Microstructure and Mechanical Properties of Ti-6Al-4V Rods Fabricated by Powder Compact Extrusion of TiH₂/Al₆₀V₄₀ Powder Blend

Nearly fully dense Ti-6Al-4V rods were fabricated by powder compact extrusion of TiH₂/Al₆₀V₄₀ powder blend. The microstructure, mechanical properties, and fracture behaviors of the Ti-6Al-4V rods extruded at various temperatures from 1100 °C to 1400 °C were investigated. The results showed that with the extrusion temperature of 1100 °C, undissolved V-rich particles still existed in the microstructure, but they disappeared once the extrusion temperature increased to 1200 °C. Nearly complete dehydrogenation of TiH₂ was achieved during rapid induction heating, holding, and extrusion. With increasing the extrusion temperature, prior β grain sizes and α/β lamella colony sizes increased dramatically, while the change of α lamella thickness was much less significant. The correlation between microstructure and mechanical properties suggests that α/β lamella interfaces, instead of colony boundaries, are responsible for strengthening. The coarse prior β grains whose sizes reached 150 μm had a deleterious effect on the tensile ductility due to localized deformation, as evidenced by the intergranular fracture. The rod extruded at 1200 °C had the best elongation to fracture of 9.3 pct while still keeping a high yield strength of 969 MPa and ultimate tensile strength of 1102 MPa.