A novel low-cost high-strength β titanium alloy: Microstructure evolution and mechanical behavior

A novel metastable β-titanium alloy (Ti-4.8Al-5.6Mo-3 V-1.5Cr-1.6Fe) with low cost and high strength was designed using the d-electron theory approach. After solution treatment at 780 °C and aging at 470, 500, and 530 °C, a multiscale structure composed of β matrix, primary αp (with a volume fraction of 21%), and precipitates αs were obtained. The density and average spacing of precipitates depended on the aging temperature. Dense αs with an average spacing (λ) of less than 100 nm were precipitated during aging at 470 °C due to a greater driving force for the formation of αs. In contrast, coarse αs with an average spacing (λ) greater than 100 nm were precipitated during aging at 530 °C due to a greater driving force for the growth of αs. The tensile properties were also sensitive to the density and spacing of precipitates αs inside the β matrix. By controlling the density and average spacing of precipitates αs inside the β matrix, a tensile strength ranging from 1512 MPa to 1648 MPa and tensile elongation ranging from 1.8% to 7.8% were achieved. Particularly, an excellent combination of high tensile strength (1512 MPa) and relatively high elongation (7.8%) was obtained by aging at 530 °C.