Microstructure and intermediate-temperature mechanical properties of powder metallurgy Ti-6Al-4V alloy prepared by the prealloyed approach

The mechanical properties of powder metallurgy (P/M) Ti-6Al-4V alloys, produced from prealloyed powders by hot isostatic pressing, were evaluated over the intermediate temperature range of 300-500 °C. A fully equiaxed or lamellar structure was observed depending on the processing temperature. Microstructural changes were attributed to the beta-transus temperature, predicted as 977 °C. As the test temperature increased from 300 to 500 °C, the strength of the Ti alloys decreased and their elongation increased, regardless of their initial microstructure. Over the entire temperature range tested, the strength and ductility of equiaxed phase morphologies were higher than those of the lamellar structure. In addition, finer equiaxed structures exhibited higher strength and lower ductility than coarser morphologies. These results were attributed to the initial microstructures of the P/M Ti-6Al-4V alloy samples, as confirmed by evaluating their fracture features.