淬火配分贝氏体钢不同位置残余奥氏体C、Mn元素表征及其稳定性
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摘要
采用部分奥氏体化-两相区保温-淬火-配分(IQ&PB)热处理工艺,借助SEM、TEM、XRD研究了淬火配分贝氏体钢组织形貌及残余奥氏体特征,利用EPMA、EBSD、纳米压痕等表征了不同位置残余奥氏体中合金元素的分布情况,结合室温拉伸应力-应变曲线,研究了C、Mn元素对不同位置残余奥氏体稳定性的影响及其相变规律。结果表明,淬火贝氏体钢室温组织中残余奥氏体以块状和薄膜状形态存在。在拉伸形变过程中,发生TRIP效应,残余奥氏体体积减小,相变优先发生在铁素体晶界,最后发生在贝氏体板条之间,C、Mn元素对残余奥氏体有稳定作用,使残余奥氏体不易发生相变。拉伸断口处应力集中,残余奥氏体完全转变为马氏体,距离断口2和4 mm处,残余奥氏体体积分数分别为3.12%和5.03%。薄膜状残余奥氏体比块状残余奥氏体稳定性更强,并且<111>γ晶向的残余奥氏体不稳定,容易向马氏体转变。
The volume fraction and stability of retained austenite play an important role in the performance of low carbon steels, while the C and Mn elements have a stabilizing effect on the thermal stability and mechanical stability of retained austenite. Therefore, the C and Mn elementals partitioning was promoted by intercritical annealing. As a result, the mechanical properties of the low carbon steels are improved. The microstructure of quenching and partitioning bainitic steels and retained austenite characteristics were studied by means of SEM, TEM and XRD. The partitioning and content of C and Mn elements in retained austenite at different locations were characterized by EPMA, EBSD and nanoindentation. The effect of C and Mn elements on the stability of retained austenite at different locations and phase change law of retained austenite were investigated by combining the tensile stress-strain curves under the treatment of intercritical annealing(partial austenitizing)-quenching and partitioning in the bainitic region process(IQ&PB). In the process of tensile deformation, the transformation induced plasticity(TRIP) effect occurs, the volume of retained austenite decreases, the transformation takes place preferentially in the ferrite grain boundary, and finally occurs between the bainite laths. C and Mn elements have a stabilizing effect on the retained austenite, which make retained austenite is not prone to phase change. The stress at the tensile fracture is concentrated, and the retained austenite is completely transformed into martensite.The volume fraction of retained austenite is 3.12% and 5.03% at 2 mm and 4 mm distances away from the fracture. Film-like retained austenite is more stable than blocky retained austenite, and the retained austenite of the <111>γcrystal orientation is unstable and easily transforms into martensite.
The volume fraction and stability of retained austenite play an important role in the performance of low carbon steels, while the C and Mn elements have a stabilizing effect on the thermal stability and mechanical stability of retained austenite. Therefore, the C and Mn elementals partitioning was promoted by intercritical annealing. As a result, the mechanical properties of the low carbon steels are improved. The microstructure of quenching and partitioning bainitic steels and retained austenite characteristics were studied by means of SEM, TEM and XRD. The partitioning and content of C and Mn elements in retained austenite at different locations were characterized by EPMA, EBSD and nanoindentation. The effect of C and Mn elements on the stability of retained austenite at different locations and phase change law of retained austenite were investigated by combining the tensile stress-strain curves under the treatment of intercritical annealing(partial austenitizing)-quenching and partitioning in the bainitic region process(IQ&PB). In the process of tensile deformation, the transformation induced plasticity(TRIP) effect occurs, the volume of retained austenite decreases, the transformation takes place preferentially in the ferrite grain boundary, and finally occurs between the bainite laths. C and Mn elements have a stabilizing effect on the retained austenite, which make retained austenite is not prone to phase change. The stress at the tensile fracture is concentrated, and the retained austenite is completely transformed into martensite.The volume fraction of retained austenite is 3.12% and 5.03% at 2 mm and 4 mm distances away from the fracture. Film-like retained austenite is more stable than blocky retained austenite, and the retained austenite of the <111>γcrystal orientation is unstable and easily transforms into martensite.
