逆转变奥氏体稳定性对中锰钢强韧性的影响

对淬火态中锰钢进行了不同温度的回火试验,研究了不同回火温度下逆转变奥氏体的含量和稳定性,及其对中锰钢强韧性能的影响。结果表明:当回火温度由630 ℃升高至670 ℃时,中锰钢室温组织中逆转变奥氏体体积分数由19%增加至42%,逆转变奥氏体稳定性不断降低;中锰钢的屈服强度由750 MPa降低至565 MPa,抗拉强度由845 MPa升高至970 MPa, -60 ℃冲击吸收能量由116 J减小至75 J。高体积分数、低稳定性的逆转变奥氏体会降低中锰钢的屈服强度,但会提高中锰钢的加工硬化能力。在冲击载荷作用下,组织中的逆转变奥氏体发生相变诱导塑性(Transformation-induced plasticity, TRIP)效应,显著提高裂纹形成功和裂纹扩展功,是中锰钢主要的韧化机制。

Effect of reversed austenite stability on strength and toughness of medium-Mn steel

A quenched medium manganese steel was tempered, and the content and stability of reversed austenite at different tempering temperatures with its effect on the strength and toughness were studied. The results show that with the tempering temperature increasing from 630 ℃ to 670 ℃, the volume fraction of reversed austenite is increased from 19% to 42%, while its stability decrease constantly; and the yield strength decreases from 750 MPa to 565 MPa, the tensile strength increases from 845 MPa to 970 MPa, the impact toughness at -60 ℃ decreases from 116 J to 75 J. The large volume fraction of reversed austenite with poor stability reduces the yield strength of the steel, but improves the work-hardening ability significantly. The transformation-induced plasticity effect of reversed austenite can increase the crack initiation and propagation energy effectively under impact loading, which is the main toughening mechanism of the medium manganese steel.