Journal articles: 'Austenitic stainless steel. Grain boundaries'

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Dehghan-Manshadi, A., Hossein Beladi, Matthew R. Barnett, and Peter D. Hodgson. "Recrystallization in 304 Austenitic Stainless Steel." Materials Science Forum 467-470 (October 2004): 1163–68. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.1163.

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A 304 austenitic stainless steel was deformed using hot torsion to study the evolution of dynamic recrystallization (DRX). The initial nucleation of dynamically recrystallization occurred by the bulging of pre-existing high angle grain boundaries at a strain much lower than the peak strain. At the peak stress, only a low fraction of the prior grain boundaries were covered with new DRX grains. Beyond the peak stress, new DRX grains formed layers near the initial DRX and a necklace structure was developed. Several different mechanisms appeared to be operative in the formation of new high angle boundaries and grains. The recrystallization behaviour after deformation showed a classic transition from strain dependent to strain independent softening. This occurred at a strain beyond the peak, where the fraction of dynamic recrystallization was only 50%.

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Kokawa, Hiroyuki, W. Z. Jin, Zhan Jie Wang, M. Michiuchi, Yutaka S. Sato, Wei Dong, and Yasuyuki Katada. "Grain Boundary Engineering of High-Nitrogen Austenitic Stainless Steel." Materials Science Forum 539-543 (March 2007): 4962–67. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4962.

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Large amount of nitrogen addition into an austenitic stainless steel can improve the mechanical properties and corrosion resistance remarkably as far as the nitrogen is in solid solution. However, once the nitrogen precipitates as nitride, it results in deteriorations in the properties of the high nitrogen austenitic stain steel. During welding, a high nitrogen austenitic stainless steel is ready to precipitate rapidly immense amounts of chromium nitride in the heat affected zone (HAZ), as intergranular or cellular morphologies at or from grain boundaries into grain interiors. The nitride precipitation reduces seriously the local mechanical properties and corrosion resistance. The present authors have demonstrated that a thermomechanical-processing as grain boundary engineering (GBE) inhibited intergranular chromium carbide precipitation in the HAZ of a type 304 austenitic stainless steel during welding and improved the intergranular corrosion resistance drastically. In the present study, the thermomechanical-processing was applied to a high nitrogen austenitic stainless steel containing 1 mass% nitrogen to suppress the nitride precipitation at or from grain boundaries in the HAZ during welding by GBE. GBE increases the frequency of coincidence site lattice (CSL) boundaries in the material so as to improve the intergranular properties, because of strong resistance of CSL boundaries to intergranular deteriorations. The optimum parameters in the thermomechanical-processing brought a very high frequency of CSL boundaries in the high nitrogen austenitic stainless steel. The GBE suppressed the intergranular and cellular nitride precipitation in the HAZ of the high nitrogen austenitic stainless steel during welding.

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Wang, Min, and Hong Zhen Guo. "Influence of Deformation Heat Treatment on the Ultra-Fine Structure of Austenitic Stainless Steel." Materials Science Forum 551-552 (July 2007): 421–25. http://dx.doi.org/10.4028/www.scientific.net/msf.551-552.421.

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According to accommodate-state and big bulk 18-8 type austenitic stainless steel has the weakness of coarse-grained and low strength. Optical microscopy，electron microscopy and X-ray diffraction were used to analyze microstructure and grain size of austenitic stainless steel specimens after deformation heat treatment. The paper investigates the influence of recrystallization annealing on the ultra-fine structure of cold deformation austenitic stainless steel. The results show that austenitic stainless steel can produce deformation-induced martensite by cold rolling deformation， and that the content of martensite increases with deformation degree. During the annealing, ultra-fine grains can be obtained by the reversal transformation-induced martensite(M′→ γ ). After severe cold deformation, inside austenitic grains imported austenitic-martensite(γ /M) phase boundaries shall serve to add a great deal of forming nucleus location for recrystallization, to enhance forming nucleus ratio and refine grain. 1Cr18Ni9Ti austenitic stainless steel by severe cold deformation and recrystallization annealing can acquire ultra-fine grains.

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Meng, Li Jun, Hui Xing, and Jian Sun. "Precipitation Behavior in AL6XN Austenitic Stainless Steel." Materials Science Forum 654-656 (June 2010): 2330–33. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2330.

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The precipitation behavior in the AL6XN austenitic stainless steel after creep deformation at temperatures 500~750 °C up to 3600 hours has been studied by electron microscope. The results showed that precipitates were hardly observed for the steel crept at 500~550 °C, and that the precipitates of carbides were mainly found at grain boundaries in samples crept at 600 °C. When the creep temperature was increased to 650~750 °C, a high density precipitates was found both at grain boundaries and within grains. The electron diffraction pattern and energy-dispersive X-ray spectroscopy analyses confirmed that these precipitates are  and Laves phases.

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Caul, M. D., and V. Randle. "Grain-Boundary Characteristics in Austenitic Steel." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 344–45. http://dx.doi.org/10.1017/s0424820100164180.

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Grain boundaries are an active area of research interest due to their effect on material property and structure relationships. In order to discuss material properties with regard to grain boundaries it is necessary to know the boundary type. The optimum technique for performing this task is Electron Backscatter Diflfraction (EBSD) in concert with the Scanning Electron Microscope (SEM). By collecting texture measurements in the form of individual orientations from grains it is possible to obtain misorientation measurements from grain boundaries. These measurements are three of the five degrees of freedom necessary to geometrically describe a grain boundary. The other two can be obtained by a serial sectioning technique.Grain boundaries in austenitic steel specimens, isothermally aged at either 700°C or 800°C, have been evaluated with the aim of relating boundary geometry to Cr2N precipitate formation. Samples were analysed using SEM and EBSD in order to obtain orientation measurements of individual grains to misorientations at grain boundaries and to Cr2N precipitates. These precipitates are detrimental to room temperature properties of high nitrogen stainless steels, so a reduction in their formation at grain boundaries would be advantageous. The steel is therefore an ideal candidate material for relating boundaries to material properties. The 700°C isothermally aged sample induces precipitate formation at grain boundaries whereas precipitation by cellular decomposition of austenite occurs in the 800 CC sample. The 700°C sample was used to categorise boundary types using the CSL model and relate this to Cr2N formation. The 800°C sample was used to examine the effect of aging temperature on boundary inclination. Therefore all five degrees of freedom in grain boundary geometry were obtained.

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Shen, Lie, Liang Wang, Jiu Jun Xu, and Ying Chun Shan. "Effect of Pre-Shot Peening on Plasma Nitriding Kinetics of Austenitic Stainless Steel." Advanced Materials Research 634-638 (January 2013): 2955–59. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.2955.

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The fine grains and strain-induced martensite were fabricated in the surface layer of AISI 304 austenitic stainless steel by shot peening treatment. The shot peening effects on the microstructure evolution and nitrogen diffusion kinetics in the plasma nitriding process were investigated by optical microscopy and X-ray diffraction. The results indicated that when nitriding treatments carried out at 450°C for times ranging from 0 to 36h, the strain-induced martensite transformed to supersaturated nitrogen solid solution (expanded austenite), and slip bands and grain boundaries induced by shot peening in the surface layer lowered the activation energy for nitrogen diffusion and evidently enhanced the nitriding efficiency of austenitic stainless steel.

