Decomposition of $\langle {c}+{a}\rangle$ Dislocations in Magnesium Alloys

Abstract

In this paper, molecular dynamics simulations are performed to investigate the decomposition of $\langle c+a \rangle$ dislocations on both pyramidal-I and pyramidal-II planes. The pyramidal-I dislocations are decomposed into $\langle c \rangle$ and $\langle a \rangle$ dislocations under shear stress at 0–400 K, which all reside on the basal plane. At 500–700 K, the dislocations are transited onto the basal plane at zero stress, then decomposed into $\langle c \rangle$ and $\langle a \rangle$ dislocations under shear loading. In particular, at 700 K, the dislocation is possibly decomposed spontaneously at zero stress. For the pyramidal-II dislocations, the core is glissile below 400 K. At 500 K, the dislocation is transited onto the basal plane under shear loading. At 600–700 K, basal $\langle c+a \rangle$ dislocation is formed at zero stress, but then decomposed under shear loading. The dislocation core energy is calculated to explain the observations. It is found that the energy of decomposed $\langle c+a \rangle$ dislocation is high, the energy of pyramidal $\langle c+a \rangle$ dislocation is intermediate, and the energy of basal $\langle c+a \rangle$ dislocation is low. Our results provide new insights into the behaviors of pyramidal dislocations and temperature effects.