Improvement of ductility in Ti-5Al-5Mo-5V-3Cr alloy by network-like precipitation of blocky α phase

The effect of two-step aging on the microstructures and mechanical properties of a solution treated (ST) and a high-pressure torsion (HPT) deformed Ti-5Al-5Mo-5V-3Cr alloy were investigated. The HPT deformed samples exhibit a similar ultimate tensile strength but much better ductility compared with the ST samples. In the HPT deformed samples, the β phase is surrounded by a continuously connected blocky primary α phase, forming network-like structure. The plastic deformation occurs preferentially inside the softer β phase during tensile deformation and leads to a significant strain hardening of the β phase. When the strain-hardened β phase strength becomes comparable to the primary α phase, the whole structure is deformed in a more homogeneous manner until fracture, improving the ductility by avoiding localized plastic instability.