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1
Antoine, P., B. Soenen, and Nuri Akdut. "Static Strain Aging in Cold Rolled Metastable Austenitic Stainless Steels." Materials Science Forum 539-543 (March 2007): 4891–96. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4891.
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Transformation of austenite to martensite during cold rolling operations is widely used to strengthen metastable austenitic stainless steel grades. Static strain aging (SSA) phenomena at low temperature, typically between 200°C and 400°C, can be used for additional increase in yield strength due to the presence of α’-martensite in the cold rolled metastable austenitic stainless steels. Indeed, SSA in austenitic stainless steel affects mainly in α’-martensite. The SSA response of three industrial stainless steel grades was investigated in order to understand the aspects of the aging phenomena at low temperature in metastable austenitic stainless steels. In this study, the optimization of, both, deformation and time-temperature parameters of the static aging treatment permitted an increase in yield strength up to 300 MPa while maintaining an acceptable total elongation in a commercial 301LN steel grade. Deformed metastable austenitic steels containing the “body-centered” α’-martensite are strengthened by the diffusion of interstitial solute atoms during aging at low temperature. Therefore, the carbon redistribution during aging at low temperature is explained in terms of the microstructural changes in austenite and martensite.
2
Itman Filho, André, Wandercleiton da Silva Cardoso, Leonardo Cabral Gontijo, Rosana Vilarim da Silva, and Luiz Carlos Casteletti. "Austenitic-ferritic stainless steel containing niobium." Rem: Revista Escola de Minas 66, no. 4 (December 2013): 467–71. http://dx.doi.org/10.1590/s0370-44672013000400010.
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The austenitic-ferritic stainless steels present a better combination of mechanical properties and stress corrosion resistance than the ferritic or austenitic ones. The microstructures of these steels depend on the chemical compositions and heat treatments. In these steels, solidification starts at about 1450ºC with the formation of ferrite, austenite at about 1300ºC and sigma phase in the range of 600 to 950ºC.The latter undertakes the corrosion resistance and the toughness of these steels. According to literature, niobium has a great influence in the transformation phase of austenitic-ferritic stainless steels. This study evaluated the effect of niobium in the microstructure, microhardness and charge transfer resistance of one austenitic-ferritic stainless steel. The samples were annealed at 1050ºC and aged at 850ºC to promote formation of the sigma phase. The corrosion testes were carried out in artificial saliva solution. The addition of 0.5% Nb in the steel led to the formation of the Laves phase.This phase, associated with the sigma phase, increases the hardness of the steel, although with a reduction in the values of the charge transfer resistance.
3
Gołębiowski, Bartosz, and Wiesław Świątnicki. "Microstructural Changes Induced during Hydrogen Charging Process in Stainless Steels with and without Nitrided Layers." Solid State Phenomena 186 (March 2012): 305–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.186.305.
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The purpose of this study is to analyze the effect of glow discharge nitriding on hydrogen degradation of two types of steels: two-phase austenitic-ferritic and single-phase austenitic. The nitriding process resulted in formation of surface layers composed of expanded austenite (S phase), and in the case of two-phase steel of expanded austenite and expanded ferrite. Microstructural changes occurring under the influence of hydrogen on steels without and with nitrided layers were investigated with the use of scanning (SEM) and transmission (TEM) electron microscopy techniques. It was shown that the density of cracks formed during cathodic hydrogen charging is higher on the surface of the non-nitrided steels compared to the nitrided steels after identical hydrogen charging process. Moreover in non nitrided steel hydrogenation leads to considerable increase of dislocation density, which results from the high concentration of hydrogen absorbed to the steel during its cathodic charging. This leads in turn to high stress concentration and local embrittlement giving rise to cracks formation. Conversely nitriding reduces the absorption of hydrogen and prevents structural changes resulting in hydrogen embrittlement. The conducted studies show that glow discharge nitriding can be used to increase resistance to hydrogen embrittlement of austenitic and austenitic ferritic stainless steels.
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Maznichevsky, Alexander N., Radii V. Sprikut, and Yuri N. Goikhenberg. "Investigation of Nitrogen Containing Austenitic Stainless Steel." Materials Science Forum 989 (May 2020): 152–59. http://dx.doi.org/10.4028/www.scientific.net/msf.989.152.
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An important factor in solving the problem of stainless steel corrosion resistance is carbon concentration reduction. However, a decrease in carbon content of austenitic steels leads to a drop in level of their strength properties. Theoretically, nitrogen alloying can lead to a strength increase in all types of austenitic corrosion-resistant steels. Practically, nitrogen alloying is effectively only with low-carbon compositions. This work shows the effect of nitrogen on the mechanical properties of middle-alloying nitrogen, containing stainless steel, and a study of AISI 304L and pilot steel with different nitrogen content (from 0.16 to 0.30 wt. %). Nitrogen increases strength of steel, which is approximately 30-60% higher than for steel without nitrogen, but reduces technological plasticity. Pilot steels show high corrosion resistance and fine austenite grains.
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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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Adachi, Shinichiro, Motoo Egawa, Takuto Yamaguchi, and Nobuhiro Ueda. "Low-Temperature Plasma Nitriding for Austenitic Stainless Steel Layers with Various Nickel Contents Fabricated via Direct Laser Metal Deposition." Coatings 10, no. 4 (April 7, 2020): 365. http://dx.doi.org/10.3390/coatings10040365.
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In this study, low-temperature plasma nitriding is applied to austenitic stainless steels at temperatures below 450 °C. This enhances the wear resistance of the steels with maintaining corrosion resistance, by producing expanded austenite (known as the S-phase), which dissolves excessive nitrogen. Austenitic stainless steels contain nickel, which has the potential to play an important role in the formation and properties of the S-phase. In this experiment, austenitic stainless steel layers with different nickel contents were processed using direct laser metal deposition, and subsequently treated using low-temperature plasma nitriding. As a result, the stainless steel layers with high nickel contents formed the S-phase, similar to the AISI 316L stainless steel. The thickness and Vickers hardness of the S-phase layers varied with respect to the nickel contents. Due to lesser chromium atoms binding to nitrogen, the chromium content relatively decreased. Moreover, there was no evident change in the wear and corrosion resistances due to the nickel contents.
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Li, Zhuang, Di Wu, Wei Lv, Zhen Zheng, and Shao Pu Kang. "Investigations on Low Environmental Impact Machining Processes of Free Cutting Austenitic Stainless Steels." Applied Mechanics and Materials 377 (August 2013): 112–16. http://dx.doi.org/10.4028/www.scientific.net/amm.377.112.
