Influence of cold sprayed aluminum coating on the mechanical properties of friction stir welded 2024 aluminum alloy joints

Cold sprayed aluminum coatings enhanced obviously the corrosion resistance of friction stir welding(FSW) joints, but the influence of cold sprayed Al coatings on the mechanical properties of FSW joints is still unclear. The effect of cold sprayed Al coatings on the mechanical properties of FSW joints is investigated by tensile tests and fatigue tests. Microstructure change of FSW joints before and after cold spraying is also examined by transmission electron microscope(TEM) and differential scanning calorimetry(DSC). Results show that the mechanical properties of the FSW AA2024-T3 joints are improved after cold spraying. Tensile strength and elongation of coated specimen increase by about 27 MPa and 60.5%, respectively, compared to those of 393.3 MPa and 4.3% of as-welded specimen. When the fatigue life is 1×10⁷ cycles, the fatigue strength corresponding to a 50% survival probability of coated specimens is 29.1% higher than that of the as-welded specimen, and the fatigue strength corresponding to a 95% survival probability of coated specimens is 30.9% higher than that of the as-welded specimens. After cold spraying, the volume fractions of S phase and Guinier-Preston-Bagaryatskii(GBP) zone in nugget zone increases, which is possibly a main reason for the improvement of the mechanical properties.