大变形共析钢时效析出机制探讨

Study on precipitation mechanism of heavily cold drawn and annealed eutectoid steel

通过电阻方法研究了应变为2.89的共析钢在时效过程中析出动力学过程。研究表明,时效过程分为两个阶段:低于200℃(3600s),电阻率随着时效时间先增加后降低;200～298℃,电阻率随时效时间延长而降低。并揭示了大变形共析钢时效机制:大变形后获得的过饱和铁素体和高浓度界面偏聚碳为碳化物析出提供热力学驱动力,而高能界面处为渗碳体晶粒形核提供有效形核位置,碳原子的长程扩散控制着析出碳化物长大。

Precipitation kinetics of a heavily-cold-drawn eutectoid steel during aging was studied by means of electrical resistivity measurement. The results show that resistivity of the cold drawn steel increases firstly and then decreases with increasing aging time, however, resistivity of the steel decreases with increasing aging time at 200～298 ℃. It is suggested that the supersaturated ferrite and segregation of carbon atoms at interface between ferrite and cementite in the heavily cold drawn steel provide the driving force for nucleation of carbides, and the high energy interface between ferrite and cementite supplies the effective nucleation site for carbide nucleation. The growth of precipitates is controlled by the long-rang diffusion of carbon atoms.