Journal articles: 'Austenite'

1

Lu, Lilin, Jiaqi Ni, Zhixian Peng, Haijun Zhang, and Jing Liu. "Hydrogen Embrittlement and Improved Resistance of Al Addition in Twinning-Induced Plasticity Steel: First-Principles Study." Materials 12, no. 8 (April 24, 2019): 1341. http://dx.doi.org/10.3390/ma12081341.

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Understanding the mechanism of hydrogen embrittlement (HE) of austenitic steels and developing an effective strategy to improve resistance to HE are of great concern but challenging. In this work, first-principles studies were performed to investigate the HE mechanism and the improved resistance of Al-containing austenite to HE. Our results demonstrate that interstitial hydrogen atoms have different site preferences in Al-free and Al-containing austenites. The calculated binding energies and diffusion barriers of interstitial hydrogen atoms in Al-containing austenite are remarkably higher than those in Al-free austenite, indicating that the presence of Al is more favorable for reducing hydrogen mobility. In Al-free austenite, interstitial hydrogen atoms caused a remarkable increase in lattice compressive stress and a distinct decrease in bulk, shear, and Young’s moduli. Whereas in Al-containing austenite, the lattice compressive stress and the mechanical deterioration induced by interstitial hydrogen atoms were effectively suppressed.

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2

Berecz, Tibor, and Peter J. Szabo. "Crystallographic relations during decomposition of the ferritic phase by isothermal ageing of duplex stainless steel." Journal of Applied Crystallography 46, no. 1 (December 8, 2012): 135–41. http://dx.doi.org/10.1107/s0021889812044536.

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In highly alloyed and duplex stainless steels the range of alloying elements leads to many different phases precipitating at higher temperatures. Duplex stainless steels consist of almost equal ratios of austenite and ferrite, and between 923 and 1273 K the ferrite begins decomposing into secondary austenite (γ2) and the σ phase. Several orientation relations between the austenitic, ferritic and σ phases have been determined by other researchers. The calculation and testing of mathematical expressions for these orientations are important for a close understanding of changes in duplex steel hardness, ductility, and other qualitative measures imposed by annealing or heat ageing. The method described in this article also offers an approach for determining parent phase orientations from inherited orientations in other metallic microstructures. When the orientation relations of adjacent grains calculated from mathematical equations and those measured by electron backscatter diffraction were compared, naturally it was found that the average orientation differs less between grains that inherit matrix structure from common parents. However, it was also found that the degree of difference depended on the variants involved in the orientations. This phenomenon can be explained by features of the microstructure and decomposition of the ferritic phase: initially the microstructure contains only primary austenite (γ1) and ferrite, then after a while it contains [beside primary (γ1) austenite] increasing amounts of secondary (γ2) austenite and the σ phase, and decreasing amounts of ferrite. The presence of two variants of austenite makes it difficult to verify parent relations for secondary (γ2) austenites.

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3

Feng, Yun Li, Shao Qiang Yuan, and Meng Song. "Microstructure Evolution of Undercooled Austenite during Deformation for Medium-Carbon Si-Mn Steel." Materials Science Forum 704-705 (December 2011): 903–6. http://dx.doi.org/10.4028/www.scientific.net/msf.704-705.903.

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The microstructure evolution of a medium-carbon Si-Mn steel during deformation of undercooled austenite at different degree of deformation, temperatures and strain rates has been investigated by means of a hot compression simulation test, metallographic microscope, scanning electron microscope and transmission electron microscopy. Also, the mechanism of carbide spheroidized during deformed process has been discussed. The experiment results demonstrate that the process of evolution experienced three stages: that is, strain-induced transformation, austenite eutectoid decomposed to carbides and ferrite matrix, and spheroidization of pearlite at the range of A3-Ar3. The austenitic grains would be refined for the extra-product of ferrite above the Ar3. The eutectoid reaction was induced on the grain boundaries of ferrite and non-transformed austenite and deformation bands with the increasing volume of deformation. An optimum combination of deformation temperature and strain rate is important to obtian the dulplex microstructure consisting of ultrafine ferrites and dispersed carbide particles. The fine spheroidized microstructures are obtained while the deformed temperature reaches 650°C with ≥1.0, meanwhile, The carbides precipate in globular and shot-rod shapes. Keywords: Medium-carbon Si-Mn steel, Undercooled austentite, Microstructure evolution, Deformation induced transformation, Carbide spheroidization

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4

Reis, Adriano Gonçalves, Danieli Aparecida Pereira Reis, Antônio Jorge Abdalla, Antônio Augusto Couto, and Jorge Otubo. "An In Situ High-Temperature X-Ray Diffraction Study of Phase Transformations in Maraging 300 Steel." Defect and Diffusion Forum 371 (February 2017): 73–77. http://dx.doi.org/10.4028/www.scientific.net/ddf.371.73.

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An in situ high-temperature X-ray diffraction (HTXRD) study in maraging 300 steel was carried out to study the martensite to austenite transformation and effect of time of exposure in the austenite reversion below austenite start temperature. Solution annealed materials were subjected to controlled heating-holding cycles. The first sample was heated at a rate of 10 oC/min from room temperature to 800 oC, showing that the microstructure is completely martensitic (α’110) until 600 oC. From 650 oC until 800 oC, the microstructure is gradually changing from martensitic to austenitic, showed by the increasing peaks of γ111 and reducing peaks of α’110. At 800 oC the microstructure is completely austenitic (γ111). Another sample was heated at 10 oC/min from room temperature to 600 oC and held for 4 hours. At 600 oC, at 0 h time of exposure, only a martensitic peak was observed. An austenite peak can be observed after some time of exposure at this temperature. The volume fraction of austenite increased with increasing time of exposure at 600 oC, reaching 50/50 volume fraction after 4 hours of exposure. XRD diffraction patterns for the same sample that was held for 4 hours at 600 oC and then cooled down in air to room temperature showed the same intensity of austenite and martensitic peaks found in situ at 600 oC for 4 hours (retained austenite), with the volume fraction of 50/50 of austenite and martensite phases. The HTXRD technique can be used to identify and quantify martensite to austenite transformation and austenite retention.

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5

Gautam, J. Prakash, A. Miroux, Jaap Moerman, and Leo Kestens. "Tnr Dependent Hot Rolling Microstructure and Texture Development in C-Mn Dual Phase and HSLA Steels." Defect and Diffusion Forum 391 (February 2019): 120–27. http://dx.doi.org/10.4028/www.scientific.net/ddf.391.120.

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No recrystallization of austenite, Tnr, has an important influence on the transformed phase fractions and the final crystallographic texture after hot deformation. This paper investigates the evolution of microstructure and texture components during hot-rolling in two austenitic region based on Tnr along with three different cooling trajectory and coiling in dual-phase steels and high strength low alloys steel. The recrystallization of the austenite, the austenite deformation followed by the austenite-to-ferrite transformation influence the final microstructure and texture in dual phase steels, have been examined by means of optical microscopy, X-ray diffraction (XRD) measurements. Recrystallized and deformed austenite have clearly different texture components and, due to the specific lattice correspondence relations between the parent austenite phase and its transformation products, the resulting ferrite textures are different as well.

