Hot tensile deformation behavior and globularization mechanism of bimodal microstructured Ti-6Al-2Zr-1Mo-1V alloy
(1. School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou 310018, China;
2. Advanced Science Institute, Saitama Institute of Technology, Fukaya 3690293, Japan;
3. School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China)
2. Advanced Science Institute, Saitama Institute of Technology, Fukaya 3690293, Japan;
3. School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China)
Abstract: The hot deformation behavior, microstructure evolution and fracture characteristics of bimodal microstructured Ti-6Al-2Zr-1Mo-1V alloy were investigated by isothermal tensile tests. Results reveal that flow softening is caused by dynamic globularization of the bimodal microstructure, which also results in a relatively high stress exponent and thermal activation energy. The corresponding SEM, EBSD and TEM observations indicate that the dynamic globularization at 750 and 800 °C is accomplished by the formation of α/α sub-grain boundary and penetration of the β phase. However, dynamic recrystallization (DRX) is the main globularization mechanism at 850 °C, which was proved by the generation of fine grains with a necklace-like character due to the transformation of low-angle boundaries (LABs) into high-angle boundaries (HABs). With an increase in the deformation temperature or a decrease in the strain rate, the fracture mechanism changes from microvoid coalescence to intergranular fracture.
Key words: titanium alloy; bimodal microstructure; deformation behavior; globularization mechanism; fracture morphology