Effect of aging time on microstructure and mechanical properties of AA6061 friction stir welding joints

Abstract

This study was to determine the influences of post-weld heat treatment (PWHT) on the tensile and microstructure properties of friction stir-welded AA6061 aluminum alloy joints. Friction stir welding (FSW) of aluminum alloys has the potential to retain good mechanical and metallurgical properties. 3mm plate AA6061 aluminum alloy was used to fabricate the joints. Solution heat treatment, quenching plus an artificial aging treatment with different times of aging were adopted. The fracture surface of the welded specimens was analyzed by using a scanning electron microscope, and an optical microscope was used for microstructure analysis, where finer dimples were obtained and formed inter-metallic compound at the highest aging time. Tensile properties were improved by about 4.7% after PWHT for 16 hrs. In addition, hardness increased with the increase of the aging time at the top region. A simple artificial aging treatment was able to enhance the tensile properties of the friction stir-welded AA6061 aluminum alloy joints.