Molecular Dynamics Analyses of Deformation Behavior of Long-Period-Stacking-Ordered Structures

Magnesium alloys containing long-period-stacking ordered (LPSO) phases have attracted considerable attention because they have been reported to exhibit excellent mechanical properties, including high strength and reasonable ductility. It is thought that the LPSO phase plays a critical role in producing these favorable mechanical properties. We analyze the deformation behavior of the LPSO phases with different stacking sequences using molecular dynamics simulations. To highlight the specific deformation behavior of the LPSO phases, we also perform deformation analyses of hexagonal-close-packed and face-centered-cubic (FCC) structures. We focus on the influence of the stacking order rather than the segregated atoms around the FCC-structured layers, and we model an LPSO structure by single element composition where the interatomic interaction is described by a smoothed Lennard-Jones potential. Our simulations indicate that an LPSO structure with a shorter stacking sequence tends to exhibit a higher compressive flow stress, because FCC-structured layers inhibit twinning deformations and non-basal slips. Kinking deformation is observed for an LPSO structure when both compression and shear deformation are present. It is shown that the first-order pyramidal-hcþ ai dislocation disarranges the stacking of an LPSO structure and leaves behind many lattice defects. In addition, those lattice defects activate numerous basal slips. Finally, basal dislocations arrange in a line and generate a misorientation angle. Furthermore, this angle originates the compressive deformation. We also observed some prismatic-hai dislocations and cross slips to the basal plane. These results suggest the importance of non-basal slips for kinking deformation. [doi:10.2320/matertrans.MI201211]