Cold metal transfer welding of AlSi7Mg alloy sheets prepared by selective laser melting

Abstract

Cold metal transfer (CMT) welding of AlSi7Mg alloy sheets prepared by selective laser melting (SLM) was employed using ER4047 and ER5356 filler wire. Effect of the filler wires on hydrogen pores, microstructures and mechanical properties of welded joints was studied. As a result, CMT welding of AlSi7Mg alloy sheets using ER5356 wire reduces the porosity, refines the grains, increases the fraction of high angle grain boundaries (HAGBs), modifies the eutectic Si-rich morphology, and improves the solid solution strengthening of Si elements in the α-Al matrix of the microstructures in the weld metal (WM). Additionally, the morphology of eutectic Si-rich phases in heat affected zone (HAZ) of the welded joint is noticeably changed from the continuous cellular networks in base metal (BM) to totally globularized particles, as a result of the increased welding heat effect with decreasing distance to the WM. Compared with the ER4047 wire, the welded joint with ER5356 wire achieves higher WM hardness and higher ultimate tensile strength (UTS), which have been increased by 13.9 % and 18.6 %, respectively. The enhanced mechanical properties of the welded joints with ER5356 wire are mainly attributed to the reduced porosity and the improved microstructures in the WM.