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Sample records for eutectoids

  1. Detecting the Extent of Eutectoid Transformation in U-10Mo

    Energy Technology Data Exchange (ETDEWEB)

    Devaraj, Arun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jana, Saumyadeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McInnis, Colleen A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lombardo, Nicholas J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sweet, Lucas E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Manandhar, Sandeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-08-31

    During eutectoid transformation of U-10Mo alloy, uniform metastable γ UMo phase is expected to transform to a mixture of α-U and γ’-U2Mo phase. The presence of transformation products in final U-10Mo fuel, especially the α phase is considered detrimental for fuel irradiation performance, so it is critical to accurately evaluate the extent of transformation in the final U-10Mo alloy. This phase transformation can cause a volume change that induces a density change in final alloy. To understand this density and volume change, we developed a theoretical model to calculate the volume expansion and resultant density change of U-10Mo alloy as a function of the extent of eutectoid transformation. Based on the theoretically calculated density change for 0 to 100% transformation, we conclude that an experimental density measurement system will be challenging to employ to reliably detect and quantify the extent of transformation. Subsequently, to assess the ability of various methods to detect the transformation in U-10Mo, we annealed U-10Mo alloy samples at 500°C for various times to achieve in low, medium, and high extent of transformation. After the heat treatment at 500°C, the samples were metallographically polished and subjected to optical microscopy and x-ray diffraction (XRD) methods. Based on our assessment, optical microscopy and image processing can be used to determine the transformed area fraction, which can then be correlated with the α phase volume fraction measured by XRD analysis. XRD analysis of U-10Mo aged at 500°C detected only α phase and no γ’ was detected. To further validate the XRD results, atom probe tomography (APT) was used to understand the composition of transformed regions in U-10Mo alloys aged at 500°C for 10 hours. Based on the APT results, the lamellar transformation product was found to comprise α phase with close to 0 at% Mo and γ phase with 28–32 at% Mo, and the Mo concentration was highest at the

  2. Detecting the Extent of Cellular Decomposition after Sub-Eutectoid Annealing in Rolled UMo Foils

    Energy Technology Data Exchange (ETDEWEB)

    Kautz, Elizabeth J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jana, Saumyadeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Devaraj, Arun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sweet, Lucas E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-07-31

    This report presents an automated image processing approach to quantifying microstructure image data, specifically the extent of eutectoid (cellular) decomposition in rolled U-10Mo foils. An image processing approach is used here to be able to quantitatively describe microstructure image data in order to relate microstructure to processing parameters (time, temperature, deformation).

  3. Thermal Microstructural Multiscale Simulation of Solidification and Eutectoid Transformation of Hypereutectic Gray Cast Iron

    Science.gov (United States)

    Urrutia, Alejandro; Celentano, Diego J.; Gunasegaram, Dayalan R.; Deeva, Natalia

    2014-08-01

    Although the gray cast iron solidification process has been the subject of several modeling studies, almost all available models appear to deal with only the more widely used hypoeutectic compositions. Models related to hypereutectic gray iron compositions with lamellar (or flake) graphite, and in particular for the proeutectic and eutectoid zones, are hard to find in the open literature. Hence, in the present work, a thermal microstructural multiscale model is proposed to describe the solidification and eutectoid transformation of a slightly hypereutectic composition leading to lamellar graphite gray iron morphology. The main predictions were: (a) temperature evolutions; (b) fractions of graphite, ferrite, and pearlite; (c) density; and (d) size of ferrite, pearlite, and gray eutectic grains; (e) average interlamellar graphite spacing; and (f) its thickness. The predicted cooling curves and fractions for castings with two different compositions and two different pouring temperatures were validated using experimental data. The differences between this model and existing models for hypoeutectic compositions are discussed.

  4. Determination of processing maps for the warm working of vanadium microalloyed eutectoid steels

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    Rastegari, H., E-mail: rastegary@birjandut.ac.ir [Department of Engineering, Birjand University of Technology, South Khorasan 97198-66981 (Iran, Islamic Republic of); Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Najafizadeh, A. [Fould Institute of Technology, Fouldshahar, Isfahan 8491663763 (Iran, Islamic Republic of); Somani, M.C.; Porter, D.A. [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Ghassemali, E.; Jarfors, A.E.W. [Jönköping University, School of Engineering, Department of Materials and Manufacturing, P.O. Box 1026, SE-551 11 Jönköping (Sweden)

    2016-03-21

    Microalloying of an eutectoid steel with V may facilitate formation of dispersed nano-scaled VC particles in the microstructure during thermomechanical processing or subsequent heat treatment. In this research, the constitutive flow behavior of vanadium microalloyed eutectoid steel has been investigated in the temperature range 620–770 °C at strain rates in the range 0.01–10 s{sup −1}. Microstructural characterization of the deformed specimens was conducted using SEM and EBSD techniques. In this context, various deformation mechanisms occurring during warm deformation have been characterized and delineated through construction of a processing map by establishing a power dissipation map and an instability map for the steel and superimposing them. The results show that the pearlitic microstructure exhibits several deformation mechanisms within these warm working conditions. Dynamic spheroidization of cementite lamella takes place in the range 660–720 °C and 0.01–0.1 s{sup −1} with a power dissipation efficiency of 27–33%, characterizing a safe window of processing this steel. The presence of vanadium carbides at grain boundaries strengthened the pearlitic microstructure and retarded the occurrence of some deformation defects during low temperature, high speed deformation in the range 620–720 °C and 1–10 s{sup −1}.

  5. Corrosión bajo tensión de aceros eutectoides con trefilado progresivo

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    Ovejero, E.

    1998-05-01

    Full Text Available The consequences of the microstructural evolution in an eutectoid steel that has undergone a cold drawing process are studied. This manufacturing technique produces changes in the steel microstructure: a progressive orientation and slenderising of the pearlite colonies and an orientation and packing of the pearlite lamellae, thus reducing the interlamellar spacing. In addition, the experimental results of the stress corrosion cracking tests show that cold drawing produces resistant anisotropy in the steel and thus the stress corrosion cracking resistance is a directional property which seems to depend on the orientation of the microstructure in relation to the cold drawing direction. As a consequence, a transversal crack tends to change its propagation direction approaching the wire axis and a crack growth in mode I evolves to a mixed mode propagation.

    Se estudian las consecuencias de la evolución microestructural en un acero eutectoide que ha sufrido un proceso de trefilado progresivo. Esta técnica de fabricación origina una serie de cambios en la microestructura del acero: una orientación progresiva y un estiramiento de las colonias de perlita y una orientación y densificación de las láminas de perlita, reduciendo así el espaciado interlaminar. Por otra parte, los resultados experimentales de los ensayos de corrosión bajo tensión demuestran que el trefilado produce anisotropía resistente en el acero, y así la resistencia a la corrosión bajo tensión es una propiedad direccional que parece depender de la orientación de la microestuctura con respecto a la dirección del trefilado. Como consecuencia, una fisura transversal tiende a cambiar su dirección de propagación para aproximarse a la del eje del alambre, y un crecimiento en modo I evoluciona hacia una propagación en modo mixto.

  6. Effect of Cooling Rate on Microstructure and Mechanical Properties of Eutectoid Steel Under Cyclic Heat Treatment

    Science.gov (United States)

    Maji, Soma; Subhani, Amir Raza; Show, Bijay Kumar; Maity, Joydeep

    2017-07-01

    A systematic study has been carried out to ascertain the effect of cooling rate on structure and mechanical properties of eutectoid steel subjected to a novel incomplete austenitization-based cyclic heat treatment process up to 4 cycles. Each cycle consists of a short-duration holding (6 min) at 775 °C (above A1) followed by cooling at different rates (furnace cooling, forced air cooling and ice-brine quenching). Microstructure and properties are found to be strongly dependent on cooling rate. In pearlitic transformation regime, lamellar disintegration completes in 61 h and 48 min for cyclic furnace cooling. This leads to a spheroidized structure possessing a lower hardness and strength than that obtained in as-received annealed condition. On contrary, lamellar disintegration does not occur for cyclic forced air cooling with high air flow rate (78 m3 h-1). Rather, a novel microstructure consisting of submicroscopic cementite particles in a `interweaved pearlite' matrix is developed after 4 cycles. This provides an enhancement in hardness (395 HV), yield strength (473 MPa) and UTS (830 MPa) along with retention of a reasonable ductility (%Elongation = 19) as compared to as-received annealed condition (hardness = 222 HV, YS = 358 MPa, UTS = 740 MPa, %Elongation = 21).

  7. Tribo-chemical behavior of eutectoid steel during rolling contact friction

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    Zhou, Y.; Cai, Z.B. [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031 (China); Peng, J.F. [Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China); Cao, B.B. [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031 (China); Jin, X.S. [Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China); Zhu, M.H., E-mail: zhuminhao@swjtu.cn [Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu 610031 (China); Tribology Research Institute, State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031 (China)

    2016-12-01

    Highlights: • Tribo-chemical behavior was investigated during rolling contact friction. • Tribo-film may weaken the absorptive ability of O/C atoms on the surface. • Tribo-film is related to a low friction coefficient at rolling friction condition. - Abstract: The tribo-chemical behavior of the eutectoid steel during rolling contact friction is investigated via scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and electron probe X-ray microanalysis. The worn surface is divided into three zones: matrix zone (without friction), tribo-film zone (formed during friction) and delamination zone (tribo-film spalling). The different chemical states of atoms between those three zones and the air were investigated using the XPS analysis. The results showed that the matrix zone is composed of Fe{sub 2}O{sub 3}, FeO and metallic Fe, while the tribo-film and delamination zones only contain Fe{sub 2}O{sub 3} and FeO. Where the tribo-film is formed, the absorptive ability of O and C atoms on the top 2–3 atomic layers is probably weakened, while the exposed fresh metal in the delamination zone tends to be continuously oxidized and form tribo-film. The tribo-chemical reaction in the delamination zone is more activated than that in the other two zones. The protective nature of the tribo-film probably maintains a low friction coefficient under rolling contact friction condition.

  8. Kinetics of cellular transformation and competing precipitation mechanisms during sub-eutectoid annealing of U10Mo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jana, Saumyadeep; Devaraj, Arun; Kovarik, Libor; Arey, Bruce W.; Sweet, Lucas E.; Varga, Tamas; Lavender, Curt A.; Joshi, Vineet V.

    2017-11-01

    Transformation kinetics of metastable body-centered cubic γ-UMo phase in U-10 wt.percent Mo alloy during annealing at sub-eutectoid temperatures of 500C and 400C has been determined as a function of time using detailed microstructural characterization by scanning electron microscopy, X-ray diffraction analysis, scanning transmission electron microscopy, and atom probe tomography. Based on the results, we found that the phase transformation is initiated by cellular transformation at both the temperatures, which results in formation of a lamellar microstructure along prior γ-UMo grain boundaries.

