Synthesis mechanism and microstructure evolution of titanium matrix composites with a multiscale configuration

Configuration-structured titanium matrix composites (TMCs) are promising candidates for next-generation lightweight aero-engine hot-section components due to their excellent room- and high-temperature mechanical properties. In this work, a novel multiscale configuration was proposed and successfully constructed in Ti55 (Ti-5.5Al-4Sn-2Zr-1Mo-0.25Si-1Nd) matrix composites via powder metallurgy, achieving an excellent strength-ductility synergy. Network-distributed TiB and (Ti,Zr)₅Si₃ were tailored along the prior particle boundaries and α/β interfaces, while Nd₅Sn₃ nanoparticles were uniformly dispersed in the matrix. Moreover, a comprehensive statistical analysis was conducted on the size and spatial distribution characteristics of different phases at various sintering temperatures. As the temperature increased, TiB and Nd₅Sn₃ underwent a pronounced coarsening due to Ostwald ripening. Besides, the spatial distribution of Nd₅Sn₃ evolved from a network-like morphology to a uniform dispersion due to the secondary precipitation. Different from the transformation-independent coarsening process, (Ti,Zr)₅Si₃ exhibited obvious size refinement and redistribution from powder boundaries to α/β interfaces, which was governed by a transformation-induced dissolution and precipitation process. Meanwhile, the pinning effects of reinforcements resulted in an interesting staged coarsening process of the matrix. This work established a quantitative correlation between sintering temperature and microstructure evolution, which could provide valuable guidance for configuration design of advanced TMCs.