应变速率对低温拉伸316LN奥氏体不锈钢微观组织和力学性能的影响

Effect of Strain Rate on Microstructure Evolution and Mechanical Property of 316LN Austenitic Stainless Steel at Cryogenic Temperature

以两种应变速率(5×10^(-4)s^(-1)和1×10^(-2)s^(-1),分别代表慢速拉伸和快速拉伸)对316LN奥氏体不锈钢板状试样进行低温(-40℃)单轴拉伸实验,借助金相显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)、X射线衍射仪(XRD)及三维形貌轮廓仪分析了拉伸变形过程中的微观组织演变和力学性能变化规律。结果表明,316LN奥氏体不锈钢在低温拉伸条件下发生形变诱导马氏体相变,且马氏体转变量随着应变速率的增加而减少;屈服强度随着应变速率的增加而升高,抗拉强度和延伸率则随着应变速率的增加而降低;拉伸断口形貌均呈现出典型的韧性断裂特征。变形组织均以位错缠结和T-M(Twin-matrix)层片状组织为主,随着应变速率的增加,位错缠结程度加剧,T-M层片状组织的层片间距减小。

The uniaxial tensile property of 316 LN austenitic stainless steel（ASS） plate at-40 ℃was examined by strain rates of 5×10^（-4） s^（-1） and 1×10^（-2） s^（-1） respectively, while the microstructure evolution was characterized by means of OM, TEM, SEM, XRD and 3 D profile profiler. The results showed that the deformation induced martensite transformation occurred in 316 LN austenitic stainless steel at cryogenictemperature, and the martensite transformation decreased with the increase of strain rate. The yield strength increased with the increase of strain rate, while the tensile strength and elongation decreased with the increase of strain rate. The tensile fractured surface showed typical ductile fracture. The deformed microstructure composed mainly of dislocation tangles and T-M（twin-matrix）lamellar structures.With the increase of strain rate, the dislocation tangles aggravated and the interlamellar spacing of T-M（twin-matrix）lamellar structures reduced.