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Journal articles on the topic 'Retained austenite'

Author: Grafiati
Published: 4 June 2021
Last updated: 18 February 2022

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1

Kawasaki, Yoshiyasu, Yuki Toji, Yokota Takeshi, and Yoshimasa Funakawa. "Effects of Tensile Testing Temperature on Mechanical Properties and Deformation Behavior in Medium Mn Steels." Materials Science Forum 1016 (January 2021): 1823–29. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1823.

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In single-phase austenitic steels, the optimum deformation temperature in the tensile test to obtain high tensile strength-elongation balance (TS×El) and work hardening rate (dσ/dε) depends on control of the stability of austenite. In order to clarify the effects of the deformation temperature in complex phase steels containing austenite, in this study, the effects of the tensile testing temperature on mechanical properties and deformation behavior were investigated in detail using steel A and steel B with a chemical composition of 0.15C-0.5Si-5.0Mn (wt%). Steels A and B consisted of ferrite and retained austenite, but contained different volume fractions of retained austenite, namely, 29 % and 17 % as a result of annealing at 660 °C and 620 °C for 2 h, respectively. The stability of the retained austenite of steel B was higher than that of steel A. In steel A, TS×El and dσ/dε achieved their maximum values at 20 °C, decreased from 20 to 100 °C, and then remained almost unchanged at more than 150 °C. On the other hand, in steel B, TS×El and dσ/dε achieved their maximum values at -40 °C, decreased from -40 to 50 °C and remained almost unchanged at more than 100 °C. These results can be explained by the stability of retained austenite and the transformation rate from retained austenite to martensite. It should be noted that control of the stability of retained austenite and the transformation rate from retained austenite to martensite led to an adjustment of the optimum deformation temperature to achieve the high TS×El and dσ/dε in medium Mn steels, in the same manner as in single-phase austenitic steels.
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2

Higuera-Cobos, Oscar Fabián, Florina-Diana Dumitru, and Dairo Hernán Mesa-Grajales. "Improvement of abrasive wear resistance of the high chromium cast iron ASTM A-532 through thermal treatment cycles." REVISTA FACULTAD DE INGENIERÍA 25, no. 41 (January 22, 2016): 93. http://dx.doi.org/10.19053/01211129.4141.

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<p>High-Chromium White Cast Iron is a material highly used in mining and drilling shafts for oil extraction, due to its high wear resistance. However, because of the austenitic matrix found in the as-cast state, an adequate heat treatment cycle is necessary. This paper studies the effects of different cooling media after a destabilization treatment on the microstructure, hardening and abrasion resistance behaviors of a hypoeutectic high chromium white cast iron. The results show that although air cooling followed by immersion in CO2 can effectively reduce the retained austenite, this is not enough to transform completely the retained austenite into martensite. The low retained austenite percentages improve bulk hardness, but they decrease the abrasion resistance of the high chromium cast iron. The best combination of hardness and wear resistance was found in the samples cooled in air, due to the percentage of retained austenite and a moderate precipitation of chromium carbide.</p>
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3

Sugimoto, Koh Ichi, Junya Kobayashi, Yuji Nakajima, and Takuya Kochi. "The Effects of Cooling Rate on Retained Austenite Characteristics of a 0.2C-1.5Si-1.5Mn-1.0Cr-0.05Nb TRIP-Aided Martensitic Steel." Materials Science Forum 783-786 (May 2014): 1015–20. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1015.

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With the aim of increasing the volume fraction and stability of the retained austenite characteristics in a transformation-induced plasticity (TRIP)-aided steel with wider lath-martensite structure matrix, the effects of varying the post-hot-working cooling rate of a 0.2%C-1.5%Si-1.5%Mn-1.0%Cr-0.05%Nb (mass%) steel on the retained austenite characteristics were investigated. When, after hot-working at 950°C, the steel was cooled to room temperature from 430°C above the martensite-start temperature using cooling rates lower than 3°C/s, the steel attained a higher volume fraction of metastable retained austenite and lower volume fractions of a finely dispersed martensite-austenite complex phase, carbide, and pro-eutectoid ferrite, although the volume fraction of bainitic ferrite increased. This was associated with a marked carbon-enrichment in the untransformed austenite, which was mainly due to the promoted bainitic ferrite, the initial lath martensite, and the refined prior austenitic grain.
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4

Matsuda, Hiroshi, Hisata Noro, Yasunobu Nagataki, and Yoshihiro Hosoya. "Effect of Retained Austenite Stability on Mechanical Properties of 590MPa Grade TRIP Sheet Steels." Materials Science Forum 638-642 (January 2010): 3374–79. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3374.

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Industrial low alloy TRIP sheet steels contain blocky and lath-shaped retained austenite. In the present study, transformation behaviour of blocky and lath-shaped retained austenite during straining was investigated to clarify its effect on mechanical properties. Two types of TRIP steels containing almost the same amount but the different morphology of retained austenite were used. A steel containing large amount of lath-shaped retained austenite exhibits superior ductility, and sustains high work-hardenability in a high strain region. On the contrast, a steel containing large amount of blocky retained austenite exhibits low ductility. The work-hardenability increased steeply to the maximum at a low strain region, and then reduced in a high strain region. The stability of the blocky austenite has been found to be poor with respected to martensite transformation. The lath-shaped retained austenite remains until a high strain region whereas the blocky retained austenite transformed into martensite in a low strain region. Carbon content was higher in the lath-shaped retained austenite than in the blocky retained austenite. Stability of retained austenite is, however, inexplicable only by the carbon content, and would be affected by the different morphology and the resulting restraint conditions.
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5

Ravi Kumar, B. "Progress of Recrystallisation in Cold Rolled Austenitic Stainless Steel during Cyclic Thermal Process." Materials Science Forum 702-703 (December 2011): 627–30. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.627.

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The present study aims to understand the evolution of microstructure leading to nano/ultrafine grain formation during cyclic thermal process. A commercial grade of AISI 304L austenitic SS was cold rolled which resulted in a creation of a dual microstructure having strain induced martensite (43%) and heavily deformed retained austenite. The dual phase microstructure was subjected to cyclic thermal annealing process at 825 °C. The events occurring in; a) retained austenite and b) reverted austenite formed by phase reversion of strain induced martensite, during annealing treatment, were studied by the Electron backscattered diffraction (EBSD). The study revealed recrystallisation process of the two austenite grains, which resulted into ultrafine grain formation during cyclic thermal process.
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6

Zhuang, Bao Tong, Hai Tao Jiang, Di Tang, Zhen Li Mi, and Zhen Kuai. "Study of Retained Austenite in Q&P Steel for Automobile." Advanced Materials Research 482-484 (February 2012): 1436–41. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1436.

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Retained austenite of Q&P (Quenching and Partitioning) processed 0.2C-1.51Si-1.84Mn steel heated in intercritical region and full austenite region are investigated. The results show that the maximum volume fraction of retained austenite heated in intercritical and full austenite region is 13.39% and 5.23% respectively. Carbon partitioning completed within 10 s for both heating modes. The microstructure after full austenitization consisted of martensite laths and thin, inter-lath retained austenite film. Austenite blocks is observed as well after partial austenitization.The distribution of retained austenite is related to the amount of grain boundaries by EBSD techniques.
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7

Grajcar, Adam, Krzysztof Radwański, and Hanna J. Krztoń. "Microstructural Analysis of a Thermomechanically Processed Si-Al TRIP Steel Characterized by EBSD and X-Ray Techniques." Solid State Phenomena 203-204 (June 2013): 34–37. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.34.

