volume fractions of α' and ε' phases were obtained by the two types of target materials. The plots of α' volume fraction obtained by the X-ray diffraction methods vs. that by VSM showed a good linear correlation. (author)

Martensitic textures: Multiscale consequences of elastic compatibility

International Nuclear Information System (INIS)

Shenoy, S.R.; Lookman, T.; Saxena, A.; Bishop, A.R.

2001-03-01

We show that a free energy entirely in the order-parameter strain variable(s), rather than the displacement field, provides a unified understanding of martensitic textures. We use compatibility equations, linking the strain tensor components in the bulk and at interfaces, that induce anisotropic order-parameter strain interactions. These two long-range bulk/interface potentials, together with local compositional fluctuations, drive the formation of global elastic textures. Relaxational simulations show the spontaneous formation (and evolution under stress/temperature quenches) of equal width parallel twins, branched twins, and tweed, including characteristic scaling of twin width with twin length. (author)

Morphogenesis of the radiation-induced mutant limb deformity (ld) of the common mouse

International Nuclear Information System (INIS)

Selow, J.; Winkler, W.

1980-01-01

Findings obtained in the thoracic and pelvic extremities of mice of the incest strain C57B1/10; i.e. animals homozygous with regard to the radiation-induced mutation 'limb deformity', are summarized and compared with the findings in non-deformed mice. Further, the deformities and their causes are discussed against the background of other findings. Conclusions may be drawn for the evaluation of the present findings. (orig./MG) [de

Self-stabilization of untransformed austenite by hydrostatic pressure via martensitic transformation

International Nuclear Information System (INIS)

Nakada, Nobuo; Ishibashi, Yuji; Tsuchiyama, Toshihiro; Takaki, Setsuo

2016-01-01

For improving the understanding of austenite stability in steel, hydrostatic pressure in untransformed austenite that is generated via martensitic transformation was evaluated from macro- and micro-viewpoints, and its effect on austenite stability was investigated in a Fe-27%Ni austenitic alloy. X-ray diffractometry revealed that the lattice parameter of untransformed austenite is continuously decreased via martensitic transformation only when martensite becomes the dominant phase in the microstructure. This suggests that the untransformed austenite is isotropically compressed by the surrounding martensite grains, i.e., hydrostatic pressure is generated in untransformed austenite dynamically at a later stage of martensitic transformation. On the other hand, microscopic strain mapping using the electron backscatter diffraction technique indicated that a finer untransformed austenite grain has a higher hydrostatic pressure, while a high density of dislocations is also introduced in untransformed austenite near the austenite/martensite interface because of lattice-invariant shear characterized by non-thermoelastic martensitic transformation. Furthermore, it was experimentally demonstrated that the hydrostatic pressure stabilizes the untransformed austenite; however, the austenite stabilization effect alone is not large enough to fully explain a large gap between martensite start and finish temperatures in steel.

Stress Relaxation Effects in TiNi SMA During Superelastic Deformation: Experiment and Constitutive Model

Science.gov (United States)

Pieczyska, Elżbieta A.; Kowalewski, Zbigniew L.; Dunić, Vladimir Lj.

2017-12-01

This paper presents an investigation of thermomechanical effects related to the phenomena of stress relaxation occurring in TiNi SMA subjected to modified program of displacement-controlled tension. The deformation data were taken from testing machine, whereas the temperature changes accompanying the exothermic/endothermic martensite forward/reverse transformation were measured by infrared camera. At the advanced stages of the transformations, the strain was kept constant for a few minutes and the SMA load and temperature were recorded continuously. As a consequence, the stress and temperature changed significantly during the loading stops. A large stress drop, caused by the transformation, was observed during the relaxation stage in both courses of the SMA loading and unloading. Moreover, the non-uniform temperature distribution, reflecting macroscopically inhomogeneous transformation, lapsed while the strain was kept constant, yet restarted at the end of the relaxation stop and developed at the reloading stage. Along with the experimental results, the mechanical and thermal responses induced by the transformation were obtained by 3D coupled thermomechanical numerical analysis, realized in partitioned approach. Latent heat production was correlated with an amount of the martensitic volume fraction. The stress and temperature drops recorded during the experiment were satisfactorily reproduced by the model proposed for the SMA thermomechanical coupling.

Crystallographic features of lath martensite in low-carbon steel

International Nuclear Information System (INIS)

Kitahara, Hiromoto; Ueji, Rintaro; Tsuji, Nobuhiro; Minamino, Yoritoshi

2006-01-01

Electron backscattering diffraction with field-emission scanning electron microscopy was used to analyze crystallographically the lath martensite structure in a 0.20% carbon steel. The crystallographic features of the lath martensite structure, of the order of the prior austenite grain size or larger, were clarified. Although the orientations of the martensite crystals were scattered around the ideal variant orientations, the martensite in this steel maintained the Kurdjumov-Sachs (K-S) orientation relationship. The procedures of the crystallographic analysis of the martensite (ferrite) phase with the K-S orientation relationship were explained in detail. Variant analysis showed that all 24 possible variants did not necessarily appear within a single prior austenite grain and that all six variants did not necessarily appear within each packet. Specific combinations of two variants appeared within local regions (sub-blocks), indicating a strict rule for variant selection. Prior austenite grain boundaries and most of the packet boundaries were clearly recognized. However, it was difficult to determine the block boundaries within the sub-blocks

Microstructure-based modelling of the long-term monotonic and cyclic creep of the martensitic steel X 20(22) CrMoV 12 1

International Nuclear Information System (INIS)

Henes, D.; Straub, S.; Blum, W.; Moehlig, H.; Granacher, J.; Berger, C.

1999-01-01

The current state of development of the composite model of deformation of the martensitic steel X 20(22) CrMoV 12 1 under conditions of creep is briefly described. The model is able to reproduce differences in monotonic creep strength of different melts with slightly different initial microstructures and to simulate cyclic creep with alternating phases of tension and compression. (orig.)

Binary gas mixture adsorption-induced deformation of microporous carbons by Monte Carlo simulation.

