Effect of vacuum heat treatment on microstructure and microhardness of cold-sprayed TiN particle-reinforced Al alloy-based composites

Cold spraying (CS) demonstrates great potentials in fabrication of metal matrix composites. The effect of post-spray heat treatment at 250 °C, 350 °C and 450 °C for 2. h on the microstructure and properties of CS Al5356/TiN composites was examined in this study. The results show that the heat treatment has little effect on the distribution of TiN particles in the matrix of all the composites. The pure Al5356 deposit presents large pores between the deposited particles after heat treatment, which is a common phenomenon for CS metallic coatings having an apparent increasing porosity during annealing. The adhesion between the deposit and substrate could be enhanced through atom diffusion, especially at elevated temperatures. However, the microhardness of all the deposits is significantly reduced after heat treatment because of the release of work-hardening effect within the as-sprayed metallic particles.