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6

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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7

Silva Leite, Carla Gabriela, Eli Jorge da Cruz Junior, Mattia Lago, Andrea Zambon, Irene Calliari, and Vicente Afonso Ventrella. "Nd: YAG Pulsed Laser Dissimilar Welding of UNS S32750 Duplex with 316L Austenitic Stainless Steel." Materials 12, no. 18 (September 9, 2019): 2906. http://dx.doi.org/10.3390/ma12182906.

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Duplex stainless steels (DSSs), a particular category of stainless steels, are employed in all kinds of industrial applications where excellent corrosion resistance and high strength are necessary. These good properties are provided by their biphasic microstructure, consisting of ferrite and austenite in almost equal volume fractions of phases. In the present work, Nd: YAG pulsed laser dissimilar welding of UNS S32750 super duplex stainless steel (SDSS) with 316L austenitic stainless steel (ASS), with different heat inputs, was investigated. The results showed that the fusion zone microstructure observed consisted of a ferrite matrix with grain boundary austenite (GBA), Widmanstätten austenite (WA) and intragranular austenite (IA), with the same proportion of ferrite and austenite phases. Changes in the heat input (between 45, 90 and 120 J/mm) did not significantly affect the ferrite/austenite phase balance and the microhardness in the fusion zone.

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8

Pinedo, Carlos Eduardo, and André Paulo Tschiptschin. "Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel." Rem: Revista Escola de Minas 66, no. 2 (June 2013): 209–14. http://dx.doi.org/10.1590/s0370-44672013000200011.

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In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462) stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC) without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% carbon supersaturation and expansion of the FCC lattice. For the duplex stainless steel AISI F51, the austenitic grains transformed to carbon expanded austenite (γC), the ferritic grains transformed to carbon expanded ferrite (αC) and M23C6 type carbides precipitated in the nitrided case. Hardness of the carburized case of the F51 duplex steel reached 1600 HV due to the combined effects of austenite and ferrite lattice expansion with a fine and dispersed precipitation of M23C6 carbides.

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9

Kang, Jun-Yun, Jaecheol Yun, Byunghwan Kim, Jungho Choe, Sangsun Yang, Seong-Jun Park, Ji-Hun Yu, and Yong-Jin Kim. "Micro-Texture Analyses of a Cold-Work Tool Steel for Additive Manufacturing." Materials 13, no. 3 (February 9, 2020): 788. http://dx.doi.org/10.3390/ma13030788.

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Small objects of an alloy tool steel were built by selective laser melting at different scan speeds, and their microstructures were analyzed using electron backscatter diffraction (EBSD). To present an explicit correlation with the local thermal cycles in the objects, prior austenite grains were reconstructed using the EBSD mapping data. Extensive growth of austenitic grains after solidification could be detected by the disagreement between the networks of carbides and austenite grain boundaries. A rapid laser scan at 2000 mm/s led to less growth, but retained a larger amount of austenite than a slow one at 50 mm/s. The rapid scan also exhibited definite evolution of Goss-type textures in austenite, which could be attributed to the growth of austenitic grains under a steep temperature gradient. The local variations in the microstructures and the textures enabled us to speculate the locally different thermal cycles determined by the different process conditions, that is, scan speeds.

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10

Stone, H. J., M. J. Peet, H. K. D. H. Bhadeshia, P. J. Withers, S. S. Babu, and E. D. Specht. "Synchrotron X-ray studies of austenite and bainitic ferrite." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 464, no. 2092 (January 29, 2008): 1009–27. http://dx.doi.org/10.1098/rspa.2007.0201.

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High-resolution synchrotron X-ray diffraction has been used to conduct in situ studies of the temporal evolution of phases during the isothermal growth of bainite. Two populations of austenitic material were identified: one corresponding to the initial austenite and the other to the carbon-enriched austenite associated with the bainitic ferrite. The observed lattice parameters and the asymmetry of the peaks from the residual austenite have been interpreted in terms of the carbon partitioning due to the transformation. The results are contrasted with an earlier study in which the austenite unit cell appeared to split into two distinct densities prior to the onset of transformation.

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11

Ding, Hua, Degang Liu, Minghui Cai, and Yu Zhang. "Austenite-Based Fe-Mn-Al-C Lightweight Steels: Research and Prospective." Metals 12, no. 10 (September 22, 2022): 1572. http://dx.doi.org/10.3390/met12101572.

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Fe-Mn-Al-C lightweight steels have been investigated intensely in the last a few years. There are basically four types of Fe-Mn-Al-C steels, ferritic, ferrite-based duplex/triplex (ferrite + austenite, ferrite + austenite + martensite), austenite-based duplex (ferrite + austenite), and single-austenitic. Among these steels, austenite-based lightweight steels generally exhibit high strength, good ductility, and outstanding weight reduction effects. Due to the addition of Al and high C content, κ’-carbide and κ-carbide are prone to form in the austenite grain interior and at grain boundaries of lightweight steels, respectively, and play critical roles in controlling the microstructures and mechanical properties of the steels. The microstructural evolution, strengthening mechanisms, and deformation behaviors of these lightweight steels are quite different from those of the mild conventional steels and TRIP/TWIP steels due to their high stacking fault energies. The relationship between the microstructures and mechanical properties has been widely investigated, and several deformation mechanisms have also been proposed for austenite-based lightweight steels. In this paper, the current research works are reviewed and the prospectives of the austenite-based Fe-Mn-Al-C lightweight steels are discussed.

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12

Yao, Sheng Jie, Lei Sun, Hai Hui Zhu, and Guo Dong Wang. "Microstructure Evolution Behavior of 22MnB5 Pickling Plate during Double Cold Reduction and Rapid Heating Process." Advanced Materials Research 1063 (December 2014): 47–54. http://dx.doi.org/10.4028/www.scientific.net/amr.1063.47.

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The microstructure evolution during rapid induction heating process of 22MnB5 steel after double cold rolling was investigated, and the effects of deformation, heating temperature and heating rate on austenitic grain size and micro-hardness of quenched samples were discussed. The results show that the austenite begins to when heated to 850 °C and the austenite grains grow significantly when heated to 950 °C during rapid induction heating process. With the deformation increasing, the austenite grain size decreases, and the austenite grain refinement weakened when the deformation increases to a certain extent; but the influence of cold rolling on micro-hardness after quenching is not significant. In addition, there is little effect of heating rate on the 22MnB5 steel austenite with large cold deformation and a certain effect on the micro-hardness after quenching.

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13

Ohtani, Shintaro, Satoshi Morooka, and Osamu Umezawa. "Microstructural Analysis of Type 304 Metal Sleeve." Materials Science Forum 702-703 (December 2011): 959–62. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.959.

