Influence of microstructure on strain controlled low cycle fatigue crack initiation and propagation of Ti-55531 alloy

Low cycle fatigue (LCF) crack initiation and propagation behavior of Ti-55531 alloy with lamellar and bimodal microstructures were comparatively investigated at room temperature. Results indicated that the two micro-structures displayed different sensitivity to the change of cyclic strain, which resulted in significantly different cyclic deformation, fatigue crack nucleation, and crack propagation behavior of two microstructures. Finally, it was found that cyclic lives of two microstructures were entirely different. Moreover, besides slips and deformation twins, stacking faults promoting cracking of alpha(s)/beta interface may be another important LCF microcrack nucleation mechanism of Ti alloys, which hasn't been revealed by other researchers.

Automated summary

This study comparatively investigated the crack initiation and propagation behavior of Ti-55531 alloy with lamellar and bimodal microstructures under low cycle fatigue. Results showed that the two microstructures exhibited significant differences in cyclic deformation and fatigue behavior due to their different sensitivities to cyclic strain. Additionally, stacking faults were identified as another important mechanism for crack nucleation at the alpha(s)/beta interface of Ti alloys.