Effect of strain rate on the mechanical properties of a tungsten particle reinforced titanium matrix composite

Refractory metal particles can potentially be used to reinforce titanium matrix composites. In this research, a titanium matrix composite reinforced by 20 wt.% tungsten particles (20W_P/Ti) was fabricated by powder metallurgy. The mechanical properties of 20W_P/Ti were then evaluated over a broad strain rate range of 10⁻³–4 × 10³ s⁻¹. The microstructure of the composite consisted of W particle reinforcements, W diffusion regions, and an alloyed Ti matrix. The interdiffusion between W and Ti atoms produced broad diffusion regions and the Kirkendall effect. The W diffusion regions were a complex multiple-phase mixture of micron-sized β-Ti grains, nanoscale ω-Ti and α″-Ti phases and W nanoparticles. 20W_P/Ti exhibited excellent mechanical properties due to the presence of multiple strengthening mechanisms including reinforcing phase strengthening, solid solution strengthening, and precipitation strengthening. The addition of W particle reinforcing phases suppressed the adiabatic shear sensitivity of the composite. When the strain rate exceeded 1400 s⁻¹, the dynamic strength of 20W_P/Ti declined upon increasing the strain rate, attributing to a mass of Kirkendall pores and the thermal softening effect of the β-Ti phase in the W diffusion region at high strain rates.