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In order to form thin metal sleeve with the thickness of 0.03 mm, type 304 austenitic steel sheet was deeply drawn to a cup and spinning method applied to its body. The sleeve shows high strength with a dual-phase microstructure of fine austenite and transformed martensite. Pancaked austenite and martensite grains were highly elongated along RD (drawing direction) in the layer structure, and their grain width was about 100 nm. Dynamically recovered austenite grains were highly aligned from {101} to {101}. The strain-induced martensite grains mainly showed two components of {001} and {111}. Recover and recrystallization of the sleeve appeared at the temperature from 873 K to 1073 K. Annealed at 1073 K the austenite grains were mostly recrystallized with intensifying {101}, and the martensite grains were also reverse-transformed to austenite.

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14

Pernach, Monika, Krzysztof Bzowski, Roman Kuziak, and Maciej Pietrzyk. "Experimental Validation of the Carbon Diffusion Model for Transformation of Ferritic-Pearlitic Microstructure into Austenite during Continuous Annealing of Dual Phase Steels." Materials Science Forum 762 (July 2013): 699–704. http://dx.doi.org/10.4028/www.scientific.net/msf.762.699.

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Modeling of the transformation of the starting ferritic-pearlitic microstructure into austenite during heating in continuous annealing process was the objective of the work. Kinetics of this transformation was predicted by solving Avrami equation as well as carbon diffusion equation with a moving boundary. Mathematical and numerical models describing austenitic phase transformation were created for the 1D and 2D domains. Developed models were solved using the Finite Difference, as well as the Finite Element Method. Results of the numerical simulations include austenite volume fraction and carbon segregation profiles in the austenite. The former were compared with the experimental data obtained in laboratory simulations of the continuous annealing. Developed and validated model was applied to simulation of the austenitic transformation during annealing of DP steels.

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15

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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16

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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17

Pyshmintsev, I. Yu, S. M. Bityukov, and A. A. Gusev. "Effect of retained austenite on mechanical properties of steel with 15 % Cr." Izvestiya. Ferrous Metallurgy 66, no. 5 (November 11, 2023): 571–79. http://dx.doi.org/10.17073/0368-0797-2023-5-571-579.

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The paper considers the study of influence of retained austenite on the mechanical properties of steel of the austenite-martensitic class based on 15 % Cr after various heat treatment. Significant amount of retained austenite remains in the steel microstructure after quenching and subsequent tempering or heating in the intercritical temperature range that makes difficult to achieve a high yield strength. Destabilization of retained austenite with subsequent transformation into newly formed martensite is provided by multi-stage heat treatment which includes quenching, heating in the intercritical temperature range or above the AC3 point and final tempering. It was established that retained austenite remains in the microstructure of two-phase steel and has the form of blocks and thin layers located in the inter-lath space. Tensile testing of steel based on 15 % Cr showed that multi-stage heat treatment provides a high-strength condition corresponding to strength groups Q125 and Q135. A comparative analysis of deformation behavior of semi-austenitic steel in various states indicates that the beginning of the martensitic transformation after the final tempering shifts into the elastic region during tension and leads to the formation of stress-assisted martensite. It was determined that block-shaped retained austenite in steel with 15 % Cr predominantly undergoes martensitic transformation during tensile and impact tests at a subzero temperature. This is supposed to be the reason for the noticeably lower impact toughness of semi-austenitic steel with 15 % Cr compared to martensitic steel with 13 % Cr at equal strength.

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18

Cizek, Pavel. "Microstructure Evolution and Softening Processes in Hot Deformed Austenitic and Duplex Stainless Steels." Materials Science Forum 753 (March 2013): 66–71. http://dx.doi.org/10.4028/www.scientific.net/msf.753.66.

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The microstructure evolution and softening processes occurring in 22Cr-19Ni-3Mo austenitic and 21Cr-10Ni-3Mo duplex stainless steels deformed in torsion at 900 and 1200 °C were studied in the present work. Austenite was observed to soften in both steels via dynamic recovery (DRV) and dynamic recrystallisation (DRX) for the low and high deformation temperatures, respectively. At 900 °C, an “organised”, self-screening austenite deformation substructure largely comprising microbands, locally accompanied by micro-shear bands, was formed. By contrast, a “random”, accommodating austenite deformation substructure composed of equiaxed subgrains formed at 1200 °C. In the single-phase steel, DRX of austenite largely occurred through strain-induced grain boundary migration accompanied by (multiple) twinning. In the duplex steel, this softening mechanism was complemented by the formation of DRX grains through subgrain growth in the austenite/ferrite interface regions and by large-scale subgrain coalescence. At 900 °C, the duplex steel displayed limited stress-assisted phase transformations between austenite and ferrite, characterised by the dissolution of the primary austenite, formation of Widmanstätten secondary austenite and gradual globularisation of the transformed regions with strain. The softening process within ferrite was classified as “extended DRV”, characterised by a continuous increase in misorientations across the sub-boundaries with strain, for both deformation temperatures.

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19

Harwarth, Michael, Adam Brauer, Qiuliang Huang, Mehdi Pourabdoli, and Javad Mola. "Influence of Carbon on the Microstructure Evolution and Hardness of Fe–13Cr–xC (x = 0–0.7 wt.%) Stainless Steel." Materials 14, no. 17 (September 4, 2021): 5063. http://dx.doi.org/10.3390/ma14175063.

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The influence of carbon on the phase transformation behavior of stainless steels with the base chemical composition Fe–13Cr (wt.%), and carbon concentrations in the range of 0–0.7 wt.%, was studied at temperatures between −196 °C and liquidus temperature. Based on differential scanning calorimetry (DSC) measurements, the solidification mode changed from ferritic to ferritic–austenitic as the carbon concentration increased. The DSC results were in fair agreement with the thermodynamic equilibrium calculation results. In contrast to alloys containing nearly 0% C and 0.1% C, alloys containing 0.2–0.7% C exhibited a fully austenitic phase stability range without delta ferrite at high temperatures. Quenching to room temperature (RT) after heat treatment in the austenite range resulted in the partial transformation to martensite. Due to the decrease in the martensite start temperature, the fraction of retained austenite increased with the carbon concentration. The austenite fraction was reduced by cooling to −196 °C. The variation in hardness with carbon concentration for as-quenched steels with martensitic–austenitic microstructures indicated a maximum at intermediate carbon concentrations. Given the steady increase in the tetragonality of martensite at higher carbon concentrations, as confirmed by X-ray diffraction measurements, the variation in hardness with carbon concentration is governed by the amount and stability of austenite.

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20

Aftandiliants, Y. G. "The effect of heat treatment on the mechanical properties of modified stainless steels." Metaloznavstvo ta obrobka metalìv 102, no. 2 (June 30, 2022): 45–51. http://dx.doi.org/10.15407/mom2022.02.045.

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The paper presents the results of the study of the influence of structure on the mechanical properties of microalloyed and modified austenitic stainless steels. It is shown that the mechanical properties of cast austenitic stainless steels with a probability of 95 % and an error of 0.46 to 13.2 % are determined by such structural parameters as austenite grain size, carbide phase and ferrite content in austenite after quenching, quantity, size and distance between oxide, titanium sulfides and carbonitrides particles. Mathematical models of the structure influence on the yield strength, reduction of area and toughness of stainless steels are built. The structure parameter effectiveness is shown and it is shown that to increase the efficiency of strength, reduction of area and toughness of stainless steels at normal temperature structural factors affect in the following sequence: austenite grain size, volume fraction, size and distribution of titanium carbonitrides and sulfides, the total quantity of non-metallic inclusions, carbides and ferrite in austenite after hardening of stainless steel, as well as the volume fraction, size and distribution of oxide inclusions. Keywords: steel, structure, mechanical properties, strength, ductility, toughness.

