Type and density of dislocations in a plastically deformed long-period stacking ordered magnesium alloy

The density and type of dislocations were studied in a plastically deformed long-period stacking ordered (LPSO) phase of a Mg89Y7Zn4 (at.%) alloy. The volume fraction of the LPSO phase was as high as ∼85%. The plastic deformation was carried out by uniaxial compression up to the strain of ∼25% in both as-cast and extruded states. The order of magnitude of the dislocation density was ∼1014 m−2 after compression to the strain of ∼25% for both as-cast and extruded materials. It was also found that most of the dislocations formed in the LPSO phase during extrusion and compression were of -type. The as-cast sample did not exhibit a strong crystallographic texture, but extrusion caused a texture in which the normal vector of the basal plane was perpendicular to the extrusion axis. The texture developed during extrusion yielded an anisotropic evolution of the dislocation density during subsequent compression. Namely, the density of dislocations developed during compression was lower when the deformation was carried out parallel to the extrusion axis.