Science.gov (United States)

Cornette, Valeria; de Oliveira, J C Alexandre; Yelpo, Víctor; Azevedo, Diana; López, Raúl H

2018-07-15

Considering the thermodynamic grand potential for more than one adsorbate in an isothermal system, we generalize the model of adsorption-induced deformation of microporous carbons developed by Kowalczyk et al. [1]. We report a comprehensive study of the effects of adsorption-induced deformation of carbonaceous amorphous porous materials due to adsorption of carbon dioxide, methane and their mixtures. The adsorption process is simulated by using the Grand Canonical Monte Carlo (GCMC) method and the calculations are then used to analyze experimental isotherms for the pure gases and mixtures with different molar fraction in the gas phase. The pore size distribution determined from an experimental isotherm is used for predicting the adsorption-induced deformation of both pure gases and their mixtures. The volumetric strain (ε) predictions from the GCMC method are compared against relevant experiments with good agreement found in the cases of pure gases. Copyright © 2018 Elsevier Inc. All rights reserved.

Radiation swelling of steels with lath martensite-austenic structure

International Nuclear Information System (INIS)

Sagaradze, V.V.; Pavlov, V.A.; Alyab'ev, V.M.; Lapin, S.S.; Ermishkin, V.A.; Antonova, O.V.

1987-01-01

Influence of electron radiation in the column of the JEM-1000 electron microscope on radiation swelling of austenite as austenitic fields and thin plates surrounded by α-martensite crystals is investigated. Formation of lath structure of alternating dispersive plates of martensite and invert austenite formed as a result of partial inverse martensite transformation α→γ is shown to restrain radiation swelling and formation of vacancy voids in stainless steels

Ferritic/martensitic steels: Promises and problems

International Nuclear Information System (INIS)

Klueh, R.L.; Ehrlich, K.; Abe, F.

1992-01-01

Ferritic/martensitic steels are candidate structural materials for fusion reactors because of their higher swelling resistance, higher thermal conductivity, lower thermal expansion, and better liquid-metal compatibility than austenitic steels. Irradiation effects will ultimately determine the applicability of these steels, and the effects of irradiation on microstructure and swelling, and on the tensile, fatigue, and impact properties of the ferritic/martensitic steels are discussed. Most irradiation studies have been carried out in fast reactors, where little transmutation helium forms. Helium has been shown to enhance swelling and affect tensile and fracture behavior, making helium a critical issue, since high helium concentrations will be generated in conjunction with displacement damage in a fusion reactor. These issues are reviewed to evaluate the status of ferritic/martensitic steels and to assess the research required to insure that such steels are viable candidates for fusion applications

Mesoscale models for stacking faults, deformation twins and martensitic transformations: Linking atomistics to continuum

Science.gov (United States)

Kibey, Sandeep A.

We present a hierarchical approach that spans multiple length scales to describe defect formation---in particular, formation of stacking faults (SFs) and deformation twins---in fcc crystals. We link the energy pathways (calculated here via ab initio density functional theory, DFT) associated with formation of stacking faults and twins to corresponding heterogeneous defect nucleation models (described through mesoscale dislocation mechanics). Through the generalized Peieirls-Nabarro model, we first correlate the width of intrinsic SFs in fcc alloy systems to their nucleation pathways called generalized stacking fault energies (GSFE). We then establish a qualitative dependence of twinning tendency in fee metals and alloys---specifically, in pure Cu and dilute Cu-xAl (x= 5.0 and 8.3 at.%)---on their twin-energy pathways called the generalized planar fault energies (GPFE). We also link the twinning behavior of Cu-Al alloys to their electronic structure by determining the effect of solute Al on the valence charge density redistribution at the SF through ab initio DFT. Further, while several efforts have been undertaken to incorporate twinning for predicting stress-strain response of fcc materials, a fundamental law for critical twinning stress has not yet emerged. We resolve this long-standing issue by linking quantitatively the twin-energy pathways (GPFE) obtained via ab initio DFT to heterogeneous, dislocation-based twin nucleation models. We establish an analytical expression that quantitatively predicts the critical twinning stress in fcc metals in agreement with experiments without requiring any empiricism at any length scale. Our theory connects twinning stress to twin-energy pathways and predicts a monotonic relation between stress and unstable twin stacking fault energy revealing the physics of twinning. We further demonstrate that the theory holds for fcc alloys as well. Our theory inherently accounts for directional nature of twinning which available

Evaluation of temper embrittlement of martensitic and ferritic-martensitic steels by acoustic emission

International Nuclear Information System (INIS)

Lu, Yusho; Takahashi, Hideaki; Shoji, Tetsuo

1987-01-01

Martensitic (HT-9) and ferritic-martensitic steels (9Cr-2Mo) are considered as fusion first wall materials. In this investigation in order to understand the sensitivity of temper embrittlement in these steels under actual service condition, fracture toughness testing was made by use of acoustic emission technique. The temper embrittlement was characterized in terms of fracture toughness. The fracture toughness of these steels under 500 deg C, 100 hrs, and 1000 hrs heat treatment was decreased and their changes in micro-fracture process have been observed. The fracture toughness changes by temper embrittlement was discussed by the characteristic of AE, AE spectrum analysis and fractographic investigation. The relation between micro-fracture processes and AE has been clarified. (author)

The instability of the spiral wave induced by the deformation of elastic excitable media

International Nuclear Information System (INIS)

Ma Jun; Jia Ya; Wang Chunni; Li Shirong

2008-01-01

There are some similarities between the spiral wave in excitable media and in cardiac tissue. Much evidence shows that the appearance and instability of the spiral wave in cardiac tissue can be linked to one kind of heart disease. There are many models that can be used to investigate the formation and instability of the spiral wave. Cardiac tissue is excitable and elastic, and it is interesting to simulate the transition and instability of the spiral wave induced by media deformation. For simplicity, a class of the modified Fitzhugh-Nagumo (MFHN) model, which can generate a stable rotating spiral wave, meandering spiral wave and turbulence within appropriate parameter regions, will be used to simulate the instability of the spiral wave induced by the periodical deformation of media. In the two-dimensional case, the total acreage of elastic media is supposed to be invariable in the presence of deformation, and the problem is described with L x x L y = N x ΔxN x Δy = L' x L' y = N x Δx'N x Δy'. In our studies, elastic media are decentralized into N x N sites and the space of the adjacent sites is changed to simulate the deformation of elastic media. Based on the nonlinear dynamics theory, the deformation effect on media is simplified and simulated by perturbing the diffusion coefficients D x and D y with different periodical signals, but the perturbed diffusion coefficients are compensatory. The snapshots of our numerical results find that the spiral wave can coexist with the spiral turbulence, instability of the spiral wave and weak deformation of the spiral wave in different conditions. The ratio parameter ε and the frequency of deformation forcing play a deterministic role in inducing instability of the spiral wave. Extensive studies confirm that the instability of the spiral wave can be induced and developed only if an appropriate frequency for deformation is used. We analyze the power spectrum for the time series of the mean activator of four sampled sites

