中文摘要：

通过CO2激光器对试件进行激光表面热处理,对比处理前后试样的疲劳寿命,找出了最优激光工艺参数,并对其进行疲劳断口及表面微观结构分析,探求其微观机理.研究结果表明：激光表面热处理时激光扫描速率、功率密度对处理效果有显著影响;对于25μm厚工业纯Cu薄膜材料,激光功率密度为208 kW/cm^2,扫描速率为25mm/s时,激光表面处理效果最佳,试件的疲劳寿命提高了2～3倍;在扫描电镜观测下发现,激光表面处理后试件表面形成1层淬硬区并产生残余压应力,使试件的疲劳强度明显增加,且激光表面处理的试件裂纹萌生后扩展至断裂的过程较为缓慢,断口出现疲劳条纹.

英文摘要：

The influence of laser surface heat treatment on fatigue properties is investigated for the rolled polycrystalline copper thin films in this paper.The aim is to find optimal conditions of treatment,which will extend the material resistance to fatigue failure,and explore the mechanisms of fatigue fracture and surface micro-structure,by changing the laser process parameters.Results show that scanning speed and power density of laser treatment have greater influence on the fatigue life of specimens,which is more than two to three times the original specimens life at laser power density of 208 kW/cm^2,laser scanning speed of 25 mm/s for 25 μm thick rolled polycrystalline copper thin films.SEM observation results for fracture surface show that the hardened layer and the residual compressive stress are formed on the surface area of specimens,which makes the fatigue strength of specimens significantly increase.Since the crack growth rate for laser heat treatment specimens is slower than that of the original specimens,some fatigue striations are formed in the fatigue propagation region.