Rules to identify and track the evolution dynamics of {101̄2} twin variants in hexagonal close-packed metals

Abstract

Twinning evolution laws derived based on physics are required to model plasticity and texture evolution resulting from the twinning in hexagonal close-packed structures. Atomistic simulations are employed to study the evolution of $\left\{10\bar{1}2\right\}$ twins in Ti at 5 K temperature. The misorientation angle between the twinned region and parent matrix differs from the expected misorientation angle of 85.03${}^{\circ }$. This closely aligns with the experimental findings. The deviation of twinning from $\left\{10\bar{1}2\right\}$ twin plane makes it difficult to identify conjugate twins, leading to their coalescence. Both the c-vector and disorientation angle analyses are unable to track the variant type of the conjugate twins. The disorientation angle analysis can identify the conjugate twin variants but is unable to identify the variant type of the twin. The c-vector analysis can identify the conjugate twin variants as well as the variant type of the twin but is unable to track the variant type of the twin during its evolution. A set of rules are proposed to track the variant type of the twin during its evolution. These rules should help to understand the twin evolution dynamics in HCP metals and can be applied to study the twinning evolution dynamics at ambient conditions, even though they are designed for twinning evolution at 5 K temperature. The fundamental understanding of twin evolution dynamics should motivate the construction of the physics-based evolution laws for twinning.