Grain Rotation Accommodated GBS Mechanism for the Ti-6Al-4V Alloy during Superplastic Deformation

An investigation of flow behavior and the deformation mechanism for Ti-6Al-4V alloy during the superplastic deformation process is presented in this paper. Constant strain rate tensile tests were performed at 890-950 degrees C and strain rates of 10(-2), 10(-3), and 10(-4)/s. Then, surface observation by Optical Microscope (OM), Scanning Electron Microscopy (SEM), and Electron Back-scattered Diffraction (EBSD) was applied to obtain the microstructure mechanism. With pole figure maps (PF) for alpha-phase, obvious texture gradually changed in the main deformation direction. For the titanium alloy, the evolution of texture in deformed samples was attributed to grain rotation (GR). Significant grain rearrangement occurred between grains after deformation. A complete grain rotation accommodated grain boundary sliding (GBS) deformation mechanism is proposed, which can explain texture evolution without grain deformation.