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In the present paper, sulfur, RE (rare earth) and bismuth were added to an austenite stainless steel. Low environmental impact machining processes of free cutting austenitic stainless steels was investigated by machinability testing. The results show that a significant amount of grey and dispersed inclusions were found in steel B. The inclusions are typical sulfide inclusions, and bismuth element is attached to double end of manganese sulfide inclusions. Some inclusions exhibit globular shape due to the presence of rare earths elements in steel B. Chip morphology was improved in steel B under the same turning conditions. The machinability of steel B is much better than that of steel A. This is attributed to the presence of free-cutting additives of sulfur, RE and bismuth in the austenitic stainless steels. Satisfactory mechanical properties were also obtained under the conditions of our experiments. The reasons why satisfactory mechanical properties were obtained may lie in that the sulfides and bismuth are soft phase, and the presence of rare earths elements contributes to the improvement of the toughness of the austenitic stainless steels.
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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
9
Gontijo, L. C., R. Machado, L. C. Casteletti, S. E. Kuri, and Pedro A. P. Nascente. "Study of the S Phases Formed on Plasma-Nitrided Austenitic and Ferritic Stainless Steels." Materials Science Forum 638-642 (January 2010): 775–80. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.775.
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An expanded austenite layer is formed on the surfaces of austenitic stainless steels that are nitrided under low-temperature plasma. This S phase is an iron alloy metastable phase supersaturated with nitrogen. We have identified a similar expanded ferrite or ferritic S phase for nitrided ferritic (BCC) stainless steels. Samples of austenitic AISI 304L and AISI 316L and ferritic AISI 409L stainless steels were plasma-nitrided at 350, 400, 450 and 500°C, and the structural and corrosion characteristics of the modified layers were analyzed by X-ray diffraction (XRD) and electrochemical tests. For the austenitic AISI 304L stainless steel, the results showed that a hard S phase layer was formed on the surface, without corrosion resistance degradation, by using low plasma temperatures (350 and 400°C). A similar behavior was observed for the austenitic AISI 316L stainless steel: the modified layers formed at 350 and 400°C were constituted mainly by the S phase. Plasma-nitriding treatment of the ferritic AISI 409L stainless steel caused the formation of a layer having high amount of nitrogen. XRD measurements indicated high strain states for the modified layers formed on the three stainless steels, being more pronounced for the ferritic S phase.
10
Berezovskaya, Vera V., Eugeny A. Merkushkin, and Ksenia A. Mamchits. "Structure and Phase Transformations in High Nitrogen and High Interstitial Steels of Different Alloying Systems - Short Review." Defect and Diffusion Forum 410 (August 17, 2021): 167–72. http://dx.doi.org/10.4028/www.scientific.net/ddf.410.167.
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The features of the structure evolution under thermal effect of Cr, Cr-Ni, Cr-Ni-Mn, and Cr-Mn-austenitic stainless steels with high nitrogen content and a total high content of carbon and nitrogen are analyzed. When studying the structure, we used light and electron microscopy, X-ray diffraction, dilatometry analysis and electrical resistance measurements. Fine structure and aging processes of austenite, nature and morphology of excess phases, as well as character of phase transformations and their relationship with the properties of steels have been studied. It is shown that Cr-Mn-steels with a high content of (C + N), having a homogeneous structure of austenite without excess phases, surpass Cr-Ni austenitic steels in mechanical and corrosion properties, have higher process ability than Cr-Mn-N-steel and are comparable with them in mechanical properties.
11
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.
12
Monteiro, Waldemar Alfredo, Silvio Andre Lima Pereira, and Jan Vatavuk. "Nitriding Process Characterization of Cold Worked AISI 304 and 316 Austenitic Stainless Steels." Journal of Metallurgy 2017 (January 18, 2017): 1–7. http://dx.doi.org/10.1155/2017/1052706.
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The nitriding behavior of austenitic stainless steels (AISI 304 and 316) was studied by different cold work degree (0% (after heat treated), 10%, 20%, 30%, and 40%) before nitride processing. The microstructure, layer thickness, hardness, and chemical microcomposition were evaluated employing optical microscopy, Vickers hardness, and scanning electron microscopy techniques (WDS microanalysis). The initial cold work (previous plastic deformations) in both AISI 304 and 306 austenitic stainless steels does not show special influence in all applied nitriding kinetics (in layer thicknesses). The nitriding processes have formed two layers, one external layer formed by expanded austenite with high nitrogen content, followed by another thinner layer just below formed by expanded austenite with a high presence of carbon (back diffusion). An enhanced diffusion can be observed on AISI 304 steel comparing with AISI 316 steel (a nitrided layer thicker can be noticed in the AISI 304 steel). The mechanical strength of both steels after nitriding processes reveals significant hardness values, almost 1100 HV, on the nitrided layers.
13
Nikulina, Aelita, Aleksandr Smirnov, and Alexandra Chevakinskaya. "Formation of a Transition Zone Structure in Welded Joints between Dissimilar Steels." Applied Mechanics and Materials 698 (December 2014): 283–87. http://dx.doi.org/10.4028/www.scientific.net/amm.698.283.
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The results of structural research of welded joints between pearlitic high-carbon steel and austenitic chrome-nickel steel obtained by contact welding are presented. As a result of the diffusion process and mechanical mixing of steels local alloyed areas surrounded by pearlitic colonies of high-carbon steel are formed in the transition zone of the weld. The transmission electron microscopy (TEM) has been employed. The formation of the austenitic-martensitic microstructure occurs due to reducing the amount of alloying elements in local areas as compared to the original austenitic chrome-nickel steel chemical composition. Both austenite and martensite have crystallographic characteristics with the following orientation relationships: [211] γ-Fe || [011] α-Fe; [11-1] γ-Fe || [-110] α-Fe. The presence of high-strength local regions in the transition area may lead to a significant reduction in сrack resistance of dissimilar steels welded joints.
14
Kowalski, Jakub, Łukasz Licznerski, Milena Supernak-Marczewska, and Krzysztof Emilianowicz. "Influence of Process of Straightening Ship Hull Structure Made of 316L Stainless Steel on Corrosion Resistance and Mechanical Properties." Polish Maritime Research 27, no. 4 (December 1, 2020): 103–11. http://dx.doi.org/10.2478/pomr-2020-0070.
