Relationship between lamellar α evolution and flow behavior during isothermal deformation of Ti-5Al-5Mo-5V-1Cr-1Fe near β titanium alloy

Ti-5Al-5Mo-5V-1Cr-1Fe near β titanium alloy was thermally deformed at 700-800 °C and strain rates of 10−1-10−3 s−1. The relationship between lamellar α evolution and flow softening behavior of this alloy was investigated. The evolution of lamellar α includes the buckling, fragmentation and spheroidization sequentially. By increasing the temperature and decreasing the strain rate, both the peak stress and flow softening extent in the true stress/strain curves were reduced, and the buckling of lamellar α up to fragmentation was enhanced. The transition of lamellar α evolution from buckling to fragmentation contributes to the flow softening greatly, leading to the sharp reduction of flow softening extent. After obvious occurrence of the fragmentation of lamellar α, the reduction of flow softening extent decreases gradually.