镁合金激光表面熔凝技术分析

Technical analysis of laser surface melting on Mg alloy

为了研究不同激光工艺参量对镁合金熔凝层组织和性能的影响,采用高功率快速扫描(13J/mm^2～33J/mm^2)和低功率慢速扫描(100J/mm^2～250J/mm^2)两套能量密度相差较大的激光熔凝技术对镁合金表面进行真空激光熔凝处理。结果表明,两套激光工艺处理下熔凝层均由α-Mg和β-Mg_(17)Al_(12)相所组成,但β-Mg_(17)Al_(12)所占的比例在低功率慢速扫描下较高,约为16%;熔凝层组织均为典型的树枝晶,高功率快速扫描熔凝层枝晶尺寸远远小于低功率慢速扫描熔凝层的枝晶尺寸;在高功率快速扫描处理工艺下,熔凝层的硬度、耐磨性分别是低功率慢速扫描处理下熔凝层的1.5倍和3倍;高功率快速扫描处理下熔凝层的耐蚀性也较低功率慢速扫描处理下熔凝层的耐蚀性显著提高。

In order to study the influence of different laser parameters on the microstructure and property of the melted layer of Mg alloy, two laser melting techniques at high power, rapidly scanning speed （13J/mm^2 -33J/mm^2） and low power, slowly scanning speed（ 100J/mm^2 - 250J/mm^2 ） were used to melt the surface of Mg alloy respectively. The results showed that the melted layers with both the techniques were composed of α-Mg and β-Mg17 Al12 phases, however, the melted layers at low power, slowly scanning speed had more β-Mg17 Al12, about 16%. The microstructure of the melted layers were typical dendrite, however, the dendritic spacing of the melted layers at high power, rapidly scanning speed was much smaller. The microhardness and wear resistance of the melted layers at high power ,rapidly scanning speed were 1.5 and 3 times of that of the muted layers at low power, slowly scanning speed ,respectively. The melted layers at high power,rapidly scanning speed had better corrosion resistance too.