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

Abstract

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 α 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 α phase below 900 °C. The spheroidization of α lamellae can be attributed to the instability of subgrain boundaries appeared in the α phase during hot deformation. The β phase wadges into the α/α subgrain boundary and α/β interface migration induced the α 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.