选区激光熔化316L不锈钢高应变率压缩下的塑性变形行为

Plastic Deformation Behavior of Selective Laser Melting 316L Stainless Steel under High Strain Rate Compression

对选区激光熔化316L不锈钢(SLM-316L)的高应变率(1000、2000、3000 s^(-1))压缩力学性能进行测试,用扫描电镜和背散射衍射(EBSD)等手段表征冲击加载前后试样的微观结构,并分析晶体结构的差异以及位错滑移、孪生行为等微观变形机制。结果表明:SLM-316L不锈钢在高应变率载荷作用下有显著的应变率强化效应,其微观组织由截面呈不规则多边形的柱状胞晶密排结构组成,高应变率加载使晶体取向的择优性降低、小角度晶界和孪晶界数量增加,且孪晶界在小角度晶界的交叉缠绕区分布密集,试样的塑性变形过程伴随着位错滑移及孪生行为。

The selective laser melting 316L stainless steel(SLM-316L)was prepared with preferred process parameters,and then the effect of high strain rate compression on the plastic deformation behavior of SLM 316L stainless steel by high strain rates(1000,2000 and 3000 s^(-1))was assessed by means of split Hopkinson pressure bar,scanning electron microscope and backscattered electron diffractometer in terms of the microstructure and microscopic deformation such as dislocation slip and twinning etc.Results show that SLM-316L stainless steel exhibits a significant strain rate strengthening effect by high strain-rate loading,and its microstructure is composed of closely packed columnar grains with irregular polygonal cross section.High strain rate loading decreases the degree of preferred orientation of grains and increases the number of small-angle grain boundaries and twin boundaries,and the twin boundaries are densely emerge in the cross-twisting region of small-angle grain boundaries.The plastic deformation process of the SLM-316L stainless steel is accompanied by dislocation slip and twinning behavior.