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The work focuses on the analysis of microstructural features of retained austenite in a thermomechanically processed Si-Al TRIP-type steel microalloyed with Nb and Ti. Austenite amount was determined using XRD and EBSD. Combined methods of LM, SEM and EBSD were applied to reveal the morphology, grain size and distribution of structural constituents. It is possible to retain 14% of  phase enriched in C to about 1.14 wt.%. Retained austenite is uniformly located as blocky grains with a diameter up to 4.5 m in a fine-grained ferritic matrix or between bainitic ferrite laths as thin layers. Special crystallographic relationships between bainitic ferrite and retained austenite were identified on the basis of the analysis of misorientation angles and image quality values.
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8

Haidemenopoulos, G. N., M. Grujicic, G. B. Olson, and Morris Cohen. "Transformation microyielding of retained austenite." Acta Metallurgica 37, no. 6 (June 1989): 1677–82. http://dx.doi.org/10.1016/0001-6160(89)90134-x.

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9

Yin, Yun Yang, Fang Fang, Wei Chen, and Yong Tao Fu. "Effect of Thermomechanical Parameters on the Microstructure and Retained Austenite Characteristics in a Hot-Rolled TRIP Steel." Advanced Materials Research 295-297 (July 2011): 1294–99. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.1294.

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The influence of thermomechanical parameters on the microstructure and retained austenite characteristics in a hot rolled Al-Si-Mn transformation induced plasticity (TRIP) steel based on dynamic transformation of undercooled austenite was investigated, in an effort to produce a desired microstructure and better control retained content. The results show that strain rate had a minor effect on the microstructure, but the volume fraction of retained austenite decreased with increasing strain rate. Decreasing coiling temperature caused a decrease in volume fraction of retained austenite and decrease in the size of bainitic ferrite platelets. Increasing the isothermal holding time during bainite treatment, the volume fraction of retained austenite first gradually increased then decreased. Moreover, The deformation of undercooled austenite not only can influenc the transformation of bainite, but also can refine the grain size of bainite, increase the chemical and mechanical stabilization of retained austenite.
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10

Hell, Jean Christophe, Moukrane Dehmas, Guillaume Geandier, Nathalie Gey, Sebastien Allain, Alain Hazotte, and Jean Philippe Chateau. "Influence of the Austempering Temperature on the Microstructure and Crystallography of a Carbide-Free Bainitic Steel." Solid State Phenomena 172-174 (June 2011): 797–802. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.797.

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We elaborated two carbide-free bainitic steels with different microstructures through specific heat treatments and alloy design. EBSD analysis was used to point out major differences in these microstructures. In-situ characterizations of the bainitic transformation were performed by high energy synchrotron diffraction to go further into the study of each phase characteristics. The elaborated microstructures exhibited various phase fractions of bainitic ferrite, retained austenite and blocks of martensite and retained austenite. Moreover, the volume fraction of retained austenite increased with higher austempering temperatures. On the other hand, the austempering temperatures showed a strong influence on the kinetics of the bainitic transformation. Isothermal transformation under Ms showed a two stage transformation which led first to the formation of self-tempered martensite and then to bainitic ferrite. Furthermore, the evolution of the austenitic cell parameter showed enrichment in carbon ruled by diffusional mechanisms.
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11

Wang, Bin, Yanping He, Ye Liu, Yong Tian, Jinglin You, Zhaodong Wang, and Guodong Wang. "Mechanism of the Microstructural Evolution of 18Cr2Ni4WA Steel during Vacuum Low-Pressure Carburizing Heat Treatment and Its Effect on Case Hardness." Materials 13, no. 10 (May 20, 2020): 2352. http://dx.doi.org/10.3390/ma13102352.

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In this study, vacuum low-pressure carburizing heat treatments were carried out on 18Cr2Ni4WA case-carburized alloy steel. The evolution and phase transformation mechanism of the microstructure of the carburized layer during low-temperature tempering and its effect on the surface hardness were studied. The results showed that the carburized layer of the 18Cr2Ni4WA steel was composed of a large quantity of martensite and retained austenite. The type of martensite matrix changed from acicular martensite to lath martensite from the surface to the core. The hardness of the carburized layer gradually decreased as the carbon content decreased. A thermodynamic model was used to show that the low-carbon retained austenite was easier to transform into martensite at lower temperatures, since the high-carbon retained austenite was more thermally stable than the low-carbon retained austenite. The mechanical stability—not the thermal stability—of the retained austenite in the carburized layer dominated after carburizing and quenching, and cryogenic treatment had a limited effect on promoting the martensite formation. During low-temperature tempering, the solid-solution carbon content of the martensite decreased, the compressive stress on the retained austenite was reduced and the mechanical stability of the retained austenite decreased. Therefore, during cooling after low-temperature tempering, the low-carbon retained austenite transformed into martensite, whereas the high-carbon retained austenite still remained in the microstructure. The changes in the martensite matrix hardness had a far greater effect than the transformation of the retained austenite to martensite on the case hardness of the carburized layer.
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12

Wang, Kai Kai, Zhun Li Tan, Gu Hui Gao, Xiao Lu Gui, and Bing Zhe Bai. "Effect of Retained Austenite Stability on Mechanical Properties of Bainitic Rail Steel." Advanced Materials Research 1004-1005 (August 2014): 198–202. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.198.

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Retained austenite has an important effect on strength and toughness of 20Mn2SiCrMo bainitic rail steel. In this work, the stability of retained austenite and mechanical properties have been studied. The results show that impact toughness of experimental steel has close relationship with the stability of retained austenite. When tempered at lower than 350°C, retained austenite owns good thermal stability, corresponding to relatively high impact toughness.
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13

Xu, Xin, Ren Dong Liu, Bao Yu Xu, Hong Liang Yi, and Guo Dong Wang. "Effect of Annealing Temperature on Austenite Stability of a δ-TRIP Steel." Key Engineering Materials 818 (August 2019): 82–86. http://dx.doi.org/10.4028/www.scientific.net/kem.818.82.

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In this work, a novel type of δ-TRIP steel was designed, and the content and stability of retained austenite in δ-TRIP specimens under different annealing processes were detected and studied, respectively. The volume fraction of austenite was determined by X-ray diffraction (XRD). The microstructure and mechanical properties were analyzed systematically. The results show that a complex microstructure composed of three phases (ferrite, bainite and retained austenite) was obtained in the δ-TRIP steel. With the increasing of annealing temperature, both retained austenite and bainite content in the specimen increased, while the carbon content in retained austenite decreased, leading to a poor stability for retained austenite. Both tensile and yield strength improved with the increasing of annealing temperature, while the elongation reduced. The feature of retained austenite led to an excellent combination of ductility and strength, which was better than traditional TRIP steel.
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14

Kwon, Eui Pyo, Shun Fujieda, Kozo Shinoda, and Shigeru Suzuki. "Effect of Phosphorus on Microstructure, Mechanical Properties, and Formation of Retained Austenite in TRIP Steels." Key Engineering Materials 508 (March 2012): 128–32. http://dx.doi.org/10.4028/www.scientific.net/kem.508.128.