  9. Phase transformations in the Zn-Al eutectoid alloy after quenching from the high temperature triclinic beta phase

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval-Jimenez, A., E-mail: asandovalj@correo.unam.mx [Instituto Nacional de Investigaciones Nucleares, Dpto. de Aceleradores, Carretera Mexico-Toluca S/N, La Marquesa, Ocoyoacac, Mexico, C.P. 52750, ESIME, Unidad Culhuacan, Dpto. Ing. Mecanica, IPN (Mexico); Negrete, J. [Instituto de Metalurgia, Universidad Autonoma de San Luis Potosi, SLP 78210 (Mexico); Torres-Villasenor, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-360, Mexico D.F. 04510 (Mexico)

    2010-11-15

    Ribbons of the Zn-Al eutectoid alloy obtained by melt-spinning, were heat treated at 350 deg. C during 30 min in a free atmosphere furnace, and then quenched in liquid nitrogen. The temperature correspond to {beta} phase zone, which has a triclinic crystalline structure [1, 2]. Some evidence, obtained by X-ray diffraction, show that the structures present in the just quenched material are both close-packed hexagonal ({eta}-phase) and rhombohedral (R-phase). X-ray diffractograms taken in the same ribbons after annealed 500 h at room temperature, show that the R phase its transform to {alpha} and {eta} phases.

  10. Hydrogen-induced changes in the crystalline structure and mechanical properties of a Zn-Al eutectoid alloy rapidly solidified

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval Jimenez, Alberto; Iturbe Garcia, Jose Luis [Instituto Nacional de Investigaciones Nucleares, Ocoyoacac, Estado de Mexico (Mexico)]. E-mail: alberto.sandoval@inin.gob.mx; asandovalj@correo.unam.mx; Negrete Sanchez, Jesus [Universidad Autonoma de San Luis Potosi, San Luis Potosi (Mexico); Torres Villasenor, Gabriel [Instituto de Investigaciones en Materiales, UNAM, Mexico D.F. (Mexico)

    2009-09-15

    Ribbon fractions of a zinc-aluminum eutectoid (Zn40.8Al%at.) alloy, obtained by rapid solidification using melt spinning technique, were submitted to a thermo-hydrogenation process by periods of 1, 6, 18, 24, 30, and 48 hours, to 200 degrees Celsius and 20 atmospheres. Thermo-hydrogenated samples were analyzed by transmission electron microscopy (TEM). Hydrogen-induced changes were produced, such as microstructure refining, development of crystalline defects, microhardness changes and modification of stable crystalline structures to {alpha}R meta-stable phase at room temperature. [Spanish] Fracciones de tiras de una aleacion eutectoide de zinc-aluminio (Zn40.8Al%at.), obtenidas mediante solidificacion rapida usando la tecnica de melt spinning, se sometieron a un proceso de termohidrogenacion por periodos de 1, 6, 18, 24, 30 y 48 horas, a 200 grados centigrados y 20 atmosferas. Las muestras termohidrogenadas se analizaron por microscopia electronica de transmision (MET). Se produjeron cambios inducidos por hidrogeno, tales como la refinacion de la microestructura, el desarrollo de defectos cristalinos, cambios de microdureza y modificacion de las estructuras cristalinas estables a fase metaestable {alpha}R a temperatura ambiente.

  11. COMPUTER MODELING OF THE ROLLING TECHNOLOGICAL REGIMES INFLUENCE ON MICROSTRUCTURE OF EUTECTOID COLONIES OF ROD PEARLITE

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    A. N. Chichko

    2010-01-01

    Full Text Available Interconnection between the parameters of the rolled wire production technology and characteristics of its microstructure is shown. The correlation interconnections between the characteristics of the rolled wire microstructure, calculated by method of image processing, and technology of its receipt in conditions of RUP «BMZ» are determined. 

  12. Analysis of Plastic Flow Instability During Superplastic Deformation of the Zn-Al Eutectoid Alloy Modified with 2 wt.% Cu

    Science.gov (United States)

    Ramos-Azpeitia, Mitsuo; Elizabeth Martínez-Flores, E.; Hernandez-Rivera, Jose Luis; Torres-Villaseñor, Gabriel

    2017-10-01

    The aim of this work is to analyze the plastic flow instability in Zn-21Al-2Cu alloy deformed under 10-3 s-1 and 513 K, which are optimum conditions for inducing superplastic behavior in this alloy. An evaluation using the Hart and Wilkinson-Caceres criteria showed that the limited stability of plastic flow observed in this alloy is related to low values of the strain-rate sensitivity index (m) and the strain-hardening coefficient (γ), combined with the tendency of these parameters to decrease depending on true strain (ɛ). The reduction in m and γ values could be associated with the early onset of plastic instability and with microstructural changes observed as function of the strain. Grain growth induced by deformation seems to be important during the first stage of deformation of this alloy. However, when ɛ > 0.4 this growth is accompanied by other microstructural rearrangements. These results suggest that in this alloy, a grain boundary sliding mechanism acts to allow a steady superplastic flow only for ɛ 0.7 as another mechanism is thought to take over.

  13. Application of the system free energy theory to the ferrite/pearlite transformation in hypo-eutectoid steel; Akyosekiko no ferrite pearlite hentai ni taisuru soshiki jiyu energy riron no oyo

    Energy Technology Data Exchange (ETDEWEB)

    Toda, Y.; Miyazaki, T. [Nagoya Institute of Technology, Nagoya (Japan)

    1998-12-01

    The kinetics of pearlite transformation in Fe-0.5mass%C steel has theoretically been investigated based on the system free energy theory proposed by us, by which the kinetics of phase transformation for each phase can be estimated according to its energy priority. The inter-lamellar spacing of pearlite is precisely predicted by the energy analysis, and the calculated time-temperature-transformation diagrams consist with the experimental ones. It is obvious that the system free energy theory is also effective for analyzing the lamellar structure produced by, e.g., the pearlite transformation in steel. (author)

  14. Revising the Subsystem Nurse’s A-Phase-Silicocarnotite within the System Ca3(PO4)2–Ca2SiO4

    Science.gov (United States)

    Ros-Tárraga, Patricia; Mazón, Patricia; Meseguer-Olmo, Luis; De Aza, Piedad N.

    2016-01-01

    The subsystem Nurse’s A-phase-silicocarnotite within the system Ca3(PO4)2–Ca2SiO4 was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca3(PO4)2 and 40.5 wt % Ca2SiO4, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca3(PO4)2 and 45 wt % Ca2SiO4. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material. PMID:28773447

  15. Revising the Subsystem Nurse’s A-Phase-Silicocarnotite within the System Ca3(PO42–Ca2SiO4

    Directory of Open Access Journals (Sweden)

    Patricia Ros-Tárraga

    2016-04-01

    Full Text Available The subsystem Nurse’s A-phase-silicocarnotite within the system Ca3(PO42–Ca2SiO4 was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca3(PO42 and 40.5 wt % Ca2SiO4, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca3(PO42 and 45 wt % Ca2SiO4. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material.

  16. Revising the Subsystem Nurse's A-Phase-Silicocarnotite within the System Ca₃(PO₄)₂-Ca₂SiO₄.

    Science.gov (United States)

    Ros-Tárraga, Patricia; Mazón, Patricia; Meseguer-Olmo, Luis; De Aza, Piedad N

    2016-04-28

    The subsystem Nurse's A-phase-silicocarnotite within the system Ca₃(PO₄)₂-Ca₂SiO₄ was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca₃(PO₄)₂ and 40.5 wt % Ca₂SiO₄, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca₃(PO₄)₂ and 45 wt % Ca₂SiO₄. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material.

  17. Influence of Solution Heat Treatment on Structure and Mechanical Properties of ZnAl22Cu3 Alloy

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    Michalik R.

    2016-09-01

    Full Text Available The influence of solution heat treatment at 385°C over 10 h with cooling in water on the structure, hardness and strength of the ZnAl22Cu3 eutectoid alloy is presented in the paper. The eutectoid ZnAl22Cu3 alloy is characterized by a dendritic structure. Dendrites are composed of a supersaturated solid solution of Al in Zn. In the interdendritic spaces a eutectoid mixture is present, with an absence of the ε (CuZn4 phase. Solution heat treatment of the ZnAl22Cu3 alloy causes the occurrence of precipitates rich in Zn and Cu, possibly ε phase. Solution heat treatment at 385°C initially causes a significant decrease of the alloy hardness, although longer solution heat treatment causes a significant increase of the hardness as compared to the as-cast alloy.

  18. Microstructure and transformation kinetics in bainitic steels

    NARCIS (Netherlands)

    Luzginova, N.V.

    2008-01-01

    With the aim of reaching a better understanding of the microstructure evolution and the overall phase transformation kinetics in hyper-eutectoid steels a commercial SAE 52100 bearing steel and 7 model alloys with different concentrations of chromium, cobalt and aluminum have been studied in this

  19. The Cementite Spheroidization Process in High-Carbon Steels with Different Chromium Contents

    NARCIS (Netherlands)

    Luzginova, N.V.; Zhao, L.; Sietsma, J.

    2008-01-01

    The cementite spheroidization process is investigated in hypereutectoid steels with different chromium (Cr) contents. A spheroidized structure in high-carbon steel is usually obtained by a divorced eutectoid transformation (DET) reaction, which occurs during slow cooling of austenite with fine

  20. Gamma stability and powder formation of UMo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, F.B.V.; Andrade, D.A.; Angelo, G.; Belchior Junior, A.; Torres, W.M.; Umbehaun, P.E., E-mail: wmtorres@ipen.br, E-mail: umbehaun@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Angelo, E., E-mail: eangelo@mackenzie.br [Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil). Grupo de Simulacao Numerica (GSN)

    2015-07-01

    A study of the hydrogen embrittlement as well as a research on the relation between gamma decomposition and powder formation of uranium molybdenum alloys were previously presented. In this study a comparison regarding the hypo-eutectoid and hyper-eutectoid molybdenum additions is presented. Gamma uranium molybdenum alloys have been considered as the fuel phase in plate type fuel elements for material and test reactors (MTR). Regarding their usage as a dispersion phase in aluminum matrix, it is necessary to convert the as cast structure into powder, and one of the techniques considered for this purpose is the hydration-dehydration (HDH). This paper shows that, under specific conditions of heating and cooling, γ-UMo fragmentation may occur with non-reactive or reactive mechanisms. Following the production of the alloys by induction melting, samples of the alloys were thermally treated under a constant flow of hydrogen. It was observed that, even without a massive hydration-dehydration process, the alloys fragmented under specific conditions of thermal treatment, during the thermal shock phase of the experiments. Also, there is a relation between absorption and the rate of gamma decomposition or the gamma phase stability of the alloy and this phenomenon can be related to the eutectoid transformation temperature. This study was carried out to search for a new method for the production of powders and for the evaluation of important physical parameter such as the eutectoid transformation temperature, as an alternative to the existing ones. (author)

  1. Characterization of nitrides in an AISI 1010 steel; Caracterizacion de nitruros en un acero AISI 1010

    Energy Technology Data Exchange (ETDEWEB)

    Naquid G, C. [Instituto Nacional de Investigaciones Nucleares, Gerencia de Ciencia de Materiales, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    1998-07-01

    It was characterized the phase formation in the 1010 carbon steel nitrided in a plasma reactor nearby to eutectoid point. The microstructure and identification of these ones were evaluated by Optical microscopy (OM), Dilatometry and X-ray diffraction (XRD). (Author)

  2. Phase transformation kinetics in rolled U-10 wt. % Mo foil: Effect of post-rolling heat treatment and prior γ-UMo grain size

    Energy Technology Data Exchange (ETDEWEB)

    Jana, Saumyadeep; Overman, Nicole; Varga, Tamas; Lavender, Curt; Joshi, Vineet V.

