Analysis of heat input effect on the mechanical properties of Al-6061-T6 alloy weld joints

Plates of AA6061-T6 with 4.8 mm of thickness were welded with an ER4043 electrode (1.19 mm in diameter) using the typical simple butt joint to investigate the effect on the mechanical properties of aluminum alloy 6061-T6 due to the Gas Metal Arc Welding (GMAW) process. The parameters involved in the welding process were related to the variation of the yield strength and microhardness. A transient thermal analysis was developed to model the problem in a numerical form using Finite Element Method (FEM) and these results were compared with experimental data showing good agreement. It was observed that the amount of energy absorbed by the base material determines the maximum temperatures reached by the aluminum and microstructural changes produced by high metal temperatures, significantly influence the properties of the alloy. For a case with 120 A, 18.0 V and 5.26 mm/s in travel speed, the reduction of yield strength was 45.1% and for Vickers microhardness was 45.2%. For another case with 140 A, 20.5 V and 5.36 mm/s in travel speed, the reductions were 40.9% and 38.4% for yield strength and Vickers microhardness respectively. The transformation of precipitates β″ in β′ and β explain these changes.