The instability of the spiral wave induced by the deformation of elastic excitable media

Science.gov (United States)

Ma, Jun; Jia, Ya; Wang, Chun-Ni; Li, Shi-Rong

2008-09-01

There are some similarities between the spiral wave in excitable media and in cardiac tissue. Much evidence shows that the appearance and instability of the spiral wave in cardiac tissue can be linked to one kind of heart disease. There are many models that can be used to investigate the formation and instability of the spiral wave. Cardiac tissue is excitable and elastic, and it is interesting to simulate the transition and instability of the spiral wave induced by media deformation. For simplicity, a class of the modified Fitzhugh-Nagumo (MFHN) model, which can generate a stable rotating spiral wave, meandering spiral wave and turbulence within appropriate parameter regions, will be used to simulate the instability of the spiral wave induced by the periodical deformation of media. In the two-dimensional case, the total acreage of elastic media is supposed to be invariable in the presence of deformation, and the problem is described with Lx × Ly = N × ΔxN × Δy = L'xL'y = N × Δx'N × Δy'. In our studies, elastic media are decentralized into N × N sites and the space of the adjacent sites is changed to simulate the deformation of elastic media. Based on the nonlinear dynamics theory, the deformation effect on media is simplified and simulated by perturbing the diffusion coefficients Dx and Dy with different periodical signals, but the perturbed diffusion coefficients are compensatory. The snapshots of our numerical results find that the spiral wave can coexist with the spiral turbulence, instability of the spiral wave and weak deformation of the spiral wave in different conditions. The ratio parameter ɛ and the frequency of deformation forcing play a deterministic role in inducing instability of the spiral wave. Extensive studies confirm that the instability of the spiral wave can be induced and developed only if an appropriate frequency for deformation is used. We analyze the power spectrum for the time series of the mean activator of four sampled sites

Acoustic recognition of stress induced martensitic transformations in Cu-based shape memory alloys

Czech Academy of Sciences Publication Activity Database

Novák, Václav; Landa, Michal; Šittner, Petr

2003-01-01

Roč. 112, - (2003), s. 593-596 ISSN 1155-4339 R&D Projects: GA AV ČR IAA1048107; GA ČR GA106/01/0396 Institutional research plan: CEZ:AV0Z1010914 Keywords : shape memory alloys(SMA) * Cu-based SMA * Martensitic phase transformation * acoustic emission Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.319, year: 2003

Typhoon-Induced Ground Deformation

Science.gov (United States)

Mouyen, M.; Canitano, A.; Chao, B. F.; Hsu, Y.-J.; Steer, P.; Longuevergne, L.; Boy, J.-P.

2017-11-01

Geodetic instruments now offer compelling sensitivity, allowing to investigate how solid Earth and surface processes interact. By combining surface air pressure data, nontidal sea level variations model, and rainfall data, we systematically analyze the volumetric deformation of the shallow crust at seven borehole strainmeters in Taiwan induced by 31 tropical cyclones (typhoons) that made landfall to the island from 2004 to 2013. The typhoon's signature consists in a ground dilatation due to air pressure drop, generally followed by a larger ground compression. We show that this compression phase can be mostly explained by the mass loading of rainwater that falls on the ground and concentrates in the valleys towards the strainmeter sensitivity zone. Further, our analysis shows that borehole strainmeters can help quantifying the amount of rainwater accumulating and flowing over a watershed during heavy rainfalls, which is a useful constraint for building hydrological models.

Phase-field simulation of lenticular martensite and inheritance of the accommodation dislocations

Directory of Open Access Journals (Sweden)

Kundin Julia

2015-01-01

Full Text Available A phase-field simulation is performed to study the substructure evolution of lenticular martensite in TRIP steels. The evolution of martensitic phase variants and dislocations is calculated by a coupled phase-field micro-elasticity model. The simulations at isothermal conditions show that during the phase transformation, the accommodation dislocations evolving in the austenite are inherited by the martensitic phase and cause the further evolution of a single martensitic variant in the direction of the dislocation slip. As a result of the interaction, a change of the growth mode from twining to slip can be observed in accordance to the substructure formation of lenticular martensite. This interaction between the dislocations and martensitic phase depends on dislocation slip systems and the orientation of the martensitic variants as well as on the energy barriers for the phase transformation and for the dislocation motion.

Precipitate-induced R-phase in martensitic transformation of as-spun and annealed Ti51Ni49 ribbons

International Nuclear Information System (INIS)

Wu, Ling-Mei; Chang, Shih-Hang; Wu, Shyi-Kaan

2010-01-01

Differential scanning calorimetry (DSC) results indicate that a two-step B2 → R → B19' martensitic transformation and a one-step B19' → B2 transformation exhibit in as-spun and in 200-600 o C annealed Ti 51 Ni 49 ribbons. Guinier-Preston (GP) zones and Ti 2 Ni precipitates are formed in ribbons annealed at ≤300 o C and ≥400 o C, respectively, and a conspicuous increase of DSC transformation peak temperature occurs in between 300 o C and 400 o C. The sizes of GP zones and Ti 2 Ni precipitates increase with increased annealing temperature. Transmission electron microscope (TEM) observations show that GP zones can induce the R-phase and both of them are formed along B2 directions. DSC and TEM tests show that Ti 2 Ni precipitates can induce the R-phase more than GP zones and the induced R-phase plates are also found along B2 directions. Experimental results show that the growing direction of R-phase plates is strongly confined by that of GP zones and Ti 2 Ni precipitates. The length of R-phase plates can reach about 2 μm in 300 o C annealed ribbon.

Reversible twin boundary migration between α″ martensites in a Ti-Nb-Zr-Sn alloy

Energy Technology Data Exchange (ETDEWEB)

Yao, Tingting; Du, Kui, E-mail: kuidu@imr.ac.cn; Wang, Haoliang; Qi, Lu; He, Suyun; Hao, Yulin; Yang, Rui; Ye, Hengqiang

2017-03-14

Cyclic tensile loading tests and transmission electron microscopy investigation are conducted on a Ti-24Nb-4Zr-8Sn (wt%) alloy. Under tensile strain less than 3.3%, most of the deformation strain recovers after unloading but significant energy dissipation occurs during the loading-unloading cycle. Reversible migration of twin boundaries between α″ martensite variants, in virtue of dislocation movement on the twin boundaries, has been revealed by time resolved high-resolution transmission electron microscopy. This twin boundary migration contributes to the energy dissipation effect and consequently the damping property of the titanium alloy.

