Regulating interface structure and shear performance of extruded NiTi fiber reinforced Al-based composites via heat treatments

Abstract

Superior interfacial bonding is necessary to improve the performance of aluminum matrix composites. In this work, the Al/NiTi composite plate was fabricated by a novel composite extrusion technique, and the effects of heat treatment parameters on the interfacial structure and shear failure behavior of the composite plates were systematically investigated. The results indicate that different heat treatment processes induce the formation of interface structures with significant differences in Al/NiTi composites. The annealed composite plate forms an inhomogeneous multilayer transition interface: Ti–O layer, Ti₂Ni and TiNi mixed layer, and discontinuous Al₃Ti layer. The discontinuous brittle intermetallic compounds weaken the interfacial bonding, resulting in mainly interface debonding. However, the failure mechanism of the directly aged composite becomes primarily matrix failure, accompanied by severe sliding friction and mechanical interlocking, attributed to the formation of aluminum-side fine grain zone and nanocrystalline/amorphous transition zone at the interface. The aged composite exhibits superior interfacial shear properties compared to extruded and annealed composites. The structure-performance-mechanism correlation was established between interfacial structure and shear behavior in composite extruded plates, thus providing a strategy for obtaining Al/NiTi composites with excellent properties.