Twinning behavior of pure titanium during rolling at room and cryogenic temperatures

Abstract

Abstract Twinning activity of pure titanium during rolling at room and cryogenic temperatures was investigated by electron backscattered diffraction (EBSD) technology. Because cryogenic temperature facilitates twin formation, cryogenically processed samples exhibited greater hardness than those processed at room temperature. Schmid factor (SF) analysis of twin variant selection behavior revealed that the variant selection was insensitive to temperature. Both moderate and low SF variants formed, which led to multiple variants within the grain. Furthermore, twin-twin intersections were more likely to occur at cryogenic temperatures due to the coexistence of multiple variants and twin types within a grain. At a strain of 20%, higher-order sequential twinning was common during rolling at cryogenic temperature, indeed, a twinning sequence of CTW→ETW→CTW→ETW by lattice rotation was observed. The formation of low SF and anomalous variants during rolling can be explained by displacement gradient tensors and geometric compatibility factors.