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In this Study, Influences of P on the Microstructure, Mechanical Properties, and Retained Austenite Characteristics in Transformation Induced Plasticity (TRIP) Steels Were Investigated. Microstructure of 0.2mass%P Containing TRIP Steel Was Inhomogeneous and it Resulted in Deterioration of the Mechanical Properties. Retained Austenite Characteristics such as Volume Fraction and Carbon Concentration Were Also Affected by P. The Stability of Retained Austenite in P Containing TRIP Steel Was Different from that in P-Free TRIP Steel. Such Difference in the Stability of Retained Austenite Was Attributed to the Effect of the Carbon Concentration in Retained Austenite as Well as their Different Microstructure.
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15

Olina, Anna, Miroslav Píška, Martin Petrenec, Charles Hervoches, Přemysl Beran, Jiří Pechoušek, and Petr Král. "Assessment of Retained Austenite in Fine Grained Inductive Heat Treated Spring Steel." Materials 12, no. 24 (December 5, 2019): 4063. http://dx.doi.org/10.3390/ma12244063.

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Advanced thermomechanical hot rolling is becoming a widely used technology for the production of fine-grained spring steel. Different rapid phase transformations during the inductive heat treatment of such steel causes the inhomogeneous mixture of martensitic, bainitic, and austenitic phases that affects the service properties of the steel. An important task is to assess the amount of retained austenite and its distribution over the cross-section of the inductive quenched and tempered wire in order to evaluate the mechanical properties of the material. Three different analytical methods were used for the comparative quantitative assessment of the amount of retained austenite in both the core and rim areas of the sample cross-section: neutron diffraction—for the bulk of the material, Mössbauer spectroscopy—for measurement in a surface layer, and the metallographic investigations carried by the EBSD. The methods confirmed the excessive amount of retained austenite in the core area that could negatively affect the plasticity of the material.
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16

Emadoddin, E., A. Akbarzadeh, R. Petrov, L. Kestens, and H. Pirgazi. "Influence of cold-rolling reduction on retained austenite texture in cold-rolled and intercritically annealed TRIP-assisted steel." Journal of Applied Crystallography 44, no. 6 (November 12, 2011): 1190–97. http://dx.doi.org/10.1107/s0021889811041069.

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The newly developed multiphase transformation-induced plasticity (TRIP) steels are of interest for industrial applications because of their excellent combination of high strength and ductility. Their performance can be successfully controlled by designing an optimum balance in the volume fractions of ferrite, bainite and retained austenite. The characteristics of the retained austenite are considered to be the main key to achieving the desired final properties. Against this background, the effects of retained austenite characteristics, such as volume fraction, carbon concentration, size and shape, on the behaviour of TRIP steels have been studied. The crystallographic orientation of the retained austenite was measured by electron backscattered diffraction (EBSD). The effect of initial cold-rolling reduction on the microtexture development of the retained austenite was studied on an aluminium-containing TRIP steel. The results show that, by increasing the cold-rolling reduction before the final austempering, the main components of the face-centred cubic phase,i.e.copper, brass and Goss, dominate the texture of the retained austenite. In contrast, the copper and Goss components of the retained austenite are absent in the texture of lightly deformed sheets. The features of the preferred orientation of the retained austenite are discussed and explained in terms of the annealing texture of the recrystallized ferrite and bainite.
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17

Grajcar, Adam, Aleksandra Kozłowska, Krzysztof Radwański, and Adam Skowronek. "Quantitative Analysis of Microstructure Evolution in Hot-Rolled Multiphase Steel Subjected to Interrupted Tensile Test." Metals 9, no. 12 (December 3, 2019): 1304. http://dx.doi.org/10.3390/met9121304.

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A quantitative analysis of the microstructure evolution in thermomechanically processed Si-Al multiphase steel with Nb and Ti microadditions was performed in the study. The tendency of strain-induced martensitic transformation of retained austenite was analyzed during a tensile test interrupted at incremental strain levels. Optical micrographs and electron backscatter diffraction (EBSD) maps were obtained at each deformation step. The quantitative analysis of the martensitic transformation progress as a function of strain was performed. The results showed that the stability of retained austenite is mostly related to its grain size and morphology. Large, blocky-type grains of retained austenite located in a ferritic matrix easily transformed into martensite during an initial step of straining. The highest mechanical stability showed small austenitic grains and thin layers located in bainitic islands. It was found that the extent of martensitic transformation decreased as the deformation level increased.
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18

Wakita, Masayuki, Yoshitaka Adachi, and Yo Tomota. "Crystallography and Mechanical Properties of Ultrafine TRIP-Aided Multi-Phase Steels." Materials Science Forum 539-543 (March 2007): 4351–56. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4351.

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This study aims at examining thermomechanical controlled process to realize ultrafine TRIP-aided multi-phase microstructures in low carbon steels. Heavy deformation at a supercooled austenite region was found to lead the formation of 2 μm ferrite as well as retained austenite with high volume fraction. The morphology of retained austenite was changed from film-like shape to granular shape with lowering finish rolling temperature in austenite field. This ultrafine TRIP-aided multi-phase steel showed good balance of tensile strength with total elongation, ie. 1080MPa and 26.9%. A novel in-situ neutron diffraction measurement demonstrated that the retained granular austenite transformed to martensite at a relatively large strain compared with the retained film austenite. The therein-underlying mechanism of the good mechanical properties was discussed from the view points of the morphological and thermodynamical stabilization of retained austenite.
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19

Landesberger, Martin, Robert Koos, Michael Hofmann, Xiaohu Li, Torben Boll, Winfried Petry, and Wolfram Volk. "Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content." Materials 13, no. 22 (November 21, 2020): 5266. http://dx.doi.org/10.3390/ma13225266.

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The phase transformation to ausferrite during austempered ductile iron (ADI) heat treatment can be significantly influenced by the alloying element Mo. Utilizing neutron diffraction, the phase transformation from austenite to ausferrite was monitored in-situ during the heat treatment. In addition to the phase volume fractions, the carbon enrichment of retained austenite was investigated. The results from neutron diffraction were compared to the macroscopic length change from dilatometer measurements. They show that the dilatometer data are only of limited use for the investigation of ausferrite formation. However, they allow deriving the time of maximum carbon accumulation in the retained austenite. In addition, the transformation of austenite during ausferritization was investigated using metallographic methods. Finally, the distribution of the alloying elements in the vicinity of the austenite/ferrite interface zone was shown by atom probe tomography (APT) measurements. C and Mn were enriched within the interface, while Si concentration was reduced. The Mo concentration in ferrite, interface and austentite stayed at the same level. The delay of austenite decay during Stage II reaction caused by Mo was studied in detail at 400 °C for the initial material as well as for 0.25 mass % and 0.50 mass % Mo additions.
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20

Hu, Jun, Wen Quan Cao, Jie Shi, and Han Dong. "Study on the Mechanical Stability of Retained Austenite in Cold-Rolled Medium-Mn Steel." Advanced Materials Research 936 (June 2014): 1283–89. http://dx.doi.org/10.4028/www.scientific.net/amr.936.1283.

