配分时间对Q&P钢力学性能及显微组织的影响

设计了一种中碳中锰QP(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。

Influence of Partition Time on Mechanical Properties and Microstructure of Q&P Steel

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 mecha-nical 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.