Micromechanical behavior of Ti-2Al-2.5Zr alloy under cyclic loading using crystal plasticity modeling

The intergranular stress was investigated at grain boundaries (GBs) of Ti-2Al-2.5Zr alloy under cyclic loading. The crystal plasticity (CP) simulations revealed that the strain incompatibility between soft-soft grains due to shear direction difference, which forced the slight activation of tension twins (TT) near GBs. Twin boundaries (TBs) and GBs constituted new triple junctions, leading to further stress concentration and fatigue damage initiation. While the strain quantity difference at soft-hard GBs induced the moderate stress jump and stable stress evolution, which was insufficient to generate fatigue cracks. The EBSD-based CP model successfully pre-dicted the twin activation and fatigue cracks at GBs.

Automated summary

The intergranular stress at grain boundaries of Ti-2Al-2.5Zr alloy under cyclic loading was investigated. Crystal plasticity simulations revealed that strain incompatibility between soft-soft grains caused the activation of tension twins near grain boundaries. Twin boundaries and grain boundaries constituted new triple junctions, leading to further stress concentration and fatigue damage initiation. A moderate stress jump and stable stress evolution were observed at soft-hard grain boundaries due to strain quantity difference, which was insufficient to generate fatigue cracks. The EBSD-based CP model successfully predicted twin activation and fatigue cracks at grain boundaries.