Unexpected ductility achieved by carbon microalloying in TiB/Ti64 composites

This study introduces an innovative carbon microalloying strategy to enhance the ductility of network structural TiB/Ti64 composites. The microalloyed composite with 0.07 wt.% carbon element demonstrated a remarkable increase of 117% in elongation (reaching 18%) coupled with a nearly 60 MPa improvement in yield strength (reaching 955 MPa), compared with conventional TiB/Ti64 composites. Carbon exhibited minor enrichment at network boundaries due to matrix lattice distortion induced by TiB whiskers. To explore the contribution of carbon microalloying to the strength-ductility synergy, deformation and fracture behavior were investigated via in-situ methods. Dynamic dislocation pinning via Cottrell atmospheres of carbon atoms was experimentally verified, simultaneously enhancing composite strength and strain-hardening capacity. Concurrently, slight carbon enrichment reduced strain energy near TiB whiskers and diminished strain gradients at crack tips, effectively suppressing rapid crack propagation. This work clarifies the effect of solute carbon on mechanical behaviors and provides guidance for optimizing the mechanical properties of titanium matrix composites.