中文摘要：

对20CrNiMo钢进行表面激光冲击强化处理,利用金相显微镜和透射电镜观察试样表面的塑性变形区域进行观察,分析了表面微观强化的过程。实验结果表明,激光冲击能够导致试样表面的硬度增加30%,残余压应力有较大程度的提高。从TEM照片可以观察到,在20CrNiMo钢表面为严重塑性变形区,此区域出现了晶粒细化,其演变过程为珠光体被打断成若干碎片,产生亚微米级亚晶结构,同时激光冲击导致材料表面整齐的纤维组织沿不同方向滑移,继而出现无定形态,最终在无定形态中出现了次级的珠光体晶粒。

英文摘要：

The evolution process of grain refinement is investigated by the metallographic microscope and transmission electron microscope（TEM）observations in the top surface,the sever plastic deformation layer,the minor plastic deformation layer and the substrate after a single laser shock processing.The results showed that laser shock processing could lead to an increase in surface hardness 30%,residual compressive stress had a great degree of improvement.From the TEM photos,the severe plastic deformation zone is observe red on the surface of 20 CrNiMo,this area appears to grain refinement.The evolution is that pearlite is interrupted into several pieces and generates sub micro sub grain structure.Laser shock leads to the neat fibrous tissue of material along different directions slipping,the amorphous form appears.Finally,the secondary pearlite grain appears in the amorphous form.