    2017-12-01

    The effect of sub-eutectoid heat treatment on the phase transformation behavior in rolled U-10 wt.percent Mo (U10Mo) foils was systematically investigated. The as-cast 5 mm thick foils were initially homogenized at 900 degrees C for 48 hours and were hot rolled to 2 mm and later cold rolled down to 0.2 mm. Three starting microstructures were evaluated: (i) hot- + cold-rolled to 0.2 mm (as-rolled condition), (ii) hot- + cold-rolled to 0.2 mm + annealed at 700 deg. C for 1 hour, and (iii) hot- + cold-rolled to 0.2 mm + annealed at 1000 deg. C for 60 hours. U10Mo rolled foils went through various degrees of decomposition when subjected to the sub-eutectoid heat-treatment step and formed a lamellar microstructure through a cellular reaction mostly along the previous γ-UMo grain boundaries.

  3. ADI after Austenitising from Intercritical Temperature

    Directory of Open Access Journals (Sweden)

    Kowalskia A.

    2013-03-01

    Full Text Available ADI subjected to austenitising at intercritical temperatures contains in its matrix the precipitates of pre-eutectoid ferrite. Studies were carried out on the ductile iron of the following chemical composition: C = 3,80%, Si = 2,30%, Mn = 0,28%, P = 0,060%, S = 0,010%, Mg = 0,065%, Ni = 0,60%, Cu = 0,70%, Mo = 0,21% This cast iron was austenitised at three different temperatures, i.e. 800, 815 and 830oC and austempered at 360 and 380oC. For each variant of the cast iron heat treatment, the mechanical properties, i.e. YS, TS, EL and Hardness, were measured, and structure of the matrix was examined. Higher plastic properties were obtained owing to the presence of certain amount of pre-eutectoid ferrite. The properties were visualised using fuzzy logic model in a MATLAB. software.

  4. ADI After Austenitising From Intercritical Temperature

    Directory of Open Access Journals (Sweden)

    A. Kowalski

    2013-01-01

    Full Text Available ADI subjected to austenitising at intercritical temperatures contains in its matrix the precipitates of pre-eutectoid ferrite. Studies were carried out on the ductile iron of the following chemical composition: C = 3,80%, Si = 2,30%, Mn = 0,28%, P = 0,060%, S = 0,010%, Mg = 0,065%, Ni = 0,60%, Cu = 0,70%, Mo = 0,21% This cast iron was austenitised at three different temperatures, i.e. 800, 815 and 830oC and austempered at 360 and 380oC. For each variant of the cast iron heat treatment, the mechanical properties, i.e. YS, TS, EL and Hardness, were measured, and structure of the matrix was examined. Higher plastic properties were obtained owing to the presence of certain amount of pre-eutectoid ferrite. The properties were visualised using fuzzy logic model in a MATLAB. software.

  5. Optimisation of post-drawing treatments by means of neutron diffraction

    OpenAIRE

    Ruiz Hervías, Jesús; Atienza Riera, José Miguel; Elices Calafat, Manuel; Oliver, E.C

    2008-01-01

    The mechanical properties and the durability of cold-drawn eutectoid wires (especially in aggressive environments) are influenced by the residual stresses generated during the drawing process. Steelmakers have devised procedures (thermomechanical treatments after drawing) attempting to relieve them in order to improve wire performance. In thiswork neutron diffraction measurements have been used to ascertain the role of temperature and applied force – during post-drawing treatments – on the re...

  6. Thermomechanical process optimization of U-10 wt% Mo – Part 1: high-temperature compressive properties and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Vineet V., E-mail: vineet.joshi@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Nyberg, Eric A.; Lavender, Curt A.; Paxton, Dean [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Garmestani, Hamid [Georgia Institute of Technology, Atlanta, GA 30332 (United States); Burkes, Douglas E. [Pacific Northwest National Laboratory, Richland, WA 99354 (United States)

    2015-10-15

    Nuclear power research facilities require alternatives to existing highly enriched uranium alloy fuel. One option for a high density metal fuel is uranium alloyed with 10 wt% molybdenum (U–10Mo). Fuel fabrication process development requires specific mechanical property data that, to date has been unavailable. In this work, as-cast samples were compression tested at three strain rates over a temperature range of 400–800 °C to provide data for hot rolling and extrusion modeling. The results indicate that with increasing test temperature the U–10Mo flow stress decreases and becomes more sensitive to strain rate. In addition, above the eutectoid transformation temperature, the drop in material flow stress is prominent and shows a strain-softening behavior, especially at lower strain rates. Room temperature X-ray diffraction and scanning electron microscopy combined with energy dispersive spectroscopy analysis of the as-cast and compression tested samples were conducted. The analysis revealed that the as-cast samples and the samples tested below the eutectoid transformation temperature were predominantly γ phase with varying concentration of molybdenum, whereas the ones tested above the eutectoid transformation temperature underwent significant homogenization.

  7. Isothermal transformation behavior in 12%Cr-0.3%C steel; 12%Cr-0.3%C ko ni okeru koon hentai kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Mikami, M. [Japan Casting and Forging Corp., Kitakyushu (Japan); Tsuchiyama, T.; Takaki, S. [Kyushu Univearsity, Fukuoka (Japan)

    2001-01-01

    In order to get fine grain of large martensitic stainless steels products, it is available to use the isothermal transformation before the austenitizing. When 12%Cr-0.3%C steel is subjected to the full solution treatment and following isothermal transformation at 900-1,020K, it is observed that the microstructures are affected by the isothermal ageing temperature. The microstructure transformed isothermally at 1,020K is the full eutectoid structure where carbides precipitate homogeneously. On the other hand, the microstructure transformed at 900K is the mixed heterogeneous structure: the eutectoid structure where carbides precipitate densely around the edge of prior austenite grains and the ferrite structure where carbides hardly precipitate in the center of prior austenite grains. These phenomena are concerned with the decreasing in carbon content in the untransformed austenite as the eutectoid transformation progresses. The amount of decreasing in carbon at 900K is larger than at 1,020K, which causes the shortage of carbon in austenite in the last period of isothermal transformation. In the case of the isothermal transformation at 900K, the reason of why there are the ferrite structures with no carbide in the center of prior austenite grains is that the massive transformation is induced by the shortage of carbon in untransformed austenite. (author)

  8. Failure Mechanism of a Stellite Coating on Heat-Resistant Steel

    Science.gov (United States)

    Wang, Dong; Zhao, Haixing; Wang, Huang; Li, Yuyan; Liu, Xia; He, Guo

    2017-09-01

    The Stellite 21 coating on the heat-resistant steel X12CrMoWVNbN10-1-1 (so-called COSTE) used in a steam turbine valve was found to be fatigue broken after service at around 873 K (600 °C) for about 8 years. In order to investigate the failure mechanism, a fresh Stellite 21 coating was also prepared on the same COSTE steel substrate by using the similar deposition parameters for comparison. It was found that the Stellite 21 coating was significantly diluted by the steel, resulting in a thin Fe-rich layer in the coating close to the fusion line. Such high Fe concentration together with the incessant Fe diffusion from the steel substrate to the coating during the service condition (about 873 K (600 °C) for long time) induced the eutectoid decomposition of the fcc α-Co(Fe,Cr,Mo) solid solution, forming an irregular eutectoid microstructure that was composed of the primitive cubic α'-FeCo(Cr,Mo) phase and the tetragonal σ-CrCo(Fe,Mo) phase. The brittle nature of such α'/ σ eutectoid microstructure contributed to the fatigue fracture of the Stellite 21 coating, resulting in an intergranular rupture mode.

  9. Structure and mechanical properties of a eutectic high-temperature Nb-Si alloy grown by directional solidification

    Science.gov (United States)

    Karpov, M. I.; Vnukov, V. I.; Korzhov, V. P.; Stroganova, T. S.; Zheltyakova, I. S.; Prokhorov, D. V.; Gnesin, I. B.; Kiiko, V. M.; Kolobov, Yu. R.; Golosov, E. V.; Nekrasov, A. N.

    2014-04-01

    The structure and the short-term high-temperature strength of Ni-18.7 at % Si (Nb-Nb3Si eutectic) alloys fabricated by vacuum electron-beam zone melting and induction melting in an argon atmosphere are studied. The structure of the samples prepared by vacuum electron-beam zone melting is characterized by the presence of primary Nb5Si3 intermetallic precipitates and the absence of its secondary precipitates. The structure of the samples prepared by induction melting in an argon atmosphere has two characteristic zones, namely, eutectic and eutectoid ones.

  10. Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys.

    Science.gov (United States)

    1985-01-24

    Ti-7.15% Cr alloy in order to take advantage of the subsitutional character of both parent and product phases during the formation of proeutectoid...operative at higher reaction tempera- -. tures in at least ten other Ti-X eutectoid systems. By the term "bainite" we mean the product of a non-lamellar, i.e...1). In this program, the "generalized micro- structural" definition of bainite (1,6) is being employed: bainite is the product of a non-lamellar

  11. Morphology of Upper and Lower Bainite with 0.7 Mass Pct C

    Science.gov (United States)

    Yin, Jiaqing; Hillert, Mats; Borgenstam, Annika

    2017-09-01

    There has been an on-going discussion on the difference in formation mechanisms of upper and lower bainite. Various suggestions have been supported by reference to observed morphologies and illustrated with idealized sketches of morphologies. In order to obtain a better basis for discussions about the difference in mechanism, the morphology of bainite in an Fe-C alloy with 0.7 mass pct carbon was now studied in some detail from 823 K to 548 K (550 °C to 275 °C) at temperature intervals of 50 K or less. The work focused on bainite seen to start from a grain boundary in the plane of polish and showing an advancing tip in the remaining austenite. The results indicate that there is no essential difference with temperature regarding the ferritic skeleton of feathery bainite. The second stage of bainite formation, which involves the formation of both ferrite and cementite, was regarded as a eutectoid transformation and the resulting morphologies were analyzed in terms of two modes, degenerate and cooperative eutectoid transformation. There was no sharp difference between upper and lower bainite. Ways to define the difference were discussed.

  12. Thermomechanical process optimization of U-10wt% Mo – Part 2: The effect of homogenization on the mechanical properties and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Nyberg, Eric A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Paxton, Dean M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-07-09

    Low-enriched uranium alloyed with 10 wt% molybdenum (U-10Mo) is currently being investigated as an alternative fuel for the highly enriched uranium used in several of the United States’ high performance research reactors. Development of the methods to fabricate the U-10Mo fuel plates is currently underway and requires fundamental understanding of the mechanical properties at the expected processing temperatures. In the first part of this series, it was determined that the as-cast U-10Mo had a dendritic microstructure with chemical inhomogeneity and underwent eutectoid transformation during hot compression testing. In the present (second) part of the work, the as-cast samples were heat treated at several temperatures and times to homogenize the Mo content. Like the previous as-cast material, the “homogenized” materials were then tested under compression between 500 and 800°C. The as-cast samples and those treated at 800°C for 24 hours had grain sizes of 25-30 μm, whereas those treated at 1000°C for 16 hours had grain sizes around 250 μm before testing. Upon compression testing, it was determined that the heat treatment had effects on the mechanical properties and the precipitation of the lamellar phase at sub-eutectoid temperatures.

  13. Thermomechanical process optimization of U-10wt% Mo – Part 2: The effect of homogenization on the mechanical properties and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Vineet V., E-mail: vineet.joshi@pnnl.gov; Nyberg, Eric A.; Lavender, Curt A.; Paxton, Dean; Burkes, Douglas E.

