为了研究激光冲击处理对AZ31B镁合金冲击韧性的影响，采用波长为1064 nm，脉冲宽度为15 ns，脉冲能量为10 J，光斑直径为3 mm的钕玻璃脉冲激光对变形镁合金AZ31B试样表面进行冲击处理。利用透射电子显微镜(TEM)观测激光冲击试样的微观结构，利用X-350A型X射线应力仪测定试样表面残余应力，利用JB-300B型冲击试验机测定试样冲击功的大小，利用扫描电子显微镜(SEM)观测夏比冲击试样断口。实验结果表明：根据优化的工艺参数，激光冲击处理能在AZ31B镁合金上制备出纳米结构表层，表面晶粒尺寸大约为20 nm；激光冲击处理改变了试样表面的应力状态，由残余拉应力17 MPa转变为残余压应力-125 MPa；激光冲击之后AZ31B镁合金试样的平均冲击功由5.4 J增大到9.2 J，提高了70.4%。AZ31B镁合金激光冲击试样冲击韧性提高的机理是表面纳米化及残余压应力共同作用的结果。

In order to investigate the effect of laser shock processing (LSP) on impact toughness of AZ31B magnesium alloy, AZ31B magnesium alloy samples are treated by using NdYAG laser with a wavelength of 1064 nm, a pulse width of 15 ns, a pulse energy of 10 J and a spot diameter of 3 mm. The surface layer structures of laser treated samples are analyzed by using transmission electron microscopy (TEM). Surface residual stress is assessed by using X-ray diffraction technology, the value of impact energy of samples are examined by an impact tester (Model JB-300B), and the fracture surface morphologies of charpy impacting samples are characterized by scanning electron microscopy (SEM). Test results show that a nanostructured surface layer can be fabricated on AZ31B magnesium alloy by using optimized laser parameters, and surface grain size is about 20 nm. The surface residual stress is converted from tensile stress (17 MPa) to compressive stress (-125 MPa) by LSP. The mean impact energy of samples is changed from 5.3833 J to 9.2333 J and increases by 71.5% after LSP. The impact toughness improvement of samples by LSP is attributed to a combination of surface nanocrystallization and residual compressive stress.