Knoop hardness anisotropy and predicted and observed slip patterns in MgO

Abstract

Results are presented of the Knoop hardness anisotropy on {001} and {110} faces of MgO. Specimens were etched to show dislocation positions. This etching was repeated after chemical surface stripping, so as to reveal the three-dimensional arrangements of dislocations around indentations made in low-index directions on the two surfaces. These dislocation arrangements are compared with those predicted by two hardness-anisotropy models. Additionally, the influence of elastic recovery and surface pile-up on measured hardness has been investigated.