C和Mn元素配分行为对冷轧中锰TRIP钢组织性能的影响
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摘要
采用冷轧+两相区温轧退火(CR+WR+IA)热处理工艺,研究了两相区退火时间对超细晶铁素体与奥氏体中组织形貌演变、C和Mn元素配分行为以及力学性能的影响。结果表明,冷轧试验钢经两相区形变退火处理后,获得了由铁素体、残余奥氏体或新生马氏体组成的超细晶复相组织。在645℃随退火时间的延长,形变马氏体向逆相变奥氏体配分的C、Mn元素增多,C、Mn元素富集位置增加,同时富Mn区形变马氏体回复再结晶现象明显;伴随少量碳化物溶解,试验钢的屈服强度由741 MPa持续降低到325 MPa。两相区退火10 min时,试验钢力学性能最佳,此时抗拉强度达到最大值1 141 MPa,断后伸长率及均匀伸长率分别为23.6%和18.1%,强塑积达到26.928 GPa·%。
The effect of intercritical annealing time on the microstructure evolution, C and Mn elements partitioning behavior, and mechanical properties of ultrafine-grained ferrite and austenite was studied by means of a new heat treatment process of cold rolling followed by warm rolling and intercritical annealing at two-phase region(CR+WR+IA). The results showed that the ultrafine-grained multiphase microstructure composed of ferrite, retained austenite or fresh martensite was obtained after cold-rolled experimental steel treated by intercritical deformation annealing. With prolonging the annealing time at 645 ℃, C and Mn elements constantly diffused from deformed martensite to reverted austenite, resulting in the increase in enrichment sites of C and Mn elements. Meanwhile, recrystallization phenomenon of deformed martensite was obvious in the Mn-rich region. With a small amount of carbide precipitation and dissolution, the yield strength of experimental steel was continuously decreased from 741 to 325 MPa. After intercritical annealing for 10 min, the best comprehensive performance of experimental steel was reached. At this time, the tensile strength reached a maximum value of 1 141 MPa, the elongation after fracture and uniform elongation were 23.6% and 18.1%, respectively, and the product of strength and elongation reached 26.928 GPa·%.
The effect of intercritical annealing time on the microstructure evolution, C and Mn elements partitioning behavior, and mechanical properties of ultrafine-grained ferrite and austenite was studied by means of a new heat treatment process of cold rolling followed by warm rolling and intercritical annealing at two-phase region(CR+WR+IA). The results showed that the ultrafine-grained multiphase microstructure composed of ferrite, retained austenite or fresh martensite was obtained after cold-rolled experimental steel treated by intercritical deformation annealing. With prolonging the annealing time at 645 ℃, C and Mn elements constantly diffused from deformed martensite to reverted austenite, resulting in the increase in enrichment sites of C and Mn elements. Meanwhile, recrystallization phenomenon of deformed martensite was obvious in the Mn-rich region. With a small amount of carbide precipitation and dissolution, the yield strength of experimental steel was continuously decreased from 741 to 325 MPa. After intercritical annealing for 10 min, the best comprehensive performance of experimental steel was reached. At this time, the tensile strength reached a maximum value of 1 141 MPa, the elongation after fracture and uniform elongation were 23.6% and 18.1%, respectively, and the product of strength and elongation reached 26.928 GPa·%.
引文
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[3] Luo H,Shi J,Wang C,et al.Experimental and numerical analysis on formation of stable austenite during the intercritical annealing of 5Mn steel[J].Acta Materialia,2011,59(10):4002.
[4] 董瀚,曹文全,时捷,等.第3代汽车钢的组织与性能调控技术[J].钢铁,2011,46(6):1.(Dong H,Cao W Q,Shi J,et al.Microstructure and performance control technology of the 3rd generation auto sheet steels[J].Iron and Steel,2011,46(6):1.)
[5] 宋丽娜,兰鹏,刘春秀,等.第3代汽车用中锰钢的研究现状[J].钢铁研究学报,2015,27(7):1.(Song L N,Lan P,Liu C X,et al.Research situation of medium manganese steel for 3rd generation automobile sheet[J].Journal of Iron and Steel Research,2015,27(7):1.)
[6] 田亚强,张宏军,陈连生,等.合金元素配分行为对残余奥氏体和力学性能的影响[J].金属学报,2014,50(5):531.(Tian Y Q,Zhang H J,Chen L S,et al.Effect of alloy elements partitioning behavior on retained austenite and mechanical property in low carbon high strength steel[J].Acta Metallurgica Sinica,2014,50(5):531.)
[7] Danoix F,Sauvage X,Huin D,et al.A direct evidence of solute interactions with a moving ferrite/austenite interface in a model Fe-C-Mn alloy[J].Scripta Materialia,2016,121:61.
[8] Han J,Silva A K D,Ponge D,et al.The effects of prior austenite grain boundaries and microstructural morphology on the impact toughness of intercritically annealed medium Mn steel[J].Acta Materialia,2017,122:199.
[9] 陈连生,李跃,张明山,等.两相区位错增殖对Mn元素配分及低碳钢贝氏体组织的影响[J].金属学报,2017,53(11):1418.(Chen L S,Li Y,Zhang M S,et al.Effect of intercritical dislocation multiplication to Mn partitioning and microstructure evolution of bainite in low carbon steel[J].Acta Metallurgica Sinica,2017,53(11):1418.)
[10] Khlestov V M,Konopleva E V,Mcqueen H J.Effect of deformation in controlled rolling on ferrite nucleation[J].Canadian Metallurgical Quarterly,2001,40(2):221.
[11] Lee S,Cooman B C D.Influence of carbide precipitation and dissolution on the microstructure of ultra-fine-grained intercritically annealed medium manganese steel[J].Metallurgical and Materials Transactions,2016,47A(7):3263.
[12] Miyamoto G,Oh J C,Hono K,et al.Effect of partitioning of Mn and Si on the growth kinetics of cementite in tempered Fe-0.6 mass% C martensite[J].Acta Materialia,2007,55(15):5027.
[13] 李小龙,郭正洪,戎咏华,等.基于屈服平台理论开发的600 MPa级高强塑性螺纹钢的研究[J].金属学报,2014,50(4):439.(Li X L,Guo Z H,Rong Y H,et al.600 MPa grade rebar with high ductility developed based on theory of yield plateau[J].Acta Metallurgica Sinica,2014,50(4):439.)
[14] 王昌,徐海峰,黄崇湘,等.中锰钢逆相变退火组织的演变及锰的配分行为[J].钢铁研究学报,2016,28(4):38.(Wang C,Xu H F,Huang C X,et al.Evolution of ART-annealed microstructure and partition behavior of manganese in medium manganese steel[J].Journal of Iron and Steel Research,2016,28(4):38.)
[15] Nabarro F R N.Distribution of solute atoms round a moving dislocation[J].Materials Science and Engineering,2005,400A(1):22.
[16] Silva A K D,Leyson G,Kuzmina M,et al.Confined chemical and structural states at dislocations in Fe-9wt%Mn steels: A correlative TEM-atom probe study combined with multiscale modelling[J].Acta Materialia,2017,124:305.