[SY-C13] Symposium C-13

[SY-C13] The Minimum Energy Pathways Identifications of Twinning Dislocation Loop Nucleation of Extension Twinning in Magnesium

^○Xiao-Zhi Tang¹, Qun Zu², Lixin Sun⁴, Yue Fan³, Ya-Fang Guo¹ (1.Inst. of Mechanics, Beijing Jiaotong Univ., China, 2.Schl. of Mechanical Engineering, Hebei Univ. of Tech., China, 3.Dept. of Mechanical Engineering, Univ. of Michigan, United States of America, 4.Dept. of Nuclear Science and Engineering, MIT, United States of America)

The twinning dislocation loop nucleation on the coherent twin boundary in magnesium is investigated by potential energy approaches, and also the dynamic simulations at various temperatures and strain rates.

Based on our numerical results of extension twinning, the single lattice transformation within the coherent twin boundary migration is identified to be the elementary migration process, and its stress-free potential energy barrier is lower than the thermal energy at room temperature. The migration can be triggered thermally once the shear stress makes the transformed lattice at a low energy state. Both the nucleation energy and the critical radius of a twinning dislocation loop are calculated. We believe our discoveries pursue a better understanding of the plasticity of hexagonal close-packed metals.