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Ritoni, Marcio, M. Martins, F. C. Nascimento, and Paulo Roberto Mei. "Phase Transformations on ASTM a 744 Gr. CN3MN Superaustenitic Stainless Steel after Heat Treatment." Defect and Diffusion Forum 312-315 (April 2011): 56–63. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.56.

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The superaustenitic stainless steel ASTM A 744 Gr. CN3MN (22Cr-25Ni-7Mo-0.2N) has as mainly characteristic high corrosion resistance in severe environment. As the corrosion resistance depends on the microstructure, it was investigated the phase transformations after a solution treatment at 1200°C. Thermocalc calculation for 53Fe-25Ni-22Cr alloy indicates austenitic phase between 1300 and 800°C and austenite + sigma phase below 800°C. The as-cast steel studied presented 2.7 % of precipitates volume fraction and the precipitates were located on the grain boundaries and inside the austenitic grains. X-ray diffraction confirmed the presence of sigma phase in as-cast sample. Scanning electron microscopy showed that the level of Cr and Mo was higher in the precipitates than in the austenitic matrix and the Ni content was higher in matrix compared to precipitates. After heating at 1200°C during 90 minutes, the precipitate volume fraction was reduced to 2.1 % and the grain boundaries precipitates were dissolved. The microstructural analyses made through transmission electron microscopy and X-ray diffraction showed the presence sigma phase and M6C carbide.

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Wasnik, D. N., Vivekanand Kain, I. Samajdar, Bert Verlinden, and P. K. De. "Effects of Overall Grain Boundary Nature on Localized Corrosion in Austenitic Stainless Steels." Materials Science Forum 467-470 (October 2004): 813–18. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.813.

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Thermo-mechanical processing of type 304 and type 316L stainless steels done by (a) cold rolling to a reduction in thickness of 20 to 80 percent and (b) solution annealing to obtain a medium size of grains led to a considerable improvement in resistance to both sensitization and intergranular corrosion. The nature of the resultant grain boundaries was examined in a scanning electron microscope using orientation imaging microscopy in electron back scattered diffraction mode. Fraction of random and special grain boundaries were established for each set of thermo-mechanical processing. After appropriate sensitization treatments, the degrees of sensitization of these stainless steels were evaluated by double loop electrochemical potentiokinetic reactivation tests. Standard ASTM tests were used to evaluate susceptibility to intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC). These studies showed that a particular combination of thermomechanical processing led to formation of over 75 percent random grain boundaries in the steels and this imparted resistance to sensitization and to IGC and IGSCC. This opens a new concept in grain boundary (GB) engineering of a high fraction of random GB increasing the resistance to localized corrosion like IGC and IGSCC. Textural studies were carried out with the help of X-ray and MTM-FHM software. It showed significant change of texture in type 304 stainless steel, while no change in the texture of type 316L stainless steel after cold rolling and annealing.

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Briant, C. L. "Nitrogen segregation to grain boundaries in austenitic stainless steel." Scripta Metallurgica 21, no. 1 (January 1987): 71–74. http://dx.doi.org/10.1016/0036-9748(87)90409-1.

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Zhang, Shu Cai, Hong Chun Zhu, De Gang Liu, Hao Feng, Hua Bing Li, Zhou Hua Jiang, Guang Wei Fan, Wei Zhang, and Lei Ying Wang. "Research on Precipitation Kinetics of Super Austenitic Stainless Steel with High Mo and N." Applied Mechanics and Materials 687-691 (November 2014): 4197–201. http://dx.doi.org/10.4028/www.scientific.net/amm.687-691.4197.

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The precipitates and precipitation kinetics of super austenitic stainless steel with high Mo and N (HHSASS) were investigated by optical microscope (OM), scanning electron microscope (SEM) and quantitative metallography method. The results show that the TTP curves are C-shaped, the “nose” temperatures of precipitation are found to be 1000°C with the incubation periods of 120s and 600s, respectively. At 1000°C, some precipitates form as ellipsoidal-shaped and connect along the grain boundaries first. Then a few precipitates start forming as needle-shaped within austenite grains. Until aging for 300min, the field is filled with needle-shaped precipitates. The main precipitates in HHSASS are Sigma phase and Chi phase that are rich in Cr and Mo. The precipitates on the grain boundaries are ellipsoidal-shaped and those in the austenite grains are needle-shaped. About the structures of precipitates need to be further researched.

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Wang, Wei Guo, Xiao Ying Fang, and Hong Guo. "A Comparison of Grain Boundary Character Distributions between Grain Boundary Engineered Austenitic Stainless Steel and Pb-Ca Based Alloy." Materials Science Forum 753 (March 2013): 83–86. http://dx.doi.org/10.4028/www.scientific.net/msf.753.83.

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Though there developed same concentrations of special grain boundaries (SBs) in grain boundary engineered (GBE) austenitic stainless steel (304 stainless steel) and a Pb-Ca based alloy, the makeup of SBs, size distribution of clusters of grains with ∑3n (n=1,2,3) orientation relationships (∑3n CG), and grain orientations (textures) are quite different between the two specimens, suggesting there have two different mechanisms separately governing the evolution of grain boundary character distributions (GBCDs) in the two types of materials during GBE processing.

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Zou, De Ning, Rong Liu, Jiao Li, Kun Wu, and Xiao Hua Liu. "Precipitation Behavior of High-Nitrogen Low-Nickel Austenitic Stainless Steel at Intermediate Temperature." Materials Science Forum 724 (June 2012): 359–62. http://dx.doi.org/10.4028/www.scientific.net/msf.724.359.

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The precipitation behavior of nitrides and carbides occurred in aging process for 10Cr21Mn16NiN austenitic stainless steel at intermediate temperature was investigated by use of thermodynamic calculation, metallography and electron microscopy analysis. The precipitates evolved from chain-like initiatively along grain boundaries at lower aging temperature, to that along grain boundaries and inside the grain of austenite with more content as the temperature rising gradually. When aging at 800 °C, precipitates became layered tablet shaped and the composition was ascertained the mixture of Cr2N and M23C6. At a certain temperature, the volume fraction of precipitates for the aged testing steel by air cooling was slightly higher than that by water quenching.

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Májlinger, Kornél, and Péter János Szabó. "Intercrystalline Cracking of Austenitic Steel during Brazing." Materials Science Forum 729 (November 2012): 442–47. http://dx.doi.org/10.4028/www.scientific.net/msf.729.442.

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During brazing of austenitic stainless steel with copper based brazing material a common failure occurs, namely that the brazing material solutes along grain boundaries, which look like cracks. This unfortunate effect occurred when AISI 304 steel is brazed. To avoid this unwanted effect since the cracks propagate mainly on high angle grain boundaries our goal was to enhance the number of special coincident site lattice type grain boundaries with thermomechanical treatment. Experiments were performed for 1, 48 and 72 hour heat treatments at different level of cold rolled materials. After the thermomechanical treatment significant decrease in the crack size was found in depth and width, respectively. The grain boundaries were investigated on electro polished samples in an electron microscope with electron backscattered diffraction technique. The brazing was made with Boehler SG-CuSi3 brazing material.