High Strain Rate and Shock-Induced Deformation in Metals

Science.gov (United States)

Ravelo, Ramon

2012-02-01

Large-scale non-equilibrium molecular Dynamics (MD) simulations are now commonly used to study material deformation at high strain rates (10^9-10^12 s-1). They can provide detailed information-- such as defect morphology, dislocation densities, and temperature and stress profiles, unavailable or hard to measure experimentally. Computational studies of shock-induced plasticity and melting in fcc and bcc single, mono-crystal metals, exhibit generic characteristics: high elastic limits, large directional anisotropies in the yield stress and pre-melting much below the equilibrium melt temperature for shock wave propagation along specific crystallographic directions. These generic features in the response of single crystals subjected to high strain rates of deformation can be explained from the changes in the energy landscape of the uniaxially compressed crystal lattice. For time scales relevant to dynamic shock loading, the directional-dependence of the yield strength in single crystals is shown to be due to the onset of instabilities in elastic-wave propagation velocities. The elastic-plastic transition threshold can accurately be predicted by a wave-propagation stability analysis. These strain-induced instabilities create incipient defect structures, which can be quite different from the ones, which characterize the long-time, asymptotic state of the compressed solid. With increase compression and strain rate, plastic deformation via extended defects gives way to amorphization associated with the loss in shear rigidity along specific deformation paths. The hot amorphous or (super-cooled liquid) metal re-crystallizes at rates, which depend on the temperature difference between the amorphous solid and the equilibrium melt line. This plastic-amorphous transition threshold can be computed from shear-waves stability analyses. Examples from selected fcc and bcc metals will be presented employing semi-empirical potentials of the embedded atom method (EAM) type as well as

Microstructure and Deformation Response of TRIP-Steel Syntactic Foams to Quasi-Static and Dynamic Compressive Loads

Science.gov (United States)

Ehinger, David; Weise, Jörg; Baumeister, Joachim; Funk, Alexander; Krüger, Lutz; Martin, Ulrich

2018-01-01

The implementation of hollow S60HS glass microspheres and Fillite 106 cenospheres in a martensitically transformable AISI 304L stainless steel matrix was realized by means of metal injection molding of feedstock with varying fractions of the filler material. The so-called TRIP-steel syntactic foams were studied with respect to their behavior under quasi-static compression and dynamic impact loading. The interplay between matrix material behavior and foam structure was discussed in relation to the findings of micro-structural investigations, electron back scatter diffraction EBSD phase analyses and magnetic measurements. During processing, the cenospheres remained relatively stable retaining their shape while the glass microspheres underwent disintegration associated with the formation of pre-cracked irregular inclusions. Consequently, the AISI 304L/Fillite 106 syntactic foams exhibited a higher compression stress level and energy absorption capability as compared to the S60HS-containing variants. The α′ -martensite kinetic of the steel matrix was significantly influenced by material composition, strain rate and arising deformation temperature. The highest ferromagnetic α′-martensite phase fraction was detected for the AISI 304L/S60HS batches and the lowest for the TRIP-steel bulk material. Quasi-adiabatic sample heating, a gradual decrease in strain rate and an enhanced degree of damage controlled the mechanical deformation response of the studied syntactic foams under dynamic impact loading. PMID:29695107

Strain direction dependency of martensitic transformation in austenitic stainless steels: The effect of gamma-texture

NARCIS (Netherlands)

Hilkhuijsen, P.; Geijselaers, Hubertus J.M.; Bor, Teunis Cornelis; Perdahcioglu, Emin Semih; van den Boogaard, Antonius H.; Akkerman, Remko

2013-01-01

Uniaxial tensile tests on both a non-textured and a highly textured, fully austenitic stainless steel were performed in both the rolling and the transverse directions. Both materials show mechanically induced phase transformation from the austenitic FCC to the martensitic BCC phase. Differences in

Multifractal Analysis of Seismically Induced Soft-Sediment Deformation Structures Imaged by X-Ray Computed Tomography

Science.gov (United States)

Nakashima, Yoshito; Komatsubara, Junko

Unconsolidated soft sediments deform and mix complexly by seismically induced fluidization. Such geological soft-sediment deformation structures (SSDSs) recorded in boring cores were imaged by X-ray computed tomography (CT), which enables visualization of the inhomogeneous spatial distribution of iron-bearing mineral grains as strong X-ray absorbers in the deformed strata. Multifractal analysis was applied to the two-dimensional (2D) CT images with various degrees of deformation and mixing. The results show that the distribution of the iron-bearing mineral grains is multifractal for less deformed/mixed strata and almost monofractal for fully mixed (i.e. almost homogenized) strata. Computer simulations of deformation of real and synthetic digital images were performed using the egg-beater flow model. The simulations successfully reproduced the transformation from the multifractal spectra into almost monofractal spectra (i.e. almost convergence on a single point) with an increase in deformation/mixing intensity. The present study demonstrates that multifractal analysis coupled with X-ray CT and the mixing flow model is useful to quantify the complexity of seismically induced SSDSs, standing as a novel method for the evaluation of cores for seismic risk assessment.

Microstructure and tensile properties of high strength duplex ferrite-martensite (DFM) steels

International Nuclear Information System (INIS)

Chakraborti, P.C.; Mitra, M.K.

2007-01-01

Duplex ferrite-martensite (DFM) steels containing 38-80% martensite of varying morphologies were developed by batch intercritical annealing of a commercial variety vanadium bearing 0.2% C-Mn steel at different temperatures. Microstructures before intercritical annealing were found to control the morphological distribution of the phase constituents of the developed DFM steels. Tensile test results revealed best strength-ductility combination for finely distributed lamellar ferrite-martensite phase aggregate containing ∼60% martensite developed from a prior martensitic structure. Taking consideration of the modified law of mechanical mixture the experimental tensile strength data of the developed DFM steels has been formulated with some success and very good estimation for tensile strengths of pure ferrite and low carbon martensite has been made from tensile strength data of DFM steels

Depth distribution analysis of martensitic transformations in Xe implanted austenitic stainless steel

International Nuclear Information System (INIS)

Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Chechenin, N.G.; Grabaek, L.; Bohr, J.

