AM50A镁合金激光表面熔凝层的强化效果与机理

Strengthening effect and mechanism of laser surface melted AM50A magnesium alloy

采用CO2连续激光对AM50A镁合金表面进行熔凝处理，分析激光熔凝层的组织、性能和强化机理。结果表明：激光熔凝层晶粒得到高度细化，且随着扫描速度的增大，晶粒细化更为明显；熔凝层内合金元素Al的固溶度增加，声相（Mg17Al12）的含量有所减少，{印相的分布更加均匀弥散；熔凝层的显微硬度（HV55～75）明显高于基体的显微硬度（约HV40）。磨损实验表明，激光熔凝试样的磨损体积是未处理试样的35％，耐磨性有了较大提高。熔凝层的强化机理主要是细晶强化，此外合金元素Al固溶度的增加及β相的弥散析出也有一定的强化效果。

AM50A magnesium alloy was surface melted using a continuous wave CO2 laser, the microstructure properties and strengthening mechanism of the laser melted layer were analyzed. The results show that the grain of the laser surface melted layer is highly refined and the grain size decreases with increasing scanning speed. In the melted layer, the amount of element A1 in solid solution increases, the amount of fl-phase （Mg17Al12） decreases, and the distribution of β-phase becomes more uniform. The micro-hardness of the melted layer is improved to HV55-75 as compared to that of the substrate （about HV40）. The wear volume of the laser surface melted sample is 35% of the untreated sample, the wear resistance of the laser surface melted layer is improved obviously. The main strengthening mechanism of the laser surface melted layer is grain refinement, the increase of element Al in solid solution and the dispersive precipitation offl-phase can also result in strengthening the melted layer.