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The mechanical stability of the retained austenite in the cold-rolled medium-Mn steel was studied. Tensile tests were carried out to measure the mechanical properties of the annealed steel. Scanning electron microscopy was applied to characterize the microstructure evolution during the tensile process; X-ray diffraction analysis was used to determine the residual austenite content in the deformed steel. It was found that the volume fraction of retained austenite gradually decreases with strain .The value of the stability coefficient of retained austenite k was small in the test steel, which indicated high mechanical stability of retained austenite. Due to TRIP effect, the high mechanical stability of the retained austenite strongly delays the onset of necking, which resulted in good comprehensive mechanical properties with ultrahigh strength and plasticity.
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21

Goryany, Vyacheslav, Eckart Hofmann, and Josef Mauk. "Influence of cooling conditions and amount of retained austenite on the fracture of austempered ductile iron." Journal of the Serbian Chemical Society 73, no. 1 (2008): 113–19. http://dx.doi.org/10.2298/jsc0801113g.

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SEM Analysis of fracture surfaces from tensile test specimens of thick-walled, austempered ductile irons (diameter 160 mm) shows different fracture behavior depending on the austenite retained in the matrix. The results show ductile fractures only in areas containing retained austenite sections. In section areas without or with a very low content of retained austenite, only brittle fracture without any plastic deformation occurs. The content of retained austenite determines the amount of ductile fracture in the microstructure.
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22

Xie, Zhenjia, Lin Xiong, Gang Han, Xuelin Wang, and Chengjia Shang. "Thermal Stability of Retained Austenite and Properties of A Multi-Phase Low Alloy Steel." Metals 8, no. 10 (October 9, 2018): 807. http://dx.doi.org/10.3390/met8100807.

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In this work, we elucidate the effects of tempering on the microstructure and properties in a low carbon low alloy steel, with particular emphasis on the thermal stability of retained austenite during high-temperature tempering at 500–700 °C for 1 h. Volume fraction of ~14% of retained austenite was obtained in the studied steel by two-step intercritical heat treatment. Results from transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated that retained austenite had high thermal stability when tempering at 500 and 600 °C for 1 h. The volume fraction was ~11–12%, the length and width remained ~0.77 and 0.21 μm, and concentration of Mn and Ni in retained austenite remained ~6.2–6.6 and ~1.6 wt %, respectively. However, when tempering at 700 °C for 1 h, the volume fraction of retained austenite was decreased largely to ~8%. The underlying reason could be attributed to the growth of austenite during high-temperature holding, leading to a depletion of alloy contents and a decrease in stability. Moreover, for samples tempered at 700 °C for 1 h, retained austenite rapidly transformed into martensite at a strain of 2–10%, and a dramatic increase in work hardening was observed. This indicated that the mechanical stability of retained austenite decreased.
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23

Zhang, Yucheng, Ping Lai, Huiping Jia, Xinhua Ju, and Guibin Cui. "Investigation of Test Parameters on EBSD Analysis of Retained Austenite in TRIP and Pipeline Steels." Metals 9, no. 1 (January 16, 2019): 94. http://dx.doi.org/10.3390/met9010094.

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In this article we discuss the effect of different test parameters on the analysis of retained austenite in TRIP590, TRIP780 and X90 steels, by means of Electron Backscattered Diffraction (EBSD) and X-ray Diffraction (XRD), respectively. By analyzing the measuring retained austenite content under different conditions, the optimal test parameters were obtained. The retained austenite content measured both by the EBSD and XRD methods were also compared. The results showed that the test parameters had a great influence on the measured results of retained austenite content in steel by the EBSD method. The higher the indexing rate, the better the precision of the measured results. The step size used for EBSD analysis should not exceed 1/5 of the average grain size of retained austenite. The scanning area for EBSD retained austenite analysis in TRIP and pipeline steels should be no less than 0.068 mm2, which is recommended to be performed by multiple small fields.
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24

Zhao, L., Niels H. van Dijk, E. R. Peekstok, Ojin Tegus, Ekkes Brück, and Jilt Sietsma. "Size Distribution of Retained Austenite in Phosphorus-Containing TRIP Steels." Materials Science Forum 539-543 (March 2007): 4321–26. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4321.

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The present work investigates the influence of phosphorus addition on the size distribution of retained austenite in TRIP steels containing 0.01%, 0.09% and 0.14% phosphorus. The size of retained austenite is measured by means of neutron depolarization technique and optical microscopy. It is found that the addition of phosphorous increases the size of the larger intergranular and inter-ferritic austenite grains and therefore also increases the volume fraction of retained austenite due to the strengthening effect of phosphorous on the surrounding ferrite and bainite grains. For all phosphorous additions the most frequently observed austenite size is around 0.2 μm, which is probably corresponds to the interlath film-type retained austenite. The average grain size from the neutron depolarization technique agrees in general with that from the optical microscopy and it is suggested that the accuracy can be improved by further development of the data analysis by taking into account the preferred shape and orientation of the austenite grains.
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25

Murakami, Toshio. "Effects of Retained Austenite Conditions on the Ductility of the Advanced High Strength Steels." Materials Science Forum 1016 (January 2021): 984–89. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.984.

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It was investigated that the effects of retained austenite (γR) conditions on ductility of advanced high strength steels for automotives. 0.4mass% C steels were heattreated in various austemper conditions to control the retained austenite conditions. In the result of the evaluation of mechanical properties of these steels, it was confirmed there were steels which indicated different elongation even if they had almost same volume fraction and carbon content of retained austenite. In order to clarify the reason, the conditions of retained austenite and work hardening behavior were investigated in detail. It was indicated that the existence of high carbon content region in a part of retained austenite promoted the deformation induced martensitic transformation in the high strain range and improved the elongation of AHSS.
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26

Grajcar, A., A. Kilarski, K. Radwanski, and R. Swadzba. "Microstructural Features of Strain-Induced Martensitic Transformation in Medium-Mn Steels with Metastable Retained Austenite/ Cechy Mikrostrukturalne Indukowanej Odkształceniem Przemiany Martenzytycznej W Stalach Sredniomanganowych Z Metastabilnym Austenitem Szczątkowym." Archives of Metallurgy and Materials 59, no. 4 (December 1, 2014): 1673–78. http://dx.doi.org/10.2478/amm-2014-0283.

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Abstract The work addresses relationships between the microstructure evolution and mechanical properties of two thermomechanically processed bainitic steels containing 3 and 5% Mn. The steels contain blocky-type and interlath metastable retained austenite embeded between laths of bainitic ferrite. To monitor the transformation behaviour of retained austenite into strain-induced martensite tensile tests were interrupted at 5%, 10%, and rupture strain. The identification of retained austenite and strain-induced martensite was carried out using light microscopy (LM), scanning electron microscopy (SEM) equipped with EBSD (Electron Backscatter Diffraction) and transmission electron microscopy (TEM). The amount of retained austenite was determined by XRD. It was found that the increase of Mn addition from 3 to 5% detrimentally decreases a volume fraction of retained austenite, its carbon content, and ductility.
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27

Smith, Ali. "Hydrogen Embrittlement and Hydrogen Trapping Behaviour in Advanced High Strength Steels." Materials Science Forum 1016 (January 2021): 1344–49. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.1344.

