VC析出相对Fe-Mn-Si-Al相变诱导塑性钢微观组织演变及力学性能的影响

Effect of Vanadium Carbide Precipitates on Microstructure Evolution and Mechanical Properties of Fe-Mn-Si-Al TRIP Steel

Fe-Mn-Si-Al相变诱导塑性钢因具有较低屈服强度和良好低周疲劳性能,有潜力替代现有抗震用低屈服点钢制造钢阻尼器。对试验用钢进行准静态拉伸和低周疲劳试验,并借助多种组织表征方法研究试验用钢变形前后的微观组织演变,揭示VC析出相及奥氏体晶粒尺寸对其力学性能的影响规律及作用机理。结果表明:奥氏体晶粒粗化可以促进ε马氏体生成交叉状多变体,从而在准静态拉伸过程中,提高试验用钢断后伸长率;而在低周疲劳变形过程中,交叉状多变体削弱ε马氏体相变可逆性,使其疲劳寿命降低。VC析出相有助于提高试验用钢的屈服强度和抗拉强度,但其对ε马氏体生长具有抑制作用,使断后伸长率降低。在低周疲劳变形过程中,VC析出相钉扎ε马氏体/奥氏体两相界面,抑制ε马氏体逆相变,从而使试验用钢的循环加工硬化程度显著提高,低周疲劳寿命降低。

Fe-Mn-Si-Al TRIP steels with low yield strengths and good low-cycle fatigue lives have the potential to be used as seismic damping steels. The quasi-static tensile test and low-cycle fatigue test are performed on an Fe-Mn-Si-Al TRIP steel. The microstructure evolution before and after deformation of the experimental steel is characterized using multiple microstructure analyses,revealing the influence and mechanism of VC precipitates and austenite grain size on mechanical properties. The austenite grain coarsening promotes the formation of crossed multi-variant ε-martensite, thereby increasing the elongation of the experimental steel during the quasi-static tension. In contrast, during the low-cycle fatigue deformation, the low-cycle fatigue life of the experimental steel is decreased since crossed multi-variants weaken the reversibility of the ε-martensitic transformation. VC precipitates improve the strength of the experimental steel but hinder the growth of ε-martensite, leading to a reduction in elongation. VC precipitates pin the interfaces between the ε-martensite and austenite and inhibit reversible ε-martensite transformation during the low-cycle fatigue deformation, resulting in significant enhancement of cyclic work hardening and a decrease in the low-cycle fatigue life of the experimental steel.