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Wang, Li Min, Zhi Hua Gong, Gang Yang, Zheng Dong Liu, and Han Sheng Bao. "Microstructure Evolution and Property of Austenitic Stainless Steel after ECAP." Applied Mechanics and Materials 268-270 (December 2012): 291–96. http://dx.doi.org/10.4028/www.scientific.net/amm.268-270.291.

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Ultrafine-grain or even nano-grain microstructure can be made by equal channel angular pressing (ECAP), mainly resulting from shear strain. The authors experimentally investigated 00Cr18Ni12 austenitic stainless steel and its mechanical properties during and after ECAP. The results showed that because of larger shear stress, many slipping bands occured inside grains, with the increase of pressing pass, the slipping bands may interact with each other to separate slipping bands into sub-grains, finally, the sub-grains transformed into new grains with large angular boundaries. The grain size was about 200nm after the 7th pass. After the 1st and 2nd pass, the tensile strength was higher 93% and 144% than that without ECAP, the yield strength was 5.3 and 6.6 times of that without ECAP respectively.

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Fujikawa, H., and Y. Iijima. "Effect of Grain Size on the High Temperature Oxidation Behaviour of Austenitic Stainless Steels." Defect and Diffusion Forum 333 (January 2013): 149–55. http://dx.doi.org/10.4028/www.scientific.net/ddf.333.149.

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The effect of grain size on high temperature oxidation behaviour of 316 steels at 700º, 850º and 1000°C in air was studied. The results show that the mass gain increases with the increase of grain size. Particularly, the gradient of mass gain is severe in at lower oxidation temperatures. In the oxidation at temperatures of more than the solid solution temperature, the grain size before the oxidation changed to coarse grain size. Therefore, in this case, it is not enough to estimate the oxidation behaviour by the grain size before the oxidation. The exfoliation of oxide scale is severe in steel with coarse grains. Over 850°C, the exfoliation was observed in 316 steel with coarse grains. At 1000°C, the oxide scale of 316 steel was exfoliated, but it was extreme in the coarse grains. Cr, Mn and Si in the oxide scale were enriched in the oxide scale of the steel with fine grains. Particularly, Si was remarkably enriched at the metal-oxide interface and grain boundaries.

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Kenik, E. A., J. T. Busby, M. K. Miller, A. M. Thuvander, and G. Was. "Grain Boundary Segregation and Irradiation-Assisted Stress Corrosion Cracking of Stainless Steels." Microscopy and Microanalysis 5, S2 (August 1999): 760–61. http://dx.doi.org/10.1017/s1431927600017128.

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Irradiation-assisted stress corrosion cracking (IASCC) of irradiated austenitic stainless steels has been attributed to both microchemical (radiation-induced segregation (RIS)) and microstructural (radiation hardening) effects. The flux of radiation-induced point defects to grain boundaries results in the depletion of Cr and Mo and the enrichment of Ni, Si, and P at the boundaries. Similar to the association of stress corrosion cracking with the depletion of Cr and Mo in thermally sensitized stainless steels, IASCC is attributed in part to similar depletion by RIS. However, in specific heats of irradiated stainless steel, “W-shaped” Cr profiles have been observed with localized enrichment of Cr, Mo and P at grain boundaries. It has been show that such profiles arise from pre-existing segregation associated with intermediate rate cooling from elevated temperatures. However, the exact mechanism responsible for the pre-existing segregation has not been identified.Two commercial heats of stainless steel (304CP and 316CP) were forced air cooled from elevated temperatures (∽1100°C) to produce pre-existing segregation.

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Macatangay, D. A., S. Thomas, N. Birbilis, and R. G. Kelly. "Unexpected Interface Corrosion and Sensitization Susceptibility in Additively Manufactured Austenitic Stainless Steel." Corrosion 74, no. 2 (December 19, 2017): 153–57. http://dx.doi.org/10.5006/2723.

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This communication describes observations of unexpected microstructural interface susceptibility to accelerated dissolution in additively manufactured (AM) Type 316L stainless steel prepared by selective laser melting. Observations include accelerated microstructural interface dissolution in the as-built condition, as well as more rapid sensitization of grain boundaries upon exposure to elevated temperature. Electrolytic etching in persulfate solution was used to evaluate the susceptibility of microstructural interfaces to accelerated dissolution in both wrought and AM 316L. Post-test optical microscopy and profilometry on AM 316L revealed that the melt pool boundaries in the as-built condition were susceptible to accelerated attack, although the small grains within the prior melt pools were not. Furthermore, short, elevated temperature exposure (1 h at 675°C) also induced sensitization of the grain boundaries. Identical testing on as-manufactured wrought 316L confirmed that no microstructural interfaces showed susceptibility to accelerated dissolution, and grain boundaries could be sensitized only by extended periods (24 h) at elevated temperature (675°C). Annealing was capable of removing sensitization in wrought 316L, but activated the surface of the AM 316L, leading to widespread, uniform dissolution.

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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.

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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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Yanushkevich, Zhanna, Andrey Belyakov, and Rustam Kaibyshev. "Structural Changes in a 304-Type Austenitic Stainless Steel Processed by Multiple Hot Rolling." Advanced Materials Research 409 (November 2011): 730–35. http://dx.doi.org/10.4028/www.scientific.net/amr.409.730.

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The microstructure evolution and the dynamic processes of grain refinement in a 304-type austenitic stainless steel during multiple calibre hot rolling at temperatures of 700-1000°C were studied. The structural changes are characterized by the elongation of original grains towards the rolling axis and the development of new fine grains, the mean size of which decreases with decreasing the deformation temperature. During multiple rolling at 1000°C, the new grains resulted from the development of discontinuous dynamic recrystallization involving a bulging of frequently corrugated grain boundaries. On the other hand, the new grain boundaries leading to remarkable refinement of original microstructure were developed at temperatures below 800°C as a result of continuous strain-induced reactions.

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Kocsisová, Edina, Mária Dománková, Ivan Slatkovský, and Martin Sahul. "Study of the Sensitization on the Grain Boundary in Austenitic Stainless Steel Aisi 316." Research Papers Faculty of Materials Science and Technology Slovak University of Technology 22, no. 341 (December 1, 2014): 131–36. http://dx.doi.org/10.2478/rput-2014-0019.

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Abstract Intergranular corrosion (IGC) is one of the major problems in austenitic stainless steels. This type of corrosion is caused by precipitation of secondary phases on grain boundaries (GB). Precipitation of the secondary phases can lead to formation of chromium depleted zones in the vicinity of grain boundaries. Mount of the sensitization of material is characterized by the degree of sensitization (DOS). Austenitic stainless steel AISI 316 as experimental material had been chosen. The samples for the study of sensitization were solution annealed on 1100 °C for 60 min followed by water quenching and then sensitization by isothermal annealing on 700 °C and 650 °C with holding time from 15 to 600 min. Transmission electron microscopy (TEM) was used for identification of secondary phases. Electron backscattered diffraction (EBSD) was applied for characterization of grain boundary structure as one of the factors which influences on DOS.

