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采用CO2激光焊接2mm厚Mg-9.8Li-2.9Al-Zn合金,通过光学显微镜(OM)、扫描电镜(SEM)系统研究焊接接头成形、气孔裂纹缺陷、显微组织演变,并采用显微硬度测量和纵向拉伸测试焊接件的室温力学性能。结果表明,激光快速加热焊缝组织明显细化,α-Mg相增多且由母材的粗大组织转变为细针状组织,亚稳定的MgLi2Al相分解为稳定的AlLi相。焊缝的显微硬度(约105HV)高于母材的显微硬度(约85HV),对焊接件纵向拉伸断裂于母材,断裂后屈服强度Rp0.2为172MPa,伸长率约为24%。
The laser welding of 2mm thick Mg-9.8Li-2.9Al-Zn alloy was used to study the forming of weld, the defects of pores and cracks, the microstructure evolution by OM and SEM, and the microhardness was measured. And longitudinal tensile testing of the weldment at room temperature mechanical properties. The results show that the microstructure of laser welded seam is obviously refined, the α-Mg phase increases and the coarse-grained microstructure of the base material changes into fine needle-like structure, and the metastable MgLi2Al phase decomposes into the stable AlLi phase. The microhardness (about 105HV) of the weld seam is higher than the microhardness of the base metal (about 85HV), the longitudinal tensile fracture of the weldment is broken to the base metal, the yield strength Rp0.2 after fracture is 172MPa and the elongation is about 24 %.