1988-01-01

In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by 'in situ' RBS/channeling analysis, X-ray diffraction and cross-section transmission electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1x10 20 m -2 . The thickness of the transformed layer increases with fluence to ≅ 150 nm at 1x10 21 m -2 , which far exceeds the range plus straggling of the implanted Xe as calculated by the TRIM computer simulation code. Simulations using the MARLOWE code indicate that the thickness of the transformed layer coincides with the range of the small fraction of ions channeled under random implantation conditions. Using cross sectional TEM on the Xe implanted crystals, the depth distribution of gas inclusions and defects can be directly observed. Using X-ray diffraction on implanted single crystals, the solid epitaxial nature of the Xe inclusions, induced prior to the martensitic transformation, was established. The lattice constant obtained from the broad diffraction peak indicates that the pressure in the inclusions is ≅ 5 GPa. (orig./BHO)

Electric anisotropy in high density polyethylene + carbon black composites induced by mechanical deformation

Energy Technology Data Exchange (ETDEWEB)

Vigueras-Santiago, E; Hernandez-Lopez, S; Camacho-Lopez, M A; Lara-Sanjuan, O, E-mail: eviguerass@uaemex.m [Laboratorio de Investigacion y Desarrollo de Materiales Avanzados (LIDMA), Facultad de Quimica, UAEM. Paseo Colon esq. con Paseo Tollocan, s/n. C.P. 50000, Toluca (Mexico)

2009-05-01

High density polyethylene + carbon black composites with electrical anisotropy was studied. Electrical anisotropy was induced by uniaxial mechanical deformation and injection moulding. We show that anisotropy depends on the carbon black concentration and percentage deformation. Resistivity had the highest anisotropy resistivity around the percolation threshold. Perpendicular resistivity showed two magnitude orders higher than parallel resistivity for injected samples, whereas resistivity showed an inverse behaviour for 100% tensile samples. Both directions were set respect to the deformation axe. Anisotropy could be explained in terms of the molecular deformation (alignment) of the polymer chains as a response of the deformation process originating a redistribution of the carbon black particles in both directions. Alignment of the polymer chains was evidenced by polarized Raman spectroscopy.

Emergent large mechanical damping in ferroelastic-martensitic systems driven by disorder

Science.gov (United States)

Ni, Yan; Zhang, Zhen; Fang, Minxia; Hao, Yanshuang; Ding, Xiangdong; Otsuka, Kazuhiro; Ren, Xiaobing

2018-05-01

Disorders and point defects strongly interplay with the phase transition and alter the properties of ferroelastic-martensitic systems. Unusual static and quasistatic behaviors, such as time-dependent phase transitions, are discovered when disorders are introduced. However, the role of disorders on the ferroelastic system in vibrational environments at moderate frequency is rarely known, investigation of which could further shed light on their application as mechanical damping materials. Here we present the emergence of large damping capacity in ferroelastic-martensitic systems [including both the T i50 -xN i50 +x alloy and (C a1 -xS rx) Ti O3 ceramics] by introducing disorder (i.e., substitutional Ni and Sr, respectively). As the level disorder increases, the damping capacity of both systems raises and eventually reaches a maximum when long-range-ordered martensite tends to vanish. Moreover, near the disorder-induced phase boundary, we observe a large mechanical damping in ferroelastic ceramics (C a1 -xS rx) Ti O3 with a figure of merit ˜2 GP a1 /2 . Microscopic and dynamic investigations indicate that such damping plateau could result from the competing evolution of density and mobility of domain boundaries when disorder is introduced. Our work provides a degree of freedom to develop ferroelastic damping materials and a potential way to tune domain-boundary-mediated functionalities for other ferroic materials.

SEM characterization of the martensitic transformation induced by mechanical compression cycling in a β-(111) Cu-20.85 Zn-6.15Al shape memory single crystal

International Nuclear Information System (INIS)

Gil, F.J.; Guilemany, J.M.

1991-01-01

On submitting a Cu-Zn-Al shape memory alloy β phase sample to stress compressions cycles, stabilization of martensitic plates which do not retransform on unloading stress, can be seen. On increasing the number of cycles a greater amount of stabilized martensite plates can be observed as well as the growth of some at the expense of others, thus producing thicker plates in preferential orientations. Finally, the aluminium rich martensite nuclei appear, situated in the intersection between different martensitic variants which contain greater stored elastic energy which in turn favours transformation. (orig.) [de

Structural analysis and martensitic transformation in equiatomic HfPd alloy

Science.gov (United States)

Hisada, S.; Matsuda, M.; Takashima, K.; Yamabe-Mitarai, Y.

2018-02-01

We investigated the crystal structure and the martensitic transformation in equiatomic HfPd alloy. The analysis of the crystal structure by electron diffraction and Rietveld refinement using X-ray diffraction data indicates that the space group of the martensitic phase is Cmcm, and the lattice parameters are a = 0.329 nm, b = 1.021 nm, and c = 0.438 nm. Martensitic variants are composed of the plate-like morphology of several hundred nm, and the boundaries between the variants have (021)Cmcm twin relations. This (021)Cmcm twin boundary seems to be sharp without ledge and steps. Differential scanning calorimetry measurement indicates that each martensitic transformation temperature is determined to be Ms = 819 K, Mf = 794 K, As = 928 K, and Af = 954 K. Based on the dimension change using a thermo-mechanical analyzer, the expansion and shrinkage of the sample occurred with the forward and reverse martensitic transformation, respectively.

Fatigue performance of superelastic NiTi near stress-induced martensitic transformation

Czech Academy of Sciences Publication Activity Database

Alarcón Tarquino, Eduardo; Heller, Luděk; Chirani, S.A.; Šittner, Petr; Kopeček, Jaromír; Saint-Sulpice, L.; Calloch, S.

