On the elastic accommodation between the structural units in the LPSO structures

Abstract

Long range periodic stacking ordered (LPSO) structures in magnesium alloy consist of regular arrangements of four layer height fcc structural units separated by several Mg layers paralleling to the base plane. The shear transformation of the structural units from hcp structure involves large transformation strain. This strain can be significantly accommodated by the combination of the structure units with different shears. In addition, the possible lowest elastic energy configuration in both R and H type of LPSO structure is obtained. For H type LPSO structure, the opposite shear directions (or Burgers vectors of the partial dislocations) are operated in nearest structural units, while all three types of shear directions are operated successively in the nearest structural units for R type LPSO structure. This study also intends to discuss the inter spacing between the structural units in terms of the elastic interaction. It is found the elastic interaction alone cannot rationalize the spacing between the structural units.