In-situ investigation of dwell fatigue damage mechanism of pure Ti using digital image correlation technique

Abstract

The damage behavior of soft-hard grain combinations in a pure Ti subjected to pure fatigue and dwell fatigue loading was investigated in-situ using the digital image correlation technique combined with the electron backscattering diffraction technique. The results show that the basal slip of hard grains only occurred under dwell fatigue loading, revealing that the basal slip is strongly time-dependent. The facet formation is mainly attributed to the time-dependent basal slip assisted by the locally high stress. The soft orientation also influenced the deformation degree of the hard grains under pure fatigue loading via the strain incompatibility between the soft and hard grains. These findings have significant implications in further understanding the effect of grain orientation-dependent strain rate sensitivity of the pure Ti on the dwell effect. • Dwell fatigue damage behavior of soft-hard grain combinations in a pure Ti was investigated by the digital image correlation technique. • In-situ observations demonstrate that the basal slip is strongly time-dependent. • Facet formation is mainly attributed to the time-dependent basal slip assisted by the locally high stress, related to the soft grain orientation.