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Abstract The AISI 316L type steel belongs to the group of chromium-nickel stainless steels. They are determined according to European standards as X2CrNiMo17-12-2 and belong to the group of austenitic stainless steels. Steels of this group are used for elements working in seawater environments, for installations in the chemical, paper, and food, industries, for architectural elements, and many others. The chemical composition of corrosion-resistant austenitic steels provides them with an austenite structure that is stable in a wide temperature range, under appropriate conditions for heating, soaking, and cooling. 316L steel plate was subjected to a technological treatment of hot straightening with an oxy-acetylene torch, which is not commonly used for this type of steel, mainly due to the lack of objective assessment of whether the austenitizing temperature has been achieved and the stability of the heat treatment process is ensured. The single-phase structure of austenite with high corrosion resistance, without precipitation of carbides, steel is obtained by supersaturation in water from 1100°C. The purpose of the presented research was to determine the usefulness of the flame straightening process for a ship structure made of 316L steel.
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Su, Yang Yu, Fan Shiong Chen, Liu Ho Chiu, and Heng Chang. "Effect of Nitrocarburized Layer on the Resistivity Properties of Stainless Steels." Advanced Materials Research 47-50 (June 2008): 670–73. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.670.
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In this study, the plasma nitrocarburizing has been used to treat AISI 316 austenitic and AISI 410 martensitic stainless steels. Treated specimens were characterized by means of morphological analysis, surface microhardness measurement, and resistivity measurement. Plasma nitrocarburizing at low temperature (420°C) produced a single phase nitrided layer of nitrogen and carbon expanded austenite (S phase) on the specimen surface, which considerably improved the resistivity property of AISI 316 austenitic stainless steel.
16
Rashev, Ts V., A. V. Eliseev, L. Ts Zhekova, and P. V. Bogev. "High nitrogen steels." Izvestiya. Ferrous Metallurgy 62, no. 7 (August 22, 2019): 503–10. http://dx.doi.org/10.17073/0368-0797-2019-7-503-510.
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The article provides a brief overview of the properties and production technology of high-nitrogen steels (HNS), which have several advantages over traditional ones. The main advantages are: up to four times higher yield strength with unique preservation of the remaining characteristics; reduction in consumption or a 100 % elimination of the use of some expensive alloying elements, such as Ni, Mo, Co, W, and others; effective alloying with unconventional elements (Ca, Zn, Pb, etc.). The basics of HNS technology, dependence of the properties on nitrogen content in steels, producing technologies for ferritic-pearlitic, martensitic and austenitic steel, their properties and applicability are discussed. Alloying with nitrogen for ferritic-pearlitic steel requires more precise adherence to the chemical composition in order to prevent the formation of insoluble nitrides during heat treatment (due to its greater solubility compared to carbon). Features of martensitic steels are associated with the possibility of formation of nitrides and carbonitrides during tempering. The possible effect of nitrogen in these steels may be as a decrease in the size of nitride particles as compared with carbide ones. Increased stability temperature of nitrides and carbonitrides provides increased mechanical and physical properties. In austenitic steels, nitrogen, due to the strong γ-forming equivalence to nickel, replaces it in a ratio of 1 kg of nitrogen ≈ 6 – 39 kg Ni. In austenitic-martensitic steels, the main role is played by thermal martensite. Stable austenite is obtained in the process of its aging at operating temperatures. Examples of effective use of HNS in important details are described.
17
Brytan, Z. "The corrosion resistance of laser surface alloyed stainless steels." Journal of Achievements in Materials and Manufacturing Engineering 2, no. 92 (December 3, 2018): 49–59. http://dx.doi.org/10.5604/01.3001.0012.9662.
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Purpose: of this paper was to examine the corrosion resistance of laser surface alloyed (LSA) stainless steels using electrochemical methods in 1M NaCl solution and 1M H2SO4 solution. The LSA conditions and alloying powder placement strategies on the material's corrosion resistance were evaluated. Design/methodology/approach: In the present work the sintered stainless steels of different microstructures (austenitic, ferritic and duplex) where laser surface alloyed (LSA) with elemental alloying powders (Cr, FeCr, Ni, FeNi) and hard powders (SiC, Si3N4) to obtain a complex steel microstructure of improved properties. Findings: The corrosion resistance of LSA stainless steels is related to process parameters, powder placing strategy, that determines dilution rate of alloying powders and resulting steel microstructure. The duplex stainless steel microstructure formed on the surface layer of austenitic stainless steel during LSA with Cr and FeCr reveal high corrosion resistance in 1M NaCl solution. The beneficial effect on corrosion resistance was also revealed for LSA with Si3N4 for studied steels in both NaCl and H2SO4 solutions. Ferritic stainless steel alloyed with Ni, FeNi result in a complex microstructure, composed of austenite, ferrite, martensite depending on the powder dilution rate, also can improve the corrosion resistance of the LSA layer. Research limitations/implications: The LSA process can be applied for single phase stainless steels as an easy method to improve surface properties, elimination of porosity and densification and corrosion resistance enhancement regarding as sintered material. Practical implications: The LSA of single phase austenitic stainless steel in order to form a duplex microstructure on the surface layers result in reasonably improved corrosion performance. Originality/value: The original LSA process of stainless steels (austenitic, ferritic and duplex) was studied regarding corrosion resistance of the alloyed layer in chloride and sulphate solutions.
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Kukareko, V. A., B. M. Gatsuro, A. N. Grigorchik, and A. N. Chichin. "Matematical modeling of the process of enlarging the austenitic grain during high-temperature heating of alloy structural steel." Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), no. 3 (October 16, 2019): 74–84. http://dx.doi.org/10.21122/1683-6065-2019-3-74-84.
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The influence of the heating rate of a typical case hardening steel 15KHGN2TA and 25KHGT on the growth of austenitic grain during long-term isothermal exposures at the high-temperature chemical-heat treatment was studied. It is shown that the change in the rate of heating case hardening steels in the temperature interval a®g transformations during chemical-thermal treatment has a significant impact on the process of growth of austenitic grains in them.Regression equations describing the dependence of the average size of austenitic grain on the heating rate, pre-annealing temperature and cementation temperature are obtained, which allow selecting the cementation modes of various steels. A phenomenological model describing the mechanism of formation and growth of austenitic grains in steels under heating at different speeds is developed.It is concluded that the slow heating of steels in the interval of phase a®g transformation contributes to the formation of a complex of small austenite grains separated by high angle boundaries with adsorbed on them by impurity atoms, which ensures higher resistance grain structure to coalescence and reduce the rate of migration of the boundaries during prolonged hightemperature austenization.