    2015-10-15

    In the first part of this series, it was determined that the as-cast U-10Mo had a dendritic microstructure with chemical inhomogeneity and underwent eutectoid transformation during hot compression testing. In the present (second) part of the work, the as-cast samples were heat treated at several temperatures and times to homogenize the Mo content. Like the previous as-cast material, the “homogenized” materials were then tested under compression between 500 and 800 °C. The as-cast samples and those treated at 800 °C for 24 h had grain sizes of 25–30 μm, whereas those treated at 1000 °C for 16 h had grain sizes around 250 μm before testing. Upon compression testing, it was determined that the heat treatment had effects on the mechanical properties and the precipitation of the lamellar phase at sub-eutectoid temperatures.

  14. Controlling factors of pearlite transformation rate of 0.4mass%C steels; 0.4mass% C ko no pearlite hentai sokudo no ritsusokuu inshi

    Energy Technology Data Exchange (ETDEWEB)

    Yamashita, T.; Narutani, T. [Kawasaki Steel Corp., Tokyo (Japan); Saito, Y. [Waseda Univearsity, Tokyo (Japan). School of Seicence and Engineering

    2000-07-01

    Kinetics of austenite to pearlite phase transformation in 0.4mass%C-X (X=Cr, Ni) steels were investigated. The isothermal transformation curves were analyzed with of the Avrami Equation: X(t)=1-exp(-Gt{sup n}) where X(t) is the fraction transformed and n and Care constants. The exponents n were found to be about 2 except for Cr steels. The value of n for steels containing 0.5 and 1.0 mass% Cr were about 3. This results indicated that the pearlite transformation in 0.4 mass% C steels in present study is controlled by the site saturation mechanism. The parameters G, transformation rate constant of pearlite, were independent of the supercooling from A{sub 1}, temperature and the driving force of pearlite transformation. These values were dependent on the energy differences of ferrite phase from supercooling austenite phase. This energy difference was equivalent to the driving force of eutectoid ferrite. The predicted transformation rate of pearlite is independent of transformation temperature and containing alloy. The pearlite transformation rate of 0.4 mass% C steels was found to be controlled by eutectoid ferrite growth. (author)

  15. Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.A.G., E-mail: galdino.ricardo@gmail.com [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Paganotti, A.; Gama, S. [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A. [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)

    2013-01-15

    The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.

  16. Dust Explosion Characteristics of Aluminum, Titanium, Zinc, and Iron-Based Alloy Powders Used in Cold Spray Processing

    Science.gov (United States)

    Sakata, K.; Tagomori, K.; Sugiyama, N.; Sasaki, S.; Shinya, Y.; Nanbu, T.; Kawashita, Y.; Narita, I.; Kuwatori, K.; Ikeda, T.; Hara, R.; Miyahara, H.

    2014-01-01

    Compared to conventional thermal spray coating, cold spray processing typically employs finer, smaller-diameter metal powders. Furthermore, cold-sprayed particles exhibit fewer surface oxides than thermally sprayed particles due to the absence of particle melting during spraying. For these reasons, it is important to consider the potential for dust explosions or fires during cold spray processing, for both industrial and R&D applications. This work examined the dust explosion characteristics of metal powders typically used in cold spray coating, for the purpose of preventing dust explosions and fires and thus protecting the health and safety of workers and guarding against property damage. In order to safely make use of the new cold spray technology in industrial settings, it is necessary to manage the risks based on an appropriate assessment of the hazards. However, there have been few research reports focused on such risk management. Therefore, in this study, the dust explosion characteristics of aluminum, titanium, zinc, carbonyl iron, and eutectoid steel containing chromium at 4 wt.% (4 wt.% Cr-eutectoid steel) powders were evaluated according to the standard protocols JIS Z 8818, IEC61241-2-3(1994-09) section 3, and JIS Z 8817. This paper reports our results concerning the dust explosion properties of the above-mentioned metal powders.

  17. Nucleation and Growth of Tetrataenite (FeNi) in Meteorites

    Science.gov (United States)

    Goldstein, J. I.; Williams, D. B.; Zhang, J.

    1992-07-01

    The mineral tetrataenite (ordered FeNi) has been observed in chondrites, stony irons, and iron meteorites (1). FeNi is an equilibrium phase in the Fe-Ni phase diagram (Figure 1) and orders to tetrataenite at ~320 degrees C (2). The phase forms at temperatures at or below the eutectoid temperature (~400 degrees C) where taenite (gamma) transforms to kamacite (alpha) plus FeNi (gamma"). An understanding of the formation of tetrataenite can lead to a new method for determining cooling rates at low temperatures (transformation sequences for the formation of tetrataenite were observed. In either sequence, during the cooling process, the taenite (gamma) phase initially undergoes a diffusionless transformation to a martensite (alpha, bcc) phase without a composition change. The martensite then decomposes either above or below the eutectoid temperature (~400 degrees C) during cooling or upon subsequent reheating. During martensite decomposition above the eutectoid, the taenite (gamma) phase nucleates by the reaction alpha(sub)2 ---> alpha + gamma and grows under volume diffusion control. The Ni composition of the taenite increases continuously following the equilibrium gamma/alpha + gamma boundary while the Ni composition of the kamacite matrix decreases following the alpha/alpha + gamma phase boundary (2), see Figure 1. Below the eutectoid temperature, the precipitate composition follows the equilibrium gamma"/alpha + gamma" boundary and reaches ~52 wt% Ni, the composition of FeNi, gamma". The kamacite (alpha) matrix composition approaches ~4 to 5 wt% Ni. The ordering transformation starts at ~320 degrees C forming the tetrataenite phase. During martensite decomposition below the eutectoid temperature, FeNi should form directly by the reaction alpha2 --> alpha + gamma" (FeNi). If this transformation sequence occurs, then the composition of kamacite and tetrataenite should also be given by the alpha/alpha + gamma" and gamma"/alpha + gamma" boundaries of the Fe-Ni phase

  18. Influence of Homogenization on the Mechanical Properties and Microstructure of the U-10Mo Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nyberg, Eric A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Paxton, Dean M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-04-01

    In Phase 1 of this study, the mechanical properties of as-cast, depleted uranium alloyed with 10 weight percent molybdenum alloy (U-10Mo) samples were evaluated by high-temperature compression testing. Compression testing was conducted at three strain rates over a temperature range of 400 to 800°C. The results indicated that with increasing test temperature, the material flow stress decreases and the material becomes more sensitive to strain rate. In addition, above the eutectoid transformation temperature (~ 550°C), the drop in material flow stress is prominent and shows a strain-softening behavior, especially at lower strain rates. In the second part of this research, we studied the effect that homogenization heat treatment had on the high temperature mechanical properties and microstructure of the cast U-10Mo alloy. Various homogenization times and temperatures were studied ranging between 800 and 1000°C for 4 to 48 hours. Based on the microstructural response in this homogenization study, a heat treatment cycle of 800°C for 24 hours and another at 1000°C for 16 hours were selected as the times at temperature to achieve a fully homogenized sample. Samples from these conditions were then compression tested at a variety of temperatures ranging from 500 to 800°C. The microstructure of these samples were compared to the as-cast samples and to a baseline sample homogenized at 1000°C for 16 hours. The results indicate that below the eutectoid temperature (~ 550°C) all three samples showed strain hardening and followed similar trends. Above the eutectoid temperature, the yield strength of the material decreased linearly. For the as-cast sample and the sample homogenized at 800°C for 24 hours, the n-values were negative, whereas for the samples homogenized at 1000°C for 16 hours the material exhibited a perfectly plastic behavior. The as-cast sample, heat treated at 800°C for 24 hours, showed significant lamellar structure transformation that seems to have

  19. Method of making active magnetic refrigerant, colossal magnetostriction and giant magnetoresistive materials based on Gd-Si-Ge alloys

    Science.gov (United States)

    Gschneidner, Jr., Karl A.; Pecharsky, Alexandra O.; Pecharsky, Vitalij K.

    2003-07-08

    Method of making an active magnetic refrigerant represented by Gd.sub.5 (Si.sub.x Ge.sub.1-x).sub.4 alloy for 0.ltoreq.x.ltoreq.1.0 comprising placing amounts of the commercially pure Gd, Si, and Ge charge components in a crucible, heating the charge contents under subambient pressure to a melting temperature of the alloy for a time sufficient to homogenize the alloy and oxidize carbon with oxygen present in the Gd charge component to reduce carbon, rapidly solidifying the alloy in the crucible, and heat treating the solidified alloy at a temperature below the melting temperature for a time effective to homogenize a microstructure of the solidified material, and then cooling sufficiently fast to prevent the eutectoid decomposition and improve magnetocaloric and/or the magnetostrictive and/or the magnetoresistive properties thereof.

  20. Influence of Microstructure on Strength and Ductility in Fully Pearlitic Steels

    Directory of Open Access Journals (Sweden)

    Jesús Toribio

    2016-12-01

    Full Text Available This article deals with the relationship between the microstructure and both strength and ductility in eutectoid pearlitic steel. It is seen how standard mechanical properties and fracture micromechanisms are affected by heat treatment and the resulting microstructure in the material. The yield stress, the ultimate tensile strength and the ductility (measured by means of the reduction in area exhibit a rising trend with the increasing cooling rate (associated with smaller pearlite interlamellar spacing and a lower pearlitic colony size, while the strain for maximum load shows a decreasing tendency with the afore-said rising cooling rate. With regard to the fracture surface, its appearance becomes more brittle for lower cooling rates, so that the fracture process zone exhibits a larger area with observable pearlite lamellae and a lower percentage of microvoids.

  1. Investigations of Temperatures of Phase Transformations of Low-Alloyed Reinforcing Steel within the Heat Treatment Temperature Range

    Directory of Open Access Journals (Sweden)

    Kargul T.

    2017-06-01

    Full Text Available The paper presents the results of DSC analysis of steel B500SP produced in the process of continuous casting, which is intended for the production reinforcement rods with high ductility. Studies were carried out in the temperature range below 1000°C in a protective atmosphere of helium during samples heating program. The main objective of the study was to determine the temperature range of austenite structure formation during heating. As a result of performed experiments: Ac1s, Ac1f – temperatures of the beginning and finish of the eutectoid transformation, Ac2 – Curie temperature of the ferrite magnetic transformation and the temperature Ac3 of transformation of proeutectoid ferrite into austenite were elaborated. Experimental determination of phase transformations temperatures of steel B500SP has great importance for production technology of reinforcement rods, because good mechanical properties of rods are formed by the special thermal treatment in Tempcore process.

  2. Heat treatment induced phase transition and microstructural evolution in electron beam surface melted Nb-Si based alloys

    Science.gov (United States)

    Guo, Yueling; Jia, Lina; Kong, Bin; Peng, Hui; Zhang, Hu

    2017-11-01

    The hardness, phase and microstructural development of Nb-18Si-24Ti-2Cr-2Al (at.%) alloys processed by electron beam surface melting (EBSM) and subsequent heat treatments were investigated. The EBSM experiments were performed using an electron beam based 3D printing system. Results showed that Nbss and Nb3Si phases were obtained via EBSM with a significantly refined microstructure. The eutectoid reaction of Nb3Si → Nbss + αNb5Si3 was triggered by heat treatments (HT) at 1200 °C or 1450 °C for 5 h. The growth and the coarsening of αNb5Si3 grains were promoted with a higher HT temperature. The hardness of the EBSM alloy was remarkably reduced by HT.