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21

GASKELL, JILLIAN, FIONN DUNNE, DIDIER FARRUGIA, and JIANGUO LIN. "A MULTISCALE CRYSTAL PLASTICITY ANALYSIS OF DEFORMATION IN A TWO-PHASE STEEL." Journal of Multiscale Modelling 01, no. 01 (January 2009): 1–19. http://dx.doi.org/10.1142/s1756973709000049.

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A rate- and lengthscale-dependent crystal plasticity model is employed with a representative volume element for a two-phase austenitic steel under hot-forming conditions to investigate the role of austenite and MnS particle crystallographic orientation on local stress and slip conditions at austenite–MnS interfaces. It was found that austenite–MnS particle interfacial stress magnifications are determined largely by the crystallographic orientation of the MnS and not significantly by the austenite orientations. However, the crystallographic orientation of an austenite grain neighboring a MnS particle has a dramatic effect on slip localization and slip magnitude in the absence of any significant change in interfacial stress magnitude. The results suggest that it is the crystallographic orientation of the MnS rather than that of the austenite which determines the onset and rapidity of void nucleation. The results also show that there are very particular combinations of austenite–MnS particle orientations which lead to the highest interfacial stresses, and that the peak stress magnification arises not from the properties of the second phase particles but from their orientation. Micromechanical models based on isotropic plasticity will not capture correctly the interfacial stresses.

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22

Nakashima, Koichi, K. Imakawa, Y. Futamura, Toshihiro Tsuchiyama, and Setsuo Takaki. "Effect of Copper Addition on Grain Growth Behavior of Austenite in Low Carbon Steels." Materials Science Forum 467-470 (October 2004): 905–10. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.905.

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The effect of copper (Cu) addition on the grain growth behavior of austenite was investigated in a low carbon steel and a Cu bearing low carbon steel. Cu addition to the steel does not affect the nucleation rate of reversed austenite on heating in the martensitic structure but markedly retards the grain growth of the austenite during holding at 1173K (austenitization). As a result, the grain size of austenite in the Cu bearing steel becomes about one-third times smaller than that in the base steel after austenitization for 14.4ks. TEM observations in the Cu bearing steel revealed that Cu particles precipitated during aging treatment had completely dissolved in 1.2ks of austenitization. Therefore, the retardation of grain growth of austenite can not be explained by the grain boundary pinning effect of Cu particles but by the dragging effect of Cu atoms in the austenitic solid solution.

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23

Yao, S. J., Lin Xiu Du, Xiang Hua Liu, and Guo Dong Wang. "Dynamic Growth of Ultra-Fine Austenite Grains Deformed above A_d3 Temperature in a Nb-V-Ti Steel." Advanced Materials Research 89-91 (January 2010): 657–62. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.657.

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Generally, three typical behaviors are recognized in hot-deformation of austenite. However, considering that those austenite grains involved in single-pass deformation are mostly on the scale of dozens of micrometers or even much larger than that, it is meaningful to investigate hot-deformation behaviors of austenite grains smaller than 10μm. In the current paper, austenite grains of different sizes were prepared through repetitive treatment of rapid reheating and quenching with changing the holding temperature and/or holding time. Kinds of true stress-true strain curves at 900oC and 950oC indicate that austenitic deformation can be gradually coordinated by grain boundary behaviors, such as grain boundary sliding and/or diffusion. Simultaneously, the macroscopic deformation is more likely to be dominated through co-operation grain boundary sliding (CGBS).

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24

Zheng, Shen Bai, Shi Jie Liu, Hong Bin Li, Bin Feng, and Xue Song Hui. "Microstructure and Properties under Alternating Magnetism after Hot Rolling." Advanced Materials Research 1004-1005 (August 2014): 1256–59. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.1256.

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The austenite steel after rolling was radiated by the alternating magnetism, and the effects that alternating magnetic on the austenite transition was studied. The result shows that the alternating magnetism promotes the austenitic grain growth of low carbon steel. If the magnetic field intensity is increased, it could provide better performance of raw materials to cold rolling processing.

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25

Zheng, Shen Bai, Shao Hui Pan, Hui Wen, and Xiaog Xiong Wang. "Effect of Austenite Transition under Pulsating Magnetism." Advanced Materials Research 634-638 (January 2013): 1704–7. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.1704.

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The austenite steel was radiated by the intermediate frequency pulsating magnetism, and the effects that pulsating magnetic on the austenite transition was studied. The result shows that the pulsating magnetism promotes the austenitic grain growth of low carbon steel. If the magnetic field intensity is increased, it could provide better performance of raw materials to cold rolling processing.

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26

Ravi Kumar, B., J. K. Sahu, and S. K. Das. "Influence of Annealing Process on Recrystallisation Behaviour of a Heavily Cold Rolled AISI 304L Stainless Steel on Ultrafine Grain Formation." Materials Science Forum 715-716 (April 2012): 334–39. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.334.

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AISI 304L austenitic stainless steel was cold rolled to 90% with and no inter-pass cooling to produced 89% and 43% of deformation induced martensite respectively. The cold rolled specimens were annealed by isothermal and cyclic thermal process. The microstructures of the cold rolled and annealed specimens were studied by the electron microscope. The observed microstructural changes were correlated with the reversion mechanism of martensite to austenite and strain heterogeneity of the microstructure. The results indicated possibility of ultrafine austenite grain formation by cyclic thermal process for austenitic stainless steels those do not readily undergo deformation induced martensite. Keywords: Austenitic stainless steel, Grain refinement, Cyclic thermal process, Ultrafine grain

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27

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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28

Odnobokova, Marina, Andrey Belyakov, Alla Kipelova, and Rustam Kaibyshev. "Formation of Ultrafine-Grained Structures in 304L and 316L Stainless Steels by Recrystallization and Reverse Phase Transformation." Materials Science Forum 838-839 (January 2016): 410–15. http://dx.doi.org/10.4028/www.scientific.net/msf.838-839.410.

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The microstructure evolution and mechanical properties of 316L and 304L austenitic stainless steels subjected to large strain cold bar rolling and subsequent annealing were studied. The cold working was accompanied by mechanical twinning and strain-induced martensitic transformation. The latter was readily developed in 304L stainless steel. The uniform microstructures consisting of elongated austenite and martensite nanocrystallites evolved at large total strains, resulting in tensile strength above 2000 MPa in the both steels. The subsequent annealing at temperatures above 700°C was accompanied by the martensite-austenite reversion followed by recrystallization, leading to ultrafine grained austenite.

