Cold spray additive manufacturing of metal matrix composites (MMCs) using a novel nano-TiB2-reinforced 7075Al powder

Abstract

A gas-atomized 7075Al (Al–Zn–Mg–Cu) composite powder reinforced with in-situ nanosized TiB2 particles was used as the novel feedstock to fabricate metal matrix composite (MMC) components by cold spraying (CS). The effect of CS processing conditions (i.e. particle impact velocity, particle impact temperature, and gas type) on microstructure evolution of the as-sprayed samples was investigated by X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM) and electron backscatter diffraction (SEM/EBSD). Mechanical performance was evaluated by microhardness and tensile test. The results indicated that the as-fabricated composite samples generally exhibit a fully dense and crack-free feature with the nanosized TiB2 particles uniformly dispersed in the Al matrix. The phase composition of the feedstock is well preserved and nanosized precipitates are formed inside the severely deformed Al grains. It was also found that a higher particle impact velocity leads to more pronounced particle deformation and enhanced grain refinement. Fracture morphologies of the composite samples display a brittle feature in the low processing condition, while slight improvement of tensile strength and elongation is obtained at a higher particle impact velocity and temperature. The advantage by integrating the nanosized TiB2 particles is that it results in an extensively refined structure to improve microhardness as well as tensile strength. This study demonstrates the potential of the gas-atomized composite powder for additive manufacturing of MMCs by CS.