超声表面滚压加工对Ti-6Al-4V合金显微组织及表面完整性的影响

摘要

采用"回"字形加工路径对退火态Ti-6Al-4V合金进行超声表面滚压加工(USRP),使用光学显微镜、透射电镜、显微维氏硬度计、X射线残余应力分析仪、表面三维形貌仪等设备对USRP后合金的显微组织和表面完整性进行表征.结果表明:USRP后Ti-6Al-4V合金表面形成了厚度约300μm的塑性变形层,塑性变形层的表面为等轴纳米晶层,次表面为晶粒取向一致的长条状纳米片晶层;USRP后Ti-6Al-4V合金的显微硬度最高达到390HV,表面粗糙度由0.76μm减小为0.23μm.随着距表面距离的增大,合金的残余压应力先增大后减小.%The ultrasonic surface rolling process (USRP)was performed on the annealed Ti-6Al-4V alloy using employing the rectangular-ambulatory-plane machining path.The microstructure and surface integrity of Ti-6Al-4V alloy after USRP were characterized by equipments such as optical microscope,transmission electron microscope,vickers indenter,X-ray diffraction residual stress analyzer and surface three-dimensional topography. The results show that a plastic deformation layer with around 300μm thickness was formed on the surface of Ti-6Al-4V alloy after USRP.The surface of plastic deformation layer was the equiaxial nanocrystal layer and the subsurface was the long strip shaped nanocrystalline laminar layer with the same grain orientation.The maximum mirco-hardness of Ti-6Al-4V alloy was 390 HV and the surface roughness reduced from 0.76μm to 0.23μm after USRP.The residual compressive stress of Ti-6Al-4V alloy increased first and then decreased with the increase of distance from surface.