Heterogeneous network structures formed in TiC/TC4/β-Ti composites for enhancing both strength and ductility

Composites of TiC/(TC18 + TC4) with designed heterogeneous network structures were spark plasma sintered using reinforcement precursors of graphene and hard β-TC18 alloy to reinforce TC4 matrix. The heterogeneous networks of TiC/(TC18 + TC4) composites are typically mixed microstructures of α+β lamellar and equiaxed β phases. The synthesized composites exhibit superior high strength and ductility (i.e., with a fracture strength of 1150 MPa and a uniform elongation of 5%), compared with those of the sintered monolithic TC4 (900 MPa-10%) and TC18 (1330 MPa-1.7%). Incompatible plastic deformation behaviors of TC18 and TC4 enhance strain hardening effect, which is the main reason for the enhanced ductility of the composites. Refinement strengthening and heterostructure-deformation induced hardening are two key mechanisms to achieve the high strength. This study provides a new strategy to simultaneously enhance strength and ductility for Ti matrix composites.