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Zhang, Hui, Yanfeng Liu, Xian Zhai, and Wenkai Xiao. "Effects of High Temperature Aging Treatment on the Microstructure and Impact Toughness of Z2CND18-12N Austenitic Stainless Steel." Metals 10, no. 12 (December 18, 2020): 1691. http://dx.doi.org/10.3390/met10121691.

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During the casting cooling process or the forging process, austenitic stainless steel will remain at around 800 °C for some time. During this period, precipitate particle behaviors in austenitic stainless steel (containing ferrite) will cause a reduction in ductility, which can lead to material cracking. In this study, the effects of aging at 800 °C on the microstructure, impact toughness and microhardness of Z2CND18-12N austenitic stainless steel were systematically investigated. The precipitation processes of the χ and σ phases were characterized by color metallography and back scattered electron (BSE) signals. The toughness was investigated by the Charpy impact test. After the aging treatment, the χ and σ phases precipitated successively in the ferrite, and as the aging duration increased, the χ-phase dissolved and the σ-phase precipitated along the austenite grain boundaries. These all lead to a decrease in toughness and an increase in microhardness. Finally, the relationship between fracture morphology and aging time is discussed herein, and a crack mechanism is given.

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Mateo, Antonio, Ina Sapezanskaia, Joan Roa, Gemma Fargas, and Abdelkrim Redjaïmia. "Transmission of Plasticity Through Grain Boundaries in a Metastable Austenitic Stainless Steel." Metals 9, no. 2 (February 15, 2019): 234. http://dx.doi.org/10.3390/met9020234.

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Austenitic metastable stainless steels have outstanding mechanical properties. Their mechanical behavior comes from the combination of different deformation mechanisms, including phase transformation. The present work aims to investigate the main deformation mechanisms through the grain boundary under monotonic and cyclic tests at the micro- and sub-micrometric length scales by using the nanoindentation technique. Within this context, this topic is relevant as damage evolution at grain boundaries is controlled by slip transfer, and the slip band-grain boundary intersections are preferred crack nucleation sites. Furthermore, in the case of metastable stainless steels, the interaction between martensitic phase and grain boundaries may have important consequences.

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Shvab, Ruslan, Eduard Hryha, Petro Shykula, Eva Dudrová, Ola Bergman, and Sven Bengtsson. "Microstructure of High Cr-Alloyed Sintered Steel – Prediction and Analysis." Materials Science Forum 782 (April 2014): 473–79. http://dx.doi.org/10.4028/www.scientific.net/msf.782.473.

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Study of microstructure of high Cr-alloyed sintered austenitic stainless steel was performed in few stages XPS analysis of powder surface, theoretical prediction of microstructure by Thermo-Calc and JMatPro software and metallographic observation of sintered material. XPS analysis showed presence of thin iron oxide layer on the surface of powder particles and oxide islands formed by Si, Mn and Cr. Theoretical prediction made by Thermo-Calc and JMatPro calculations showed presence of austenite with chromium carbides and carbonitrides in equilibrium state. Both predictions are in good agreement. Metallographic observation of sintered material showed that microstructure contains small austenitic grains with size of 3-5 μm with fine carbides (1-2 μm) and carbonitrides distributed mostly on grain boundaries. Metallographic study of material confirmed theoretical predictions.

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Gaál, Z., and Péter János Szabó. "Evolution of Special Grain Boundaries in Austenitic Steels." Materials Science Forum 537-538 (February 2007): 355–62. http://dx.doi.org/10.4028/www.scientific.net/msf.537-538.355.

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Three different types of austenitic stainless steel (SUS 304, SUS 304L and SUS 316) samples were cold formed in order to investigate the effect of cold forming on the grain boundary structure of the material. SUS 304L and SUS 316 samples were cold rolled, SUS 304 samples were tensile loaded in different manner at room temperature. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that the frequency of the special Σ3n type CSLboundaries was significantly decreased by increasing the deformation of the samples.

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Kokawa, Hiroyuki, Masahiko Shimada, Zhan Jie Wang, Yutaka S. Sato, and M. Michiuchi. "Grain Boundary Engineering for Intergranular Corrosion Resistant Austenitic Stainless Steel." Key Engineering Materials 261-263 (April 2004): 1005–10. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.1005.

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Optimum parameters in the thermomechanical treatment during grain boundary engineering (GBE) were investigated for improvement of intergranular corrosion resistance of type 304 austenitic stainless steel. The grain boundary character distribution (GBCD) was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of coincidence-site-lattice (CSL) boundaries indicated a maximum at the small pre-strain. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material for long time sensitization. The optimum thermomechanical treatment introduced a high frequency of CSL boundaries and the clear discontinuity of corrosive random boundary network in the material, and resulted in the high intergranular corrosion resistance arresting the propagation of intergranular corrosion from the surface.

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Belyakov, Andrey, Marina Odnobokova, Iaroslava Shakhova, and Rustam Kaibyshev. "Regularities of Microstructure Evolution and Strengthening Mechanisms of Austenitic Stainless Steels Subjected to Large Strain Cold Working." Materials Science Forum 879 (November 2016): 224–29. http://dx.doi.org/10.4028/www.scientific.net/msf.879.224.

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The deformation microstructures and their effects on mechanical properties of austenitic stainless steels processed by cold rolling at ambient temperature to various total strains were studied. The cold working was accompanied by the development of strain-induced martensitic transformation because of meta-stable austenite at room temperature. The strain-induced martensitic transformation and deformation twinning promoted the grain refinement during cold rolling, leading to nanocrystalline structures consisting of a mixture of austenite and martensite grains with their transverse grain sizes of 50-150 nm containing high dislocation densities. The rolled samples experienced substantial strengthening resulted from high density of strain induced grain/phase boundaries and dislocations. The yield strength of austenitic stainless steels could be increased to 2000 MPa after rolling to total strains of about 4. The martensite and austenite provided almost the same contribution to overall yield strength. The dislocation strengthening was much higher than the grain boundary strengthening at small to moderate strains of about 2, whereas the latter gradually increased approaching the level of dislocation strengthening with increasing the strain.

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Mandal, Sumantra, A. K. Bhaduri, Baldev Raj, and V. Subramanya Sarma. "Dynamic Recrystallisation during Isothermal Hot Deformation in a Titanium Modified Austenitic Stainless Steel." Materials Science Forum 715-716 (April 2012): 140–45. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.140.

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The paper discusses the microstructural evolution during dynamic recrystallisation (DRX) of a titanium-modified austenitic stainless steel (alloy D9). Isothermal hot compression tests were conducted in a Gleeble thermo-mechanical simulator in the temperature range 1173-1373K to various strains at a constant strain rate of 0.1 and 1 s-1. The extent of DRX increased with increase in strain and temperature. Nucleation of new DRX grains was found to occur by bulging of parent grain boundary. A continuous sub-grain rotation around the original grain boundaries, which would lead to the formation of DRX nucleus in sub-grain structures, could not be confirmed from the present study. Fractions of Σ3 boundaries increased almost linearly with increase in area fraction of DRX. The generation of this Σ3 boundary was accounted for in the formation of annealing twins during DRX. The possible role of annealing twins on DRX in alloy D9 is also discussed.