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Modern advanced high strength steels (AHSS) for the automotive sector often contain retained austenite which promotes remarkable combinations of strength and ductility. These high strength steels may however be subject to a risk of hydrogen embrittlement. For the current contribution, hydrogen trapping and embrittlement behaviour were investigated in AHSS compositions having different levels of retained austenite. Hydrogen permeation tests revealed that hydrogen diffusion was slower for increased levels of retained austenite, being controlled most likely by reversible trapping at austenite-matrix interfaces. External hydrogen embrittlement tests via step loading also revealed that resistance to hydrogen was lower for increased levels of retained austenite. It was suggested that during step loading the hydrogen accumulated at austenite-matrix interfaces, leading to cracking when the applied stress was high enough.
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28

Katemi, Richard J., and Jeremy Epp. "Influence of Tempering and Cryogenic Treatment on Retained Austenite and Residual Stresses in Carbonitrided 18CrNiMo7-6 Low Alloy Steel." Tanzania Journal of Engineering and Technology 38, no. 1 (June 30, 2019): 71–82. http://dx.doi.org/10.52339/tjet.v38i1.497.

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This work investigated the influence of tempering conditions coupled with cryogenic treatment on thermal stabilization of retained austenite and residual stress distributions in carbonitrided 18CrNiMo76 low alloy steel samples. The carbonitriding conditions were set to enable attaining surface carbon and nitrogen content of 0.87 and 0.34 mass.-percent respectively. After carbonitriding, some of the samples were subjected to varying tempering conditions followed by cryogenic treatment at -120 °C using nitrogen gas. Analysis of both retained austenite and residual stresses was conducted using X-ray diffraction. In the as-quenched state, carbonitrided samples contained 52 mass.-percent. Samples that were directly subjected to the cryogenic treatment after quenching retained only about 20 mass.-percent of austenite. Samples subjected to variant tempering conditions coupled with cryogenic treatment retained at least 30 masses.-percent of austenite. A thermal stabilization of retained austenite which increases with increasing temperature was identified. On tempering at 240°C for 14 hours retained austenite becomes unstable and decomposes to bainite leading to the low initial amount of retained austenite before cryogenic treatment. It can be concluded that the tempering process coupled with cryogenic treatment leads to an increasing hardness, to higher compressive residual stresses as well as to a shift of the location of maximum compressive residual stress toward the surface.
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29

Northwood, Derek O., Lily He, Erin Boyle, and Randy J. Bowers. "Retained Austenite - Residual Stress - Distortion Relationships in Carburized SAE 6820 Steel." Materials Science Forum 539-543 (March 2007): 4464–69. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4464.

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SAE 8620 steel is typically used in the carburized condition for powertrain applications in the automotive industry, e.g. gears, roller bearings, camshafts. Such steels always contain retained austenite to varying degrees in the as-hardened and also in the tempered microstructures. As well as retained austenite, heat treatment can produce residual stresses, which lead to distortion (size and shape). The intent of this study was to investigate the effect of heat treatment parameters on the amount of retained austenite, residual stress and distortion in carburized SAE 8620 steel. A specially designed specimen, the Navy C-ring, was used for this study. The steel was first normalized prior to machining the Navy C-ring specimens. The specimens were then heat treated by carburizing at 927°C or 954°C (1700°F or 1750°F) at four levels of carbon potential (0.9, 1.0, 1.1, 1.2) followed by oil quenching and tempering at either 149°C or 177°C (300°F or 350°F). The distortion of the C-ring was evaluated by dimensional measurements of the inner diameter, outer diameter, gap width and thickness for size distortion, as well as flatness, cylindricity and roundness for shape distortion. X-ray diffraction (XRD) techniques were used to determine the residual stress and the amount of retained austenite. The amount of retained austenite was also measured by optical metallography. The amount of retained austenite and the residual stress increased with increasing carburizing temperature and carbon potential and decreased upon tempering. There was not a significant further reduction in the amount of retained austenite and residual stress when the tempering temperature was increased from 149°C to 177°C. Distortion was influenced by both the amount of retained austenite and the magnitude of the residual stress. With increasing retained austenite/residual stress, the distortion became more serious. Based on the distortion data for 3 parameters (OD, gap width and flatness) for the quenched and tempered specimens, the amount of retained austenite for minimum distortion was approximately 25%.
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30

Kakefuda, Naoya, Shintaro Aizawa, Ryo Sakata, Junya Kobayashi, Goroh Itoh, and Tomohiko Hojo. "Effect of Cooling Rate below Ms Temperature on Hydrogen Embrittlement of TRIP-Aided Martensitic Steels." Materials Science Forum 1016 (January 2021): 654–59. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.654.

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Low alloy TRIP steel is expected to be applied to automobile bodies because of its high strength, high ductility, and excellent impact properties and press formability. It has been reported that the low alloy TRIP steel of hydrogen embrittlement resistance is improved by utilizing the hydrogen storage characteristics of highly stable retained austenite. Therefore, for the purpose of increasing the volume fraction of retained austenite, it was produced at various cooling rates below the martensite transformation start temperature. As a result, the volume fraction of retained austenite increased, and then the effect of hydrogen embrittlement decreased. The matrix phase and retained austenite is refined with decrees of the cooling rate. It is considered that the size and surface area of the retained austenite also affected the improvement of hydrogen embrittlement resistance.
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31

Lee, Hak Cheol, Xiao Dan Wu, Young Min Kim, and Nack J. Kim. "Effect of Second Phase on Mechanical Properties of Bainite-Base Steels." Advanced Materials Research 15-17 (February 2006): 780–85. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.780.

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Effects of acicular ferrite and retained austenite on the mechanical properties of bainite-base steels were investigated. Various morphology and volume fraction of constituent phases have been obtained by control of hot rolling conditions and alloy compositions. It has been shown that the steels containing retained austenite have better combinations of strength and ductility than the ones with no retained austenite. However, there is no noticeable change in DBTT by the incorporation of retained austenite in the microstructure since retained austenite exists as fine particles. On the other hand, DBTT of the steels are largely affected by the presence of acicular ferrite in the microstructure. EBSD analyses of fractured Charpy specimens show that cracks are deflected within the morphological packet of acicular ferrite, indicating its role in reducing the effective grain size of the steels.
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32

Pereloma, Elena V., Azdiar A. Gazder, and Ilana B. Timokhina. "Addressing Retained Austenite Stability in Advanced High Strength Steels." Materials Science Forum 738-739 (January 2013): 212–16. http://dx.doi.org/10.4028/www.scientific.net/msf.738-739.212.

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Advances in the development of new high strength steels have resulted in microstructures containing significant volume fractions of retained austenite. The transformation of retained austenite to martensite upon straining contributes towards improving the ductility. However, in order to gain from the above beneficial effect, the volume fraction, size, morphology and distribution of the retained austenite need to be controlled. In this regard, it is well known that carbon concentration in the retained austenite is responsible for its chemical stability, whereas its size and morphology determines its mechanical stability. Thus, to achieve the required mechanical properties, control of the processing parameters affecting the microstructure development is essential.
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33

Guo, Xu Hong, Chang Liu, and Quan Zhang. "The Heat Treatment Parameters and Microconstituent Content Prediction of ADI Based on Fuzzy Subtractive Clustering Method." Materials Science Forum 704-705 (December 2011): 586–91. http://dx.doi.org/10.4028/www.scientific.net/msf.704-705.586.