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29

Martin, Guilhem, Muriel Véron, B. Chéhab, R. Fourmentin, Jean Denis Mithieux, S. K. Yerra, Laurent Delannay, Thomas Pardoen, and Yves J. M. Bréchet. "Duplex Stainless Steel Microstructural Developments as Model Microstructures for Hot Ductility Investigations." Solid State Phenomena 172-174 (June 2011): 350–55. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.350.

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Duplex stainless steels (DSS) are alloys made of ferrite and austenite, with a proportion of each phase around 50%. Their main advantage in comparison with other austenitic and ferritic stainless steels is the attractive combination of high strength and corrosion resistance together with good formability and weldability. Unfortunately, DSS often present a poor hot workability. This phenomenon can stem from different factors associated to the balance of the phases, the nature of the interface, the distribution, size and shape of the second phase, and possibly also from difference in rheology between ferrite and austenite. In order to determine the specific influence of phase morphology on the hot-workability of DSS, two austenite morphologies (E: Equiaxed and W: Widmanstätten) with very similar phase ratio have been generated using appropriate heat treatments. It was checked that the latter treatments generate stable microstructures so that subsequent hot mechanical tests are performed on the microstructures of interest. One microstructure consists of a ferritic matrix with austenitic equiaxed islands while the other microstructure is composed of a ferritic matrix with Widmanstätten austenite. The latter morphology corresponds to the morphology observed in as-cast slabs.

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30

Cota Araujo, Mahira A., Jean-Marc Olive, Gilles Pecastaings, Ahmed Addad, Jérémie Bouquerel, and Jean-Bernard Vogt. "Compelling Evidence for the Role of Retained Austenite in the Formation of Low Cycle Fatigue Extrusions in a 9Ni Steel." Metals 13, no. 3 (March 8, 2023): 546. http://dx.doi.org/10.3390/met13030546.

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The 9Ni martensitic steels have a martensitic microstructure which contains retained austenite after solution heat treatment and water quenching. Under low cycle fatigue, extrusions formed at the surface of the material and were very close to martensite lath boundaries. The presence of retained austenite at martensite laths has been highly suspected to impact the cyclic plasticity. However, the nano-size of the austenitic phase makes it difficult to obtain clear evidence of its role. The paper focuses on the precise determination of these extrusions and the link with the retained austenite. The paper also emphasizes the innovative and promising use of magnetic force microscopy (MFM) to document cyclic plasticity of a 9Ni steel. It is shown that electron microscopies, even the most advanced ones, may be unsuccessful in reaching this goal, while magnetic force microscopy (MFM) overcame the difficulty. This technique has allowed imaging of both the extrusion and the retained austenite. These analyses confirm that the fatigue extrusions originated from a local displacement of martensite lath. The proposed mechanism, in which the retained austenitic film acts as a lubricant film or greasy film promoting a flowing of martensite along the interfaces, is unambiguously demonstrated.

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31

Ryś, J., and A. Zielińska-Lipiec. "Deformation of Ferrite-Austenite Banded Structure in Cold-Rolled Duplex Steel / Odkształcenie Pasmowej Struktury Ferrytu I Austenitu W Walcowanej Na Zimno Stali Duplex." Archives of Metallurgy and Materials 57, no. 4 (December 1, 2012): 1041–53. http://dx.doi.org/10.2478/v10172-012-0116-2.

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Duplex type ferritic-austenitic stainless steels develop a specific two-phase banded structure upon thermo-mechanical pre-treatment and subsequent cold-rolling. The band-like morphology of ferrite and austenite imposes different conditions on plastic deformation of both constituent phases in comparison to one-phase ferritic and austenitic steels. In the present research the ingot of a model ferritic-austenitic steel of duplex type, produced by laboratory melt, was subjected to preliminary thermo-mechanical treatment including forging and solution annealing. Afterwards cold-rolling was conducted over a wide deformation range. The investigations comprised examination of ferrite and austenite microstructures by means of optical and transmission electron microscopy and texture measurements after selected rolling reductions. The presented results indicate that deformation mechanisms operating within the bands of both constituent phases are essentially the same as compared to one-phase steels, however their appearance and contribution are changed upon deformation of two-phase banded structure. Different deformation behavior within ferrite-austenite bands in duplex steels, visible especially at higher strains, considerably affects microstructure evolution and in consequence texture formation in both phases.

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32

Kubler, R., M. Berveiller, M. Cherkaoui, and K. Inal. "Transformation Textures in Unstable Austenitic Steel." Journal of Engineering Materials and Technology 125, no. 1 (December 31, 2002): 12–17. http://dx.doi.org/10.1115/1.1525249.

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During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are coupled through kinematical constraints so that the lattice spin of the austenitic grains is different from the one due to classical slip. In this work, the lattice spin ω˙eA of the austenitic grains is related with the slip rate on the slip systems of the two phases, γ˙A and γ˙M, the evolution of the martensite volume fraction f˙ and the overall rotation rate Ω˙ of the grains. This new relation is integrated in a micromechanical model developed for unstable austenite in order to predict the evolution of the austenite texture during TRansformation Induced Plasticity (TRIP). Results for the evolution of the lattice orientation during martensitic transformation are compared with experimental data obtained by X-ray diffraction on a 304 AISI steel.

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33

Dziedzic, D., K. Muszka, and J. Majta. "Strain-Induced Austenitic Structure in Microalloyed Steels." Archives of Metallurgy and Materials 58, no. 3 (September 1, 2013): 745–50. http://dx.doi.org/10.2478/amm-2013-0064.

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Abstract Austenite morphology is one of the main factors determining austenite-ferrite transformation kinetic and effectively affects the final microstructure and properties. The basic criteria for proper assessment of the austenite transformation products, theirs refinement, is the relation between the nucleation to growth rates. The main factor accelerating both, the nucleation rate of austenite during heating, and ferrite during cooling is the presence of accumulated deformation energy. The primary aim of this work is to increase our knowledge of the effects of deformation - its accumulated energy on the austenite structure and properties. Two specific steel grades were selected for the present investigation, i.e. microalloyed and IF steel, essentially different in equilibrium transformation temperatures. Obtained austenitic microstructures were analyzed, first of all as a start point for the austenite-to-ferrite transformation. Specific case of this transformation was considered i.e. Strain Induced Dynamic Transformation SIDT. The characteristic feature of the SIDT is the strong dependence of theirs kinetic on the austenite morphology, especially grain size. Thermomechanical processing, that utilize the SIDT, is one of the most effective ways to produce ultrafine-grained steel. One of the main benefits of the austenite refinement, just before the γ→α transformation, is its significant effect on the microstructure evolution during subsequent thermomechanical processing. Experimental results clearly show how direct and positive influence the austenite grain refinement has on the composition and refinement of transformation products. Presented study was focused on Strain Induced Dynamic Reverse Transformation. It is proved that this kind of transformation is very efficient way to intensify thermomechanical processing of microalloyed steels. Dynamic transformation kinetics were analyzed based upon flow curves recorded during the SIDT process. The main effect of presented research is analyze of influence of prior microstructure on dynamically formed austenite morphology

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34

Duong, Nam, Le Thi Chieu, and Pham Mai Khanh. "Studies on the Mechanism of Work Hardening of Austenitic High Manganese Steel Alloyed with Chromium and Vanadium." Key Engineering Materials 737 (June 2017): 32–37. http://dx.doi.org/10.4028/www.scientific.net/kem.737.32.

