In this paper, the microstructures and mechanical properties of tungsten inert gas (TIG) welded joints were studied. Three zones were formed in these joints: a heat-affected zone (HAZ), a partial melting zone (PMZ) and a fusion zone (FZ). In the FZ, the microstructure consisted of only α-Al and eutectic Mg₂Si. The α-Al segregation phenomenon occurred when the welding current increased from 125 A to 135 A. The low-angle grain boundaries (LABs) found in the base material (BM) transformed into high-angle grain boundaries (HABs) in the FZ. The texture of the BM was concentrated in three specific preferred orientations, whereas the texture was eliminated in the FZ. The hardness in the FZ was 45 % higher than that in the BM. The eutectic Mg₂Si phase in the welded joints became fine and dense, and the needle-like β″ phase in the BM was replaced by a high density of fine precipitates, which led to an increase in hardness. The ultimate tensile strength (UTS) and elongation of the joints welded at 125 A were lower than those of the BM and the joints welded at 135 A. Furthermore, no cracks were generated in the joints after multiple thermal shocks.

本文研究了钨极惰性气体保护（TIG）焊接接头的组织和力学性能。在这些接头中形成了三个区域：热影响区（HAZ），部分熔化区（PMZ）和熔合区（FZ）。在FZ中，显微组织仅由α-Al和共晶Mg ₂ Si组成。当焊接电流从125 A增加到135 A时，发生α-Al偏析现象。在基材（BM）中发现的低角度晶界（LABs）在FZ中转变为高角度晶界（HABs）。BM的纹理集中在三个特定的首选方向，而F​​Z中消除了纹理。FZ的硬度比BM高45％。共晶镁₂焊接接头中的Si相变得细密，而BM中的针状β''相被高密度的细小析出物所代替，从而导致硬度增加。在125 A下焊接的接头的极限抗拉强度（UTS）和伸长率低于BM和在135 A下焊接的接头的极限抗拉强度和伸长率。此外，在多次热冲击后，接头中均未产生裂纹。