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Ductile cast iron was quenched at different austempering temperatures with different isothermal time, so there were austempered ductile iron (ADI) materials with nine different mechanical properties. Their metallographic structures were qualitatively and quantitatively analyzed with scanning electron microscope and X-ray diffraction method. Curves of the relationships between heat treatment parameters, content of retained austenite and carbon content in retained austenite were studied respectively. Models that showed their relationships were built in the base of fuzzy subtractive clustering method to research the rules of isothermal temperatures and time affecting the microconstituent of ADI. The results show that the metallographical matrix structures of ADI become ausferrite, and its mechanical properties are strengthened notably. From the curves and fuzzy models, we knew that the effect of austempering temperature on the component content of ADI was predominant, and austempering time was inferior. Thus, as the temperature increased, the content of retained austenite, carbon content in retained austenite increased markedly. Keywords: ADI, heat treatment parameters, retained austenite, carbon content of retained austenite, fuzzy subtractive clustering model
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34

Dong, Baoqi, Tingping Hou, Wen Zhou, Guohong Zhang, and Kaiming Wu. "The Role of Retained Austenite and Its Carbon Concentration on Elongation of Low Temperature Bainitic Steels at Different Austenitising Temperature." Metals 8, no. 11 (November 11, 2018): 931. http://dx.doi.org/10.3390/met8110931.

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The influence of austenitising temperature on the tensile properties of low temperature bainitic steel was investigated. With the increasing austenitising temperature, a significant change of elongation was found between 850 and 950 °C, which was changed from 1.0 ± 0.5 to 10.7 ± 2.0%; while there was a slight increase between 950 to 1050 °C (11.2 ± 1.5%). By characterising the retained austenite at necking and matrix, we found that the elongation is obviously correlated with the retained austenite content, and also determined by the volume change of retained austenite during the tensile test. The transformation induced plasticity (TRIP) effect, which contributes to the improve elongation, almost did not occur at 850 °C due to the relatively low volume percentage of retained austenite and its high carbon concentration, which resulted in a very low martensite transformation temperature. With the austenitising, the temperature was increased up to 950 and 1050 °C, and a large volume percentage of retained austenite was observed in the matrix. Meanwhile, a considerable amount of retained austenite has occurred by the TRIP effect because of a moderate carbon content.
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35

Zrník, Jozef, O. Muránsky, Petr Lukáš, Petr Šittner, and Z. Nový. "In Situ Neutron Diffraction Analysis of Phase Transformation Kinetics in TRIP Steel." Materials Science Forum 502 (December 2005): 339–44. http://dx.doi.org/10.4028/www.scientific.net/msf.502.339.

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The precise characterization of the multiphase microstructure of low alloyed TRIP steels is of great importance for the interpretation and optimisation of their mechanical properties. In-situ neutron diffraction experiment was employed for monitoring of conditioned austenite transformation to ferrite, and also for retained austenite stability evaluation during subsequent mechanical loading. The progress in austenite decomposition to ferrite is monitored at different transformation temperatures. The relevant information on the course of transformation is extracted from neutron diffraction spectra. The integrated intensities of austenite and ferrite neutron diffraction profiles over the time of transformation are then assumed as a measure of the volume fractions of both phases in dependence on transformation temperature. Useful information was also obtained on retained austenite stability in TRIP steel during mechanical testing. The in-situ neutron diffraction experiments were conducted at two different diffractometers to assess the reliability of neutron diffraction technique in monitoring the transformation of retained austenite during room temperature tensile test. In both experiments the neutron investigation was focused on the volume fraction quantification of retained austenite as well as on internal stresses rising in structure phases due to retained austenite transformation.
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36

Pashangeh, Shima, Hamid Reza Karimi Zarchi, Seyyed Sadegh Ghasemi Banadkouki, and Mahesh C. Somani. "Detection and Estimation of Retained Austenite in a High Strength Si-Bearing Bainite-Martensite-Retained Austenite Micro-Composite Steel after Quenching and Bainitic Holding (Q&B)." Metals 9, no. 5 (April 27, 2019): 492. http://dx.doi.org/10.3390/met9050492.

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To develop an advanced high strength steel with reasonable ductility based on low alloying concept as well as micro-composite microstructure essentially consisting of bainite, martensite and retained austenite, a Si-bearing, low alloy medium carbon sheet steel (DIN1.5025 grade) was subjected to typical quenching and bainitic holding (Q&B) type isothermal treatment in the bainitic region close to martensite start temperature (Ms) for different durations in the range 5s to 1h. While the low temperature bainite has the potential to provide the required high strength, a small fraction of finely divided austenite stabilized between the bainitic laths is expected to provide the desired elongation and improved work hardening. Various materials characterization techniques including conventional light metallography, field emission scanning electron microscopy FE-SEM, electron backscatter diffraction (EBSD), differential thermal analysis, X-ray diffraction (XRD) and vibrating sample magnetometry (VSM), were used to detect and estimate the volume fraction, size and morphology and distribution of retained austenite in the micro-composite samples. The results showed that the color light metallography technique using LePera’s etching reagent could clearly reveal the retained austenite in the microstructures of the samples isothermally held for shorter than 30s, beyond which an unambiguous distinction between the retained austenite and martensite was imprecise. On the contrary, the electron microscopy using a FE-SEM was not capable of identifying clearly the retained austenite from bainite and martensite. However, the EBSD images could successfully distinguish between bainite, martensite and retained austenite microphases with good contrast. Although the volume fractions of retained austenite measured by EBSD are in accord with those obtained by XRD and color light metallography, the XRD measurements showed somewhat higher fractions owing to its ability to acquisition and analyze the diffracted X-rays from very finely divided retained austenite, too. The differential thermal analysis and vibrating sample magnetometry techniques also confirmed the stabilization of retained austenite finely divided in bainite/martensite micro-composite microstructures. In addition, the peak temperatures and intensities corresponding to the decomposition of retained austenite were correlated with the related volume fractions and carbon contents measured by the XRD analysis.
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37

Ma, Yong Qing, Xiao Jing Zhang, Yu Fen Liang, and Guo Fang Liu. "A Study on Austenite Catalytic Cryogenic Treatment of Cr-W-Mo-V High Alloy Medium-Upper Carbon Steel." Advanced Materials Research 936 (June 2014): 1173–78. http://dx.doi.org/10.4028/www.scientific.net/amr.936.1173.

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The processing of austenite catalytic cryogenic treatment of two components of Cr-W-Mo-V high alloy medium-upper carbon steels and the effect on the retained austenite transformation and tempering hardness were studied in this paper. The results show that, the effect of austenite catalytic cryogenic treatment of Cr-W-Mo-V high alloy medium-upper carbon steel is better than that of direct cryogenic treatment after quenching, and the content of residual austenite reduced to below 5%, and the hardness improved by 1.5HRC than that of conventional quenching and tempering. The retained austenite catalytic temperature of Cr-W-Mo-V high alloy medium-upper carbon steel merely is higher than 10°C~20°C of the temperature for the highest tempering hardness. Catalytic temperature Tc can be determined by experimental method of conventional quenching and tempering of the steel, in which the microstructure feature is precipitation of M3C carbide particle of 0.01μm~0.03μm in martensite matrix, and the content of retained austenite decreases evidently. By cryogenic treatment after the austenite catalyzed the retained austenite of quenching are transformed into more martensite, and in the subsequent tempering processing the original quenching martensite and the martensite from retained austenite transformation almost will form synchronous precipitation hardening. Thus the tempering hardness improves evidently as well.
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38

Lan, Hui Fang, Xiang Hua Liu, and Lin Xiu Du. "Ultra-Hard Bainitic Steels Processed through Low Temperature Heat Treatment." Advanced Materials Research 156-157 (October 2010): 1708–12. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.1708.