2017-01-01

Roč. 95, Feb (2017), s. 76-89 ISSN 0142-1123 R&D Projects: GA ČR GB14-36566G; GA MŠk LO1409; GA MŠk LM2015088; GA ČR GA16-20264S; GA ČR GA14-15264S Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 Keywords : shape-memory alloys * Nitinol * superelasticity * martensitic transformation * shape memory alloys * fatigue Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.899, year: 2016

Time-temperature equivalence in Martensite tempering

Energy Technology Data Exchange (ETDEWEB)

Hackenberg, Robert E. [Los Alamos National Laboratory; Thomas, Grant A. [CSM; Speer, John G. [CSM; Matlock, David K. [CSM; Krauss, George [CSM

2008-06-16

The relationship between time and temperature is of great consequence in many materials-related processes including the tempering of martensite. In 1945, Hollomon and Jaffe quantified the 'degree of tempering' as a function of both tempering time, t, and tempering temperature, T, using the expression, T(log t + c). Here, c is thought to be a material constant and appears to decrease linearly with increasing carbon content. The Hollomon-Jaffe tempering parameter is frequently cited in the literature. This work reviews the original derivation of the tempering parameter concept, and presents the use of the characteristics diffusion distance as an alternative time-temperature relationship during martensite tempering. During the tempering of martensite, interstitial carbon atoms diffuse to form carbides. In addition, austenite decomposes, dislocations and grain boundaries rearrange, associated with iron self diffusion. Since these are all diffusional processes, it is reasonable to expect the degree of tempering to relate to the extent of diffusion.

Stress induced martensitic transformations in tension/torsion of CuAlNi single crystal tube

Czech Academy of Sciences Publication Activity Database

Šittner, Petr; Hashimoto, K.; Kato, M.; Tokuda, M.

2003-01-01

Roč. 48, - (2003), s. 1153-1159 ISSN 1359-6462 R&D Projects: GA AV ČR IAA1048107 Institutional research plan: CEZ:AV0Z1010914 Keywords : shape memory alloys(SMAs) * martensitic phase transformation * single crystal tube * tension test * torsion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.633, year: 2003

Softening mechanisms of the AISI 410 martensitic stainless steel under hot torsion simulation

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Thiago Santana de; Silva, Eden Santos; Rodrigues, Samuel Filgueiras; Nascimento, Carmem Celia Francisco; Leal, Valdemar Silva; Reis, Gedeon Silva, E-mail: samuel.filgueiras@ifma.edu.br [Instituto Federal do Maranhao (PPGEM/IFMA), Sao Luis, MA (Brazil)

2017-03-15

This study investigated the softening mechanisms of the AISI 410 martensitic stainless steel during torsion simulation under isothermal continuous in the temperature range of 900 to 1150 °C and strain rates of 0.1 to 5.0s{sup -1}. In the first part of the curves, before the peak, the results show that the critical (ε-c) and peak (ε-p) strains are elevated for higher strain rate and lower temperatures contributing for higher strain hardening rate (h). Moreover, this indicated that dynamic recrystallization (DRX) and dynamic recovery (DRV) are not effective in this region. After the peak, the reductions in stresses are associated to the different DRX/DRV competitions. For lower temperatures and higher strain rates there is a delay in the DRX while the DRV is acting predominantly (with low Avrami exponent (n) and high t{sub 0.5}). The steady state was reached after large strains showing DRX grains, formation of retained austenite and the presence of chromium carbide (Cr{sub 23}C{sub 6}) and ferrite δ at the martensitic grain boundaries. These contribute for impairing the toughness and ductility on the material. The constitutive equations at the peak strain indicated changes in the deformation mechanism, with variable strain rate sensitivity (m), which affected the final microstructure. (author)

Deformation-induced phase transformation in 4H–SiC nanopillars

International Nuclear Information System (INIS)

Chen, Bin; Wang, Jun; Zhu, Yiwei; Liao, Xiaozhou; Lu, Chunsheng; Mai, Yiu-Wing; Ringer, Simon P.; Ke, Fujiu; Shen, Yaogen

2014-01-01

The deformation behaviour of single-crystal SiC nanopillars was studied by a combination of in situ deformation transmission electron microscopy and molecular dynamics simulations. An unexpected deformation-induced phase transformation from the 4H hexagonal structure to the 3C face-centred cubic structure was observed in these nanopillars at room temperature. Atomistic simulations revealed that the 4H to 3C phase transformation follows a stick–slip process with initiation and end stresses of 12.1–14.0 and 7.9–9.0 GPa, respectively. The experimentally measured stress of 9–10 GPa for the phase transformation falls within the range of these theoretical upper and lower stresses. The reasons for the phase transformation are discussed. The finding sheds light on the understanding of phase transformation in polytypic materials at low temperature

Anomalous acoustic effect during martensitic transformations in titanium nickelide base alloys

International Nuclear Information System (INIS)

Plotnikov, V.A.; Kokhanenko, D.V.

2002-01-01

One carried out experiments to determine effect of external static stress on martensitic transformations and acoustic emission, Martensitic transformations in titanium nickelide base alloys under mechanical stress were determined to change nature of acoustic emission to anomalous one - cycling of transformations under gradual increase of mechanical stress during direct martensitic transformation was followed by increase of acoustic emission energy instead of reduction. The mentioned nature of acoustic emission is indicative of essential effect of external stress on martensitic transformations and energy dissipation during transformations [ru

In-Situ Investigation of Strain-Induced Martensitic Transformation Kinetics in an Austenitic Stainless Steel by Inductive Measurements

Directory of Open Access Journals (Sweden)

Carola Celada-Casero

2017-07-01

Full Text Available An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ to martensite (α′ phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite has been found by comparing the results to the ex-situ characterization by magnetization measurements, light optical microscopy, and X-ray diffraction. The sensor has allowed for the observation of the stepwise transformation behavior, a not-well-understood phenomena that takes place in large regions of the bulk material and that so far had only been observed by synchrotron X-ray diffraction.

Time evolution in static β-phase dynamic β-martensite coexistence (Cu-Zn-Al SMA)

International Nuclear Information System (INIS)

Isalgue, A.; Lovey, F.C.

1995-01-01

The application of a SMA implies an accurate knowledge about the eventual time - behavior of the alloys. The effects of quenching and micro-heatings were studied by calorimetric and resistance measurements and the β-martensite coexistence by stress - strain - temperature - time observations. Experimental analysis was performed using copper based single crystals (Cu-Zn-Al, e/a ∼1.48 e/a with Ms below room temperature). The phenomenological behavior establishes several time constants for each evolution. A change ΔT of temperature of the parent phase near 300 K induces an asymptotic time evolution on M S near 11 per cent. The parent to martensite coexistence produces an evolution of the equilibrium temperature (near 0.5 K) linked to the existence of an interface. (orig.)

