Post-weld heat treatment effects on the tensile properties of cold metal arc welded AA 6061-T6 aluminum joints

Abstract

Abstract Heat treatable aluminium alloys of the 6xxx series are widely used in the hood, trunk and roof sections of a car body as they offer better corrosion resistance, high strength to weight ratio and excellent weldability characteristics. Gas metal arc welding (GMAW), a high productivity process is extensively employed in the automobile sector due to its ease of automation. HAZ softening is one of the most common problems that occurs during the welding of aluminium alloys by GMAW because of its high heat input. Cold metal transfer (CMT) is the most suitable welding process for welding aluminium alloys especially for controlling HAZ softening issues that occur due to the low heat input involved in this process. However, softening continues to exist in the welded joints. In this investigation, Post -weld heat treatment (PWHT) was employed to increase joint efficiency and to minimize the HAZ softening of AA6061-T6 aluminum alloy joints welded by GMAW and CMT. The results show that the tensile strength of a post-weld heat treated CMT joint is 10 % higher i. e., 242 MPa (76 % of joint efficiency), than that of the as welded CMT joint. This is due to the nucleation of strengthening precipitates in the weld metal and heat affected zone regions.