Synergistic Enhancement of Strength and Ductility in Hetero-deformation Induced Strengthening Titanium Composites via Powder Metallurgy

Increasing yield strength of Ti by utilizing dispersive second-phase particles that impede dislocation motion is one of the most common strengthening methods. However, an improvement in strength will inevitably sacrifice ductility in dispersion-strengthened titanium matrix composites. Our group has developed a brand-new interdiffusion and self-organization strategy, resulting in pelleted hetero-structure Ti6Al4V-TiBw composites with both non-uniform distribution reinforcements and heterogeneous grain structures by utilizing the interdiffusion reaction between alloying elements and titanium. It was found that the pelleted hetero-structure Ti6Al4V-TiBw composite exhibits a remarkable 11.5% elongation, comparable to Ti6Al4V alloy, while significantly improving its strength. The good fracture elongation mainly comes from the HDI hardening effect produced by the heterogeneous grain structure of matrix and the blunting and deflection effects of the heterogeneous distribution of TiBw reinforcements on cracks. Our strategy can be applied to other composite systems for developing high-performance metal matrix composites with harmonious strength and ductility.