由于母材含有大量气源，气孔是压铸镁合金激光焊最主要的问题。在不同的激光功率密度下，采用不同的热输入对压铸镁合金激光焊气孔形成规律进行了研究。在低激光功率密度（1.6×106 W/cm2以下）焊接时，随着热输入的升高气孔率持续升高；在高激光功率密度（3.2×106 W/cm2以上）焊接时，在一定热输入下气孔率出现极小值，由此增加或减少热输入都会造成气孔率的升高，但当热输入非常低时气孔率又出现降低的趋势，即不同激光功率密度下气孔率随焊接热输入的变化存在两种不同的规律。结合压铸镁合金母材中气源行为以及焊接热过程，对两种规律的形成原因进行了讨论和实验验证，研究发现获得低气孔率焊缝的关键是抑制压铸镁合金中原子氢的析出，使其以固溶形式继续存在于焊缝中。

Welding pore is the main problem during laser welding of die-cast magnesium alloys. The influences of laser power density and heat input on pore formation regularity during laser welding of die-cast magnesium alloys are studied. The formation regularities of pore are different under low and high laser power densities. Under low laser power densities (less than 1.6×106 W/cm2), porosity increases with the increase of weld heat input; under high power densities(more than 3.2×106 W/cm2), the minimum value of porosity can be obtained at certain weld heat input, and changing weld heat input a bit higher or lower than this certain value both increase porosity, but when the weld heat input is low enough, low porosity can be obtained. The different regularities can be attributed to the influences of laser power density and weld heat input on welding thermal process and the behaviors of gas sources in weld pool. It is found that suppressing the atomic hydrogen precipitation is the key of obtaining low porosity welds.