  3. Ag-rich precipitates formation in the Cu–11%Al–10%Mn–3%Ag alloy

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.A.G., E-mail: galdino.ricardo@gmail.com [Departamento de Ciências Exatas e da Terra, UNIFESP, 09972-270 Diadema, SP (Brazil); Paganotti, A.; Jabase, L. [Departamento de Ciências Exatas e da Terra, UNIFESP, 09972-270 Diadema, SP (Brazil); Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A. [Departamento de Físico-Química, Instituto de Química, UNESP, 14801-970 Araraquara, SP (Brazil)

    2014-12-05

    Highlights: • Cu-rich nanoprecipitates are formed in the presence of Ag. • Bainite precipitation is shifted to higher temperatures in the Cu–11%Al–10%Mn–3%Ag alloy. • The eutectoid α phase and bainite α{sub 1} phase compete by the Cu atoms during precipitation process. - Abstract: The formation of Ag-rich precipitates in the Cu–11%Al–10%Mn–3%Ag alloy initially quenched from 1123 K was analyzed. The results showed that nanoprecipitates of a Cu-rich phase are produced at about 523 K. In higher temperatures these nanoparticles grow and the relative fraction of Ag dissolved in it is increased, thus forming the Ag-rich phase.

  4. Spot Feeding Spheroidal Graphite Iron with Exothermic and Insulating Ram-Up Sleeves in Vertically Parted Moulds: Efficiency, Microstructure, Dimensional Accuracy, Deformation, and Driving Force and Feeding Criteria Identification

    DEFF Research Database (Denmark)

    Vedel-Smith, Nikolaj Kjelgaard

    the castings, as well as the exothermic and insulating feeders. The thermal deformation related to the feeder combinations are investigated, and it is found that the thermal gradients created by the feeders could be signified by the deformation of the plane reverse side of the casting. The eutectoid phase...... in this dissertation is based on large-scale quantitative experiments with duplicates for statistical representation. The focus, as stated by the dissertation title, has been: ‘Spot Feeding Spherical Graphite Iron with Exothermicand Insulating Ram-Up Sleeves in Vertically Parted Moulds’. The application of spot...... feeders (ram-up sleeves) is investigated, showing that this new feeding approach can be used successfully to feed secluded sections inductile cast iron (EN-GJS-500-7). The feeder efficiency is tested using a high Silicon (Si) ductile iron (EN-GJS-450-10). The limits for the examined feeder configurations...

  5. Electric conductivity and cubic phase decomposition in the zirconia totally stabilized with magnesia by impedance spectroscopy; Condutividade eletrica e decomposicao da fase cubica na zirconia totalmente estabilizada com magnesia por espectroscopia de impendancia

    Energy Technology Data Exchange (ETDEWEB)

    Muccillo, Eliana N.S. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1996-09-01

    Electrical resistivity measurements have been done by impedance spectroscopy in Mg-fully stabilized zirconia ceramics, in order to verify the effects produced by the stabilizing cation. The results show that the intragranular component of the resistivity increases gradually for increasing dopant content. The blocking effect of charge carriers by grain boundaries also increases with the increase in the Mg content, reaching a maximum value near the eutectoid composition, and vanishing for higher concentrations. Impedance spectroscopy diagrams show markedly changes due to the cubic phase decomposition. For an aging temperature of 1100 deg C, the total resistivity increases by a factor of 100 in 3 h. For aging times longer than 8 h, there is no significant changes in the total resistivity. That means that under these experimental conditions, the cubic phase decomposition process reaches its completion in zirconia-magnesia ceramics. (author) 3 refs., 4 figs., 1 tab.

  6. Graphite nodules and local residual stresses in ductile iron: Thermo-mechanical modelingand experimental validation

    DEFF Research Database (Denmark)

    Andriollo, Tito

    Ductile iron is nowadays widely used in key industrial sectors like off-shore, transport and energy production, accounting for as much as 25 % of the total casting production in the world. It is well known that ductile iron parts, depending on their size, may contain residual stresses developing...... stages of the manufacturing process are simulated numerically, accounting for the different thermal expansion of the nodules and of the matrix during both the eutectoid transformation and the subsequent cooling to room temperature. The results show the formation of significant residual stresses...... the theoretical predictions that local stresses up to approximately half the macroscopic yield strength may remain in the ductile iron microstructure after manufacturing. Needless to say, this new type of residual stresses is expected to play an important role in determining the properties of ductile iron...

  7. Microstructures and Mechanical Properties of as-Drawn and Laboratory Annealed Pearlitic Steel Wires

    Science.gov (United States)

    Durgaprasad, A.; Giri, S.; Lenka, S.; Kundu, S.; Mishra, S.; Chandra, S.; Doherty, R. D.; Samajdar, I.

    2017-10-01

    Near eutectoid fully pearlitic wire rod (5.5 mm diameter) was taken through six stages of wire drawing (drawing strains of 0 to 2.47). The as-drawn (AD) wires were further laboratory annealed (LA) to re-austenitize and reform the pearlite. AD and LA grades, for respective wire diameters, had similar pearlite microstructure: interlamellar spacing ( λ) and pearlite alignment with the wire axis. However, LA grade had lower hardness (for both phases) and slightly lower fiber texture and residual stresses in ferrite. Surprisingly, essentially identical tensile yield strengths in AD and LA wires, measured at equivalent spacing, were found. The work hardened AD had, as expected, higher torsional yield strengths and lower tensile and torsional ductilities than LA. In both wires, stronger pearlite alignment gave significantly increased torsional ductility.

  8. The Effect of Rolling As-Cast and Homogenized U-10Mo Samples on the Microstructure Development and Recovery Curves

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Vineet V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Paxton, Dean M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lavender, Curt A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Burkes, Douglas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-07-30

    Over the past several years Pacific Northwest National Laboratory (PNNL) has been actively involved in supporting the U.S. Department of Energy National Nuclear Security Administration Office of Material Management and Minimization (formerly Global Threat Reduction Initiative). The U.S. High- Power Research Reactor (USHPRR) project is developing alternatives to existing highly enriched uranium alloy fuel to reduce the proliferation threat. One option for a high-density metal fuel is uranium alloyed with 10 wt% molybdenum (U-10Mo). Forming the U-10Mo fuel plates/foils via rolling is an effective technique and is actively being pursued as part of the baseline manufacturing process. The processing of these fuel plates requires systematic investigation/understanding of the pre- and post-rolling microstructure, end-state mechanical properties, residual stresses, and defects, their effect on the mill during processing, and eventually, their in-reactor performance. In the work documented herein, studies were conducted to determine the effect of cold and hot rolling the as-cast and homogenized U-10Mo on its microstructure and hardness. The samples were homogenized at 900°C for 48 h, then later annealed for several durations and temperatures to investigate the effect on the material’s microstructure and hardness. The rolling of the as-cast plate, both hot and cold, was observed to form a molybdenum-rich and -lean banded structure. The cold rolling was ineffective, and in some cases exacerbated the as-cast defects. The grains elongated along the rolling direction and formed a pancake shape, while the carbides fractured perpendicularly to the rolling direction and left porosity between fractured particles of UC. The subsequent annealing of these samples at sub-eutectoid temperatures led to rapid precipitation of the ' lamellar phase, mainly in the molybdenum-lean regions. Annealing the samples above the eutectoid temperature did not refine the grain size or the banded

  9. THE METALLURGICAL SPECIFICATIONS AND HARDNESS PROFILE OF A RAIL THERMITE WELD

    Directory of Open Access Journals (Sweden)

    Cevdet MERİÇ

    1998-02-01

    Full Text Available The quality of railroad construction is a important factor for comfort and safety in railroad transportation. Thermite welding being known for a long time prevents rail failure and, off road the train. It provides smoothly journey, and long life to rails and wagons. In this study, S 49 type St 70 steel rails have been welded by thermite process, hardness profile of welding zone rails has been obtained and its microstructure has been examined. In this profile maximum hardness values have been observed in front of welding region. Hardness value was 290 HB in the front of melting zone in the zone under heat effect (HAZ, 260 HB in welding zone and 220 HB in main structure. For microstructure pro-eutectoid ferrite and perlite were observed but not martensite.

  10. Phase transitions during artificial ageing of segregated as-cast U–Mo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pedrosa, Tércio Assunção, E-mail: tap@cdtn.br [CDTN/CNEN, Centro de Desenvolvimento da Tecnologia Nuclear, Av. Presidente Antônio Carlos, 6627 31270-901 Belo Horizonte, MG (Brazil); Santos, Ana Maria Matildes dos; Soares Lameiras, Fernando [CDTN/CNEN, Centro de Desenvolvimento da Tecnologia Nuclear, Av. Presidente Antônio Carlos, 6627 31270-901 Belo Horizonte, MG (Brazil); Cetlin, Paulo Roberto [Departamento de Engenharia Mecânica, Universidade Federal de Minas Gerais, Av. Presidente Antônio Carlos, 6627 31270-901 Belo Horizonte, MG (Brazil); Ferraz, Wilmar Barbosa [CDTN/CNEN, Centro de Desenvolvimento da Tecnologia Nuclear, Av. Presidente Antônio Carlos, 6627 31270-901 Belo Horizonte, MG (Brazil)

    2015-02-15

    non-lamellar constituent (NL3) in the high temperature ageing. The precipitation of oriented acicular or Widmanstätten γ′ platelets over a γ-phase matrix was observed for the hypereutectoid compositions of the U–Mo system, while the interdendritic regions with Mo contents close to the eutectoid composition were initially untransformed. This indicates a maximum in the γ stabilizing effect for the eutectoid composition, in opposition to the commonly accepted increased stabilizing effect for raised Mo additions.

  11. Machinability of clean thin-wall gray and ductile iron castings. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bates, C.E.; Littleton, H.E.; Eleftheriou, E.; Griffin, R.D.; Dwyer, Z.B.; DelSorbo, C.; Sprague, J.

    1997-02-01

    First phase was to develop a laboratory technique for evaluating the machinability of gray and ductile iron; longer term goal is to learn how to modify the foundry process to produce castings meeting all specified mechanical properties while providing improved machining behavior. Microcarbides present in the irons were found to dominate the machinability of iron. Pearlitic irons with acceptable machinability contain 8.9 to 10.5 wt% microcarbides. The weight fraction microcarbides in the iron is influenced by carbide forming element concentrations, presence of elements that retard carbon diffusion, and cooling rate from the eutectic through the eutectoid temperature range. Tool wear rate increased at higher surface machining speeds and fraction microcarbides; all irons containing above 11.5% microcarbides had poor machinability. Graphite size, shape, distribution, etc. had a lesser effect on machinability. Reducing the addition of a foundry grade Ca and Al bearing 75% FeSi inoculant from 0.5 to 0.2% increased the tool life 100%. Inoculation test castings were also poured in a class 40 gray iron; laboratory analysis is currently underway. Exploratory studies were conducted to determine if tool force could be used to predict tool life: torque and feed forces were found to correlate with machinability.

  12. Model of Cu-Al-Fe-Ni Bronze Crystallization

    Directory of Open Access Journals (Sweden)

    Pisarek B. P.

