Formation and structure of dislocation networks developed during high-temperature deformation of MgO

Cell boundaries formed, during transient as well as during steady-state creep of < 100 >-oriented MgO single crystals between 1700 K and 2100 K have been investigated by transmission electron microscopy. The observed dislocation networks in the cell boundaries can be explained by a mechanism which is characterized by two stages: (i) Formation of cell walls with a simple character by glide dislocations of primary {110} dodecahedral slip systems. (ii) Reaction of wall dislocations, acting as a 'forest', with glide dislocations, which move on diverse slip systems from the cell interior and knit together to form hexagonal networks by stress-induced climb processes analogous to the mechanism proposed by Lindroos and Miekk-Oja for f.o.c. metals.