Recovered elastic and plastic strains at residual micro-indentations in an MgO crystal

Elastic and plastic unloading effects are described for aligned diamond pyramid indentations imposed on a (001) MgO crystal surface. Substantial elastic recovery effects are explained in terms of the theoretical Hertzian behaviour for a ball indentation test. Limited reversal of the plastic deformation field occurs, involving dislocation processes which first produce an extensive amount of slip and cracking during the loading portion of the indentation cycle.