    2013-09-01

    Full Text Available According to the analysis of the current state of the knowledge shows that there is little information on the process of phase transformations that occur during the cooling Cu-Al-Fe-Ni hypo-eutectoid bronzes with additions of Cr, Mo and/or W, made additions individually or together, for the determination of: the type of crystallizing phases, crystallizing phases, order and place of their nucleation. On the basis of recorded using thermal and derivative analysis of thermal effects phases crystallization or their systems, analysis of the microstructure formed during crystallization - observed on the metallographic specimen casting ATD10-PŁ probe, analysis of the existing phase equilibrium diagrams forming elements tested Cu-Al-Fe-Ni bronze, with additions of Cr, Mo, W and/or Si developed an original model of crystallization and phase transformation in the solid state, the casting of high quality Cu-Al-Fe-Ni bronze comprising: crystallizing type phase, crystallizing phase sequence, place of nucleation.

  13. Refinement and fracture mechanisms of as-cast QT700-6 alloy by alloying method

    Directory of Open Access Journals (Sweden)

    Min-qiang Gao

    2017-01-01

    Full Text Available The as-cast QT700-6 alloy was synthesized with addition of a certain amount of copper, nickel, niobium and stannum elements by alloying method in a medium frequency induction furnace, aiming at improving its strength and toughness. Microstructures of the as-cast QT700-6 alloy were observed using a scanning-electron microscope (SEM and the mechanical properties were investigated using a universal tensile test machine. Results indicate that the ratio of pearlite/ferrite is about 9:1 and the graphite size is less than 40 μm in diameter in the as-cast QT700-6 alloy. The predominant refinement mechanism is attributed to the formation of niobium carbides, which increases the heterogeneous nucleus and hinders the growth of graphite. Meanwhile, niobium carbides also exist around the grain boundaries, which improve the strength of the ductile iron. The tensile strength and elongation of the as-cast QT700-6 alloy reach over 700 MPa and 6%, respectively, when the addition amount of niobium is 0.8%. The addition of copper and nickel elements contributed to the decrease of eutectoid transformation temperature, resulting in the decrease of pearlite lamellar spacing (about 248 nm, which is also beneficial to enhancing the tensile strength. The main fracture mechanism is cleavage fracture with the appearance of a small amount of dimples.

  14. Evolution of hardness in ultrafine-grained metals processed by high-pressure torsion

    Directory of Open Access Journals (Sweden)

    Megumi Kawasaki

    2014-10-01

    Full Text Available The processing of metals through the application of high-pressure torsion (HPT provides the potential for achieving exceptional grain refinement in bulk metals. Numerous reports are now available demonstrating the application of HPT to a range of pure metals and simple alloys. In practice, excellent grain refinement is achieved using this processing technique with the average grain size often reduced to the true nano-scale range. Contrary to the significant grain refinement achieved in metals during HPT, the models of the hardness evolution are very different depending upon the material properties. For a better understanding of the material characteristics after conventional HPT processing, this report demonstrates the hardness evolutions in simple metals including high-purity Al, commercial purity aluminum Al-1050, ZK60A magnesium alloy and Zn-22% Al eutectoid alloy after processing by HPT. Separate models of hardness evolution are described with increasing equivalent strain by HPT. Moreover, a new approach for the use of HPT is demonstrated by synthesizing an Al–Mg metal system by processing two separate commercial metals of Al-1050 and ZK60A through conventional HPT processing at room temperature.

  15. Assessment of Effects of Si-Ca-P Biphasic Ceramic on the Osteogenic Differentiation of a Population of Multipotent Adult Human Stem Cells

    Directory of Open Access Journals (Sweden)

    Patricia Ros-Tárraga

    2016-11-01

    Full Text Available A new type of bioceramic with osteogenic properties, suitable for hard tissue regeneration, was synthesised. The ceramic was designed and obtained in the Nurse’s A-phase-silicocarnotite subsystem. The selected composition was that corresponding to the eutectoid 28.39 wt % Nurse’s A-phase-71.61 wt % silicocarnotite invariant point. We report the effect of Nurse’s A-phase-silicocarnotite ceramic on the capacity of multipotent adult human mesenchymal stem cells (ahMSCs cultured under experimental conditions, known to adhere, proliferate and differentiate into osteoblast lineage cells. The results at long-term culture (28 days on the material confirmed that the undifferentiated ahMSCs cultured and in contact with the material surface adhered, spread, proliferated, and produced a mineralised extracellular matrix on the studied ceramic, and finally acquired an osteoblastic phenotype. These findings indicate that it underwent an osteoblast differentiation process. All these findings were more significant than when cells were grown on plastic, in the presence and absence of this osteogenic supplement, and were more evident when this supplement was present in the growth medium (GM. The ceramic evaluated herein was bioactive, cytocompatible and capable of promoting the proliferation and differentiation of undifferentiated ahMSCs into osteoblasts, which may be important for bone integration into the clinical setting.

  16. Ancient Blacksmiths, The Iron Age, Damascus Steels, and Modern Metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Sherby, O.D.; Wadsworth, J.

    2000-09-11

    The history of iron and Damascus steels is described through the eyes of ancient blacksmiths. For example, evidence is presented that questions why the Iron Age could not have begun at about the same time as the early Bronze Age (i.e. approximately 7000 B.C.). It is also clear that ancient blacksmiths had enough information from their forging work, together with their observation of color changes during heating and their estimate of hardness by scratch tests, to have determined some key parts of the present-day iron-carbon phase diagram. The blacksmiths' greatest artistic accomplishments were the Damascus and Japanese steel swords. The Damascus sword was famous not only for its exceptional cutting edge and toughness, but also for its beautiful surface markings. Damascus steels are ultrahigh carbon steels (UHCSs) that contain from 1.0 to 2.1%. carbon. The modern metallurgical understanding of UHCSs has revealed that remarkable properties can be obtained in these hypereutectoid steels. The results achieved in UHCSs are attributed to the ability to place the carbon, in excess of the eutectoid composition, to do useful work that enhances the high temperature processing of carbon steels and that improves the low and intermediate temperature mechanical properties.

  17. Austenite to ferrite transformation kinetics during continuous cooling

    Energy Technology Data Exchange (ETDEWEB)

    Militzer, M.; Pandi, R.; Hawbolt, E.B. [Univ. of British Columbia, Vancouver, British Columbia (Canada). Centre for Metallurgical Process Engineering

    1994-12-31

    The austenite decomposition has been investigated in a hypo-eutectoid plain carbon steel under continuous cooling conditions using a dilatometer and a Gleeble 1500 thermomechanical simulator. The experimental results were used to verify model calculations based on a fundamental approach for the dilute ternary systems Fe-C-Mn. The austenite to ferrite transformation start temperature can be predicted from a nucleation model for slow cooling rates. The formation of ferrite nuclei takes place with equilibrium composition on austenite grain boundaries. The nuclei are assumed to have a pill box shape in accordance with minimal interfacial energy. For higher cooling rates, early growth has to be taken into account to describe the transformation start. In contrast to nucleation, growth of the ferrite is characterized by paraequilibrium; i.e. only carbon can redistribute, whereas the diffusion of Mn is too slow to allow full equilibrium in the ternary system. However, Mn segregation to the moving ferrite-austenite interface has to be considered. The latter, in turn, exerts a solute drag effect on the boundary movement. Thus, growth kinetics is controlled by carbon diffusion in austenite modified by interfacial segregation of Mn. Employing a phenomenological segregation model, good agreement has been achieved with the measurements.

  18. Heat treatment of nitrided layer formed on X37CrMoV5-1 hot working tool steel

    Science.gov (United States)

    Ciski, A.; Wach, P.; Tacikowski, J.; Babul, T.; Šuchmann, P.

    2017-02-01

    The paper presents the technology consisting of combination of the nitriding process with subsequent austenitizing at temperature above eutectoid temperature of the Fe-C system and further rapid cooling. Such treatment will cause formation of the martensite in the area of the primarily nitrided layer and the additional precipitation hardening by tempering of heat treated steel. The article shows that the heat treatment process of nitrided layer formed on X37CrMoV5-1 steel leads to strengthening of surface layer, the substrate and the core of nitrided part. Heat treatment of nitrided steel with the tempering in inert (nitrogen) or active (ammonia) atmosphere can increase the thickness of the layer formed by short-term nitriding process. After the nitriding process of X37CrMoV5-1 steel the nitrided layer had a thickness of about 160 μm, while a subsurface layer of iron nitrides had a thickness of 7 μm. After subsequent quenching and tempering processes, the nitrided layer undergoes additional diffusion and its thickness is increased to about 220 μm (inert atmosphere) or 280 μm (active atmosphere). If the tempering process is carried out in an inert atmosphere, the primarily formed layer of iron nitrides disappears. Tempering in an active atmosphere leads to forming of white layer with a thickness of 7 μm. Basic properties of nitrided layers formed in such way, like the hardness and the wear resistance, are presented.

  19. TO SELECTION OF TECHNOLOGICAL SCHEME OF SOFTENING HEAT TREATMENT FOR HIGH CHROMIUM CAST IRON

    Directory of Open Access Journals (Sweden)

    V. G. Efremenko

    2014-03-01

    Full Text Available Purpose. High chromium cast irons with austenitic matrix have low machinability. The aim of work is search of new energy-saving modes of preliminary softening heat treatment enhancing the machinability of castings by forming an optimum microstructure. Methodology. Metallographic analysis, hardness testing and machinability testing are applied. Findings. It was found out that high temperature annealing with continuous cooling yields to martensite-austenite matrix in cast iron 270Х15Г2Н1MPhT, which abruptly affects the machinability of cast iron. Significant improvement of machinability is achieved by forming of structure "ferrite + granular carbides" and by decline of hardness to 37-39 HRC in the case of two-stage isothermal annealing in the subcritical temperature range or by the use of quenching and tempering (two-step or cyclic. Originality. It was found that the formation of the optimal structure of the matrix and achievement of desired hardness level needed for improving machinability of high chromium cast iron containing 3 % austenite-forming elements, can be obtained: 1 due to pearlite original austenite followed by spherodization eutectoid carbides, and 2 by getting predominantly martensite structure followed by the decay of martensite and carbides coagulation at high-temperature tempering. Practical value. The new energy-saving schemes of softening heat treatment to ensure the growth of machinability of high chromium cast iron, alloyed by higher quantity of austenite forming elements, are proposed.

