镁锂合金搅拌摩擦焊及电子束焊研究

Study on Friction Stir Welding and Electron Beam Welding of Mg Li Alloy

对一种新型α+β双相镁锂合金的搅拌摩擦焊及电子束焊进行了实验研究,为该合金在精密制造领域的应用提供参考。利用金相显微镜、扫描电镜和显微硬度测试探明接头显微组织和力学性能的演变规律和特点。结果表明,在合理的工艺参数下,镁锂合金搅拌摩擦焊接头焊核区α+β双相都得到了明显的细化,演变为等轴晶,且α相体积分数相对减少。在焊接速度为15 mm/s,聚焦电流为500~540 mA,焊接电流为8~10 mA时,5 mm厚镁锂合金电子束焊焊缝完全焊透,焊缝区域由细小的等轴晶组织组成,α相分布更加弥散,呈网状分布在β晶界上。两种工艺下焊缝区显微硬度(HV)较母材均提升了13左右。综上,采用搅拌摩擦焊及电子束焊均可实现外观成型、组织以及性能优良的镁锂合金连接。

Experimental study on friction stir welding(FSW)and electron beam welding(EBW)of a newα+βdual phase Mg Li alloy is carried out,providing reference for the application of this alloy in precision man ufacturing.The evolution characteristics of microstructure and mechanical properties of the welded joint are analyzed in detail by optical microscope,scanning electron microscope and microhardness testing.Results show that by using proper process parameters,theα+βdual phase in the nugget zone of Mg Li alloy FSW are both refined apparently and transformed into equiaxed grains.Moreover,the volume fraction ofα phase is rel atively reduced.When the welding velocity is 15 mm/s,the focus current is 500~540 mA and the welding current is 8~10 mA,Mg Li alloy of 5 mm thickness is welded with full penetration.Equiaxed grains are ob tained and theα phase is dispersively distributed in the grain boundary ofβ phase.By using the two proces ses,the microhardness(HV)of the weld zone is both approximately 13 higher than that of the base metal.In conclusion,FSW and EBW both can achieve sound joint of Mg Li alloy with good appearance,microstructure and mechanical properties.