Ti–5Al–5V–5Mo–3Cr–1Zr (Ti-55531) alloy with excellent mechanical properties fabricated by spark plasma sintering combined with in-situ aging

In this work, an economical route was provided to directly manufacture metastable β titanium alloys without routine post-heat treatment. Ti-55531 alloy with excellent mechanical properties was prepared through the powder metallurgy route, i.e., spark plasma sintering (SPS) combined with in-situ aging. Creatively, high-density dislocations were introduced into the mechanically alloyed powder to provide nucleation sites for the formation of α precipitates. The microstructure of the sintered and in-situ aged compact, such as the volume fraction and the size of the intragranular α-phase, was controlled by varying the in-situ aging temperature from 600 °C to 750 °C. As the in-situ aging temperature decreased, the intragranular α-phase experienced an increase in the volume fraction and a reduction in lamellar size. Correspondingly, the strength of the compact increased but the elongation at failure decreased. The room temperature mechanical property tests showed that the maximum ultimate tensile strength (UTS) at an in-situ aging temperature of 600 °C achieved 1288 MPa with an elongation of 4.7%, and the maximum elongation at an in-situ aging temperature of 750 °C reached 8.8% with a UTS of 1170 MPa. The yield strength (YS) was fitted to the width of the intragranular α-phase by the Hall-Petch equation in these specimens.