配分时间对QP钢力学性能及显微组织的影响

摘要

设计了一种中碳中锰Q&P(Quenching and partitioning)钢,基于热力学平衡理论计算分析了其相变过程,通过扫描电镜(SEM)、背散射电子衍射(EBSD)和透射电镜(TEM)研究了实验钢经不同热处理后的微观组织,测试了其力学性能,并采用X射线衍射仪(XRD)进一步分析了拉伸断裂前后残留奥氏体含量的演变规律.结果表明:室温下实验钢微观组织为板条状马氏体和弥散分布的残留奥氏体;残留奥氏体主要存在于马氏体板条之间和原始奥氏体晶界处;随配分时间延长,抗拉强度逐渐降低,延伸率呈现升高趋势;试样拉断后,断口处残留奥氏体含量在3.5％～4.5％之间,明显低于拉伸前的含量(6.94％～10.78％),说明大部分残留奥氏体在拉伸过程中发生了TRIP效应,提高了实验钢的塑性.%Based on the regulating and controlling theory of thermodynamic,the microstructure evolution and mechanical properties of a new designed medium-carbon-manganese steel after Q&P process was studied by SEM,EBSD and TEM.The mechanical properties was tested,and the evolution mechanism of retained austenite was discussed by XRD.The results indicated that the microstructure was consisted of lath martensite and dispersively distributed retained austenite;the retained austenite was emerged in the form of thin film between martensite laths and blocks along the grain boundaries;the strength decreased and the elongation increased with the increase of partition time;the fraction of retained austenite decreased from 6.94 ％-10.78 ％ to 3.5 ％-4.5 ％ after tensile test,which indicated the occurrence of TRIP effect and the increase of ductility.