The effect of cooling rates on the microstructure and mechanical properties of thermo-mechanically processed Ti-Al-Mo-V-Cr-Fe alloys

Two near-β titanium alloys, Ti-5Al-5Mo-5V-1Cr-1Fe and a modified one containing 2 wt% Cr (Ti-5Al-5Mo-5V-2Cr-1Fe) were produced from Ti hydride precursor powders via the cost-effective blended elemental powder metallurgy technique. The effects of two cooling rates (10 K s−1 and 1 K s−1) during thermo-mechanical processing on the microstructure and mechanical properties were investigated using X-ray diffraction and scanning electron microscopy. X-ray line profile analysis revealed that dislocation densities and microstrain in β-Ti phase are higher than in α-Ti phase for all cases. In both alloys, slower cooling results in an increase in α volume fraction and promotes morphology of continuous grain boundary α phase. A lower total elongation is obtained in both alloys under slower cooling which could be accounted for by the continuous morphology of α phase. Overall, Ti-5Al-5Mo-5V-1Cr-1Fe displays higher ultimate tensile strength and total elongation compared to Ti-5Al-5Mo-5V-2Cr-1Fe, regardless of the cooling rate.