Effect of post weld heat treatment on microstructure and mechanical properties of gas tungsten arc welded AA6061-T6 alloy

Double-V butt TIG welding process was performed on two plates of AA6061-T6 using ER5356 filler. The microstructure, mechanical and nanomechanical properties of the joint were evaluated in as-welded and after post weld heat treatment (PWHT) using XRD, FESEM, EBSD, nanoindentation and tensile tests. The results show that PWHT led to microstructural recovery of the heat affected zone (HAZ) in addition to the appearance of β-phase (Al3Mg2) at the grain boundaries of weld zone. The hardness (Hnano) in all zones increased after PWHT while the elastic modulus (Enano) was improved from 69.93 GPa to 81 GPa in weld area. All results indicate that PWHT has created a homogenous microstructure in the weld zone in addition to outstanding improvement in mechanical properties for the weld zone which surpass the base metal.