应变速率对低C高Mn TRIP/TWIP钢组织演变和力学行为的影响

研究了Fe-18Mn低C高Mn TRIP/TWIP钢在应变速率范围为1.67×10^-4-10³s^-1的室温拉伸实验过程中力学性能和组织的变化.在准静态拉伸应变速率范围内(1.67×10^-4-1.67×10^-1s^-1),应变速率对高Mn TRIP/TWIP钢的抗拉强度产生逆效应,随着应变速率的加快,抗拉强度和延伸率都降低;而在动态拉伸应变速率范围内(10¹-10³s^-1),应变速率对高Mn TRIP/TWIP钢的延伸率产生逆效应,抗拉强度和延伸率都随着应变速率的加快而增加;在应变速率为10³s^-1时,高Mn TRIP/TWIP钢抗拉强度可达到957 MPa,延伸率达到55.8%,具有较好的综合力学性能;随着应变速率的提高,马氏体转变量减少,孪生变形向多个方向发展.采用SEM,TEM和XRD等方法对变形前后的组织进行了分析,在所有应变速率范围内的拉伸变形过程中都产生了奥氏体向马氏体转变和形变孪晶,并且在应变速率为10³s^-1的高速拉伸过程中产生绝热温升效应,使得基体软化.

EFFECT OF STRAIN RATE ON MICROSTRUCTURE EVOLUTION AND MECHANICAL BEHAVIOR OF A LOW C HIGH Mn TRIP/TWIP STEELS

The microstructure and mechanical properties of Fe-18Mn low carbon high manganese TRIP/TWIP steels during tensile tests in the range of initial strain rate of 1.67×10^-4—10³ s^-1 at room temperature were studied.The inverse effect of strain rate on strength of steel was produced,the strength and ductility of steels decreased with increasing strain rate in the range of quasi-static tensile strain rate of 1.67×10^-4—1.67×=10^-1 s_-1.While inverse effect of strain rate on ductility of steels was produced in the range of dynamic tensile strain rate of 10¹—10³ s^-1,the strength and ductility of materials increased significantly with increasing strain rate.The tensile strength of high manganese TRIP/TWIP steels was 957 MPa and their elongation was 55.8%.These results indicated that Fe-18Mn steel had excellent mechanical properties and good fracture resistance.The higher the strain rates applied,the less martensite,the more directions of deformation twins.The microstructure evolution of the specimen was analyzed by SEM,TEM and XRD,martensitic transformation and deformation twins were produced during the tensile deformation,and adiabatic temperature rise effect made the matrix softening during the high-speed deformation.