Understanding and predicting damage and failure at grain boundaries in BCC Ta

Abstract

Understanding the effect of grain boundaries (GBs) on the deformation and spall behavior is critical to designing materials with tailored failure responses under dynamic loading. This understanding is hampered by the lack of in situ imaging capability with the optimum spatial and temporal resolution during dynamic experiments, as well as by the scarcity of a systematic data set that correlates boundary structure to failure, especially in BCC metals. To fill in this gap in the current understanding, molecular dynamics simulations are performed on a set of 74 bi-crystals in Ta with a [110] symmetric tilt axis. Our results show a correlation between GB misorientation angle and spall strength and also highlight the importance of GB structure itself in determining the spall strength. Specifically, we find a direct correlation between the ability of the GB to plasticity deform through slip/twinning and its spall strength. Additionally, a change in the deformation mechanism from dislocation-meditated to twinning-dominated plasticity is observed as a function of misorientation angles, which results in lowered spall strengths for high-angle GBs.