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28

Zhang, Ming Xian, Bin Yang, Sheng Long Wang, and Huan Chun Wu. "Mechanisms of Thermo-Mechanical Process on Grain Boundary Character Distribution of 316L Austenitic Stainless Steel." Materials Science Forum 850 (March 2016): 965–70. http://dx.doi.org/10.4028/www.scientific.net/msf.850.965.

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Grain boundary engineering (GBE) was carried out on 316L austenitic stainless steel with Thermo-mechanical processing (TMP), which was performed by unidirectional compression and subsequent annealing. The effect of TMP parameters including the strain and annealing time on grain boundary character distribution (GBCD) and the corresponding mechanism was investigated in the study. The results showed that high fraction of low-Σ coincident-site lattice (CSL) grain boundaries (about 55%) associating with interrupted network of random boundaries was obtained through TMP of 5% cold compression followed by annealing at 1000 °C for 45 min. The fraction of low-Σ boundaries increased with increasing the annealing time under all the experiment strain, but the mechanisms were different between the low and medium above levels of strain. Grains rotation and reaction of migratory boundaries might be the reasons of low-Σ boundaries growth in the strain of 5% and in the strain greater than or equal to 10%, respectively.

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29

Arganis-Juárez, Carlos R., Audi Vázquez, Nelson F. Garza-Montes-de-Oca, and Rafael Colás. "Sensitization of an austenitic stainless steel due to the occurrence of δ-ferrite." Corrosion Reviews 37, no. 2 (March 26, 2019): 179–86. http://dx.doi.org/10.1515/corrrev-2018-0036.

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AbstractA series of analyses were conducted on samples of an austenitic type 304 stainless steel that exhibited a high degree of sensitization (DOS) after being subjected to a solution annealing treatment at 1050°C. The DOS was detected by electrochemical potentiokinetic tests. Examination by scanning electron microscopy of etched samples revealed the presence of δ-ferrite within the austenitic matrix, and of the segregation of chromium and nickel in either phase; images obtained by atomic force microscopy revealed localized attack at the austenite/δ-ferrite interface. It was found that the DOS and the ferrite number of the steel were reduced as the material was held at the solution temperature for longer times. Aging at 650°C showed precipitation of chromium carbides at grain boundaries and at the austenite/δ-ferrite interface; this treatment increased the DOS.

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30

Samajdar, I., P. Ahmedavadi, D. N. Wasnik, Vivekanand Kain, Bert Verlinden, and P. K. Dey. "Grain Boundary Nature and Localized Corrosion in 304 Austenitic Stainless Steel." Materials Science Forum 495-497 (September 2005): 453–58. http://dx.doi.org/10.4028/www.scientific.net/msf.495-497.453.

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The present study had one broad objective – to systematically characterize effects of overall grain boundary nature on localized corrosion, intergranular corrosion (IGC) and stress corrosion cracking (IGSCC), of type 304 (UNS S 30400) austenitic stainless steel. Various combinations of cold rolling and solution annealing, were applied to alter relative the relative concentrations of ‘special’ or low CSL boundaries and to relate them with the local corrosion resistance, IGC and IGSCC, after respective sensitization treatments. It has been shown that both extreme high and low concentration of random (or high energy) boundaries can provide an effective means of control for localized corrosion, degree of sensitization (DOS), IGC and IGSCC, - the improvement in localized corrosion resistance at extreme grain boundary randomization being more effective.

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31

Gaál, Z., Péter János Szabó, and János Ginsztler. "Evolution of Special Grain Boundaries in Austenitic Steels." Materials Science Forum 589 (June 2008): 19–24. http://dx.doi.org/10.4028/www.scientific.net/msf.589.19.

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AISI 304 type austenitic stainless steel samples were subjected to different thermomechanical treatments in order to investigate the effect of thermo-mechanical treatment on the grain boundary structure of the material. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that achieving the same deformation with the same number of deformation cycles and same heat treatment temperature, the application of shorter heat treatment holding time was advantageous in aspect of grain boundary structure comparing to the thermo-mechanical treatments with longer holding time. The frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries was significantly decreased by increasing the heat treatment holding time of the samples from the very short heat treatment periods. Extending the holding time further, the frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries increased and reached the results applying the shorter heat treatment periods.

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32

Krupp, Ulrich, I. Roth, Hans Jürgen Christ, M. Kübbeler, Claus Peter Fritzen, M. Scharnweber, C. G. Oertel, and Werner Skrotzki. "The Role of Grain Orientation and Martensitic Transformation during Propagation of Short Fatigue Cracks in Austenitic Stainless Steel." Key Engineering Materials 465 (January 2011): 55–60. http://dx.doi.org/10.4028/www.scientific.net/kem.465.55.

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During high-cycle-fatigue loading of metastable austenitic steel AISI304L, the elastic anisotropy between neighboring grains causes the occurrence of stress peaks at grain boundaries, which again act as crack nucleation sites. This is in particular the case at twin boundaries. Cyclic crack tip plasticity leads to a transformation from  austenite to ´ martensite when different slip bands are activated, alternating during their operation. By means of in-situ fatigue testing in a scanning electron microscope (SEM) in combination with electron back-scattered diffraction (EBSD), the distributions of grain size, geometry, and crystallographic orientation relationship were correlated with the local occurrence of slip, martensite formation and fatigue-crack initiation and propagation. It was shown that the extent of martensite formation ahead of a propagating crack increases with increasing crack length and eventually, due to its higher specific volume, gives rise to transformation-induced crack-closure effects. The variation in the crack-propagation rate depending on the local microstructure was simulated by means of a short crack model, where the displacement fields within the crack, the adjacent plastic zone and the grain boundaries in combination with the martensite volume increase strain are superimposed by means of a boundary-element approach.

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33

Stradomski, G. "The Cracking Mechanism of Ferritic-Austenitic Cast Steel." Archives of Foundry Engineering 16, no. 4 (December 1, 2016): 153–56. http://dx.doi.org/10.1515/afe-2016-0101.

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Abstract In the high-alloy, ferritic - austenitic (duplex) stainless steels high tendency to cracking, mainly hot-is induced by micro segregation processes and change of crystallization mechanism in its final stage. The article is a continuation of the problems presented in earlier papers [1 - 4]. In the range of high temperature cracking appear one mechanism a decohesion - intergranular however, depending on the chemical composition of the steel, various structural factors decide of the occurrence of hot cracking. The low-carbon and low-alloy cast steel casting hot cracking cause are type II sulphide, in high carbon tool cast steel secondary cementite mesh and / or ledeburite segregated at the grain solidified grains boundaries, in the case of Hadfield steel phosphorus - carbide eutectic, which carrier is iron-manganese and low solubility of phosphorus in high manganese matrix. In duplex cast steel the additional factor increasing the risk of cracking it is very “rich” chemical composition and related with it processes of precipitation of many secondary phases.

