On the slip and twinning mechanisms on first order pyramidal plane of magnesium: Molecular dynamics simulations and first principal studies

Molecular dynamics simulations and first-principles calculations are carried out on first order pyramidal plane (pi(1)) of magnesium to study both compression twinning (CTW) and dislocation slip. To this end, a generalized stacking fault energy analysis is employed on dense (pi(1D)) and loose spaced (pi(1L)) pi(1) planes. The crystal shearing resistance is extracted by using aminimum-energy path (MEP) finder called the nudged elastic band (NEB) method. The MEP regarding <(1) over bar 012 >{10 (1) over bar1}(pi 1L) slip system shows that the unfaulted crystal structure is recovered in the middle of the path with non-straight and pronounced curved slip trajectories. Besides, it will be revealed that metastable configurations on the half of the MEP for <(1) over bar 012 >{10 (1) over bar1}(pi 1L) slip system are indeed related to a dissociated < c + a > extended dislocation of loose pyramidal-I < c + a > slip, 1/3 <(11) over bar 23 >{10 (1) over bar1}(pi 1L). Also, after extracting the dissociation mechanism related to this dislocation, it will be shown that loose pyramidal-I < c + a > slip can involve shuffling. Moreover, the MEP for dense pyramidal-I < a > slip, 1/3 <(1) over bar2 (1) over bar0 >{10 (1) over bar1}(pi 1D), shows transmutation of this slip into CTW in the middle of the path. This transmutation process will be further examined on CTW growth, and it will be demonstrated that this CTW mechanism is energetically more favorable compared to other twinning mechanisms. (C) 2020 The Authors. Published by Elsevier Ltd.