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Zhang, Ting, and Xing Sheng Tong. "An Investigation of Carburized Layers on Austenitic Stainless Steels." Advanced Materials Research 842 (November 2013): 307–10. http://dx.doi.org/10.4028/www.scientific.net/amr.842.307.
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In this study, low temperature plasma carburizing of austenitic stainless steels has been studied, with the aim to improve the hardness and wear resistance of austenite layers. Austenitic stainless steels were plasma carburized at 450°C, using C3H8 as carbon carrier gas. Depth profiles of hardness, hardness distribution and the friction coefficient of carburized layer were measured. The results show that carburized layers range from 10 to 20μm, causing the improvement of the hardness and wear resistance of the surface of austenitic stainless steels.
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Li, Zhuang, Di Wu, and Wei Lv. "Development of Pb-Free Austenitic Stainless Steels." Advanced Materials Research 791-793 (September 2013): 486–89. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.486.
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Pb-free austenitic stainless steels were investigated by adding sulfur, rare earth (Re) elements and bismuth. The metallurgical properties, machinability and mechanical properties of both steels were examined. The results show that a significant amount of grey, spindle shaped inclusions were discovered in austenitic stainless steels, and they should belong to MnS inclusions containing bismuth element and rare earths oxide. The addition of S, Bi and Re to austenitic stainless steels improved the machinability. The machinability of steel B is better than that of steel A in a way. The mechanical properties of steel B are better than those of steel A, especially total elongation owing to the presence of rare earth elements. From the viewpoint of life cycle assessment, it is proposed that the development of Pb-free austenitic stainless steels containing S, Bi and Re is desirable.
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Herrera, Clara, Angelo Fernando Padilha, and R. L. Plaut. "Microstructure Evolution during Annealing Treatment of Austenitic Stainless Steels." Materials Science Forum 715-716 (April 2012): 913. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.913.
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Austenitic stainless steels of the AISI 304 and 316 grades, amongst over other hundred compositions of stainless steels available in the market, are the most frequently used ones worldwide. They are selected for numerous applications due to their favorable combination of characteristics such as low price, moderate to good corrosion resistance, excellent ductility and toughness along with good weldability. Their major limitation is in the yield strength, which is relatively low (about 200 MPa), in the annealed condition. Through cold working, this value can be easily multiplied by a factor of up to six, however ductility drops. The cold worked sub-structure of the austenitic stainless steels is formed by a planar array of dislocations and strain induced martensites, α (BCC) and ε (HCP). The microstructure evolution of austenitic stainless steels, AISI 304L and 316L, during cold rolling and subsequent annealing was studied (maximum thickness reduction - 90%). Samples were initially solution annealed at 1100°C for one hour with subsequent water quenched. Following, they have been cold rolled at room temperature, with cold reductions varying between 10 and 90%. After rolling, samples with approximately 90% thickness reduction have been submitted to annealing treatments in order to study martensite reversion, recovery and recrystallization. Annealing treatments have been performed between 200 and 900°C, with 100°C interval for one hour. The resulting microstructures were investigated by optical microscopy, scanning electron microscopy (with EBSD), magnetic measurements and hardness evaluation. As received (hot rolled) austenitic stainless steel sheet presented recrystallized equiaxial grains with austenite and islands of delta ferrite, in larger quantities mainly in the centre of the sheet. The solution annealing at 1100°C for one hour eliminated delta ferrite. During rolling, the austenite partially transforms into α martensite. The 50% αmartensite reversion temperature is close to 550°C for both steels. This temperature is practically independent of the amount of αmartensite present in the steel. The 50% recrystallization temperature of the 304L steel is lower than that of the 316L steel, about 700 and 800°C, respectively. The 316L steel shows a higher recrystallization resistance, due to its higher SFE and lower storage deformation energy than the 304L steel. Recrystallization temperature is about 150°C higher that the αmartensite reversion temperature. The percentage of αmartensite has a strong influence on the recrystallized grain size, the higher the percentage of this phase the smaller will be the grain size.
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Svyazhin, Anatoly G., Ludmila M. Kaputkina, and Inga V. Smarygina. "The Low-Nickel Cryogenic Steel Alloyed by Nitrogen." Materials Science Forum 879 (November 2016): 1899–904. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1899.
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New low-nickel Cr18Ni5Mn9Mo2N and Cr19Ni6Mn10Mo2N steels can be used up to-170 °C and differs in the highest level of durabilities in the hot-rolled and tempered from austenitic area state that provides its effective application in climatic conditions of the Arctic and Antarctic. Excess of durability over level, characteristic for traditional stainless steel of the Cr18Ni9 type, is provided due to additional solid solution hardening. Alloying with nitrogen to 0,18÷0,22% usual Cr18Ni9 steel has the smaller, but also high level of mechanical properties, differs in smaller thermal and mechanical stability of austenite and can be applied in less rigid on temperature and loadings service conditions. Corrosion resistance of austenitic stable steels free from contaminations is also higher compared to steel with regular cleanliness.
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Hamada, Atef S., L. Pentti Karjalainen, Mahesh C. Somani, and R. M. Ramadan. "Deformation Mechanisms in High-Al Bearing High-Mn TWIP Steels in Hot Compression and in Tension at Low Temperatures." Materials Science Forum 550 (July 2007): 217–22. http://dx.doi.org/10.4028/www.scientific.net/msf.550.217.
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The hot deformation behaviour of two high-Mn (23-24 wt-%) TWIP steels containing 6 and 8 wt-% Al with the fully austenitic and duplex microstructures, respectively, has been investigated at temperatures of 900-1100°C. In addition, tensile properties were determined over the temperature range from -80 to 100°C. It was observed that in spite of the lower Al content, the austenitic steel possessed the hot deformation resistance about twice as high as that of the duplex steel. Whereas the flow stress curves of the austenitic steel exhibited work hardening followed by slight softening due to dynamic recrystallisation, the duplex steel showed the absence of work hardening and discontinuous yielding under similar conditions. Tensile tests at low temperatures revealed that the austenitic grade had a lower yield strength than that of the duplex grade, but much better ductility, the elongation increasing with decreasing temperature, contrary to that for the duplex steel. This can be attributed to the intense mechanical twinning in the austenitic steel, while in the duplex steel, twinning occurred in the ferrite only and the austenite showed dislocation glide.
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Bae, Hyo Ju, Kwang Kyu Ko, Hyoung Seok Park, Jae Seok Jeong, Jung Gi Kim, Hyokyung Sung, and Jae Bok Seol. "Development of 1.2 GPa Ferrite-based Lightweight Steels via Low-temperature Tempering." Korean Journal of Metals and Materials 59, no. 10 (October 5, 2021): 683–91. http://dx.doi.org/10.3365/kjmm.2021.59.10.683.
