In the present study, the effect of heat input of gas tungsten arc welding on the microstructure and mechanical properties of AZ91 magnesium alloy was investigated. The microstructural studies were performed by using an optical microscope and scanning electron microscope equipped with energy dispersive X-ray spectroscopy, and tensile test was used to evaluate the mechanical properties. It was shown that, comparing to the base metal, a fine microstructure of α(Mg) and Mg₁₇Al₁₂ phase is formed in the weld metal and the size of α(Mg) phase slightly increased with heat input during welding process. The results also indicated that the thickness of partially melted zone increased with heat input. Tensile strength of welded samples was lower than that of the base metal and it decreases with increasing heat input. Failure of the welded specimens accrues in the partially melted zone. Studying of fracture surface revealed that the interface of α(Mg) and Mg₁₇Al₁₂ compound acts as crack initiation and growth path during the tensile test. Formation of cleavage steps in the fracture surface was the dominant fracture mechanism during tensile tests.

在本研究中，研究了气体钨极电弧焊的热输入对AZ91镁合金的组织和力学性能的影响。通过使用配备有能量色散X射线光谱学的光学显微镜和扫描电子显微镜进行显微结构研究，并使用拉伸试验评价机械性能。结果表明，与贱金属相比，α（Mg）和Mg ₁₇ Al _12的微观组织微细。在焊接金属中会形成相，并且随着焊接过程中的热量输入，α（Mg）相的尺寸会略有增加。结果还表明，部分熔融区的厚度随热量输入而增加。焊接样品的拉伸强度低于母材的拉伸强度，并且随着输入热量的增加而降低。焊接试样的失效会在部分熔化的区域内产生。断裂表面的研究表明，在拉伸试验中，α（Mg）和Mg ₁₇ Al ₁₂化合物的界面充当了裂纹的萌生和扩展路径。在拉伸试验中，在断裂表面形成分裂台阶是主要的断裂机理。