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34

Ishibashi, Ryo, Toshiaki Horiuchi, J. Kuniya, M. Yamamoto, Sadahiro Tsurekawa, Hiroyuki Kokawa, T. Watanabe, and Tetsuo Shoji. "Effect of Grain Boundary Character Distribution on Stress Corrosion Cracking Behavior in Austenitic Stainless Steels." Materials Science Forum 475-479 (January 2005): 3863–66. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3863.

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The effect of grain boundary character distribution (GBCD) on intergranular stress corrosion cracking (IGSCC) in austenitic stainless steels in high temperature water was verified experimentally. GBCD control using the strain annealing method increased the fraction of low- S coincidence site lattice (CSL) boundaries and the segmentalized network of random grain boundaries in austenitic stainless steels. The fractions of low- S CSL boundaries of GBCD controlled steels were 75–85%, while those of uncontrolled steels were 60–70%. Creviced bent beam tests were conducted at 561 K in pure water containing 8 ppm dissolved oxygen for stress corrosion cracking (SCC) evaluation. The tests revealed that GBCD control suppressed IGSCC initiation or propagation and that cracks were predominantly propagated along random grain boundaries. It is considered that induced lower- S CSL boundaries result in high resistance to IGSCC.

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35

Chandra, K., Vivekanand Kain, N. Srinivasan, I. Samajdar, and A. K. Balasubrahmanian. "Temper Embrittlement and Corrosion Behaviour of Martensitic Stainless Steel 420." Advanced Materials Research 794 (September 2013): 757–65. http://dx.doi.org/10.4028/www.scientific.net/amr.794.757.

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Tempering of alloy steels in the temperature range of 400-600 °C causes temper embrittlement i.e. decrease in notch toughness of the material and the nil ductility temperature is raised to room temperature and above. The fracture in temper-embrittled steel is intergranular and propagates along prior austenitic grain boundaries. The embrittlement occurs only in the presence of specific impurities, e.g. P, Sn, Sb and As. These elements have been shown to segregate along prior austenite grain boundaries during tempering. Similar type of temper embrittlement can occur in martensitic stainless steel (SS) if tempered in the temperature range of 450-600 °C. This paper reports a case of failure of components made from martensitic SS 420 due to temper embrittlement. These components were subjected to a temperature of 120 °C in the initial stages of service and had shown brittle fractures. Scanning electron microscopic examination of the fracture surface of both the components showed intergranular fracture. The microstructures of the failed components confirmed that the materials were in hardened and tempered condition. In addition, the microstructure revealed both intergranular corrosion (IGC) and intergranular cracking. The electron backscatter diffraction study also showed retained austenite in the first components material. The material undergoing IGC might be related to a wrong heat-treatment during fabrication and subsequent pickling procedures. To confirm this, a sample each from both the components was exposed to 5% nitric acid solution at 25 °C. The results showed very high corrosion rate and the attack was intergranular in nature. The failure of both the components was concluded to be due to wrong tempering treatment in the temperature range of 450-600 °C that cause grain boundaries to become susceptible to embrittlement and corrosion.

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36

Belyakov, Andrey, Marina Tikhonova, Zhanna Yanushkevich, and Rustam Kaibyshev. "Regularities of Grain Refinement in an Austenitic Stainless Steel during Multiple Warm Working." Materials Science Forum 753 (March 2013): 411–16. http://dx.doi.org/10.4028/www.scientific.net/msf.753.411.

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The structural changes that are related to the new fine grain development in a chromium-nickel austenitic stainless steel subjected to warm working by means of multiple forging and multiple rolling were studied. The multiple warm working to a total strain of 2 at temperatures of 500-900C resulted in the development of submicrocrystalline structures with mean grain sizes of 300-850 nm, depending on processing conditions. The new fine grains resulted mainly from a kind of continuous reactions, which can be referred to as continuous dynamic recrystallization. Namely, the new grains resulted from a progressive evolution of strain-induced grain boundaries, the number and misorientation of which gradually increased during deformation. In contrast to hot working accompanied by discontinuous dynamic recrystallization, when the dynamic grain size can be expressed by a power law function of temperature compensated strain rate as D ~ Z-0.4, much weaker temperature/strain rate dependence of D ~ Z-0.1was obtained for the warm working.

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37

Ren, Zhongkai, Wanwan Fan, Jie Hou, and Tao Wang. "A Numerical Study of Slip System Evolution in Ultra-Thin Stainless Steel Foil." Materials 12, no. 11 (June 5, 2019): 1819. http://dx.doi.org/10.3390/ma12111819.

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In order to quantitatively describe the effect of the initial grain orientation on the inhomogeneous deformation of 304 austenitic stainless steel foil during tension, a three-dimensional uniaxial tension model was established, based on the crystal plasticity finite element method (CPFEM) and Voronoi polyhedron theory. A three-dimensional representative volume element (RVE) was used to simulate the slip deformation of 304 stainless steel foil with five typical grain orientations under the same engineering strain. The simulation results show that the number and characteristics of active slip systems and the deformation degree of the grain are different due to the different initial grain orientations. The slip systems preferentially initiate at grain boundaries and cause slip system activity at the interior and free surface of the grain. The Brass, S, and Copper oriented 304 stainless steel foil exhibits a high strain hardening index, which is beneficial to strengthening. However, the Cube and Goss oriented 304 stainless steel foil has a low deformation resistance and is prone to plastic deformation.

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38

Li, Jing Yuan, Fei Fang, Yi De Wang, Bo Li, and Xiang Jun Zhang. "Influences of Carbon and Nitrogen Content on the Precipitation of 18Cr18Mn Steel." Materials Science Forum 789 (April 2014): 297–302. http://dx.doi.org/10.4028/www.scientific.net/msf.789.297.

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The effect of carbon and nitrogen contents on microstructure and the mechanism of precipitation of 18Cr18Mn steels at as-cast and aging treatment state were investigated by thermodynamics calculation, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that the increase in carbon and nitrogen contents promotes the precipitation of carbides and nitrides, respectively, inhibiting σ phase precipitation during solidification process. The rod-like σ phases present in 18Cr18Mn0.44N as-cast steel with 0.025%C. The coarse lamellar structure Cr23C6 phases with a space width of 0.34μm exist in 18Cr18Mn0.44N as-cast steel with 0.16%C. However, Cr23C6 and σ phase disappear in the interior of the grains and a small amount of nitrides exist only in grain boundaries of 18Cr18Mn0.72N0.020C as-cast steel. The precipitation of Cr23C6 and σ phases are greatly inhibited in high nitrogen austenitic stainless steels at 800°C aging treatment. Additionally, Cr2N, the main precipitation phase, nucleates at austenitic grain boundary and grows towards inner grains with a lamellar morphology. Moreover, the quantity of Cr2N increases and incubation time of it decreases as nitrogen or carbon content increasing.