Measurement of lattice rotations and internal stresses in over one hundred individual grains during a stress-induced martensitic transformation

Directory of Open Access Journals (Sweden)

Hachi Younes El

2015-01-01

Full Text Available To better understand the properties of polycrystals at a microscopic scale during cyclic mechanical loading we have measured the relationship between grain orientations, their positions inside the sample and their internal stresses. In this work, in-situ 3DXRD technique was performed on over hundred grains during the stress-induced martensitic transformation in a Cu-Al-Be shape memory alloy. Information about the position, orientation, and stress field was obtained for each austenitic grain. These results have been used to develop a procedure that allows automatic processing for a large number of grains, matching them during loading and leads to a quantitative stress field. A strong heterogeneity of stress state between the grains at the surface and in the volume is evident.

Effect of pre-deformation temperature on reverse transformation characteristic in Fe-Mn-Si based alloys

International Nuclear Information System (INIS)

Wang, D.; Xing, X.; Chen, J.; Dong, Z.; Liu, W.

2000-01-01

Two alloys of A: Fe-28Mn-6Si-5Cr(wt.%) and B: Fe-13Mn-5Si-12Cr-6Ni(wt.%) with different Ms temperatures were selected to be subjected to tensile deformation under different temperatures. The effect of deformation temperature on shape memory effect (SME) and the reverse transformation kinetics were studied respectively. It was found that: (1) The best SME could be obtained by deformation at Ms temperature; (2) The As temperature varied with deformation temperature. The lower the deformation temperature was, the lower the As temperature would be; (3) Some non-transformation related strain recovery between deformation temperature and As temperature was observed to be resulted from the retraction of stacking faults. The facts that the variation of As temperature with deformation temperature, as well as the non-transformation strain recovery imply that the γ→ε martensitic transformation in Fe-Mn-Si based shape memory alloys exhibits quasithermoelastic property. (orig.)

Magnetic and magnetocaloric properties of martensitic Ni2Mn1.4Sn0.6 Heusler alloy

International Nuclear Information System (INIS)

Chernenko, Volodymyr A.; Barandiarán, Jose M.; Rodriguez Fernández, Jesus; Rojas, Daniel P.; Gutiérrez, Jon; Lázpita, Patricia; Orue, Iñaki

2012-01-01

The evolutions of magnetic properties at low temperatures and the influence of magnetic field on the temperature dependence of specific heat in martensitic Ni 2 Mn 1.4 Sn 0.6 Heusler alloy are studied. The frequency-dependent blocking temperature and considerable exchange bias below it are measured in the martensitic phase. From the analysis of the specific heat curves under magnetic field, a large inverse magnetocaloric effect manifested as the magnetic field induced rise of isothermal magnetic entropy and/or magnetic field induced adiabatic temperature decrease in the vicinity of the reverse magnetostructural transformation and a significant value of the conventional magnetocaloric effect at the Curie temperature are obtained. The Debye temperature and electronic coefficient equal to Θ D =310±2 K and γ= 16.6±0.3 mJ/K 2 mol, respectively, do not depend on the magnetic field.

Deformation-induced splitting of the monopole giant resonance in 24Mg

Directory of Open Access Journals (Sweden)

Kvasil J.

2016-01-01

Full Text Available The strong deformation splitting of the isoscalar giant monopole resonance (ISGMR, recently observed in (α, α′ reaction in prolate 24Mg, is analyzed in the framework of the Skyrme quasiparticle randomphase-approximation (QRPA approach with the Skyrme forces SkM*, SVbas and SkPδ. The calculations with these forces give close results and confirm that the low-energy E0-peak is caused by the deformation-induced coupling of ISGMR with the K = 0 branch of the isoscalar giant quadrupole resonance.

Effect of W and Ta on creep–fatigue interaction behavior of reduced activation ferritic–martensitic (RAFM) steels

Energy Technology Data Exchange (ETDEWEB)

Shankar, Vani, E-mail: vani@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India); Mariappan, K.; Sandhya, R.; Laha, K.; Jayakumar, T.; Kumar, E. Rajendra [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Institute for Plasma Research, Ahmedabad 382428 (India)

2015-11-15

Highlights: • SR correlated with deformation under CFI in RAFM steels. • Stress relaxation directly related to plastic strain accumulated, inversely to CFI life. • Optimum combination of W and Ta best for CFI life. • RAFM steels demonstrated compressive dwell sensitivity. • SR tends toward constant value at long hold. - Abstract: The aim of this work is to understand the effect of varying tungsten and tantalum contents on creep–fatigue interaction (CFI) behavior of reduced activation ferritic–martensitic (RAFM) steels. Increase in W improved CFI life. Effect of changing Ta and W upon the resultant CFI life seems to be interrelated and an optimum combination of both W and Ta works out to be the best for CFI life. Stress relaxation obtained during application of hold can be a useful parameter to relate deformation and damage in the RAFM steels.

Effect of W and Ta on creep–fatigue interaction behavior of reduced activation ferritic–martensitic (RAFM) steels

International Nuclear Information System (INIS)

Shankar, Vani; Mariappan, K.; Sandhya, R.; Laha, K.; Jayakumar, T.; Kumar, E. Rajendra

2015-01-01

Highlights: • SR correlated with deformation under CFI in RAFM steels. • Stress relaxation directly related to plastic strain accumulated, inversely to CFI life. • Optimum combination of W and Ta best for CFI life. • RAFM steels demonstrated compressive dwell sensitivity. • SR tends toward constant value at long hold. - Abstract: The aim of this work is to understand the effect of varying tungsten and tantalum contents on creep–fatigue interaction (CFI) behavior of reduced activation ferritic–martensitic (RAFM) steels. Increase in W improved CFI life. Effect of changing Ta and W upon the resultant CFI life seems to be interrelated and an optimum combination of both W and Ta works out to be the best for CFI life. Stress relaxation obtained during application of hold can be a useful parameter to relate deformation and damage in the RAFM steels.

An X-ray diffraction study of microstructural deformation induced by cyclic loading of selected steels

International Nuclear Information System (INIS)

Fourspring, P.M.; Pangborn, R.N.

