Effect of Post Weld Heat Treatment on Microstructure and Mechanical Properties of Submerged Friction Stir Welded 7A04 Aluminum Alloy

Abstract

7A04 aluminum alloy plate was jointed by submerged friction stir welding(SFSW), and welded joints were treated (Post Weld Heat Treatment, PWHT), and the effect of post weld heat treatment on the microstructure and mechanical properties in SFSW was investigated. The results show that PWHT joints exhibit dispersively distributed fine precipitates phase morphology, are significantly superior than the feature of the small amount of precipitates with dispersed distribution in SFSW joints. Compared with SFSW joints, the mechanical properties of joints are improved significantly by PWHT. The average hardness of the weld joints nugget zone is increased by 39.7HV, and the tensile strength is increased by 67MPa, reaches 96.1% of the base material, strain hardening capacity of the joints is also enhanced, the tensile fracture exhibits mixed fracture feature of microporous polymerization and cleavage.

Keywords

• post weld heat treatment
• submerged friction stir welding
• 7A04 aluminum alloy
• microstructure and mechanical property