Enhanced ductility of PM Ti-Nb-Ta alloys via reducing solution oxygen by YH₂ addition

To reduce the solution oxygen content in the matrix and enhance the ductility of Ti alloys prepared by powder metallurgy, YH₂ was added as an additive to the Ti-Nb-Ta alloy in this work. By adding 1.5 wt%YH₂, the compressive ductility increased 49 %, when the compression yield strength decreased slightly at room temperature, but the compression yield strength increased 41 % at 800°C compared with Ti-Nb-Ta without YH₂ addition. With increase of YH₂ content, the solution oxygen content in both α and β phases decreased significantly, while the proportion of ductile β phase increased. Addition of YH₂ led to in situ formation of Y₂O₃ particles, reducing the solution oxygen content and changing the distribution state of oxygen. It is revealed that under a same deformation degree at 800°C, the dislocation density in the (Ti-5 Nb-15 Ta)-1.5 Y alloy sample is much higher than in the Ti-5 Nb-15 Ta alloy, which is attributed to a strong hindering effect of Y₂O₃ particles on dislocation movement. Thus, the strength of (Ti-5 Nb-15 Ta)-1.5 Y alloy was enhanced under high temperature. This study provided a new method for enhancing room temperature ductility and high-temperature strength of powder metallurgy Ti alloys.