An alternative to increase the mechanical strength of 6061-T6 GMA weldments

Fusion welding of heat treatable aluminum alloys leads to a significant loss of strength in the heat affected zone (HAZ) due to overaging. This work was aimed to improve the mechanical properties of Al-6061 welds. Plates of 6 mm in thickness were solutionised at 530◦C for 1 h followed by water quenching and aging at 160◦C for times between 13 to 19 hours. Welding was performed with the gas metal arc welding process (GMAW). Transverse microhardness indentations and mechanical testing were performed to characterize the overaged zone and mechanical strength of the as-welded joints. It was found that samples partially aged for 16 h exhibited an increase of 30% in hardness values in the overaged zone and accordingly its mechanical strength also increased with respect to the Al-6061-T6 (21 h aging time) as welded plates. Although failure of the welds with the partially aged plates occurred in the HAZ, the larger strength of the 16 hours aged samples suggests that the heat input of the welding process reactivated the precipitation sequence in the base material and the degree of overaging was reduced.