Hot deformation behaviours and spheroidization mechanisms of Ti-5322 alloy during hot compression

The hot deformation behavior of Ti-5322 alloy are researched at compression temperatures range of 750-1050 °C and strain rate range of 0.01-10 s−1, to optimize its hot workability. Processing map analysis and microstructure observations reveal that the optimal processing parameters of Ti-5322 alloy are temperatures of 750-825 °C and strain rates of 0.01-0.05 s−1, and temperatures of 925-975 °C and strain rates of 0.01-1 s−1. The peak efficiency of power dissipation can reach 40% owing to the transformation from phase to β phase, spheroidization behavior and dynamic recrystallization of the β phase. The dynamic recrystallization was the primary form of microstructure evolution above 900 °C, while the spheroidization of phase below 900 °C. The spheroidization of lamellae can be attributed to the instability of subgrain boundaries appeared in the phase during hot deformation. The β phase wadges into the / subgrain boundary and /β interface migration induced the phase spheroidization. In addition, three instability domains are detected in the processing maps, which confirmed by the presence of microstructures with wedge cracking and adiabatic shear bands.