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Relative high carbon steel bearing Cr and Mo with microstructure consisting of nanoscaled bainitic laths and certain amount of retained austenite was produced through the combination of rolling and isothermal/multi-step heat treatment at low temperatures. The effect of the heat treatment temperature, time and path on the volume fraction of retained austenite and the width of bainitic lath was investigated. Nanoindentation was applied to inspect the separate hardness of the tiny bainite and retained austenite for different heat treatment parameters. The results showed that bainitic lath treatedt at 250°C was much thinner than that at 300°C and the volume fraction of retained austenite changed with different heat treatment temperatures, time and paths. The nanohardness of the baintic lath and retained austenite also changed with the processing of both carbon partitioning and displacive transformation for different heat treatment paths.
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39

Grajcar, Adam, and Mateusz Morawiec. "Microstructure-Property Relationships in Medium-Mn Steels with Metastable Retained Austenite." Materials Science Forum 879 (November 2016): 619–24. http://dx.doi.org/10.4028/www.scientific.net/msf.879.619.

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The study addresses relationships between the microstructure and mechanical properties of thermomechanically processed carbide-free bainitic steels containing 3% and 5% Mn. A simulated thermomechanical processing using Gleeble equipment and thermomechanical hot strip rolling were applied to produce fine-grained mixtures of blocky-type and interlath metastable retained austenite embeded between bainitic ferrite laths. To monitor the transformation behaviour of retained austenite into strain-induced martensite interrupted tensile tests were applied. The identification of morphological features of retained austenite and strain-induced martensite was carried out using scanning electron microscopy (SEM) equipped with EBSD (Electron Backscatter Diffraction). The amount of retained austenite was determined by the EBSD technique. It was found that manganese content strongly affects mechanical stability of retained austenite resulting in a different degree of TRIP effect in the investigated alloys and subsequent mechanical properties of produced sheets.
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40

Su, Yang Yu, Liu Ho Chiu, Tao Liang Chuang, Chien Lung Huang, Cheng Yen Wu, and Kuan Chueh Liao. "Retained Austenite Amount Determination Comparison in JIS SKD11 Steel Using Quantitative Metallography and X-Ray Diffraction Methods." Advanced Materials Research 482-484 (February 2012): 1165–68. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1165.

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This research compares the difference in determining the austenite amount in SKD 11 tool steel using the micrographic method as opposed to the X-ray diffraction method. Calculating the amount of retained austenite in tool steel using X-ray diffraction analysis requires first taking off the primary carbide content. By etching the SKD11 specimen using Beraha’s CdS reagent, the retained austenite, martensite and carbide are shown as white, red and blue regions in the microstructure, respectively. With quantitative metallography, the retained austenite can be distinguished as separate micro-constituents and properly counted. However, the calculated values are lower than those acquired from the X-ray diffraction. It is more accurate to evaluate the amount of retained austenite with carbide by X-ray diffraction analysis.
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41

Larionov, V. P., Ya S. Semenov, and S. G. Kas'yanov. "M�ssbauer analysis of retained austenite." Journal of Applied Mechanics and Technical Physics 33, no. 3 (1992): 477–79. http://dx.doi.org/10.1007/bf00851748.

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42

Zrník, Jozef, Ondrej Muránsky, and Petr Sittner. "Deformation Behaviour of TRIP Steel Monitored by In Situ Neutron Diffraction." Advanced Materials Research 939 (May 2014): 25–30. http://dx.doi.org/10.4028/www.scientific.net/amr.939.25.

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The paper presents results ofin-situneutron diffraction experiments aimed on monitoring the phase evolution and load distribution in transformation induced plasticity (TRIP) steel when subjected to tensile loading. Tensile deformation behaviour of two TRIP-assisted multiphase steel with slightly different microstructures resulted from different thermo-mechanical treatments applied was investigated byin-situneutron diffraction. The steel with lower retained austenite volume fraction (fγ=0.04) and higher volume fraction of needle-like bainite in the α-matrix exhibits higher yield stress (sample B, 600MPa) but considerably lower elongation in comparison to the steel with higher austenite volume fraction (fγ=0.08), granular bainite and ferrite matrix (sample A, 500 MPa). The neutron diffraction results showed that the applied tensile load is redistributed at the yielding point in a way that the retained austenite bears a significantly larger load than the α-matrix during the TRIP steel deformation. Steel sample with higher volume fraction of retained austenite and less strong ferrite matrix proved to be a better TRIP steel with respect to strength, ductility and the side effect of the strain induced austenite-martensite transformation. The transforming retained austenite in time of loading provides potential for higher ductility of experimental TRIP steel but at the same time acts as a reinforcement phase during the further plastic deformation.TRIP steel, austenite conditioning, austenite transformation, structure, retained austenite, tensile deformation, neutron diffraction, load partitioning, mechanical properties.
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43

Grajcar, Adam, Paweł Skrzypczyk, and Aleksandra Kozłowska. "Effects of Temperature and Time of Isothermal Holding on Retained Austenite Stability in Medium-Mn Steels." Applied Sciences 8, no. 11 (November 4, 2018): 2156. http://dx.doi.org/10.3390/app8112156.

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Effects of isothermal holding time and temperature on the stability of retained austenite in medium manganese bainitic steels with and without Nb microaddition were investigated. The amount of retained austenite for various variants of thermomechanical processing was determined by X-ray diffraction. Relationships between processing conditions and microstructure were revealed using light microscopy and scanning electron microscopy techniques. The isothermal holding temperatures changed from 500 to 300 °C and the time was from 60 to 1800 s. The optimal time and temperature of isothermal holding for all the investigated steels were 400 °C and 300 s, respectively. The relationships between the Mn content, amount of retained austenite, and carbon enrichment of the retained austenite (RA) were observed. The noticeable effect of Nb microaddition on the amount of retained austenite was not observed. In general, the carbon content in RA was slightly lower for the steels containing Nb. The optimum gamma phase amount was up to 18% for the 3% Mn steels, whereas it was c.a. 13% for the steels with 5% Mn. It was found that the morphology of blocky/interlath retained austenite depends substantially on the isothermal holding temperature.
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44

Lowe-Ma, C. K., W. T. Donlon, and W. E. Dowling. "Comments on determining X-ray diffraction-based volume fractions of retained austenite in steels." Powder Diffraction 16, no. 4 (December 2001): 198–204. http://dx.doi.org/10.1154/1.1402627.

