Abstract
This study investigated the changes in microstructure and mechanical properties of gas tungsten arc welded 7075 aluminum alloy joints using ER5356 and ER7150 filler wire subjected to post-weld heat treatment. The microstructure and mechanical property evolution of the welds was analyzed by both thermodynamics calculations and experimental methods. After welding, alloying elements segregated in the inter-dendritic regions, resulting in the formation of excessive intermetallic compounds. Within the welds of 7075 aluminum alloy with ER5356 filler material, the inter-dendritic region was primarily composed of the T-AlCuMgZn phase. In contrast, in the welds of 7075 aluminum alloy with ER7150 filler material, this region consisted of a eutectic mixture containing α-Al, T-AlCuMgZn, and η-MgZn2 phases. The α-Al matrix experienced limited supersaturation due to the presence of these inter-dendritic intermetallic compounds, which could not dissolve during the post-weld aging treatment. As a comparison, post-weld solutioning and aging treatment significantly improved the ultimate tensile strength of the joints. Among all the samples, the 7075 + ER7150 sample subjected to post-weld solutioning and aging treatment exhibited the highest strength and elongation, primarily attributed to the complete dissolution of the inter-dendritic intermetallic compounds and the formation of fine precipitates.
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