镁稀土合金的焊接性研究

Study on Weldability of Magnesium Rare Earth Alloy

采用手工钨极氩弧焊(TIG焊)对3mm厚的镁稀土合金(Mg-5wt%Gd-0.8wt%Zr)薄板进行对接焊,分析了其焊缝成型、接头显微组织、力学性能和断裂机理。结果表明:当电流为80～85A、焊速为4～5mm/s时,焊缝区无夹渣,成型性好,未发现裂纹和气孔缺陷。相对母材和热影响区,焊缝的晶粒明显细小,显微硬度比热影响区和母材稍高。接头抗拉强度可达母材的72.24%,接头试样从焊缝处断裂,扫描断口为典型的解理断裂,而母材试样出现明显的撕裂韧窝。

The Mg-5wt%Gd-0.8wt%Zr sheet with 3 mm thickness was welded by TIG weld. The weld bead formation, microstmcture of welded joint, mechanical properties and fracture mechanism were analyzed. The results show that there are no slag inclusion, welding crack, gas porosity in the weld bead, when the welding current （/） is 80~85A and welding speed （v） is 4~5 mm/s. The mierohardness is higher and grain size is smaller in weld bead zone, compared with the heat-affected zone and base metal. The tensile strength of the joint is up to 72.24% of that of the base metal. The fracture of tensile sample is in the weld bead. The cleavage is the main character of scanning fracture, however, the obvious tearing dimple occurs in base metal.