Fabrication of high-strength and ductile titanium matrix composites reinforced with intragranular bimodal micro/nano TiC particles by using Al₄C₃ as carbon source

Carbonaceous substances are commonly used to fabricate in-situ-TiC-reinforced titanium matrix composites (TMCs). However, those TiC tend to locate at/near primary powder boundaries, causing coarsening, agglomeration, and limited mechanical properties. Here, by using Al₄C₃ particles as carbon source, TMCs reinforced with fine TiC dispersed within the matrix grains were fabricated via powder metallurgy, which exhibit both high strength and excellent ductility. Results showed that, in TiC/Ti(Al₄C₃) (using Al₄C₃ as precursor), TiC particles with bimodal sizes of several micrometers and tens of nanometers were in situ formed inside matrix grains, resulting in a homogeneous distribution of fine TiC. Consequently, the hot-extruded TiC/Ti(Al₄C₃) exhibits remarkable advantages in strength and ductility, with increases of 52 % and 41 % over the conventional TiC/Ti(C) (using carbon black as precursor), and 57 % and 12 % over the TiC/Ti(ex-situ) (using ex-situ TiC particles), respectively. This study provides a new strategy to optimize the microstructure and mechanical properties of TMCs.