Effect of microstructural evolution on mechanical properties of friction stir welded AA2009/SiCp composite

Extruded AA2009/15%/SiCp composite was friction stir welded (FSW) and subjected to subsequent post-weld T4-treatment. FSW resulted in significant grain refinement, breaking and uniform distribution of SiC particles, dissolution of coarse needle-shaped precipitates and re-precipitation in the nugget zone, thereby increasing the hardness and longitudinal and transverse strengths of the as-FSW composite joint remarkably. Post-weld T4-treatment resulted in limited grain growth and improved weld strength. Under the T4 condition, the longitudinal and transverse tensile strengths of the weld reached 82% and 95% of the base metal, respectively. The low joining efficiency under the T4 condition was associated with the formation of the Cu2FeAl7 phase.