Structure-property relationship in NiTi-enhanced 6061 Al matrix composites processed by hybrid hot pressing and extrusion

This study systematically investigates the influence of NiTi content on the microstructure evolution and mechanical properties of 6061 aluminum matrix composites, with particular emphasis on elucidating underlying mechanisms. XRD analysis confirms distinct NiTi phase diffraction peaks in all NiTi-containing composites. Microstructural characterization reveals that at 6 vol% NiTi content, a stable AlTiSi reaction layer (∼130 nm thick) forms at the reinforcement-matrix interface. Tribological measurements demonstrate a consistent reduction in both average friction coefficient and surface roughness with increasing NiTi content, decreasing from 0.85 to 85.625 μm for unreinforced matrix to 0.23 and 5.471 μm for the 30 vol% NiTi composite, respectively. The ultimate tensile strength exhibits a non-monotonic dependence on NiTi content, reaching an optimal value of 381 MPa at 6 vol% NiTi before decreasing at higher concentrations. Remarkably, the composite maintains excellent ductility (16.0% elongation) at this optimal composition, with significant ductility reduction occurring only at higher NiTi loadings. This mechanical behavior originates from strong interfacial bonding at NiTi/matrix interfaces, which effectively prevents reinforcement pull-out during deformation. The developed NiTi p /6061 Al composites achieve an exceptional balance between high ultimate tensile strength and good plasticity. These findings provide both fundamental insights and practical guidelines for designing high-performance metal particle-reinforced aluminum matrix composites.