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Previously reported low-Mn ferritic-based lightweight steels are potential candidates for industrial applications, however, they typically exhibit lower strength, with < 1 GPa and lower strength-ductility balance, than medium- and high-Mn austenitic lightweight steels. Herein, we introduce a low-temperature tempering-induced partitioning (LTP) treatment that avoids the strength-ductility dilemma of low-Mn ferriticbased steels. When the LTP process was performed at 330 oC for 665 s, the strength of typical ferritic base Fe-2.8Mn5.7Al0.3C (wt%) steel with heterogeneously sized metastable austenite grains embedded in a ferrite matrix, exceeded 1.1 GPa. Notably, the increased strength-ductility balance of the LTP-processed ferritic steel was comparable to that of the high-Mn based austenitic lightweight steel series. Using microscale to nearatomic scale characterization we found that the simultaneous improvement in strength and total elongation could be attributed to size-dependent dislocation movement, and controlled deformation-induced martensitic transformation.
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Bae, Hyo Ju, Kwang Kyu Ko, Hyoung Seok Park, Jae Seok Jeong, Jung Gi Kim, Hyokyung Sung, and Jae Bok Seol. "Development of 1.2 GPa Ferrite-based Lightweight Steels via Low-temperature Tempering." Korean Journal of Metals and Materials 59, no. 10 (October 5, 2021): 683–91. http://dx.doi.org/10.3365/kjmm.2021.59.10.695.
Full textAbstract:
Previously reported low-Mn ferritic-based lightweight steels are potential candidates for industrial applications, however, they typically exhibit lower strength, with < 1 GPa and lower strength-ductility balance, than medium- and high-Mn austenitic lightweight steels. Herein, we introduce a low-temperature tempering-induced partitioning (LTP) treatment that avoids the strength-ductility dilemma of low-Mn ferriticbased steels. When the LTP process was performed at 330 oC for 665 s, the strength of typical ferritic base Fe-2.8Mn5.7Al0.3C (wt%) steel with heterogeneously sized metastable austenite grains embedded in a ferrite matrix, exceeded 1.1 GPa. Notably, the increased strength-ductility balance of the LTP-processed ferritic steel was comparable to that of the high-Mn based austenitic lightweight steel series. Using microscale to nearatomic scale characterization we found that the simultaneous improvement in strength and total elongation could be attributed to size-dependent dislocation movement, and controlled deformation-induced martensitic transformation.
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Li, Dong Sheng, Dan Li, Hong Dou, Pei Gao, Yu Liu, Xiao Jun Chen, Xin Chun Jiang, and Jing Juan Pei. "High-Temperature Oxidation Resistance of Austenitic Stainless Steels." Key Engineering Materials 575-576 (September 2013): 414–17. http://dx.doi.org/10.4028/www.scientific.net/kem.575-576.414.
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The oxidation kinetic curves of four kinds of austenitic stainless steel at 700°C was measured by weighting method. It is showed that the oxidation curves of those austenitic stainless steels follow the parabolic law. The mass gain of 800Al steel. is the least of all. The surfacemorphology and structure of the oxide scale were studied by scanning electron microscopy and X-ray diffraction methods. It is found that adense oxide scale formed at 700°C in all four austenitic stainless steels. In austenitic stainless steel with high Mn content, scales are mainly composed of Mn2O3 and the spinel MnFe2O4. Scales of austenitic stainless steel with high Cr content but without element Al are composed by Cr2O3 and the small amount of spinel FeCr2O4 . Scales of austenitic stainless steel with element Al and Cr are composed of (Fe0.6Cr0.4)2O3 and Al oxide, showing the excellent oxidation resistance property.
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Jabłońska, Magdalena, Dariusz Kuc, Grzegorz Niewielski, and Bartosz Chmiela. "Influence of the Thermo-Mechanical Treatment on the Properties and Microstructure of High Manganese Austenitic-Ferritic Steel." Solid State Phenomena 226 (January 2015): 75–78. http://dx.doi.org/10.4028/www.scientific.net/ssp.226.75.
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New generation high-strength austenitic and austenitic-ferritic manganese steels represent a valid potential in applications for components in the automotive and railway industry due to the perfect combination of high mechanical properties and formability. Applying this new steels with their combination of properties allows for reduce the weight of vehicles by the use reduced cross-section components and thus to reduce fuel consumption. The development and implementation of industrial production and the use as construction materials such interesting and promising steel is conditioned to improve their casting properties and susceptibility to deformation during thermomechanical processes conditions. In this work, applied an new high manganese austenitic-ferritic steel for analysis the influence of the cooling medium in thermomechanical processes on the mechanical properties and structure of researched steel. The steel was hot rolled with finish temperature 900°C and next cooled with different conditions. Change the cooling conditions effect on the changes in the microstructure of the tested steel, observed grain refinement of austenite and ferrite morphology change. Also are changing the mechanical characteristics of the tested steel.
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Weber, Sebastian, Mauro Martin, and Werner Theisen. "Development of Lean Alloyed Austenitic Stainless Steels with Reduced Tendency to Hydrogen Environment Embrittlement." Materials Science Forum 706-709 (January 2012): 1041–46. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1041.
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Hydrogen gas is believed to play a more important role for energy supply in future instationary and mobile applications. In most cases, metallic materials are embrittled when hydrogen atoms are dissolved interstitially into their lattice. Concerning steels, in particular the ductility of ferritic grades is degraded in the presence of hydrogen. In contrast, austenitic steels usually show a lower tendency to hydrogen embrittlement. However, the so-called “metastable” austenitic steels are prone to hydrogen environmental embrittlement (HEE), too. Here, AISI 304 type austenitic steel was tensile tested in air at ambient pressure and in a 400 bar hydrogen gas atmosphere at room temperature. The screening of different alloys in the compositional range of the AISI 304 standard was performed with the ambition to optimize alloying for hydrogen applications. The results of the mechanical tests reveal the influence of the alloying elements Cr, Ni, Mn and Si on HEE. Besides nickel, a positive influence of silicon and chromium was found. Experimental results are supported by thermodynamic equilibrium calculations concerning austenite stability and stacking fault energy. All in all, the results of this work are useful for alloy design for hydrogen applications. A concept for a lean alloyed austenitic stainless steel is finally presented.
