Microplasticity behavior study of equiaxed near-b titanium alloy under high-cycle fatigue loading: Crystal plasticity simulations and experiments

A crystal plasticity finite element (CPFE) model has been developed to study the microplasticity behavior of Ti-5553 alloy with equiaxed dual-phase microstructure under high-cycle fatigue (HCF) loading process. The microstructure and density distributions of geometrically necessary dislocations (GNDs) after HCF loading were characterized by electron backscattered diffraction (EBSD). Experimental results show that the microplasticity accumulation behavior happens in α phase during the HCF loading process. The developed CPFE model captures the essential physics of microplasticity accumulation in the primary α phase and stress concentration at the softer α/b interface. Besides, the effect of stress levels and volume fraction of primary α phase on microplasticity behavior was discussed. Results indicate that the stress concentration can be taken as fatigue indicator parameter (FIP) for high stress level HCF loading conditions, while the cumulative shear strain can be taken as FIP for low volume fraction of primary α phase conditions. This work provides a strategy not only contributing to understand the microplasticity behavior during HCF loading process but also choosing a suitable FIP for different loading conditions and microstructure states.