为研究激光冲击强化对TiAl合金组织和性能的影响, 利用波长为1 064 nm、脉宽为20 ns、单脉冲能量为0~22 J的Nd:YAG激光器对TiAl合金试件进行了实验研究。采用显微硬度计、表面粗糙度仪和扫描电镜分别测量了激光冲击强化前后的表面显微硬度、粗糙度和表面微观形貌, 利用X射线应力分析仪测量了激光冲击强化表面残余应力和晶面极性, 并分析了其高温稳定性。实验结果表明: 当单脉冲能量增加到9 J时, 表面显微硬度增加了33.4%, 粗糙度由0.042 μm增大到了0.285 μm, 表面残余压应力由20 MPa增加到了297 MPa, 表面微观形貌出现了凸凹不平, 局部纹理和层状微结构。将9 J激光冲击强化后的试件在650 ℃下保温4 h后, 残余压应力值从297 MPa降到230 MPa, 显微硬度值从377 HV0.2降到345 HV0.2, (002)晶面取向有向中心移回的趋势。得到的数据显示, 激光冲击强化能够极大地改善TiAl合金的组织和性能, 且具有一定的高温稳定性。

To study the effect of laser peening on microstructures and properties of TiAl alloy, TiAl alloy samples were treated by a Nd:YAG laser system with a wavelength of 1 064 nm, a pulse-width of 20 ns, and a pulse-energy of range 0-22 J. The surface micro-hardness, roughness, and microstructural characteristics of the samples before and after laser peening were tested with a micro-hardness tester, a roughness tester and a Scanning Electron Microscope (SEM). The residual stress and pole figures of TiAl alloy were tested with X-ray Diffraction (XRD) and their high-temperature stabilities were analyzed. The experimental results show that the surface micro-hardness increases up to 33.4%, the roughness increases from 0.042 μm to 0.285 μm, the compress residual stress increases from 20 MPa to 297 MPa with the pulse energy up to 9 J, and the local textures and typical lamellar microstructures are generated. When the samples are heated for 4 h at 650 ℃, the residual stress value and micro hardness values have droped from 297 MPa to 230 MPa, and 377 HV0.2 to 345HV0.2 respectively, and the (002) poles shift back to the center slightly. It concludes that the laser peening improves microstructures and properties of TiAl alloy significantly.