Effect of hot rolling and heat treatment on microstructure and tensile properties of high strength beta titanium alloy sheets

Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe is a high-strength β titanium alloy that shows excellent tensile properties. This paper presents the effect of hot rolling and heat treatment on the microstructure and tensile properties of this alloy. Microstructure observation shows that the α+β rolled alloy leads to smaller β grain size than the β rolled alloy in all heat treatment conditions. Solution treatment of the alloy in the α+β field can also lead to smaller β grain than solution in the β field. Tensile results indicated that the strength of the alloy was improved greatly by aging heat treatment, which was attributed to the secondary α phase. The 790 °C rolled alloy can obtain an ultimate strength of 1744 MPa by solution at 800 °C plus aging at 440 °C. The strength decreases and ductility increases with the increase of aging temperature. Moreover, the ductility of the alloy is significantly determined by the rolling and solution procedure. Rolling and solution treated at the α+β field results in better ductility than rolling and solution at the β field. Therefore, to obtain the high ductility, the α+β rolling and α+β solution should be chosen as long as possible before aging heat treatment.