Processing-structure-property aspects of particulate- and whisker-reinforced titanium matrix composites

The demand for lightweight, high performance and high temperature materials for advanced structural applications is increasing in many industrial sectors. Cost-effective discontinuously reinforced titanium matrix composites (TMCs) exhibit high strength, high stiffness, excellent wear resistance and high temperature durability. Hence, TiC_p/Ti-6Al-4V and TiB_w/Ti composites have been used commercially as structural materials for exhaust valves in automotive engines. They are also attractive materials for usage in aerospace, advanced military, biomedical engineering sectors and sporting goods. Titanium boride whisker (TiB_w) is considered an effective ceramic reinforcement for titanium since it can be synthesized in situ in titanium matrix during composite fabrication. The TiB whiskers strengthen the composites remarkably via a load-transfer mechanism. Moreover, in situ TiB whiskers also enhance creep and high-cycle fatigue resistances of Ti-based composites when compared to un-reinforced Ti alloys. In this review, state-of-the-art developments on processing, microstructural characterization and mechanical properties of particulate and whisker reinforced TMCs are discussed. Particular attention is given to the structural-mechanical property relationships of high performance TMCs. This review provides useful guidance to those working on the development of novel Ti-based composites for advanced structural applications.