Cold sprayed AA2024/Al2O3 metal matrix composites improved by friction stir processing: Microstructure characterization, mechanical performance and strengthening mechanisms

In this study, friction stir processing (FSP) was employed as the strengthening method to modify the microstructure and mechanical properties of cold sprayed AA2024/Al2O3 metal matrix composites. Scanning electron microscopy and optical microscopy identify that FSP improves notably the refinement and dispersion of Al2O3 particles. Nanoindentation results show that the hardness and elastic modulus of cold sprayed AA2024 particles decrease with FSP, which are mainly attributed to the dissolution of the Guinier Preston Bagaryatskii (GPB) zone. Higher Vickers hardness values are reached for the FSPed specimens due to the uniform distribution and refinement of reinforcing particles. The tensile properties of cold sprayed AA2024/Al2O3 composites are remarkably enhanced by FSP, with an increase of 25.9% in the ultimate tensile strength and 27.4% in elongation. The improved interparticle bonding and the dispersion strengthening of the refined Al2O3 particles are the main strengthening mechanisms responsible for these enhancements.