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Topolska, S., and J. Łabanowski. "Environmental Degradation of Dissimilar Austenitic 316L and Duplex 2205 Stainless Steels Welded Joints." Archives of Metallurgy and Materials 62, no. 4 (December 1, 2017): 2107–12. http://dx.doi.org/10.1515/amm-2017-0312.
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AbstractThe paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement was determined in slow strain rate tests (SSRT) with the strain rate of 2.2 × 10−6s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.
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Setargew, Nega, and Daniel J. Parker. "Zinc diffusion induced precipitation of σ-phase in austenitic stainless steel." Metallurgical Research & Technology 116, no. 6 (2019): 618. http://dx.doi.org/10.1051/metal/2019040.
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Zinc diffusion-induced degradation of AISI 316LN austenitic stainless steel pot equipment used in 55%Al-Zn and Zn-Al-Mg coating metal baths is described. SEM/EDS analyses results showed that the diffused zinc reacts with nickel from the austenite matrix and results in the formation of Ni-Zn intermetallic compounds. The Ni-Zn intermetallic phase and the nickel depleted zones form a periodic and alternating layered structure and a mechanism for its formation is proposed. The role of cavities and interconnected porosity in zinc vapour diffusion-induced degradation and formation of Ni-Zn intermediate phases is also discussed. The formation of Ni-Zn intermediate phases and the depletion of nickel in the austenite matrix results in the precipitation of σ-phase and α-ferrite in the nickel depleted regions of the matrix. This reaction will lead to increased susceptibility to intergranular cracking and accelerated corrosion of immersed pot equipment in the coating bath. Zinc diffusion induced precipitation of σ-phase in austenitic stainless steels that we are reporting in this work is a new insight with important implications for the performance of austenitic stainless steels in zinc containing metal coating baths and other process industries. This new insight will further lead to improved understanding of the role of substitutional diffusion and the redistribution of alloying elements in the precipitation of σ-phase in austenitic stainless steels.
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Maia, A. R. B., C. R. Guinâncio, R. L. Germano, Paulo Rangel Rios, and Ivani de S. Bott. "Use of Zirconium in Microalloyed Steels." Advanced Materials Research 15-17 (February 2006): 834–39. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.834.
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In this work, three Zr microalloyed steels with different levels of Zr were compared with plain C-Mn, Nb and Nb-Ti steels. Austenitic grain size was compared as a function of temperature for these steels. A qualitative assessment of the potential of Zr to delay austenite recrystallization, was also undertaken. Of course, the actual use of Zr depends on many considerations: cost, availability and behavior during steel refining among others but this preliminary assessment was encouraging. It showed that the addition of Zr was able to prevent grain growth at typical reheating temperatures, around 1200oC. Also, Zr was able to delay austenite recrystallization.
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Imbert, C. A. C., and H. J. McQueen. "Static Recrystallization of Tool Steels." Materials Science Forum 539-543 (March 2007): 4458–63. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4458.
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Double-twist torsion tests were used to determine static softening in the hot working range of three tool steels – W1, a carbon steel (1.03% C - 0.8% other elements), A2 and D2, a medium and a high alloy steel, containing 8.45% and 14.82% alloying elements. The carbon steel, that was single-phase austenite in the hot-working range, experienced rapid static recrystallization due to increased diffusion rate caused by C in hot austenite, very little alloying solute and no carbides. Carbides in alloy tool steels, which exist throughout the hot-working range, have a retarding effect on the progress of recrystallization but are responsible for enhancing initiation due to formation of nuclei at the strain concentration near the particle/matrix interface. Static recrystallization (SRX) of the alloy tool steels was compared with austenitic stainless steels, with similar strengths but much greater alloying content, and with microalloyed steels, as well as with the dynamic recrystallization kinetics.
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Li, Zhuang, Di Wu, Wei Lv, Shao Pu Kang, and Zhen Zheng. "Effect of Rare Earth Elements on Machining Characteristics of Austenitic Stainless Steels without Lead Addition." Applied Mechanics and Materials 377 (August 2013): 128–32. http://dx.doi.org/10.4028/www.scientific.net/amm.377.128.
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Rare earth elements (REE) are harmless for human health. REE addition contributes to the improvement of the machinability of the steels. In the present paper, machining characteristics of austenitic stainless steels without lead addition were investigated by adding free-machining elements, such as sulfur, REE and bismuth. The results have shown that large numbers of rounded, globular shaped inclusions were obtained for both steels. The machinability of steel B is better than that of steel A, and the cutting forces of steel B are lower than those of steel A at various cutting speeds. Lead can be substituted by REE and bismuth in free machinable austenitic stainless steels. REE significantly affects machining characteristics of austenitic stainless steels without lead addition. The mechanical properties of both steels were similar, and their fracture exhibited ductile characteristics. Satisfactory machinability and mechanical properties can be obtained for both steels.
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Safonov, E. N., and M. V. Mironova. "Surface Electric Arc Hardening of Low-Carbon Steels." Materials Science Forum 989 (May 2020): 318–23. http://dx.doi.org/10.4028/www.scientific.net/msf.989.318.
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Examined geometric characteristics, microhardness and features of structure formation in the heat affected zone of steels 09G2, 20L, 20FL. These studies were carried out after surface quenching by a magnetically controlled (scanning) DC electric arc in a protective argon atmosphere. It is shown that electric arc hardening forms on the treated surface of the steel a thin layer of martensitic-austenitic structure with varying composition and hardness. A ferrite-austenitic structure is formed in the region of transition from the base metal to the heat-strengthened metal. This structure contains crushed ferrite grain and winding boundaries between the structural components. On the periphery of austenitic grains martensitic layer is observed. Repeated heating, occurring during heat treatment of the adjacent surface area, is accompanied by a partial decay of martensite and austenite of a pre-hardened structure with the formation of bainite-and sorbitol-like tempering structures. On the surface, experienced repeated heating, the volume fraction of austenite increases. The dependences allowing to control the structural state and depth of the hardening zone are established.
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Padilha, A. F., and P. R. Rios. "Decomposition of Austenite in Austenitic Stainless Steels." ISIJ International 42, no. 4 (2002): 325–27. http://dx.doi.org/10.2355/isijinternational.42.325.
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Skorupski, Robert, Marek Smaga, Dietmar Eifler, Regina Schmitt, and Ralf Müller. "Influence of Morphology of Deformation Induced α´-Martensite on Stress-Strain Response in a Two Phase Austenitic-Martensitic-Steel." Key Engineering Materials 592-593 (November 2013): 582–85. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.582.
