Microstructure and mechanical properties of friction plug welding joints for dissimilar aluminum alloys

Abstract

In this paper, friction plug welding(FPW) process of 10 mm thick 2219-T87 aluminum alloy with 2A14-T6 aluminum plug are performed. The defect characteristics, microstructures and phase distribution, mechanical properties, fracture morphology of FPW joints are observed and tested respectively. The results show: Defect-free FPW joints are obtained with a 30 kN or 35 kN welding pressure and a 7 500 r/min rotational speed; The FPW joint can be divided into six parts, plug metal(PM), plug thermo-mechanically affected zone (PTMAZ), recrystallized zone (RZ), thermo-mechanically affected zone(TMAZ), heat affected zone (HAZ) and base metal(BM); Hardness test results indicate that the highest hardness locates in base metal, followed by the plug zone and plug thermo-mechanically affected zone, with the lowest hardness occurred in thermo-mechanically affected zone and heat affected zone; The tensile strength and elongation of FPW joints can reach to 312 MPa and 4.1%, respectively; The initial fracture locates at the interface of TMAZ and HAZ on the bottom surface, finally fractures at PTMAZ, exhibiting dimple morphology.