含Co不锈钢析出相的模拟研究与强韧性能变化

Simulation study of precipitate phases and variation of strength and toughness of Co-containing stainless steel

采用数值模拟、组织表征和性能测试等方法,研究了添加Co对马氏体时效硬化不锈钢微观组织和力学性能的影响。根据Thermo-Calc热力学及动力学计算结果:6wt%Co条件下,ε-Cu相的析出温度升高且孕育时间变长,相同时效条件下ε-Cu相的平均半径会逐渐减小。借助光学显微镜(OM)及透射电镜(TEM)分析发现,固溶+时效处理后含Co试验钢超低碳板条马氏体细化,弥散分布的ε-Cu相尺寸变小且析出量增加,薄膜状逆变奥氏体数量增多且尺寸增大。由于板条马氏体的位错强化、ε-Cu相的析出强化以及逆变奥氏体相的增韧作用,含Co试验钢的抗拉强度、硬度、伸长率及冲击吸收能量分别达到1346 MPa、433 HV0.5、16%和73 J。

Influence of Co addition on the microstructure and mechanical properties of maraging stainless steel was studied by using numerical simulation,microstructure characterization and performance test.According to the thermodynamic and kinetic calculation with Thermo-Calc software,the results show that with addition of 6wt%Co,the precipitation temperature ofε-Cu phase rises and the incubation time becomes longer,and under the same aging condition the average radius ofε-Cu precipitates decreases.The optical microscopy(OM)and transmission electron microscopy(TEM)analysis results show that for the Co-containing tested steel after solution treatment and aging,the ultra-low carbon lath martensite is refined obviously,the dispersedε-Cu phase size becomes smaller and the precipitation amount increases gradually,and the film-like inverted austenite increases in amount and in size.Owing to the dislocation strengthening of lath martensite,the precipitation strengthening ofε-Cu phase and the toughening effect of the inverted austenite phase,the strength,hardness,elongation and impact absorbed energy of the tested Co-containing steel reach 1350 MPa,433 HV0.5,16%and 75 J,respectively.