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This article studies the mechanism of work hardening of austenitic high manganese steel alloyed with chromium and vanadium. The steel was annealed at 650°C before austenitizing at 1100°C, and then was quenched with water. We have observed that after the heat treatment, the size of austenite grain was small (1,950μm2 - level 6). The hardness of the steel was 223HB and the toughness was 115J/cm2. After impact loading, there was no martensite but twinning and sliding in the microstructure of the steel. The nano austenite was found in the microstructure. The steel was also hardened by small austenite grain and the carbide particles were finely dispersed in the microstructure.

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35

Luo, Haiwen, Jilt Sietsma, and Sybrand van der Zwaag. "Characteristics of the Static Recrystallization Kinetics of an Intercritically Deformed C-Mn Steel." Materials Science Forum 467-470 (October 2004): 293–98. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.293.

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The austenite recrystallization kinetics in the intercritical region of a C-Mn steel is investigated by means of stress relaxation tests. It is found that the Avrami exponent, n, decreases significantly with decreasing temperature, i.e. with increasing ferrite fraction. This behaviour deviates from that of austenite recrystallization in the purely austenitic state, in which case the Avrami exponent is constant and independent of temperature and deformation. To interpret this, the influence of spatial variation of the plastic strain in the intercritical austenite grains on recrystallization kinetics is modelled quantitatively. The modelling results seem to indicate that the strain heterogeneity is responsible for the decreasing Avrami exponent with decreasing intercritical temperature.

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36

Qin, Xiao Mei, Li Qing Chen, and Hong Shuang Di. "Effect of Process Parameters on Microstructures of 30Mn20Al3 Steel." Advanced Materials Research 97-101 (March 2010): 378–81. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.378.

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The microstructures of 30Mn20Al3 non-magnetic steel after different finishing temperature and cooling rates have been studied by multi-pass compression test in a thermal-mechanical simulator. The results show that the microstructure of this steel is totally of austenitic with amounts of twins. At the same cooling rate, larger amount of thicker twins appear when lowering finishing temperature. The austenite grain size is related to finishing temperature and cooling rate. The critical temperature of austenite recrystallization is determined as 950~1000°C. When the finishing temperature is about 1000°C and cooling rate higher than 15°C/s, fine and uniform austenite grains can be obtained.

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37

Lopata, V., M. Chernovol, E. Solovuch, and O. Dudan. "Use of structural anomalies in steel gas-thermal coatings during increased wear-out." Problems of tribology 102, no. 4 (December 24, 2021): 61–67. http://dx.doi.org/10.31891/2079-1372-2021-102-4-61-67.

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The structure of gas-thermal coatings made of wire materials has been studied by determining the most efficient methods of controlling the process of structure formation to achieve the highest physical and mechanical properties of renewable surfaces of vehicle parts. The effect of formation of anomaly amount of residual austenite in sprayed steel coatings was established. Technologies of application of the “austenitic effect” is suggested here to increase a coating wear-resistance. It is determined that the main factors influencing the content of residual austenite in hardened steel are the cooling rate of steel, the concentration of alloying elements in the austenitic phase, as well as thermal stabilization of austenite during self-tempering. It is shown that to ensure the formation in the structure of sprayed coatings of alloy structural, tool and corrosion-resistant steels of metastable austenite, which has a low flow temperature of deformation gamma-alpha transformation, which corresponds to the operating temperatures of sliding friction units, it is necessary to achieve certain coating conditions. wire spraying, cooling rate of molten particles and the degree of their oxidation). One of the most probable reasons for the appearance of the "austenitic effect" in coatings is the heating of the surface layer to a temperature that promotes thermal stabilization of austenite, as well as saturation of melt droplets with alloying elements (primarily chromium) and impurities (carbon, nitrogen) in flames. The relatively low flight speed of molten steel particles and the high concentration of propane containing carbon in the combustion products contribute to the deep saturation of the melt droplets with carbon. It is likely that these circumstances are associated with a high content of residual austenite in the coatings obtained by gas-flame spraying. An additional factor that increases the resistance of austenite in the sprayed coating may be the saturation of the droplets of the melt with carbon during melting and spraying using a propane flame. The studies under discussion have suggested that both for the method of gas-flame spraying and for the method of electric arc spraying, there are modes and steels for spraying that allow the formation of large amounts of metastable austenite in coatings, which in the process of tribocoupling will turn into martensite.On the basis of the carried-out researches technologies of restoration of details of vehicles by drawing multipurpose coverings in which the choice of a method of heating of a wire at spraying is carried out depending on temperature of the beginning of martensitic transformation of a wire material are offered.

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38

Abreu, Hamilton F. G., Nathanael Morais, Flavio Herculando, Marcelo Gomes Da Silva, and Alex Nascimento. "Variant Selection in Austenitic Stainless Steel Samples after Cold Rolling and Tension Deformation." Solid State Phenomena 172-174 (June 2011): 55–60. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.55.

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The deformation process can induce the precipitation of martensite in austenitic stainless steels. When shear stress is applied at temperatures near Ms, displacive transformation (martensitic transformation) mode is activated. When external stresses are applied, the work done contributes to a change in free energy either raising or lowering the Ms-temperature. Orientation relationships during austenite to martensite phase transformation were investigated in an austenitic stainless steel samples deformed by cold rolling and deformed in a tension test. EBSD (electron backscatter diffraction) and X-ray diffraction techniques were used to evaluate parent austenite texture and martensite texture after transformation. The observed orientation relationship between austenite and martensite was compared with the predicted orientation relationship by the phenomenological theory of martensite crystallography (PMTC). Aspects related to variant selection were discussed based on the criterion for the action of applied stress in the martensitic transformation postulated by Patel and Cohen. Results showed a very good agreement between measured and calculated results.

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39

Martin, Stefan, Christiane Ullrich, Daniel Šimek, Ulrich Martin, and David Rafaja. "Stacking fault model of ∊-martensite and itsDIFFaXimplementation." Journal of Applied Crystallography 44, no. 4 (June 28, 2011): 779–87. http://dx.doi.org/10.1107/s0021889811019558.

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Plastic deformation of highly alloyed austenitic transformation-induced plasticity (TRIP) steels with low stacking fault energy leads typically to the formation of ∊-martensite within the original austenite. The ∊-martensite is often described as a phase having a hexagonal close-packed crystal structure. In this contribution, an alternative structure model is presented that describes ∊-martensite embedded in the austenitic matrixviaclustering of stacking faults in austenite. The applicability of the model was tested on experimental X-ray diffraction data measured on a CrMnNi TRIP steel after 15% compression. The model of clustered stacking faults was implemented in theDIFFaXroutine; the faulted austenite and ∊-martensite were represented by different stacking fault arrangements. The probabilities of the respective stacking fault arrangements were obtained from fitting the simulated X-ray diffraction patterns to the experimental data. The reliability of the model was proven by scanning and transmission electron microscopy. For visualization of the clusters of stacking faults, the scanning electron microscopy employed electron channelling contrast imaging and electron backscatter diffraction.