1996-06-01

X-ray double crystal diffractometry (XRDCD) was used to assess cyclic microstructural deformation in a face centered cubic (fcc) steel (AISI304) and a body centered cubic (bcc) steel (SA508 class 2). The first objective of the investigation was to determine if XRDCD could be used to effectively monitor cyclic microstructural deformation in polycrystalline Fe alloys. A second objective was to study the microstructural deformation induced by cyclic loading of polycrystalline Fe alloys. The approach used in the investigation was to induce fatigue damage in a material and to characterize the resulting microstructural deformation at discrete fractions of the fatigue life of the material. Also, characterization of microstructural deformation was carried out to identify differences in the accumulation of damage from the surface to the bulk, focusing on the following three regions: near surface (0--10 microm), subsurface (10--300 microm), and bulk. Characterization of the subsurface region was performed only on the AISI304 material because of the limited availability of the SA508 material. The results from the XRDCD data indicate a measurable change induced by fatigue from the initial state to subsequent states of both the AISI304 and the SA508 materials. Therefore, the XRDCD technique was shown to be sensitive to the microstructural deformation caused by fatigue in steels; thus, the technique can be used to monitor fatigue damage in steels. In addition, for the AISI304 material, the level of cyclic microstructural deformation in the bulk material was found to be greater than the level in the near surface material. In contrast, previous investigations have shown that the deformation is greater in the near surface than the bulk for Al alloys and bcc Fe alloys

Analysis of Low Dose Irradiation Damages in Structural Ferritic/Martensitic Steels by Proton Irradiation and Nanoindentation

International Nuclear Information System (INIS)

Waseem, Owais A.; Ryu, Ho Jin; Park, Byong Guk; Jeong, Jong Ryul; Maeng, Cheol Soo; Lee, Myoung Goo

2016-01-01

As a result, ferritic-martensitic steels find applications in the in-core and out-of-core components which include ducts, piping, pressure vessel and cladding, etc. Due to ferromagnetism of F/M steel, it has been successfully employed in solenoid type fuel injector. Although the irradiation induced degradation in ferritic martensitic steels is lower as compare to (i) reduced activation steels, (ii) austenitic steels and (iii) martensitic steels, F/M steels are still prone to irradiation induced hardening and void swelling. The irradiation behavior may become more sophisticated due to transmutation and production of helium and hydrogen. The ductile to brittle transition temperature of F/M steels is also expected to increase due to irradiation. These irradiation induced degradations may deteriorate the integrity of F/M components. As a result of these investigations, it has found that the F/M steels experience no irradiation hardening above 400 .deg. C, but below this temperature, up to 350 .deg. C, weak hardening is observed. The irradiation hardening becomes more pronounced below 300 .deg. C. Moreover, the irradiation hardening has also found dependent upon radiation damage. The hardening was found increasing with increasing dose. Due to pronounced irradiation hardening below 300 .deg. C and increasing radiation damage with increasing dose (even at low dpa), it is required to investigate the post irradiation mechanical properties of F/M steel, in order to confirm its usefulness in structural and magnetic components which experience lifetime doses as low as 1x10"-"5 dpa.

Analysis of Low Dose Irradiation Damages in Structural Ferritic/Martensitic Steels by Proton Irradiation and Nanoindentation

Energy Technology Data Exchange (ETDEWEB)

Waseem, Owais A.; Ryu, Ho Jin; Park, Byong Guk [KAIST, Daejeon (Korea, Republic of); Jeong, Jong Ryul [Chungnam University, Daejeon (Korea, Republic of); Maeng, Cheol Soo; Lee, Myoung Goo [KEPCO, Daejeon (Korea, Republic of)

2016-05-15

As a result, ferritic-martensitic steels find applications in the in-core and out-of-core components which include ducts, piping, pressure vessel and cladding, etc. Due to ferromagnetism of F/M steel, it has been successfully employed in solenoid type fuel injector. Although the irradiation induced degradation in ferritic martensitic steels is lower as compare to (i) reduced activation steels, (ii) austenitic steels and (iii) martensitic steels, F/M steels are still prone to irradiation induced hardening and void swelling. The irradiation behavior may become more sophisticated due to transmutation and production of helium and hydrogen. The ductile to brittle transition temperature of F/M steels is also expected to increase due to irradiation. These irradiation induced degradations may deteriorate the integrity of F/M components. As a result of these investigations, it has found that the F/M steels experience no irradiation hardening above 400 .deg. C, but below this temperature, up to 350 .deg. C, weak hardening is observed. The irradiation hardening becomes more pronounced below 300 .deg. C. Moreover, the irradiation hardening has also found dependent upon radiation damage. The hardening was found increasing with increasing dose. Due to pronounced irradiation hardening below 300 .deg. C and increasing radiation damage with increasing dose (even at low dpa), it is required to investigate the post irradiation mechanical properties of F/M steel, in order to confirm its usefulness in structural and magnetic components which experience lifetime doses as low as 1x10{sup -5} dpa.

Theoretical and experimental study of carburisation and decarburisation of a meta-stable austenitic steel

Directory of Open Access Journals (Sweden)

Charles West

2005-12-01

Full Text Available Metastable austenitic stainless steels are known to undergo a partial transformation of austenite to martensite as a consequence of plastic deformation. In the case of cyclic loading, a certain level of plastic strain must be exceeded, and phase formation takes place after an incubation period, during which the necessary amount of plastic deformation is accumulated. The susceptibility of the austenitic phase to deformation-induced martensite formation is strongly affected by the temperature of loading and the stability of austenite, which itself depends on the chemical composition. A key element in this regard is carbon which stabilizes the austenitic phase. It is shown in this study that the carbon concentration can be analysed systematically and reproducible by means of annealing treatments, if the parameters of these treatments are carefully defined on the basis of advanced theoretical thermodynamic and kinetic considerations. First results on the effect of carbon concentration and temperature of fatigue testing on the austenite/martensite transformation are presented, in order to illustrate the significance of these parameters on the martensite formation rate.

Three-dimensional modeling for deformation of austenitic NiTi shape memory alloys under high strain rate

Science.gov (United States)

Yu, Hao; Young, Marcus L.

2018-01-01

A three-dimensional model for phase transformation of shape memory alloys (SMAs) during high strain rate deformation is developed and is then calibrated based on experimental results from an austenitic NiTi SMA. Stress, strain, and martensitic volume fraction distribution during high strain rate deformation are simulated using finite element analysis software ABAQUS/standard. For the first time, this paper presents a theoretical study of the microscopic band structure during high strain rate compressive deformation. The microscopic transformation band is generated by the phase front and leads to minor fluctuations in sample deformation. The strain rate effect on phase transformation is studied using the model. Both the starting stress for transformation and the slope of the stress-strain curve during phase transformation increase with increasing strain rate.

Superalgebras, their quantum deformations and the induced representation method