Correlation of fatigue damage mechanisms with acoustic emissions in a titanium alloy having multiple main microtextures

This paper aims to investigate the correlation of fatigue damage mechanisms with acoustic emissions in a titanium alloy having multiple main microtextures. In the study, electron backscatter diffraction (EBSD) was used to analyze the texture state, the fatigue fracture characteristics were observed by scanning electron microscopy (SEM), and the dislocation morphology, length, and behavior during fatigue were analyzed by transmission electron microscopy (TEM). At the same time, AE was used to monitor the fatigue damage behavior of the alloy in real-time throughout the entire process. The results show that the fatigue life of the sample with multiple main textures is about 33 % lower than that of the main texture unitary sample. As for the characteristics of secondary cracks on the fracture surface, the average length and number density of secondary cracks are higher in the sample with multiple main textures, and not only the majority of secondary cracks are nearly parallel to the fatigue strip, but also a few micro-cracks are nearly perpendicular to the fatigue strip. This phenomenon is attributed to the existence of obvious orientation difference. The obvious orientation difference promotes the earlier dissociation of a larger number of grain boundary dislocations into Shockley partial dislocation pairs at the microscopic level, resulting in collective motion to form a small sliding step with a large number of secondary cracks. In addition, by analyzing and studying the correlation between fracture characteristics and AE characteristics, AE characterization of fracture characteristics at different crack propagation stages has been achieved, or the AE characterization method for fracture is found. It will contribute to the in-depth understanding of crack propagation mechanism in multi-texture alloys under fatigue condition.