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40

Mustofa, Salim, M. Dani, Parikin Parikin, Toto Sudiro, Bambang Hermanto, D. R. Adhika, Andon Insani, Syahbuddin Syahbuddin, Takanori Hino, and C. A. Huang. "HRPD and TEM Study of P/M 58Fe17Cr25Ni Austenitic Stainless Steel Synthesized by Spark Plasma Sintering." Acta Metallurgica Slovaca 28, no. 4 (December 13, 2022): 224–29. http://dx.doi.org/10.36547/ams.28.4.1548.

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58Fe17Cr25Ni austenite stainless steel has been fabricated using metal powder through sintering with a spark plasma at temperatures of 900 and 950°C for 5 minutes. High purity Fe, Ni and Cr powders were used as materials for this steel. Before sintering, the powder was mixed in a milling equipment which was processed for 5 hours, then it is formed into a coin by pressing it under a load of 25 tons. High resolution powder neutron diffractometer was used for identifying the crystal structure in the 58Fe17Cr25Ni austenitic stainless steel. The sintering process at temperatures of 900C and 950°C generally forms microstructure having matrix of equiaxed austenite grains, with a crystal structure of face-centered cubic which included in the Fm3m space group. Some particles with high Cr content, a'-Cr, are distributed in all austenite grains. The austenite grains seen in the 58Fe17Cr25Niaustenitic stainless steel sintered at 900°C are twin grains. Dislocations, slip planes and bands are also existed in those grains. These defects are expected to decrease with increasing sintering temperatures up to 950° C. This change was followed by the appearance of air bubbles and sub-grains as the dominant sub-structures in the 58Fe17Cr25Ni austenitic stainless steel sintered at 950°C.

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41

Aišman, David, Bohuslav Mašek, and Štěpán Jeníček. "Unconventional Microstructures in Tool Steel Obtained by Semi-Solid Processing and Subsequent Heat Treatment." Solid State Phenomena 217-218 (September 2014): 235–40. http://dx.doi.org/10.4028/www.scientific.net/ssp.217-218.235.

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Mechanical properties of all metals depend predominantly on the type and morphology of their microstructure. Microstructure attributes can be altered by various heat treating and thermomechanical treatment procedures. One of the advanced techniques profoundly affecting the microstructure evolution is semi-solid processing. It can produce unconventional microstructures even in conventional steel types. Moreover, subsequent heat treatment can also deliver a wide range of microstructures and correspondingly varied mechanical properties. In the present experimental programme, the X210Cr12 ledeburitic tool steel was studied. Its initial annealed microstructure consisted of ferritic matrix, chromium carbides and globular cementite particles. The semi-solid processed structure, on the other hand, contained polyhedral austenite grains embedded in carbide-austenite network. The austenite volume fraction exceeded 95 %. This microstructure was then altered by subsequent heat treatment or thermomechanical treatment. The experimental programme comprised three stages. At the first stage, the effects of the rate of cooling from the semi-solid region to the ambient temperature on the nature and morphology of the ledeburitic network and the austenitic grain size were explored. The second stage was aimed at the impact of tensile and compressive deformation applied after transition through semi-solid state on the microstructure evolution and, in particular, on grain size. Once suitable processing conditions and parameters were identified, the treatment led to a recrystallized austenitic microstructure with an average grain size of less than 3 μm. As high volume fractions of austenite were obtained, the third stage involved exploring the effects of thermal exposure. The stability of austenite and the decomposition of austenite into other microstructure constituents were mapped. Metallographic observation revealed a resulting wide range of microstructures from fine pearlite to martensite, depending on the heat treating schedule.

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42

Kim, Sung Joon. "Effects of Manganese Content and Heat Treatment Condition on Mechanical Properties and Microstructures of Fine-Grained Low Carbon TRIP-Aided Steels." Materials Science Forum 638-642 (January 2010): 3313–18. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3313.

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The mechanical properties and microstructures of alternative low carbon TRIP-aided steels in which manganese contents mediate between conventional low-alloyed TRIP-aided steels and TWIP steel have been investigated. A variety of microstructures, from a single austenite phase to multiple phase mixtures, was attained according to chemical compositions as well as heat treatment schedule. By means of reverse transformation of martensite combined with controlled annealing, a remarkable grain refinement being responsible for stabilization of austenite could be achieved. In case of the duplex (+ ) microstructures in 6Mn and 7Mn alloys, large amount of retained austenite more than 30 % contributed to substantial improvement of ductility compared to the conventional TRIP-aided steels having similar tensile strength level. In nearly single austenitic 13Mn alloy, the annealed sheet steel exhibited high tensile strength of 1.3 GPa with sufficient ductility due to the stain induced martensite transformation of fine grained austenite.

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43

Liu, Jin Hai, Guo Lu Li, Xiao Yan Hao, Xue Bo Zhao, and Xing Chuan Xia. "Influence of Sulfur on the Microstructure and Properties of High Nickel Austenite Grey Iron." Advanced Materials Research 97-101 (March 2010): 1024–28. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.1024.

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The influence of sulfur on the microstructure and properties of austenite grey iron with 14-16% Ni was studied. The results showed that the crystallizing temperature of primary austenite increases and the the eutectic temperature does not changes greatly with addition of sulfur. When the content of sulfur is lower than 0.046%, the undercooled graphite existed mainly, the hardness of austenite grey iron and the sensibility of cross section become higher. When the sulfur increases to 0.08%, the A type of flake graphite distributed mainly, and the hardness and the sensibility of cross section reaches the lowest. When the sulfur is over 0.11%, the dentritic primary austenite developed largely, the space interval of austenitic dentrite reduced, and a large amount of interdentritic graphite formed, and the hardness and the sensibility of cross section increased again. In additon, the surface roughness of machined casting is influenced by the morphology of flake graphite.

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44

Chaves, J. I., S. F. Medina, Manuel Gómez, L. Rancel, and Pilar Valles. "Pinning Forces Exerted by TiN Particles in Austenite of Structural Steels and Comparison with Driving Forces for Grain Growth and for Static Recrystallisation." Materials Science Forum 550 (July 2007): 405–10. http://dx.doi.org/10.4028/www.scientific.net/msf.550.405.

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In this work the pinning forces exerted by TiN particles in the austenitic phase in two Ti microalloyed steels have been determined and compared with the driving forces for austenite grain growth and for static recrystallisation between hot rolling passes, respectively. TiN precipitate sizes were measured by transmission electron microscopy (TEM) and the precipitated volumes were calculated. These results were then used to calculate pinning forces. The driving forces for recrystallisation were found to be approximately two orders of magnitude higher than the pinning forces, which explains why the austenite in these steels barely experiences hardening during rolling and why the accumulated stress prior to the austenite→ferrite transformation is insufficient (low dislocation density) to refine the ferritic grain.

