热作模具钢在高温热机械应力循环下的疲劳断裂行为

High Temperature Fatigue and Fracture Behavior of Hot Work Die Steel under Mechanical and Thermo-mechanical Cyclic Loads

研究了热作模具钢在应力控制下的等温疲劳和同相热机械疲劳寿命 ,发现在相同的应力幅下 ,同相热机械疲劳寿命低于上限温度的等温疲劳寿命。通过研究疲劳过程中的循环应变响应和疲劳断口特征时发现 ,等温疲劳条件下 ,滞后环朝压缩方向发展 ,疲劳裂纹主要为穿晶萌生与扩展 ;在热机械疲劳条件下 ,滞后环朝拉伸方向发展 ,疲劳裂纹主要沿晶萌生与扩展。

The fatigue lives of in-phase thermo-mechanical fatigue (TMF) and isothermal fatigue (IF) were carried out in cast hot work die steel in stress control in this paper. At the same stress amplitude, the lives obtained under in-phase thermo-mechanical fatigue conditions are lower than those obtained under isothermal fatigue conditions at the maximum temperature. In TMF tests, the hysteresis loops move in the tensile direction and the path of the crack initiation and growth is mainly intergranular. In IF tests, the hysteresis loops move in the compressive direction and the path of the crack growth is transgranular.