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39

Gebril, Mohamed A., M. S. Aldlemey, Farag I. Haider, and Naji Ali. "Effect of Austenizing and Tempering Time on Corrosion Rate of Austenitic Stainless Steel in Oxalic Acid." Advanced Materials Research 980 (June 2014): 46–51. http://dx.doi.org/10.4028/www.scientific.net/amr.980.46.

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The aim of this work is to study the effect of austenizing time, tempering process and tempering time on corrosion rate of austenitic stainless steel in oxalic acid. The samples of typical 304 stainless steel were heated to 1050°C for 10, 20 and 30 minutes and quenched to room temperature in water, then tempered at 250°C, 400°C and 600°C for 30, 60 minutes for each tempering time. These samples were then immersed in 0.1M of oxalic acid and then their weight losses were measured after 30 days. The result obtained show that corrosion rate of all austenitic stainless steel samples decreased with an increase austenizing time, this behaviour is due to more homogenously of austenite, and the corrosion rate will be increased with increase the tempering temperature and tempering time, this behaviour is due different phases at microstructure below 400°C, and above of 400 to 600°C the corrosion rate will be increased due to formation of carbides which are non-uniform distributed at the grain boundaries and causes intergranular corrosion.

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40

Shi, Feng, Xiao Wu Li, Yang Qi, and Chun Ming Liu. "Effects of Cold Deformation on Precipitation in Fe-18Cr-12Mn-0.48N High-Nitrogen Austenitic Stainless Steel." Key Engineering Materials 531-532 (December 2012): 97–102. http://dx.doi.org/10.4028/www.scientific.net/kem.531-532.97.

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The precipitation behaviors were investigated during isothermally aging at 700°C and 800°C after cold compressed by 30% in thickness in Fe-18Cr-12Mn-0.48N high-nitrogen austenitic stainless steel by using optical microscopy (OM), laser scanning confocal microscopy (LSCM) and transmission electron microscopy (TEM). The results show that precipitation morphology in cold-deformed sample is the same as non-cold-deformed sample, which also displays discontinuous cellular way. Cold deformation accelerates the precipitation of M2N phase. The precipitation occurs at not only grain boundaries but also twin grain boundaries in the experimental steel. In cold-deformed sample, besides the long-strip M2N precipitates, intermetallic phase-σ phase owning bct structure and lattice parameters of a=0.8800nm and c=0.4544nm were observed along grain boundaries and inside the grain.

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41

Jeng, Sheng-Long, Dai-Ping Su, Jing-Ting Lee, and Jiunn-Yuan Huang. "Effects of Electromagnetic Stirring on the Cast Austenitic Stainless Steel Weldments by Gas Tungsten Arc Welding." Metals 8, no. 8 (August 10, 2018): 630. http://dx.doi.org/10.3390/met8080630.

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Cast austenitic stainless steel (CASS) often contains high contents of silicon, phosphorus, and sulfur to prompt low melting phases to form in the welds. As a result, welding defects can be induced to degrade the welds. This study’s purpose was to investigate the effects of electromagnetic stirring (EMS) on the CASS weldments. The results showed that the ferrites in the heat affected zone (HAZ) had tortuous grain boundaries, while those that were close to the fusion lines had transformed austenites. EMS could reduce the influence of the welding heat to make the grain boundaries less tortuous and the transformed austenites smaller. Although their temperature profiles were almost the same, the gas-tungsten-arc-welding (GTAW) weld had smaller grains with massive ferrite colonies and more precipitates, while the GTAW+EMS weld had denser ferrite colonies with multi-orientations, but fewer precipitates. The hardness of the base metals and HAZs were typically higher than that of the welds. For both of the welds, the root was the region with the highest hardness. The hardness decreased from the root to the cap regions along the thickness direction. The GTAW weld had a higher hardness than the GTAW+EMS weld. At room temperature, the GTAW+EMS weld had a higher notched tensile strength and elongation than the GTAW weld. This could be attributed to the observation that the GTAW+EMS weld had dense and intersecting dendrites and that more austenites were deformed during tensile testing.

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42

Das, Arpan. "Enigma of dislocation patterning due to slip in fatigued austenite." International Journal of Damage Mechanics 27, no. 2 (October 23, 2016): 218–37. http://dx.doi.org/10.1177/1056789516674765.

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Strain controlled low cycle fatigue experiments on multiple specimens are performed by systematically varying strain amplitudes of austenitic stainless steel under laboratory atmosphere. Different dislocation substructures/patterns developed due to strain cycling are characterised, measured by analytical transmission electron microscope and austenite grains’ misorientation, extent of different types of grain boundaries, grain connectivity, slip-system activity are also measured by electron backscatter diffraction experiments. Present investigation clearly reveals the enigma of dislocation patterning through slip system activity during cyclic plastic deformation of austenite at different strain amplitudes. It has been experimentally examined that with the increase in strain amplitude, the activity of single slip system decreases and multiple slip system increases, which in turn help to decrease the dislocation cell size and to vary in their geometric configurations and patterns.

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43

Kulakov, Mykola, Jianglin Huang, Michail Ntovas, and Shanmukha Moturu. "Microstructure Evolution During Hot Deformation of REX734 Austenitic Stainless Steel." Metallurgical and Materials Transactions A 51, no. 2 (December 4, 2019): 845–54. http://dx.doi.org/10.1007/s11661-019-05558-6.

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AbstractMechanical properties of a REX734 austenitic stainless steel were examined through compression testing over a wide range of temperatures (1173 K to 1373 K (900 °C to 1100 °C)) and strain rates (0.1 to 40 s−1) that cover deformation conditions encountered in different metalworking processes. The evolution of microstructure was studied using electron microscopy combined with electron backscatter diffraction and energy-dispersive spectroscopy. Partially recrystallized microstructures were obtained after compression testing at 1173 K (900 °C), while after deformation at 1273 K and 1373 K (1000 °C and 1100 °C), the material was fully recrystallized almost in all examined cases. The role of dynamic and metadynamic restoration processes in the formation of final microstructure was investigated. Σ3 twin boundaries lost their twin character and transformed into general high-angle grain boundaries as a result of deformation, while during recrystallization new Σ3 twin boundaries formed. The evolution of precipitates during compression testing and their role in the recrystallization process was also discussed.

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44

Clark, Ronald N., Choen May Chan, W. Steve Walters, Dirk Engelberg, and Geraint Williams. "Intergranular and Pitting Corrosion in Sensitized and Unsensitized 20Cr-25Ni-Nb Austenitic Stainless Steel." Corrosion 77, no. 5 (February 16, 2021): 552–63. http://dx.doi.org/10.5006/3725.

