An EBSD and TEM Study on the Microstructural Evolution of in situ Synthesized (TiB+TiC)⁄Ti Matrix Composites during Superplastic Deformation

Abstract

Microstructures of in situ synthesized (TiB+TiC)⁄Ti matrix composites after superplastic deformation at 980°C with a strain rate of 5×10⁻³ s⁻¹ have been studied. Optical microscope (OM) and scanning electron microcioy (SEM) observations indicate that the mean grain size decreased. Electron back-scattered diffraction (EBSD) and transmission electron microcopy (TEM) observations reveal that the density of sub-grain boundaries and high angle grain boundaries increased during superplastic deformation, clearly indicating that dislocation sliding and climbing are important processes during superplastic deformation. The experiment results indicate the superplastic deformation is controlled by grain boundary sliding and dislocation motion, which is consistent with the result deduced from activation energy.