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In this research work specimens of the metastable austenitic steels AISI 304 and AISI 347 with one phase (fully austenitic) and two phase (austenitic-α ́-martensitic) microstructure were monotonically loaded at ambient temperature. Using stress-strain and temperature measurements the deformation behavior was characterized in detail. To study the influence of morphology of deformation induced α ́-martensite on the stress-strain response a phase field model for α ́-martensite transformations was developed. With this approach it was possible to model the two phase austenite-α ́-martensite microstructure and investigate the deformation behavior on the micro level. With optical microscopy, magnetic and x-ray measurements the microstructure characterization of fully austenitic and austenitic-α ́-martensitic steels was realized.
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Ueda, Keiji, Daichi Izumi, Toshinori Ishida, and Yoshiaki Murakami. "Effect of Alloying Element on Mechanical Properties of High Strength Austenitic Steel." Materials Science Forum 1016 (January 2021): 678–84. http://dx.doi.org/10.4028/www.scientific.net/msf.1016.678.
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A high strength austenitic steel is expected as a structural material for cryogenic use because fcc material does not cause a cleavage fracture despite high strength. High manganese steel which is a strong candidate material of the cryogenic high strength austenitic steel was originally famous for the Hadfield steel and widely applicable in actual use. In general, an excellent cryogenic toughness of the high manganese steels is achieved by obtaining stable fcc microstructure with an adequate amount manganese which is a typical austenite former alloy. However, as addition of manganese is not effective for increasing strength, other strengthening alloying elements like carbon and chromium need to be added. In this study, an effect of alloying elements on strength and cryogenic toughness of the high manganese austenitic steel is studied.
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Astafurov, Sergey, and Elena Astafurova. "Phase Composition of Austenitic Stainless Steels in Additive Manufacturing: A Review." Metals 11, no. 7 (June 30, 2021): 1052. http://dx.doi.org/10.3390/met11071052.
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Additive manufacturing (AM) is among the novel industrial technologies for fast prototyping of complex parts made from different constructional and functional materials. This review is focused on phase composition of additively manufactured chromium-nickel austenitic stainless steels. Being produced by conventional methods, they typically have single-phase austenitic structure, but phase composition of the steels could vary in AM. Comprehensive analysis of recent studies shows that, depending on AM technique, chemical composition, and AM process parameters, additively manufactured austenitic stainless steels could be characterized by both single-phase austenitic and multiphase structures (austenite, ferrite, σ-phase, and segregations of alloying elements). Presence of ferrite and other phases in AM steels strongly influences their properties, in particular, could increase strength characteristics and decrease ductility and corrosion resistance of the steels. Data in review give a state-of-art in mutual connection of AM method, chemical composition of raw material, and resultant phase composition of AM-fabricated Cr-Ni steels of 300-series. The possible directions for future investigations are discussed as well.
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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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Cheng, Wei Chun, Kun Hsien Lee, Shu Mao Lin, and Shao Yu Chien. "The Observation of Austenite to Ferrite Martensitic Transformation in an Fe-Mn-Al Austenitic Steel after Cooling from High Temperature." Materials Science Forum 879 (November 2016): 335–38. http://dx.doi.org/10.4028/www.scientific.net/msf.879.335.
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Fe-Mn-Al steels with low density have the potential to substitute for TRIP (transformation induced plasticity) steels. For the development of Fe-Mn-Al TRIP steels, phase transformations play an important role. Our methods of studying the phase transformations of the Fe-16.7 Mn-3.4 Al (wt%) austenitic steel include heating and cooling. We have studied the martensitic transformation of the ternary Fe-Mn-Al steel. Single austenite phase is the equilibrium phase at 1373 K, and dual phases of ferrite and austenite are stable at low temperatures. It is noteworthy that lath martensite forms in the prior austenite grains after cooling from 1373 K via quenching, air-cooling, and/or furnace-cooling. The crystal structure of the martensite belongs to body-centered cubic. The formation mechanism of the ferritic martensite is different from the traditional martensite in steels. Ferrite is the stable phase at low temperature.
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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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Liu, Hongbo, Jianhua Liu, Bowei Wu, Xiaofeng Su, Shiqi Li, and Hao Ding. "Influence of Ti on the Hot Ductility of High-manganese Austenitic Steels." High Temperature Materials and Processes 36, no. 7 (July 26, 2017): 725–32. http://dx.doi.org/10.1515/htmp-2016-0005.
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AbstractThe influence of Ti addition (~0.10 wt%) on hot ductility of as-cast high-manganese austenitic steels has been examined over the temperature range 650–1,250 °C under a constant strain rate of 10−3 s−1 using Gleeble3500 thermal simulation testing machine. The fracture surfaces and particles precipitated at different tensile temperatures were characterized by means of scanning electron microscope and X-ray energy dispersive spectrometry (SEM–EDS). Hot ductility as a function of reduction curves shows that adding 0.10 wt% Ti made the ductility worse in the almost entire range of testing temperatures. The phases’ equilibrium diagrams of precipitates in Ti-bearing high-Mn austenitic steel were calculated by the Thermo-Calc software. The calculation result shows that 0.1 wt% Ti addition would cause Ti(C,N) precipitated at 1,499 °C, which is higher than the liquidus temperature of high-Mn austenitic steel. It indicated that Ti(C,N) particles start forming in the liquid high-Mn austenitic steel. The SEM–EDS results show that Ti(C,N) and TiC particles could be found along the austenite grain boundaries or at triple junction, and they would accelerate the extension of the cracks along the grain boundaries.
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Shakhova, Iaroslava, Andrey Belyakov, Rustam Kaibyshev, Yuuji Kimura, and Kaneaki Tsuzaki. "Submicrocrystalline Structures and Tensile Behaviour of Stainless Steels Subjected to Large Strain Deformation and Subsequent Annealing." Advanced Materials Research 409 (November 2011): 607–12. http://dx.doi.org/10.4028/www.scientific.net/amr.409.607.
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Tensile behaviour of two steels with submicrocrystalline structures, i.e. a 304-type austenitic steel and an Fe-27%Cr-9%Ni austenitic-ferritic steel, was studied. The starting materials were subjected to large strain rolling and swaging to a total strain of ∼4 at ambient temperature. The severe deformation resulted in a partial martensitic transformation and the development of highly elongated austenite/ferrite (sub) grains aligned along the deformation axis. In the cold worked state, the transverse grain/subgrain size was about 100 nm in the 304-type steel and about 150 nm in the Fe-27%Cr-9%Ni steel. The grain refinement by severe plastic deformation resulted in increase of ultimate tensile strength to 2000 MPa and 1800 MPa in 304-type and Fe-27%Cr-9%Ni steels, respectively. The phase transformation and recrystallization took place concurrently upon annealing, leading to the development of submicrocrystalline structure consisting of austenite and ferrite grains. No significant softening took place under annealing at temperatures below 600°C. The tensile strength was 1920 MPa in 304-type steel and 1710 MPa in Fe-27%Cr-9%Ni steel after annealing at 500°C for 2 hours.