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45

Gigović-Gekić, Almaida, Hasan Avdušinović, Amna Hodžić, and Ermina Mandžuka. "Effect of Temperature and Time on Decomposition of δ-ferrite in Austenitic Stainless Steel." Materials and Geoenvironment 67, no. 2 (July 27, 2020): 65–71. http://dx.doi.org/10.2478/rmzmag-2020-0007.

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AbstractMicrostructure of austenitic stainless steel is primarily monophasic, i.e. austenitic. However, precipitation of the δ-ferrite in the austenite matrix is possible depending on the chemical composition of steel. δ-Ferrite is stable on room temperature but it transforms into σ-phase, carbides and austenite during heat treatment. In this work, the results of analysis of influence of temperature and time on decomposition of δ-ferrite are presented. Magnetic induction method, microstructure and hardness analyses were used for testing the degree of decomposition of the δ-ferrite. Analysis of results showed that increase in temperature and time increases the degree of decomposition of δ-ferrite.

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46

Kurniawan, Perwita, Millenino Bergas Sartoyo, Aditya Nugraha, and Adi Nugroho. "Analisis Pengaruh Parameter Hardening terhadap Distorsi Spesimen CT58 dengan Metode Taguchi." JMPM (Jurnal Material dan Proses Manufaktur) 7, no. 2 (December 12, 2023): 152–59. http://dx.doi.org/10.18196/jmpm.v7i2.20073.

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Penelitian ini membahas masalah distorsi komponen mesin rokok setelah proses hardening. Penelitian ini berfokus pada perubahan dimensi diameter dalam lubang, lebar gap, dan kerataan pada komponen. Temperatur austenit, media quench, dan temperatur tempering diperiksa untuk menentukan pengaruhnya terhadap distorsi. Komponen terbuat dari kelompok baja mesin S45C setara AISI 1045. Penelitian ini menggunakan spesimen bernama CT58 dengan variasi temperature Austenite 820˚C 840˚C 860˚C, lalu variasi media quenching oli, oli+air, dan air dan variasi temperature Tempering 200˚C, 250˚C, dan 300˚C. Penelitian ini menggunakan Design of Experiment, dilanjutkan dengan analisis statistik dengan aplikasi minitab. Hasil penelitian didapatkan bahwa distorsi pada spesimen CT58 paling besar dipengaruhi oleh suhu Austenite dan diikuti oleh media Quench dan suhu Tempering. Temperatur austenit 820°C, media quench oli, dan temperatur tempering 250°C merupakan parameter pengerasan terbaik untuk aspek Inner Diameter. Temperatur austenit 820°C, media quench oli, dan temperatur tempering 250°C merupakan parameter pengerasan terbaik untuk aspek Gap Width. Temperatur austenit 820°C, media quench oli, dan temperatur tempering 250°C merupakan parameter pengerasan terbaik untuk aspek Flatness.

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47

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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Hedström, Peter, Jonathan Almer, Ulrich Lienert, and Magnus Odén. "Evolution of Residual Strains in Metastable Austenitic Stainless Steels and the Accompanying Strain Induced Martensitic Transformation." Materials Science Forum 524-525 (September 2006): 821–26. http://dx.doi.org/10.4028/www.scientific.net/msf.524-525.821.

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The deformation behavior of metastable austenitic stainless steel AISI 301, suffering different initial cold rolling reduction, has been investigated during uniaxial tensile loading. In situ highenergy x-ray diffraction was employed to characterize the residual strain evolution and the strain induced martensitic transformation. Moreover, the 3DXRD technique was employed to characterize the deformation behavior of individual austenite grains during elastic and early plastic deformation. The cold rolling reduction was found to induce compressive residual strains in the austenite along rolling direction and balancing tensile residual strains in the ά-martensite. The opposite residual strain state was found in the transverse direction. The residual strain states of five individual austenite grains in the bulk of a sample suffering 2% cold rolling reduction was found to be divergent. The difference among the grains, considering both the residual strains and the evolution of these, could not be solely explained by elastic and plastic anisotropy. The strain states of the five austenite grains are also a consequence of the local neighborhood.

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Bai, Yaping, Meng Li, Chao Cheng, Jianping Li, Yongchun Guo, and Zhong Yang. "Study on Microstructure and In Situ Tensile Deformation Behavior of Fe-25Mn-xAl-8Ni-C Alloy Prepared by Vacuum Arc Melting." Metals 11, no. 5 (May 17, 2021): 814. http://dx.doi.org/10.3390/met11050814.

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In this study, Fe-25Mn-xAl-8Ni-C alloys (x = 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%) were prepared by a vacuum arc melting method, and the microstructure of this series of alloys and the in situ tensile deformation behavior were studied. The results showed that Fe-25Mn-xAl-8Ni-C alloys mainly contained austenite phase with a small amount of NiAl compound. With the content of Al increasing, the amount of austenite decreased while the amount of NiAl compound increased. When the Al content increased to 12 wt.%, the interface between austenite and NiAl compound and austenitic internal started to precipitate k-carbide phase. In situ tensile results also showed that as the content of Al increased, the alloy elongation decreased gradually, and the tensile strength first increased and then decreased. When the Al content was up to 11 wt.%, the elongation and tensile strength were 2.6% and 702.5 MPa, respectively; the results of in situ tensile dynamic observations show that during the process of stretching, austenite deformed first, and crack initiation mainly occurred at the interface between austenite and NiAl compound, and propagated along the interface, resulting in fracture of the alloy.

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Hosseini, Mir Mehrdad, Jacques Lanteigne, Carlo Baillargeon, Mohammad Jahazi, and Henri Champliaud. "Development of a Flow Rule Based on a Unified Plasticity Model for 13Cr-4Ni Low-Carbon Martensitic Stainless Steel Subject to Post-Weld Heat Treatment." Metals 14, no. 7 (July 21, 2024): 834. http://dx.doi.org/10.3390/met14070834.

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This study aims to develop a flow rule for evaluating the relaxation and redistribution of residual stresses during the post-weld heat treatment (PWHT) of hydroelectric runners made from low-carbon martensitic stainless steel (13Cr-4Ni composition). During the PWHT, austenite reforms in the filler metal and surrounding areas of the base metal near welded joints. The evolving inelastic strain rate with reformed austenite led to defining two distinct flow rules in the pure martensitic (α′) and austenitic (γ) phases. A linear rule of mixture was then applied to assess global effective stress based on the inelastic strain rate and current austenite fraction during the PWHT. A unified constitutive model incorporating drag stress and back stress, evolving with creep and plastic deformation mechanisms during the PWHT, described the stress–strain behavior. To validate this analysis, a third flow rule was determined in the 18% tempered austenitic microstructure, compared with the rule of mixture’s effective stress contribution from each phase on the inelastic strain rate. Isothermal constant strain rate tests in stabilized crystalline microstructures evaluated constants specific to their respective flow rules. This study demonstrates the stability of reformed austenite at elevated temperatures during slow cooling and its significant influence on the mechanical properties of 13Cr-4Ni steels. The effectiveness of estimating yield stress using the rule of mixture based on individual phase behaviors is also confirmed.

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Journal articles on the topic 'Austenite'

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