初始组织形态对中碳钢温变形组织演变的影响

中碳钢温变形过程的组织演变包含铁素体动态回复、再结晶和渗碳体的析出球化等过程.采用Gleeble1500热模拟试验机研究了初始组织形态对含碳0.48%(质量分数)的中碳钢在温变形中上述复杂过程的影响.结果表明:初始组织为珠光体 先共析铁素体的试样在温加工变形中渗碳体层片发生了扭折、溶断到逐渐球化的过程,在铁素体回复再结晶的同时伴随着细小弥散的渗碳体颗粒从过饱和铁素体中析出,得到微米级铁素体晶粒和颗粒状渗碳体弥散分布的复相组织,但等轴状铁素体晶粒与弥散的渗碳体颗粒沿变形方向呈带状不均匀分布.温加工变形促进初始组织为马氏体的中碳钢中渗碳体析出和铁素体回复与再结晶.由于初始条件下碳的分布在微观尺度下相对均匀,变形后获得细小等轴铁素体与均匀分布颗粒状渗碳体的组织.

Effect of initial microstructure on the microstructure evolution of medium carbon steel during warm deformation

The microstructure evolution of medium carbon steel during warm deformation includes dynamic recovery and recrystallization of ferrite,precipitation and spheroidization of cementite.The effect of initial microstructure on the microstructure evolution of a medium carbon steel(0.48% C in mass fraction)during warm deformation was investigated by hot uniaxial compression tests.The results indicate that the lamellar structure of pearlite in the initial microstructure of pearlite ferrite is kinked,dissolved and spheroidized during warm deformation,with dynamic recovery and dynamic recrystallization of ferrite,the carbides precipitate from supersaturated ferrite,and then the duplex microstructure consisting of sub-micrometer ferrite grains and cementite particles is obtained,while the heterogeneous and zonal distribution of cementite particles and ferrite grains appear along the deformation direction.When the initial microstructure is martensite,the decomposition of martensite and the recovery and recrystallization of ferrite are enhanced by warm deformation.Because of the uniform distribution of carbon in the matrix,the fine equiaxed ferrite grains and homogeneously distributed cementite particles are formed.