中文摘要：

对TC4钛合金的熔覆试样进行激光冲击强化试验,比较了激光冲击强化前后试样的显微硬度、表面残余应力、显微组织和疲劳性能.TC4钛合金熔覆后,修复区表面残余拉应力为225 MPa,激光冲击强化消除了熔覆产生的拉应力,产生了449 MPa的残余压应力,在基体残留的压应力高达672 MPa;激光冲击强化后,修复区硬度由强化前的333 HV提高到381 HV.TEM显示：3次冲击后,在TC4材料表面形成了纳米晶层.对强化前后的激光熔覆试样进行高周疲劳试验,结果表明：激光冲击强化提高熔覆后钛合金疲劳强度达15.8%.经分析,冲击后细化晶粒和残余压应力对高周疲劳性能的提高起到了关键作用.

英文摘要：

The laser cladded samples of TC4 titanium alloy was shocked by pulse laser to compare the hardness, surface residual stress, microstructure and the fatigue life of samples before and after laser shock processing（LSP）. The surface residual tensile stress in heat affect zone（AFZ） of laser cladded sample is 225 MPa. LSP reliefs the tensile stress and generates 449 MPa compressive stress, and the sur- face residual compressive stress after LSP in metal matrix reaches 672 MPa. The hardness in AFZ after la- ser cladding is 333 HV, while that is 381 HV after LSP. A nanocrystalline surface layer is found by TEM after three impacts. The high cycle fatigue tests of laser cladded samples were carried out before and after LSP. The results show that LSP treatment can improve the high cycle fatigue endurance limit of laser cladding titanium alloy by 15.8%. The nanocrystalline grained surface layer with residual compressive stress makes great contribution to the fatigue properties improvement of titanium alloy.