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Effect of Austenite Pre-deformation on Isothermal Martensite Transformation in an Fe-20.5Ni-4.8Mn Alloy
Fuxing YIN,Jianxin ZHANG,Nanju GUTsukio TadakiKen,ichi Shimizu,

材料科学技术学报 , 1995,
Abstract: With electron microscopy the investigation on isothermal martensite transformation in an Fe20.5Ni-4.8Mn alloy has been carried out to clarify the effect of austenite state on the transformation, by applying pre-deformation to austenite before isothermal holding. Under the condition without pre-deformation, the isothermal martensite products are lath martensite with {111}fhabit planes. Dislocations in austenite seem to contribute to nucleation of martensite, and in this nascent Stage austenite substructure has no obvious effect on martensite growth. The consequent thickening of martensite laths is apparently influenced by local austenite states, resulting in the changes in orientation, morphology as well as substructure of martensite lath. The kinetics of isothermal martensite transformation is controlled by intedece dislocation determined nucleation of martensite in primary stage, but to a larger extent, by the austenite accommodation for the shape strain of martensite in the thickening Stage

WEN Cui'e,LIN Jianguo,ZHOU Yajian
金属学报(英文版) , 1996,
Abstract: The morphology and amount of the retained austenite in the duplex microstructure of martensite and tower bainite of a tow,alloy cold die steel(it is called GD steel for short) with high strength and high toughness have been investigated.The thermal and mechanical stabilities of the retained austenite were analyzed.Furthermore the effects of retained austenite on the mechanical properties of the steel were studied.The results show that the morphology and amount of retained austenite vary with silicon content in the steel.Retained austenite with high stability was responsible for the simultaneous increase in strength and toughness of the steel.The duplex microstructure of martensite and abnormal lower bainite of the steel with the maximum silicon content exhibits a relatively good strength-toughness combination.
Deformation at Room and Low Temperatures and Martensite Transformation in Resistance Spot Welding Duplex γ & α(δ) Materials of 301L Stainless Steel
材料科学技术学报 , 2007,
Abstract: Transformation induced plasticity (TRIP) and twinning induced plasticity (TWlP) effects had been widely studied in single austenite steel. But in duplex γ & α(δ) phase, such as welding materials of stainless steel, they had been less studied. Tensile shear loading experiment of resistance spot welding specimens prepared with 2 mm 301L sheets, was carried out at 15℃ and -50℃. Optical microscopy and scanning electron microscopy (SEM) as well as X-ray diffraction (XRD) were used to investigate the microstructure of weld nugget, and specimens fracture surface. The results showed that the initial weld nugget was composed of 8.4% α(δ) ferrite and 91.6% austenite. Tensile shear load bearing capacity of spot welding specimen at -50℃ was 24.8 kN, 17.7% higher than that at 15℃. About 78.5 vol. pct. martensite transformation was induced by plastic deformation at -50℃, while about 67.9 vol. pct transformation induced at 15℃. The plasticity of spot welding joint decreased with the decline of experimental temperature.
Deformation-induced Microstructures of High-Mn Austenite Steel
Qixun DAI Shupeng HUO Jiangsu Institute of Technology,Zhenjiang,China,

材料科学技术学报 , 1993,
Abstract: Deformation-induced microstructures of high-Mn austenite steel was investigated bymetallography,X-ray diffraction and SEM.The ε-martensite and slip-bands are deformation-in-duced on the{111} planes,and appear as thin straight laths with 60~80° alignment difference be-tween them.It was found that ε-martensite and slip bands are kinked at fcc twin boundaries with thekinked angle 35~40°.The bands of equilateral triangle in the microstructure of tensile deformationare presented.
Processing of a duplex stainless steel by equal channel angular extrusion
Farias, F.A.;Pontes, M.J.H.;Cintho, O.M.;
Matéria (Rio de Janeiro) , 2010, DOI: 10.1590/S1517-70762010000200036
Abstract: a uns s32205 duplex stainless steel was processed by ecae in three different velocities, at room temperature, and heat treated in different temperatures and times to evaluate recrystallization. attrition forces promoted great deformation heterogeneity in the samples sections, with hardness increase, and morphology changes in the grains and changing orientation through the processed samples. in treated samples surface, two types of distinct structures was formed, with surfaces positioned in 90o and 120o angles, probably because the annihilation of pilled dislocations in ferrite based centered cubic structure and austenite face centered cubic structure, respectively. the induced martensite by cold deformation was also observed. some samples demonstrate located points of recrystallization in grain boundaries for some treatment conditions, the number of recrystallization nuclei increased with the increase of treatment time.
Stabilization of Austenite in Quenched Alloy Steels