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Advanced gas-cooled reactor (AGR) oxide fuels used in the United Kingdom are clad in bespoke grade 20%Cr-25%Ni-Nb austenitic stainless steel. Electrochemistry was first applied to correlate the breakdown potential with chloride ion concentration, temperature, and pH for this alloy. At near-neutral pH the unsensitized material exhibited a linear Eb = A + B log10[Cl−] relationship, where A = 0.7 VSCE and B = –0.098 V/decade. Scanning Kelvin probe force microscopy revealed that grain boundary regions in the heat-treated material were up to 65 mV less noble to the matrix, whereas undissolved niobium carbide (NbC) precipitates were up to 55 mV more noble to the matrix. In situ time-lapse microscopy and postcorrosion observations confirmed that sensitized grain boundaries were susceptible to pitting corrosion, further developing along intergranular corrosion pathways. It has, however, been shown that microgalvanic coupling between the Nb precipitates and matrix and/or sensitized grain boundary regions is not a factor in corrosion initiation as all experiments were performed under external potential control. Postcorrosion observations showed the presence of pits at NbC precipitates promoting grain boundary corrosion. It is postulated that corrosion initiates at NbC precipitates as a pit, and when in close vicinity to Cr-depleted grain boundaries, then propagates along grain boundaries as intergranular corrosion.

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45

Yvell, Karin, and Göran Engberg. "Deformation Structures in a Duplex Stainless Steel." Materials Science Forum 941 (December 2018): 176–81. http://dx.doi.org/10.4028/www.scientific.net/msf.941.176.

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The evolution of the deformation structure with strain has been studied using electron backscatter diffraction (EBSD). Samples from interrupted uniaxial tensile tests and from a cyclic tension/compression test were investigated. The evolution of low angle boundaries (LABs) was studied using boundary maps and by measuring the LAB density. From calculations of local misorientations, smaller orientation changes in the substructure can be illustrated. The different orientations developed with strain within a grain, due to operation of different slip systems in different parts of the grain, were studied using a misorientation profile showing substantial orientation changes after a true strain of 0.24. The texture evolution with increasing strain was followed by using inverse pole figures (IPFs). The observed substructure development in the ferritic and austenitic phases could be successfully correlated with the stress-strain curve from a tensile test. LABs were first observed in the different phases when the strain hardening rate changed in appearance indicating that cross slip started to operate as a significant dislocation recovery mechanism. The evolution of the deformation structure is concluded to occur in a similar manner in the austenitic and ferritic phases but with different texture evolution for the two phases.

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46

Jiang, Na Yun, and Fu Shun Liu. "Aging Precipitation Evolving Process and its Effects on Mechanical Properties of 0Cr21Ni6Mn9N Austenitic Stainless Steel." Materials Science Forum 816 (April 2015): 255–61. http://dx.doi.org/10.4028/www.scientific.net/msf.816.255.

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The solution treatment (ST) and the the second phase morphology changing duing the aging precipitation process of 0Cr21Ni6Mn9N austenitic stainless steel were investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) with EDS and transmission electron microscope (TEM). The results showed that the precipitation phase was Cr2N which initially nucleated along austenitic grain boundaries and then grew towards into the inner grains in strip morphology. Also, with the longer aging time the proportion of Cr2N increased. The mechanical properties of alloys with and without the presence of the precipitation Cr2N were also studied. It was observed that due to the exiting of the precipitation Cr2N, the strength of 2169N stainless steel reduced during a certain range of aging time, and then improved when the aging time reached to 48h, while the elongation decreased thoroughly.

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47

Gaál, Zoltán, Péter János Szabó, János Ginsztler, and László Dévényi. "Grain Boundary Investigation of AISI 304 Type Steel Using EBSD." Materials Science Forum 659 (September 2010): 307–11. http://dx.doi.org/10.4028/www.scientific.net/msf.659.307.

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This paper deals with the investigation of grain boundary engineering processes in case of AISI 304 type austenitic stainless steel. The effects of the thermo-mechanical treatments for the modification of the grain boundary structure are demonstrated on the special grain boundaries. The proper thermo-mechanical treatments can increase the fraction of the CSL-boundaries. Since the CSL-boundaries are resistant against intergranular degradation processes, materials owning enhanced properties can be developed due to these treatments. The investigation of the grain boundary character distribution is carried out by automated electron back scattered diffraction (EBSD) measurements after different thermo-mechanical treatment processes. The effect of the heat treatment duration on the grain boundary structure is examined; the optimal treatment is represented. It is shown by experimental results, that the parameter settings of the evaluation method strongly influence the obtained results.

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48

Keskitalo, Markku, Atef Hamada, Mikko Hietala, Matias Jaskari, and Antti Järvenpää. "Microstructure and Formability of Laser Welded Dissimilar Butt Joints of Austenitic-Ferritic Stainless Steels." Key Engineering Materials 883 (April 2021): 258–65. http://dx.doi.org/10.4028/www.scientific.net/kem.883.258.

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Dissimilar laser welding of ferritic, type EN 1.4509, and austenitic, type EN 1.4307, stainless steel sheets was conducted at different energy inputs 30 and 80 J/mm and under different shield gases Ar and N and without shielding gas to evaluate the microstructure and hardness of the welded zone. The formability tests, using Erichsen principle, were carried out to determine the deformation behaviour of the dissimilar welded joints under biaxial straining. The fusion zone microstructure analysis revealed that the predominant phase structure is columnar coarse ferritic grains with slightly small content of austenite in the ferrite grain boundaries. The formability of the welded joints under Ar and N shielding gases is significantly improved, i.e., higher plasticity, compared with welded joints without shielding gas at both energy inputs.

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49

Dey, Rima, Soumitra Tarafder, and S. Sivaprasad. "Influence of multiaxial cyclic plastic loading on grain boundary misorientation profile in austenitic stainless steel." MATEC Web of Conferences 300 (2019): 08007. http://dx.doi.org/10.1051/matecconf/201930008007.

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304LN stainless was subjected to multiaxial loading employing different waveforms and load paths. The grain boundary misorientation profile so obtained post deformation was compared across loading conditions. It was found that the uniaxial and proportional conditions of loading result in more of twins, contrary to non-proportional loading conditions that resulted in substantially higher low angle grain boundaries. Also, under non-proportional loading the trapezoidal load path resulted in remarkably altered distribution of the grain boundaries compared to its contemporaries. Predominant martensitic transformation was found to be dominant mechanism of deformation for trapezoidal loading that also contributed to the altered misorientation profile.

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50

Shi, F., Li Jun Wang, Wen Fang Cui, Z. B. Li, M. Z. Xu, and Chun Ming Liu. "Hot Ductility of Fe-18Cr-12Mn-0.55N High Nitrogen Austenitic Stainless Steel." Materials Science Forum 575-578 (April 2008): 1056–61. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.1056.

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The hot ductility of Fe-18Cr-12Mn-0.55N high nitrogen austenitic stainless steel was investigated in Gleeble-2000 thermomechanical simulator. The experimental results show that the hot ductility curve of test steel is comprised of high-temperature brittlement region at the test temperatures higher than 1150°C, high-temperature ductility region at the test temperatures from 850°C to 1150°C and middle-temperature half brittlement region at the test temperatures lower than 850°C. High-temperature brittlement and middle-temperature half brittlement are caused by the appearances of δ ferrite and the precipitation of Cr2N phase at austenitic grain boundaries, respectively, and the excellent hot ductility at test temperatures between the two brittlement temperature regions results from the stable single phase austenitic microstructure.

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Journal articles on the topic 'Austenitic stainless steel. Grain boundaries'

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