为了研究激光冲击强化对镁合金性能的影响, 采用钕玻璃脉冲激光(波长1054 nm, 脉冲宽度23 ns)对AM50镁合金试样表面进行冲击强化处理, 并对其表面形貌、微观组织、显微硬度、残余应力进行实验测试与分析。结果表明,在激光功率密度为3.1 GW/cm2的强脉冲激光作用下, 试样表面留下光亮致密的微凹坑, 凹坑深约27 μm; 表层材料发生高应变速率的塑性变形, 材料内产生大量位错与孪晶, 强化层深度约0.8 mm; 冲击区的显微硬度明显增加, 表层材料的显微硬度比基体约提高58%; 冲击区表面存在残余压应力, 数值高达-146 MPa。实验结果表明, 激光冲击镁合金的强化效果明显。

In order to study the effect of laser shock processing (LSP) on the properties of magnesium alloy, an AM50 magnesium alloy sample was processed with Nd∶glass laser with the wavelength of 1054 nm and pulse width of 23 ns, and its surface figure, microstructure, micro-hardness and residual stress were examined and analyzed. The experimental results show that a bright dense shallow dent forms in the laser shocked area with laser power density of 3.1 GW/cm2, and the dent depth is about 27 μm. Ultrahigh strain rate plastic deformation takes place in the surface layer and results in extensive formation of dislocations and twins, and the depth of strengthening layer is about 0.8 mm. Laser shock processing improves hardness and residual stress of AM50 magnesium alloy significantly, surface micro-hardness increases by up to 58% and the compressive residual stress on the surface of laser shocked area reaches up to -146 MPa. The experiment results show that the effect of laser shock evidently strengthens the magnesium alloy.