KANG Mokuang,ZHU Ming,
,朱 明

金属学报 , 2005,
Abstract: Retained austenite exists in alloy steels both continuously quenched and isothermally quenched, so its content relates to the austenitic stabilization. The article focuses on the investigation for the austenitic stabilization in isothermally quenched microstructures from duplex phase (martensite-M, bainite-B) temperature region. Within a certain isothermal time, the relationship of the amount of retained austenite (AR.) vs isothermal temperature is a saddle-like curve, and the valley value for testing steel is less than that of continuous quenching with a same cooling medium, which proves that isothermal soak does not increase retained austenitic quantity on certain condition. By adjusting the content ratios of AR/M and AR/B on the saddle-like curve, an isothermal quenching of the less deformation or a meta-bainitic isothermal quenching with strength-toughness optimized combination can be achieved. Austenitic stabilization is the synthetic effect of thermal, chemical, phase induced and macro-thermal stress stabilized mechanisms. The martensite critical point Mc has not the special physical meaning.
Deformation induced martensite in an AISI 301LN stainless steel: characterization and influence on pitting corrosion resistance
Abreu, Hamilton Ferreira Gomes de;Carvalho, Sheyla Santana de;Lima Neto, Pedro de;Santos, Ricardo Pires dos;Freire, Válder Nogueira;Silva, Paulo Maria de Oliveira;Tavares, Sérgio Souto Maior;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000400007
Abstract: in austenitic stainless steels, plastic deformation can induce martensite formation. the induced martensite is related to the austenite (g) instability at temperatures close or below room temperature. the metastability of austenite stainless steels increases with the decreasing of stacking fault energy (sfe). in this work, the deformation induced martensite was analyzed by x ray diffraction, electron back scatter diffraction (ebsd), magnetic methods and atomic force microscope (afm) in samples of a low sfe austenitic stainless steel, aisi 301ln and compared with a medium sfe stainless steel, aisi 316l. both techniques, x ray diffraction and ebsd, presented similar quantities for the a?-martensite. texture results indicate that the crystallographic orientation of the formed a?-martensite is {001}<110> and {103}<110>. the morphology of a?-martensite was analyzed by afm. corrosion tests showed that deformation reduces pitting corrosion and generalized corrosion resistance in both steels.
Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steels  [PDF]
Hung-Wei Yen,Steve Woei Ooi,Mehdi Eizadjou,Andrew Breen,Ching-Yuan Huang,H. K. D. H. Bhadeshia,Simon P. Ringer
Physics , 2014, DOI: 10.1016/j.actamat.2014.09.017
Abstract: This work explains the occurrence of transformation-induced plasticity via stress-assisted martensite, when designing ultrafine-grained duplex steels. It is found that, when the austenite is reduced to a fine scale of about 300 nm, the initial deformation-induced microstructure can be dominated by parallel lamellae of epsilon martensite or mechanical twinning, which cannot efficiently provide nucleation sites for strain-induced martensite. Hence, alpha martensite nucleation occurs independently by a stress-assisted process that enhances transformation-induced plasticity in ultrafine-grained austenite. This metallurgical principle was validated experimentally by using a combination of transmission Kikuchi diffraction mapping, transmission electron microscopy, and atom probe microscopy, and demonstrated theoretically by the thermodynamics model of stress-assisted martensite.

FANG Zhi,WU Yinshun,ZHANG Lin,LI Jie,

腐蚀科学与防护技术 , 1997,
Abstract: The effect of deformation induced martensite on the corrosion of type 304 stainless steel in the active state was studied by electrochemical method. The results showed that the amount of transformed martensite increased with the elongation, the electrochemical activity of the material also inceased. By measuring the electrochemical parameters of each single phase, it was found that the corrosion potential of martensite was 55 mV negative than that of austenite, which was the main reason of selective corrosion of martensite.
Hot Deformation Behavior of an As-cast Duplex Stainless Steel
Hot Deformation Behavior of an As—cast Duplex Stainless Steel

Pingli MAO,Ke YANG,Guoyue SU,

材料科学技术学报 , 2003,
Abstract: The hot deformation behavior of an as-cast 0Cr17Mn14Mo2N duplex stainless steel has been studied by hot compression test at the temperature range from 1000℃ to 1200℃, and the strain rates are 0.1 s-1, 1 s-1 and 5 s-1,respectively. It was found that during hot deformation there is only dynamic recovery taking place within the δ-ferrite phase, but the γ-austenite phase undergoes dynamic recrystallization. The activation energy of the steel for hot compression is estimated to be 480 k J/mol.
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