  20. Effect of quenching rate on martensitic transformation temperature in Cu-Al-Ni shape memory alloys; Cu-Al-Ni keijo kioku gokin no maltensite hentai ondo ni oyobosu yakiire reikyakusokudo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakaniwa, M.; Sugimoto, K.; Kamei, K.; Nakamura, Y.; Sugimoto, T. [Kansai University, Osaka (Japan). Faculty of Engineering

    1995-08-20

    Experiments were carried out for Cu-xAl-5Ni-2Mn-1Ti shape memory alloys (x= 11.45, 11.77, 11.88 mass%) in order to examine the effect of quenching rate on the transformation temperatures (Ms, Mf, As and Af). The quenching rate was varied from 5 to 1{times}10{sup 4} K/s by changing the temperature of quenching media. The transformation temperatures were determined by DSC measurements for all the samples quenched and are plotted as a faction of quenching rate. It was found that all the transformation temperatures decreased by about 10 K, when the quenching rate was increased 10 times as large as its initial value. The reason was explained by considering the degree of order in the beta-phase. The primary {alpha}- and {gamma}2-phases do not precipitate even during air-cooling on quenching in the alloys with 11.77 and 11.88%Al, being close to the eutectoid composition. Therefore, no remarkable change in martensitic transformation temperature with reducing quenching rate was observed in these alloys. In other words, it can be concluded that these alloys are suitable for heat treatments in practice, where the specimens are cooled more slowly. 20 refs., 5 figs., 2 tabs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-09-01

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

  2. Thermal stability of {l_brace}1 1 0{r_brace}facet terminated gold nanobelts

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ying [Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Str. 1, D-40237 Duesseldorf (Germany); Milenkovic, Srdjan [Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Str. 1, D-40237 Duesseldorf (Germany); IMDEA Materials Institute, C/ Profesor Aranguren s/n, 28040 Madrid (Spain); Hassel, Achim Walter, E-mail: hassel@elchem.de [Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Str. 1, D-40237 Duesseldorf (Germany); Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University, Altenberger Str. 69, A-4040 Linz (Austria)

    2012-06-15

    A precise knowledge and understanding of the thermal stability of nanowires is a prerequisite for the reliable implementation of nanowire-based devices. Single crystalline Au nanobelts with {l_brace}1 1 0{r_brace}surface either in free standing arrays with identical crystallographic orientation or lying on the substrate were prepared by a combination of directional eutectoid decomposition followed by phase selective etching process. The thermal stability in the temperature range 500-700 Degree-Sign C of the obtained free standing and lying Au nanobelts were investigated in situ with a scanning electron microscope equipped with a high temperature stage. The results suggested that free standing Au nanobelts undergo morphological evolution in a different way compared with the substrate contacted lying Au nanobelts. The free standing Au nanobelts broke more easily and decayed into a chain of nanospheres following Rayleigh instability after the belt morphology changed into cylindrical wires; whereas the Au nanobelts lying on the substrate decayed into irregular particles. These findings clearly support a surface energy minimization driven mechanism. Only after transformation into a mainly {l_brace}1 1 1{r_brace}terminated structure formation of Rayleigh instabilities are observed.

  3. Microstructure and Mechanical Properties of Joints of Titanium with Stainless Steel Performed using Nickel Filler

    Directory of Open Access Journals (Sweden)

    Szwed B.

    2016-06-01

    Full Text Available Diffusion brazing was performed between titanium (Grade 2 and stainless steel (X5CrNi18-10 using as a filler a nickel foil at the temperatures of 850, 900, 950 and 1000°C. The microstructure was investigated using light microscopy and scanning electron microscopy equipped with an energy dispersive X-ray system (EDS. The structure of the joints on the titanium side was composed of the eutectoid mixture αTi+Ti2Ni and layers of intermetallic phases Ti2Ni, TiNi and TiNi3. The stainless steel-nickel interface is free from any reaction layer at 850°C, above this temperature thin layer of reaction appears. The microhardness measured across the joints reaches higher values than for titanium and stainless steel, and it achieves value from 260 to 446 HV. The highest shear strength (214 MPa was achieved for joints brazed at 900°C.

  4. Metallography and microstructure interpretation of some archaeological tin bronze vessels from Iran

    Energy Technology Data Exchange (ETDEWEB)

    Oudbashi, Omid, E-mail: o.oudbashi@aui.ac.ir [Department of Conservation of Historic Properties, Faculty of Conservation, Art University of Isfahan, Hakim Nezami Street, Sangtarashha Alley, P.O. Box 1744, Isfahan (Iran, Islamic Republic of); Davami, Parviz, E-mail: pdavami@razi-foundation.com [Faculty of Material Science and Engineering, Sharif University of Technology/Razi Applied Science Foundation, No. 27, Fernan St., Shahid Ghasem Asghari Blvd., km 21 of Karadj Makhsous Road, Tehran (Iran, Islamic Republic of)

    2014-11-15

    Archaeological excavations in western Iran have recently revealed a significant Luristan Bronzes collection from Sangtarashan archaeological site. The site and its bronze collection are dated to Iron Age II/III of western Iran (10th–7th century BC) according to archaeological research. Alloy composition, microstructure and manufacturing technique of some sheet metal vessels are determined to reveal metallurgical processes in western Iran in the first millennium BC. Experimental analyses were carried out using Scanning Electron Microscopy–Energy Dispersive X-ray Spectroscopy and Optical Microscopy/Metallography methods. The results allowed reconstructing the manufacturing process of bronze vessels in Luristan. It proved that the samples have been manufactured with a binary copper–tin alloy with a variable tin content that may relates to the application of an uncontrolled procedure to make bronze alloy (e.g. co-smelting or cementation). The presence of elongated copper sulphide inclusions showed probable use of copper sulphide ores for metal production and smelting. Based on metallographic studies, a cycle of cold working and annealing was used to shape the bronze vessels. - Highlights: • Sangtarashan vessels are made by variable Cu-Sn alloys with some impurities. • Various compositions occurred due to applying uncontrolled smelting methods. • The microstructure represents thermo-mechanical process to shape bronze vessels. • In one case, the annealing didn’t remove the eutectoid remaining from casting. • The characteristics of the bronzes are similar to other Iron Age Luristan Bronzes.

  5. History of ultrahigh carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, J.; Sherby, O.D.

    1997-06-20

    The history and development of ultrahigh carbon steels (i.e., steels containing between 1 and 2.l percent C and now known as UHCS) are described. The early use of steel compositions containing carbon contents above the eutectoid level is found in ancient weapons from around the world. For example, both Damascus and Japanese sword steels are hypereutectoid steels. Their manufacture and processing is of interest in understanding the role of carbon content in the development of modern steels. Although sporadic examples of UHCS compositions are found in steels examined in the early part of this century, it was not until the mid-1970s that the modern study began. This study had its origin in the development of superplastic behavior in steels and the recognition that increasing the carbon content was of importance in developing that property. The compositions that were optimal for superplasticity involved the development of steels that contained higher carbon contents than conventional modern steels. It was discovered, however, that the room temperature properties of these compositions were of interest in their own right. Following this discovery, a period of intense work began on understanding their manufacture, processing, and properties for both superplastic forming and room temperature applications. The development of superplastic cast irons and iron carbides, as well as those of laminated composites containing UHCS, was an important part of this history.

  6. Effect of electrode and weld current on the physical and mechanical properties of cast iron welding

    Science.gov (United States)

    Chamim, M.; Triyono, Diharjo, Kuncoro

    2017-01-01

    Metal casting industry will repair the products are defective. The repair process is often done using a Shielded Metal Arc Welding (SMAW). Preheat and post-weld heat treatment method can overcome the problem of welding cast iron. However, many of the local foundry industry does not use this method. The main problem of the method relates to the problem of cost and process. The results of testing Scanning Electron Microscopy (SEM), gray cast iron welding seen to have an important problem in the PMZ and HAZ. Hard and brittle phase formations during solidification process and after solidification formation eutectoid is carbide and martensite. The formation of martensite and carbides is caused by the high carbon content of cast iron. Consumable electrode with a nickel base material used for the welding process without preheating and PWHT methods. Nickel as an austenite stabilizer can pick up the carbon, so that the hard phase PMZ area can be reduced. Variations electric current used to get good heat input in the welding area so that nickel can diffuse well.

  7. Superplastic Forming 40 Years and Still Growing

    Science.gov (United States)

    Barnes, A. J.

    2007-08-01

    In late 1964 Backofen, Turner & Avery, at MIT, published a paper in which they described the “extraordinary formability” exhibited when fine-grain zinc-aluminum eutectoid (Zn 22 Al) was subjected to bulge testing under appropriate conditions. They concluded their research findings with the following insightful comment “ even more appealing is the thought of applying to superplastic metals forming techniques borrowed from polymer and glass processing.” Since then their insightful thought has become a substantial reality with thousands of tons of metallic sheet materials now being superplastically formed each year. This paper reviews the significant advances that have taken place over the past 40 years including alloy developments, improved forming techniques and equipment, and an ever increasing number of commercial applications. Current and likely future trends are discussed including; applications in the aerospace and automotive markets, faster-forming techniques to improve productivity, the increasing importance of computer modeling and simulation in tool design and process optimization and new alloy developments including superplastic magnesium alloys.

  8. Contribution of archaeological analogs to the estimation of average corrosion rates and long term corrosion mechanisms of low carbon steel in soil; Apport des analogues archeologiques a l'estimation des vitesses moyennes et a l'etude des mecanismes de corrosion a tres long terme des aciers non allies dans les sols

    Energy Technology Data Exchange (ETDEWEB)

    Neff, D

    2003-11-15

    In the context of the French nuclear waste storage, a multi-barriers disposal is envisaged. Wastes could be put in metallic overpacks disposed in a clay soil. As these overpacks could be made of low carbon steel, it is important to understand the corrosion behaviour of this material in soil during period of several centuries. Indeed, it is necessary to consolidate the empirical data by a phenomenological approach. This includes laboratory experiments and modelling of the phenomenon which have to be validated and completed by the study of archaeological artefacts. This was the aim of this PhD-work. To this purpose, an analytical protocol has been elaborated: about forty archaeological artefacts coming from five dated sites (2. to 16. centuries) have been studied on cross section in order to observe on the same sample all the constituents of the system: metallic substrate/corrosion products/environment. The corrosion products are divided into two zones: the Dense Product Layer (DPL) in contact with the metal, and the Transformed Medium (TM) which are the corrosion products formed around soil minerals (quartz grains). The metallic substrate has been studied by the classical methods of materials science (optical and scanning electron microscope, energy and wavelength dispersive spectroscopies). It has been verified that despite their heterogeneity of structure and composition, they are all hypo-eutectoids steels that can contain phosphorous until 0.5 wt%. The corrosion products have been analysed by local structural analytical methods as micro-diffraction under synchrotron radiation ({mu}XRD) and Raman micro-spectroscopy. These two complementary techniques and also the elemental composition analysis conducted to the characterisation of the corrosion forms. On the majority of the samples coming from four sites, the DPL are constituted by goethite including marbles of magnetite/maghemite. On the artefacts from the fifth site, a particular corrosion form has been

  9. A novel Fe–Cr–Nb matrix composite containing the TiB{sub 2} neutron absorber synthesized by mechanical alloying and final hot isostatic pressing (HIP) in the Ti-tubing

    Energy Technology Data Exchange (ETDEWEB)

    Litwa, Przemysław [Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Perkowski, Krzysztof [Department of Nanotechnology, Institute of Ceramics and Building Materials, Postępu 9, 02-676 Warsaw (Poland); Zasada, Dariusz [Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Kobus, Izabela; Konopka, Gustaw [Department of Nanotechnology, Institute of Ceramics and Building Materials, Postępu 9, 02-676 Warsaw (Poland); Czujko, Tomasz [Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland); Varin, Robert A., E-mail: robert.varin@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave., Waterloo, ON N2L 3G1 (Canada)

