激光冲击对Ti834合金残余应力及显微组织的影响

Effect of Laser Shock Processing on Residual Stress and Microstructure of Ti834 Titanium Alloy

采用表面粗糙度仪、X射线衍射仪、显微硬度计分析了激光冲击前后Ti834合金的表面粗糙度、残余应力及显微硬度分布规律,并采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对冲击区域表面形貌及显微组织进行了表征。结果表明,Ti834钛合金经激光冲击处理后表面粗糙度、显微硬度和残余压应力均随激光冲击次数的增加而增大。经1次冲击和2次冲击后形成的强化层深度分别为170和265μm。LSP能在材料表层残留高的压应力场,经1次冲击和2次冲击后残余压应力峰值均出现在次表层,分别达到-369和-511 MPa。由冲击波诱导形成的塑性变形层内可观察到大量位错缠结现象,LSP后位错密度的增加以及形变孪晶的形成有利于提升Ti834合金的机械性能。

Laser shock processing(LSP),also known as laser shot peening,is a novel surface strengthening treatment technology.The surface roughness,residual stress and microhardness distribution of Ti834 alloy before and after LSP were analyzed by surface roughometer,X-ray diffraction and microhardness tester,respectively.And the surface morphology and microstructure of the impact area were characterized by scanning electron microscope(SEM)and transmission electron microscope(TEM).The results show that the surface roughness,microhardness and residual compressive stress of Ti834 titanium alloy increase after LSP.Moreover,the depth of the strengthening layer formed after one impact and two impacts is 170 and 265μm,respectively.After LSP treatment,a high compressive stress field is produced on the surface of Ti834 alloy.The peak value of residual compressive stress,after one impact and two impacts,appears in the subsurface layer,and reaches–369 and–511 MPa,respectively.A large amount of dislocation entanglement can be observed in the plastic deformation layer induced by laser shock wave.The increase of dislocation density and the formation of deformation twins are conducive to improvement of mechanical properties of Ti834 alloy subjected to LSP.