700MPa级高塑低碳低合金钢的多相组织调控及性能  

REGULATION OF MULTI-PHASE MICROSTRUCTURE AND MECHANICAL PROPERTIES IN A 700 MPa GRADE LOW CARBON LOW ALLOY STEEL WITH GOOD DUCTILITY

作　　者：周文浩[1] 谢振家[1] 郭晖[1] 尚成嘉[1] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083

出　　处：《金属学报》2015年第4期407-416,共10页Acta Metallurgica Sinica

基　　金：国家重点基础研究发展计划资助项目2010CB630801~~

摘　　要：通过临界退火、临界回火以及回火的多步热处理方式,研究了低碳低合金钢的组织演变与力学性能.结果表明,临界退火后的组织为板条状的临界铁素体及贝氏体/马氏体的双相组织.经临界回火后,为临界铁素体、回火贝氏体/马氏体以及残余奥氏体的多相组织.残余奥氏体呈粒状和条状,分布在铁素体/贝氏体（马氏体）相界面及贝氏体/马氏体板条之间,含量高达29%,并在回火后保持稳定,主要通过C,Mn,Ni和Cu在逆转奥氏体中的富集来稳定.临界退火及回火过程中,Nb C在铁素体及贝氏体/马氏体中析出,呈球状、椭圆形或不规则形状,平均尺寸为10 nm;富Cu的析出相在临界回火及回火过程中形成,呈球状分布于铁素体及残余奥氏体中,尺寸在10~30 nm之间.通过残余奥氏体的应变诱导塑性（TRIP）效应及纳米析出相的析出强化作用,实验钢具有优异的力学性能：屈服强度高于700 MPa,抗拉强度高于900 MPa,均匀延伸率高于20%,总延伸率高于30%.ABSTRACT Low carbon and low alloy steels require good combination of strength and ductility to ensure safe- ty and stability of structures. Heat treatment in intercritical area can not only produce multi-phase microstructure, but also lead to the redistribution of alloying elements in different phases. Multi-step intercritical heat treatment is favorable to obtain retained austenite that is stabilized by repeated enrichment of alloying elements in reversed ans- tenite and nanometer-sized precipitate that are primarily formed during tempering. Excellent mechanical properties are contributed by transformation-induced-plasticity effect of retained austenite and precipitation hardening effect of nanometer-size precipitates. In this work, the microstructural evolution and relative mechanical properties were investigated in a low carbon low alloy steel processed by a three-step heat treatment, namely, intereritical anneal- ing, intercritical tempering and tempering. The microstructure was a typical dual-phase microstructure consisting of intercritical ferrite and bainite/martensite after intercritical annealing, and primarily comprised of intercritical fer- rite, tempered bainite/martensite and retained austenite after intercritical tempering. Retained austenite with vol- ume fraction of 29% distributed at the ferrite/bainite （martensite） boundaries and betweent bainitic/martensitic laths. Retained austenite was stabilized by enrichment of C, Mn, Ni and Cu in reversed austenite during the rever- sion transformation process. NbC precipitates with average size of 10 nm was formed in ferrite matrix and bainite/ martensite, while Cu-containing particles in size range of 10-30 nm precipitated in ferrite and retained austenite during intercritical tempering and tempering process. The morphology of NbC precipitates was spherical, elliptical and irregular, and copper precipitates were spherical. With the combination of transformation-induced-plasticity （TRIP） effect of retained austenite and precipitation hardening, th

关 键 词：高性能 临界热处理 多相组织 残余奥氏体 纳米析出相 

分 类 号：TG142.1[一般工业技术—材料科学与工程]