低周疲劳变形过程中Fe-33Mn-4Si合金钢的微观组织演变

Microstructure evolution of Fe-33Mn-4Si steel during low-cycle fatigue deformation

借助X射线衍射和电子背散射衍射,研究低周疲劳变形过程中Fe-33Mn-4Si合金钢的微观组织演变及其对力学行为的影响。结果表明:实验用钢的原始微观组织由奥氏体和热诱发ε马氏体两相组成。原始组织通过影响变形过程中ε马氏体相变来影响实验用钢的低周疲劳变形行为。在变形初期(100周次内),随循环周次增加,ε马氏体含量迅速增加并且马氏体不同变体之间频繁相互交叉作用,使实验用钢的平均峰值应力和循环加工硬化程度快速增加;随后至疲劳断裂,ε马氏体成为变形微观组织中主要组成相,ε马氏体含量和马氏体不同变体的交叉频次随循环周次的增加而增速放缓,导致平均峰值应力和循环加工硬化程度的增速也明显减缓。

The microstructure evolution and mechanical behavior of an Fe-33Mn-4Si alloy steel under low-cycle fatigue deformation were investigated by using the X-ray diffraction and electron backscatter diffraction techniques.Results show that the experimental steel has an initial microstructure consisting of austenite and thermally inducedε-martensite.The initial microstructure remarkably affects the low-cycle fatigue property of the experimental steel through influencing theε-martensitic transformation during deformation.At the early stage of fatigue deformation(first 100 deformation cycles),with increasing deformation cycles,a rapid increase in the volume fraction ofε-martensite and the frequency of the intersection ofε-martensite with different variants result in a quick rise in cyclic average peak stress and work hardening degree.With the continuation of cyclic deformation up to fatigue fracture,theε-martensite becomes the dominant constituent phase in the deformation microstructure,and the volume fraction ofε-martensite and the frequency of the intersection ofε-martensite increase at an appreciably slower rate,thereafter significantly slowing the increase in cyclic average peak stress and work hardening degree.