引文
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[27]Song C H,Yu H,Li L L,et al.Effect of carbon at interface of aus‐tenite on manganese segregation of low carbon and manganese steel[J].Mater Lett.,2016,174:75
[28]Yang P,Liu T Y,Lu F Y,et al.Orientation dependence of martens‐itic transformation in high Mn TRIP/TWIP steels[J].Steel Res.Int.,2012,83:368
[29]Chumlyakov Y,Panchenko E,Kireeva I,et al.Orientation depen‐dence and tension/compression asymmetry of shape memory effect and superelasticity in ferromagnetic Co40Ni33Al27,Co49Ni21Ga30and Ni54Fe19Ga27single crystals[J].Mater.Sci.Eng.,2008,A481-482:95
[2]Tirumalasetty G K,Van Huis M A,Kwakernaak C,et al.Deformation-induced austenite grain rotation and transformation in TRIP-assisted steel[J].Acta Mater.,2012,60:1311
[3]Li W J,Cai M Y,Wang D,et al.Studying on tempering transforma‐tion and internal friction for low carbon bainitic steel[J].Mater.Sci.Eng.,2017,A679:410
[4]Dan W J,Li S H,Zhang W G,et al.The effect of strain-induced martensitic transformation on mechanical properties of TRIP steel[J].Mater.Des.,2008,29:604
[5]Wang H S,Yuan G,Zhang Y X,et al.Microstructural evolution and mechanical properties of duplex TRIP steel produced by strip casting[J].Mater.Sci.Eng.,2017,A692:703
[6]Yan S,Liu X H,Liu W J,et al.Comparison on mechanical proper‐ties and microstructure of a C-Mn-Si steel treated by quenching and partitioning(Q&P)and quenching and tempering(Q&T)pro‐cesses[J].Mater.Sci.Eng.,2015,A620:58
[7]JirkováH,Ma?ek B,Wagner M F X,et al.Influence of metastable retained austenite on macro and micromechanical properties of steel processed by the Q&P process[J].J.Alloys Compd.,2014,615(Suppl.1):S163
[8]Hajyakbary F,Sietsma J,Miyamoto G,et al.Interaction of carbon partitioning,carbide precipitation and bainite formation during the Q&P process in a low C steel[J].Acta Mater.,2016,104:72
[9]Wang X D,Huang B X,Rong Y H,et al.Microstructures and sta‐bility of retained austenite in TRIP steels[J].Mater.Sci.Eng.,2006,A438-440:300
[10]Shen Y F,Qiu L N,Sun X,et al.Effects of retained austenite vol‐ume fraction,morphology,and carbon content on strength and duc‐tility of nanostructured TRIP-assisted steels[J].Mater.Sci.Eng.,2015,A636:551
[11]Jimenez-Melero E,Van Dijk N H,Zhao L.Martensitic transforma‐tion of individual grains in low-alloyed TRIP steels[J].Scr.Ma‐ter.,2007,56:421
[12]BlondéR,Jimenez-Melero E,Zhao L,et al.High-energy X-ray diffraction study on the temperature-dependent mechanical stabili‐ty of retained austenite in low-alloyed TRIP steels[J].Acta Mater.,2012,60:565
[13]Zou Y,Xu Y B,Hu Z P,et al.Austenite stability and its effect on the toughness of a high strength ultra-low carbon medium manga‐nese steel plate[J].Mater.Sci.Eng.,2016,A675:153
[14]Chen J,Lv M Y,Liu Z Y,et al.Combination of ductility and tough‐ness by the design of fine ferrite/tempered martensite-austenite mi‐crostructure in a low carbon medium manganese alloyed steel plate[J].Mater.Sci.Eng.,2015,A648:51
[15]Cai Z H,Ding H,Misra R D K,et al.Austenite stability and defor‐mation behavior in a cold-rolled transformation-induced plasticity steel with medium manganese content[J].Acta Mater.,2015,84:229
[16]Li Y J,Li X L,Yuan G,et al.Microstructure and partitioning be‐havior characteristics in low carbon steels treated by hot-rolling di‐rect quenching and dynamical partitioning processes[J].Mater Charact.,2016,121:157
[17]Tian Y Q,Zhang H J,Chen L S,et al.Comprehensive effect of C,Mn partitioning behavior on retained austenite of low carbon SiMn steel in I&Q&P process[J].J.Mater.Eng.,2016,44(4):32(田亚强,张宏军,陈连生等.低碳硅锰钢I&Q&P处理中C,Mn元素配分综合作用[J].材料工程,2016,44(4):32)
[18]Chen L S,Zhang J Y,Tian Y Q,et al.Effect of Mn pre-partitioning on C partitioning and retained austenite of Q&P steels[J].Acta Metall.Sin.,2015,51:527(陈连生,张健杨,田亚强等.预先Mn配分处理对Q&P钢中C配分及残余奥氏体的影响[J].金属学报,2015,51:527)
[19]Edmonds D V,He K,Rizzo F C,et al.Quenching and partitioning martensite-A novel steel heat treatment[J].Mater.Sci.Eng.,2006,A438:25
[20]Van Der Zwaag S,Zhao LE,Kruijver S O,et al.Thermal and me‐chanical stability of retained austenite in aluminum-containing multiphase TRIP steels[J].ISIJ Int.,2002,42:1565
[21]Sun S J,Pugh M.Manganese partitioning in dual-phase steel dur‐ing annealing[J].Mater.Sci.Eng.,2000,A276:167
[22]Chiang J,Lawrence B,Boyd J D,et al.Effect of microstructure on retained austenite stability and work hardening of TRIP steels[J].Mater.Sci.Eng.,2011,A528:4516
[23]Xiong X C,Chen B,Huang M X,et al.The effect of morphology on the stability of retained austenite in a quenched and partitioned steel[J].Scr.Mater.,2013,68:321
[24]Fischer F D,Reisner G,Werner E,et al.A new view on transfor‐mation induced plasticity(TRIP)[J].Int.J.Plast.,2000,16:723
[25]Knijf D D,Petrov R,F?jer C,et al.Effect of fresh martensite on the stability of retained austenite in quenching and partitioning steel[J].Mater.Sci.Eng.,2014,A615:107
[26]Dai Y J,Li B,Ma H E,et al.Influence of carbon on the stacking fault energy and deformation mechanics of Fe-Mn-C system alloys[J].Appl.Mech.Mater.,2015,710:9
[27]Song C H,Yu H,Li L L,et al.Effect of carbon at interface of aus‐tenite on manganese segregation of low carbon and manganese steel[J].Mater Lett.,2016,174:75
[28]Yang P,Liu T Y,Lu F Y,et al.Orientation dependence of martens‐itic transformation in high Mn TRIP/TWIP steels[J].Steel Res.Int.,2012,83:368
[29]Chumlyakov Y,Panchenko E,Kireeva I,et al.Orientation depen‐dence and tension/compression asymmetry of shape memory effect and superelasticity in ferromagnetic Co40Ni33Al27,Co49Ni21Ga30and Ni54Fe19Ga27single crystals[J].Mater.Sci.Eng.,2008,A481-482:95