Microstructural Evaluation for TIG Welding of AA6061-T6 using ER5356 Filler Metal; in Postweld and as-Weld Treatment

AA6061-T6, as a heat treatable alloy, is a sensitive alloy to any thermal cycle. Heat can be imposed to AA6061-T6 during tungsten inert gas welding (TIG) and the microstructure of alloy can be affected subsequently. The purpose of this study is to evaluate the microstructure of as-weld and postwelded samples. Heat affected zone (HAZ) in two different temperatures (solution and aging temperature) in as-weld sample was revealed. Microstructure and hardness were restored in AA6061-T6 by applying post weld heat treatment (PWHT), however, liquid cracking (LC) was found in partial melted zone (PMZ). Whereas filler metal-ER5356- was not a heat treatable alloy, however, its microstructure was changed from a dendrite one to equiaxed grains with closed boundaries and displayed higher hardness from (60) HV to (80) HV due to the post weld heat treatment (PWHT).