    2016-07-25

    The Fe–Cr–Ti-Nb elemental powders were mechanically alloyed/ball milled with TiB{sub 2} and a small quantity of Y{sub 2}O{sub 3} ceramic to synthesize a novel Fe-based alloy-ceramic powder composite that could be processed by hot isostatic pressing (HIP) for a perceived potential application as a neutron absorber in nuclear reactors. After ball milling for the 30–80 h duration relatively uniform powders with micrometric sizes were produced. With increasing milling time a fraction of TiB{sub 2} particles became covered with the much softer Fe-based alloy which resulted in the formation of a characteristic “core-mantel” structure. For the final HIP-ing process the mechanically alloyed powders were initially uniaxially pressed into rod-shaped compacts and then cold isostatically pressed (CIP-ed). Subsequently, the rod-shaped compacts were placed in the Ti-tubing and subjected to hot isostatic pressing (HIP) at 1150 °C/200 MPa pressure. The HIP-ing process resulted in the formation of the near-Ti and intermediate diffusional layers in the microstructure of HIP-ed samples which formed in accord with the Fe-Ti binary phase diagram. Those layers contain the phases such as α-Ti (HCP), the FeTi intermetallic and their hypo-eutectoid mixtures. In addition, needle-like particles were formed in both layers in accord with the Ti-B binary phase diagram. Nanohardness testing, using a Berkovich type diamond tip, shows that the nanohardness in the intermediate layer areas, corresponding to the composition of the hypo-eutectoid mixture of Ti-FeTi, equals 980.0 (±27.1) HV and correspondingly 1176.9 (±47.6) HV for the FeTi phase. The nanohardness in the sample's center in the areas with the fine mixture of Fe-based alloy and small TiB{sub 2} particles equals 1048.3 (±201.8) HV. The average microhardness of samples HIP-ed from powders milled for 30 and 80 h is 588 HV and 733 HV, respectively. - Highlights: • A Fe–Cr–Nb-based composite with TiB{sub 2} neutron

  10. Solid state phase transition and vapor pressure studies in ammonium nitrate-potassium nitrate binary system

    Science.gov (United States)

    Chien, Wen-Ming

    The solid-state phase transitions in ammonium nitrate (NH4NO 3) and potassium nitrate (KNO3) solid solutions and the equilibrium NH4NO3-KNO3 (AN-KN) phase diagram have been determined. The phase transitions and phase diagram were determined by using the differential scanning calorimetry (DSC) and high temperature X-ray diffractometry. Samples of several different compositions were made for these analyses in a special "Dry Room" with very low humidity. In the X-ray diffraction experiments, the samples were heated on Pt-Rh strip and LaB6 or Si was added for internal calibration. Equilibrium phase diagram was also calculated by using the "FactSage" computer program. A single (AN III) phase region without any phase transitions between 293 to 373 K was observed for compositions between 5 to 25wt% KNO3 in NH4NO3 that is critical for air bag gas generators. The higher temperature KNO3 (KN I) phase has a wide stability range, from 100%KNO3 to 20%KNO3 solution. There is one eutectic, two eutectoids, and two peritectoids in this phase diagram. Two newly discovered solid-state phases were found in the mid-composition range of AN-KN solid solutions. Details of phase equilibria and lattice expansions during heating have been determined. Phase diagram calculations show a reasonable match of the phase boundaries. The total vapor pressures as well as the average molecular weights of pure ammonium nitrate and 16% KNO3 solid solution were measured at various temperatures by the torsion-Knudsen effusion method. The partial pressures of NH4NO3 (PNH4NO 3), NH3 (PNH3), and HNO3 (PHNO 3) have also been determined.

  11. TERMİT KAYNAĞI İLE BİRLEŞTİRİLEN BİR RAYIN KAYNAK BÖLGESİNDEKİ SERTLİK DAĞILIMI VE METALURJİK ÖZELLİKLERİ

    Directory of Open Access Journals (Sweden)

    Cevdet MERİÇ

    1998-02-01

    Full Text Available Demiryolu taşımacılığında konfor ve emniyete tesir eden faktörler arasında rayların döşenmesi önemli bir yer tutar. Uzun yıllardan beri bilinmekte olan termit kaynağı rayların çökmesini önler, trenin yoldan çıkmasına mani olur ve sarsıntısız bir yolculuk sağlar. Bununla birlikte rayların ve vagonların ömrünü uzatarak çeşitli ekonomik faydalar da temin eder. Bu çalışmada S 49 tipi St 70 çeliğinden imal edilmiş demiryolu rayları termit kaynağı ile birleştirilmiş olup, kaynak bölgesinin sertlik profili, çıkartılmış ve mikro yapısı incelenmiştir. İnceleme sonucunda çıkarılan sertlik profilinde ITAB (Isının Tesiri Altındaki Bölge'de maksimum sertlik değerleri kaynak bölgesinin hemen önünde de tesbit edilmiştir. Isıdan etkilenen bölgede, erime bölgesinin hemen önündeki sahada sertlik değeri 290 HB 5/750 iken, kaynak bölgesinde 260 HB ve ana yapıda ise 220 HB sertlik değerleri elde edilmiştir. Mikroyapı incelemesinde pro-eutectoid ferrit ile birlikte perlit ana yapı tesbit edilmiş, martersit oluşumuna rastlanılmamıştır.

  12. Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics

    Directory of Open Access Journals (Sweden)

    Klaus-Dieter Liss

    2016-07-01

    Full Text Available Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings.

  13. Fitful and protracted magma assembly leading to a giant eruption, Youngest Toba Tuff, Indonesia

    Science.gov (United States)

    Reid, Mary R; Vazquez, Jorge A.

    2017-01-01

    The paroxysmal eruption of the 74 ka Youngest Toba Tuff (YTT) of northern Sumatra produced an extraordinary 2800 km3 of non-welded to densely welded ignimbrite and co-ignimbrite ash-fall. We report insights into the duration of YTT magma assembly obtained from ion microprobe U-Th and U-Pb dates, including continuous age spectra over >50% of final zircon growth, for pumices and a welded tuff spanning the compositional range of the YTT. A relatively large subpopulation of zircon crystals nucleated before the penultimate caldera-related eruption at 501 ka, but most zircons yielded interior dates 100-300 ka thereafter. Zircon nucleation and growth was likely episodic and from diverse conditions over protracted time intervals of >100 to >500 ka. Final zircon growth is evident as thin rim plateaus that are in Th/U chemical equilibrium with hosts, and that give crystallization ages within tens of ka of eruption. The longevity and chemical characteristics of the YTT zircons, as well as evidence for intermittent zircon isolation and remobilization associated with magma recharge, is especially favored at the cool and wet eutectoid conditions that characterize at least half of the YTT, wherein heat fluxes could dissolve major phases but have only a minor effect on larger zircon crystals. Repeated magma recharge may have contributed to the development of compositional zoning in the YTT but, considered together with limited allanite, quartz, and other mineral dating and geospeedometry, regular perturbations to the magma reservoir over >400 ka did not lead to eruption until 74 ka ago.

  14. Investigation of phase transformations of U2.5Zr7.5Nb and U3Zr9Nb alloys aging at 600 deg C

    Energy Technology Data Exchange (ETDEWEB)

    Cantagalli, Natalia Mattar; Tanure, Leandro Paulo de Almeida Reis; Braga, Daniel Martins; Santos, Ana Maria Matildes dos; Ferraz, Wilmar Barbosa [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)], e-mail: ferrazw@cdtn.br

    2009-07-01

    Investigation has been made of the effects of high-temperature aging (600 deg C) on the phase transformations in the U2.5Zr7.5Nb and U3Zr9Nb alloys. These alloys have been produced with vacuum induction melting (VIM) furnace in cast ingots. The ingots were homogenized at 1000 deg C for 24 hours in vacuum of < 10{sup -4} torr, and cooled to room temperature at a rate of 3 deg C/min. Specimens from these homogeneous materials, cut in 3 mm high and 10 mm diameter, were reheated to {gamma} phase at 850 deg C, for 1 hour, and aging at 600 deg C at different times from 0.5 to 24 hours. The phases decomposition were characterized by X-ray diffraction (XRD), metallographic, micro-probe analyze by energy dispersive spectrometry (EDS) and microhardness methods. It was verified that the decomposition of the {delta} phase proceeds in two steps. The first is a discontinuous precipitation of a lamellar two-phase aggregate composed of alpha solid solution and a metastable gamma phase. The metastable gamma phase has a constant composition at given temperature. After longer annealing, it decomposes eutectoidally into the equilibrium ({alpha} + {delta}{sub 2}) phases mixture. During this process a modification of the original lamellar microstructure takes place. The obtained metastable phases of these alloys of different compositions were analyzed in relation to their constitution, heat treatability and micrographic features and the results confronted with available distinct uranium alloys data from literature. (author)

  15. Phase transformations of (Ca, Ti)-partially stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Hon Yungshon; Shen Pouyan (Inst. of Materials Science and Engineering, Nation Sun Yat-Sen Univ., Kaohsiung (Taiwan))

    1991-01-20

    The results of phase transformation and microstructural investigation of the ZrO{sub 2}-rich corner of the CaO-TiO{sub 2}-ZrO{sub 2} system are reported. Samples of Ca-PSZ powder (where PSZ is partially stabilized zirconia) containing 10.8 mol.% CaO, had added to them 0-14 mol.% TiO{sub 2} (designated specimens 0T to 14T). The samples were sintered at 1600deg C for 6 h and studied by X-ray diffraction and electron microscopy. Saturation of TiO{sub 2} in the cubic (c) zirconia was reached at a total TiO{sub 2} addition of about 4 mol.% at 1600deg C, whereas the solubility limit in tetragonal (t) zirconia was not reached in the composition range studied. The t-zirconia precipitates remained tweed in the cubic matrix for specimens 2T and 4T, but became lenticular with the (101) habit plane for specimens having a larger TiO{sub 2} content (e.g. 8T). The amount of t-zirconia increased with increasing TiO{sub 2} content at 1600deg C. The addition of TiO{sub 2} also enhanced the eutectoid decomposition of Ca-PSZ to form the PHI{sub 1}-phase (CaZr{sub 4}O{sub 9}). Calzirtite (Ca{sub 2}Zr{sub 5}Ti{sub 2}O{sub 16}) was precipitated from the shell of the zirconia grains in specimen 8T. (orig.).

  16. THERMODYNAMICS AND KINETICS OF PHASE TRANSFORMATIONS IN PLUTONIUM ALLOYS - PART I

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P A; Kaufman, L; Liu, Z; Zhou, S

    2004-08-18

    In this report we investigate order, stability, and phase transformations for a series of actinide-based alloys. The statics and kinetics of precipitation and ordering in this class of alloys are modeled with a scheme that couples fundamental information on the alloy energetics obtained from experimental and assessed thermo-chemical data to the CALPHAD approach commonly used in industry for designing alloys with engineering specificity with the help of the Thermo-Calc software application. The CALPHAD approach is applied to the study of the equilibrium thermodynamic properties of Pu-based alloys, Pu-X, where X=Al, Fe, Ga. The assessment of the equilibrium phase diagrams in the whole range of alloy composition has been performed with the PARROT module of the Thermo-Calc application software. Predictions are made on the low temperature and Pu-rich side of the phase diagrams of Pu-Ga and Pu-Al for which controversy has been noted in the past. The validity of the assessed thermo-chemical database will be discussed by comparing predicted heats of transformation for pure Pu with measured values from differential scanning calorimetry analysis. An overall picture for the stability properties of Pu-Ga and Pu-Al that reconciles the results of past studies carried out on these alloys is proposed. Results on phase stability in the ternary Fe-Ga-Pu and Al-Fe-Pu alloys are discussed. The information collected in this study is then used to model metastability, long-term stability and aging for this class of alloys by coupling Thermo-Calc with DICTRA, a series of modules that allow the analysis of DIffusion Controlled TRAnsformations. Kinetics information is then summarized in so-called TTT (temperature-time-transformations) diagrams for the most relevant phases of actinide alloys. Specifically, results are presented on kinetics of phase transformations associated with the eutectoid-phase decomposition reaction occurring at low temperature, and with the martensitic transformation