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Retained austenite is an important characteristic of properly heat-treated steel components, particularly gears and shafts, that will be subjected to long-term use and wear. Normally, either X-ray diffraction or optical microscopy techniques are used to determine the volume percent of retained austenite present in steel components subjected to specific heat-treatment regimes. As described in the literature, a number of phenomenological, experimental, and calculation factors can influence the volume fraction of retained austenite determined from X-ray diffraction measurements. However, recent disagreement between metallurgical properties, microscopy, and service laboratory values for retained austenite led to a re-evaluation of possible reasons for the apparent discrepancies. Broad, distorted X-ray peaks from un-tempered martensite were found to yield unreliable integrated intensities whereas diffraction peaks from tempered samples were more amenable to profile fitting with standard shape functions, yielding reliable integrated intensities. Retained austenite values calculated from reliable integrated intensities were found to be consistent with values obtained by Rietveld refinement of the diffraction patterns. The experimental conditions used by service laboratories combined with a poor choice of diffraction peaks were found to be sources of retained austenite values containing significant bias.
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45

Yang, Chen, Xi Xi Cui, Zhen Bo Zhao, Gao Hua, and Cheng Liu. "Role of Bulky Retained Austenite in Austempered Ductile Iron." Advanced Materials Research 1142 (January 2017): 19–22. http://dx.doi.org/10.4028/www.scientific.net/amr.1142.19.

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In this investigation, the characteristics of bulky retained austenite in an austempered ductile iron are evaluated in two tempered conditions. which were intially tempered at 200oC for 1h before cooling to room temperature, and then tempered at 350oC for 1h. The result shows that the hardness within retained austenite areas is distributed unevenly with a range from 423 HV to 897 HV, which is attributed to the transformation from austenite to martensite during austempering. Also, the mechanism regarding the quenched marteniste formation is discussed. The poor fatigue resistance of ADI is hypothesized to be due to the amount of austenite transformed to martensite.
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46

Anoop, AD, AS Sekhar, M. Kamaraj, and K. Gopinath. "Modelling the mechanical behaviour of heat-treated AISI 52100 bearing steel with retained austenite." Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 232, no. 1 (October 20, 2015): 44–57. http://dx.doi.org/10.1177/1464420715612235.

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The mechanical properties of hardened AISI 52100 bearing steel such as flexural strength, microhardness and Young’s modulus are considerably influenced by the austenite content retained in the microstructure. A microstructure-sensitive finite element simulation approach is presented which considers the effect of retained austenite to estimate the mechanical properties. The austenite grain size is derived as a function of austenitising temperature and holding time using a modified Arrhenius type equation. The simulation strategy involves division of the two-dimensional domain using triangular elements such that a group of six neighbouring triangular elements represented a hexagonal grain of calculated size. Material inhomogeneity is introduced by enforcing austenite properties to a fraction of the elements equal to the volume percent of retained austenite in the steel. The predictions from the simulation approach for 8% and 20% retained austenite volume fractions matched well with earlier experimental results.
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47

Nyyssönen, Tuomo, Olli Oja, Petri Jussila, Ari Saastamoinen, Mahesh Somani, and Pasi Peura. "Quenching and Partitioning of Multiphase Aluminum-Added Steels." Metals 9, no. 3 (March 22, 2019): 373. http://dx.doi.org/10.3390/met9030373.

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The quenching and partitioning response following intercritical annealing was investigated for three lean TRIP-type high-Al steel compositions. Depending on the intercritical austenite fraction following annealing, the steels assumed either a ferrite/martensite/retained austenite microstructure or a multiphase structure with ferritic, bainitic and martensitic constituents along with retained austenite. The amount of retained austenite was found to correlate with the initial quench temperature and, depending on the intercritical annealing condition prior to initial quenching, with the uniform and ultimate elongations measured in tensile testing.
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48

Li, Ji Guang, Hai Liang Huang, Shang Wu Zeng, Jia Li Cao, and Tie Jun Wang. "Research on Microstructure Evolution Laws of Ultrafine Grained Metastable Automobile Steel." Applied Mechanics and Materials 423-426 (September 2013): 281–85. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.281.

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The microstructure evolution laws of ultrafine grained metastable automobile steels was studied in this paper by laser confocal scanning microscope, EBSD, XRD and TEM. Results showed that, the matrix organizations of hot-rolled steel were lath martensite and deformation ferrite, and there were a little of retained austenite film and lath between the lath martensite. After heat treatment, the matrix organizations of steel were ultrafine ferrite and retained austenite. The retained austenite transformed into martensite and ε-martensitic in the deformation process, and the strength and plasticity of steel were improved. A lot of retained austenite were obtained in the annealing process. The TRIP effects by the large fraction of metastable austenite and the ultrafine grain size add to the test steel with high strength and high plasticity.
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49

Morawiec, M., and A. Grajcar. "Some aspects of the determination of retained austenite using the Rietveld refinement." Journal of Achievements in Materials and Manufacturing Engineering 1, no. 80 (January 2, 2017): 11–17. http://dx.doi.org/10.5604/01.3001.0010.1442.

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Purpose: The aim of the paper is to show the advantage of the application of the Rietveldrefinement for determination of retained austenite amount in multiphase microstructure steels.Design/methodology/approach: The steels used for the investigation were thermomechanicallyrolled and controlled cooled to room temperature. The investigation of themicrostructure was carried out using light microscopy. X-ray diffraction investigations ofanalyzed steel were a major part of the research. The phase identification and quantitativeanalysis of retained austenite were done using the HighScore Plus software that includesthe Rietveld refinement method. The Rietveld analysis takes into account the preferredorientation that occurs during thermo-mechanical processing of steel.Findings: It was found that after the thermo-mechanical processing the microstructureof steel is composed of fine-grained bainitic matrix which includes bainite-austeniteconstituents, martensite blocks and some fraction of retained austenite. The X-ray diffractionshowed that this steel includes phases of Feα (bainite and martensite) and Feγ (retainedaustenite). The Rietveld analysis showed that the volume fraction of retained austenite is14.1%.Research limitations/implications: To confirm that Rietveld refinement methodis a good tool for the quantitative analysis of retained austenite volume fraction EBSDmeasurements should be done for comparison purposes.Practical implications: The obtained results can be used for determination of retainedaustenite fraction in AHSS steels. It is important because the retained austenite content andits mechanical stability decide about a formability level of these steel grades.Originality/value: Some methodological aspects are concerned affecting the finalquantitative results of retained austenite volume fraction is AHSS.
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50

Peng, Liang Gui, Wei Jie Liu, Xiang Hua Liu, and Ying Zhi. "Experimental Study on the Effect of Retained Austenite on the Impact Toughness of a Low-Carbon Martensite Steel." Advanced Materials Research 1095 (March 2015): 119–23. http://dx.doi.org/10.4028/www.scientific.net/amr.1095.119.

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Effect of various heat treatment processes on the impact property of a low-carbon steel was investigated. Its microstructure and morphology were also observed and characterized. Fraction of retained austenite of the tested steel varied with the change of temperature and holding time of quenching, carbon partitioning and tempering process. After Q&P treatment, the impact property of the tested steel improved with increasing volume fraction of retained austenite. After tempering, the impact property of the tested steel further improved despite the decrease of the fraction of the retained austenite. Experimental results show that the stabilization and fraction of the retained austenite from which the transformation induced plasticity (TRIP) effect originated control the toughness of the tested steel. It should be noted that the common tempering theory is insufficient to explain the current observations for the impact energy increment. Instead, it may be explained by the decomposition of the block-like retained austenite that is generally harmful to the toughness of the steel.
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