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Ermakov, Boris, S. A. Vologzhanina, Sergej M. Bobrovskij, Aleksey A. Lukyanov, and Ranita Lee. "Cast Austenitic Steels for Cryogenic Technology." Key Engineering Materials 822 (September 2019): 60–65. http://dx.doi.org/10.4028/www.scientific.net/kem.822.60.
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This article presents the results of a study of martensitic steels. Studied steels: OZH9K14N6MZD, 12X18N10TL, 07X13G28ANFL. The object of the study was the optimization of properties for use in cryogenic technology. The purpose of the study is to increase the strength and service life of products for various purposes. The destruction of steel 12X18N10TL and 07X13G28ANFL was investigated. It has been established that 07X13G28ANFL steel is more preferable for cryogenic use and is recommended by the authors.
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Juuti, Timo J., L. Pentti Karjalainen, Raimo Ruoppa, and Tero Taulavuori. "Static Strain Ageing in Some Austenitic Stainless Steels." Materials Science Forum 638-642 (January 2010): 3278–83. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3278.
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The yield strength in austenitic stainless steels can be improved by cold rolling. Recently, it has been realized that a considerable further increase can be achieved through static strain ageing (SSA). The effect of SSA in four austenitic stainless steel grades was studied. The test materials were formerly cold rolled to three different reductions of 15%, 30% and 40%. Subsequently, the steels were aged at temperature range between 160 and 400 °C with ageing times from 15 to 15000 seconds. Owing to SSA, increments over 200 MPa in yield strength were observed, while elongation decreased only slightly or even improved by 1 to 2%-units. The influence of ´-martensite on the strength increase was apparent. The maximum strength increase with relatively small drop of elongation was achieved in the steels cold rolled to 30% reduction while approximately 50% of ´- martensite was formed. However, a small increase in the yield strength was detected even in steels cold rolled to 15% reduction and containing 0 to 2% of ´-martensite only. Therefore, SSA seems also to take place in the austenite phase. To clarify the reason for improvement of the ductility in the instance of strengthening, work hardening rates were determined and found to differ considerably between aged and non-aged structures. The activation energy of the SSA process determined was found to be almost equal to the activation energy of carbon and nitrogen diffusion in the austenite phase. A mechanism resembling the Suzuki effect was suggested as the main mechanism of the SSA process.
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Lad’yanov, V. I., G. A. Dorofeev, E. V. Kuz’minykh, V. A. Karev, and A. N. Lubnin. "ALUMINOBAROTHERMIC SYNTHESIS OF HIGH-NITROGEN STEEL." Izvestiya. Ferrous Metallurgy 62, no. 2 (March 30, 2019): 154–62. http://dx.doi.org/10.17073/0368-0797-2019-2-154-162.
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High-nitrogen austenitic steels are promising materials, combining high strength, plasticity and corrosion resistance properties. However, to produce high-nitrogen steel by conventional metallurgical methods under high nitrogen pressure, powerful and complex metallurgical equipment is required. From energy-saving viewpoint, an alternative and simpler method for producing high-nitrogen steels can be aluminothermy (reduction of metal oxides by metallic aluminum) under nitrogen pressure. Thermodynamic modeling of aluminothermic reactions in a nitrogen atmosphere was carried out by the authors. Aluminothermy under nitrogen pressure was used to produce high-nitrogen nickel-free Cr – N and Cr – Mn – N stainless steels with a nitrogen content of about 1 %. Microstructure (X-ray diffraction, metallography and transmission electron microscopy techniques) and mechanical properties were examined. Thermodynamic analysis has shown that the aluminothermic reduction reactions do not go to the end. The most important parameter of the synthesis is the ratio of Al and oxygen in the charge, the correct choice of which provides a compromise between completeness of oxides reduction, content of aluminum and oxygen in steel (the degree of deoxidation), and its contamination with aluminum nitride. Cr – N steel ingots in the cast state had the structure of nitrogen perlite (ferrite-nitride mixture), and Cr – Mn – N steel – ferrite-austenite structure with attributes of austenite discontinuous decomposition with Cr2 N precipitations. Quenching resulted in complete austenization of both steels. The compliance of the austenite lattice parameter obtained from the diffractograms for quenched Cr – Mn – N steel with the parameter predicted from the known concentration dependence for Cr – Mn – N austenitic steels indicated that all alloying elements (including nitrogen) were dissolved in austenite during aging at quenching temperature and fixed in the solid solution by quenching. Study of the mechanical properties of quenched Cr – Mn – N steel has shown a combination of high strength and ductility. It is concluded that by the aluminothermic method a high-nitrogen steel can be obtained, which, by mechanical properties, is not inferior to industrial steel – analog manufacted by electroslag remelting under nitrogen pressure.
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Boemke, Annika, Marek Smaga, and Tilmann Beck. "Influence of surface morphology on the very high cycle fatigue behavior of metastable and stable austenitic Cr-Ni steels." MATEC Web of Conferences 165 (2018): 20008. http://dx.doi.org/10.1051/matecconf/201816520008.
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The present study investigates conventional and cryogenically turned specimens of metastable austenitic steel AISI 347 and stable austenitic steel AISI 904L in the VHCF regime. The cryogenic turning process includes cooling by CO2 snow and generates a surface layer on the specimens of metastable austenitic steel, which is characterized by a phase transformation from paramagnetic fcc - austenite to ferromagnetic bcc - martensite and grain refinement. The stable austenitic steel retains its purely austenitic structure after cryogenic turning, but also shows grain refinement in the surface layer. The specimens with different surface morphology were cyclically loaded at ambient temperature using an ultrasonic fatigue testing system developed and built at the authors’ institute. The testing machine operates at frequencies of approx. 20 kHz to achieve high numbers of load cycles within a reasonable time. To avoid self heating of the specimen, the tests were performed in pulse-pause mode. All specimens were tested with a load ratio of R = -1. During cyclic loading, the metastable austenitic steel partially transformed from paramagnetic fcc - austenite to ferromagnetic bcc - martensite, while no phase transformation could be detected in the stable austenitic steel.
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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.
Full textAbstract:
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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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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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.
Full textAbstract:
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.