Microstructure and texture evolution of TA32 titanium alloy during superplastic deformation

A study based on uniaxial tension tests were conducted in this paper to understand the hot deformation behaviors of TA32 alloy during superplastic deformation at a deformation temperature of 915 degrees C and an initial strain rate of 6.64 x 10(-3) s(-1). In the test, the maximum fracture elongation reached 1065%, exhibiting good superplastic deformation ability. Electron back-scattered diffraction (EBSD) was used to analyze and study evolution of microstructures and textures in the process of deformation with the following findings: During tensile deformation, the fraction of low-angle grain boundaries ( < 15 degrees, LAGBs) decreased drastically, while that of high-angle grain boundaries ( >= 15 degrees,HAGBs) increased from 45% to 96.2%. As the further straining, the role of continuous dynamic recrystallization (CDRX) was weakened, while that of discontinuous dynamic recrystallization (DDRX) was strengthened. Dynamic recrystallization helped refine coarse grains in the initial structures and reduced deformation defects in grains. The superplastic deformation mechanism of TA32 alloy was dominated by boundary sliding of high-angle grains, coordinated by dislocation motion at the softening stage and by grain rotation at the steady deformation stage respectively. In addition, the drawing force contributed to both dynamic recrystallization and rotation of grains.