WORK-HARDENING AND CREEP OF MGO

The work hardening of 〈100〉 and 〈111〉 MgO single crystals has been investigated between 0.4 and 0.7 TM using strain rates of 10-7 to 10-4s-1 in compression. A steady-state flow stress is developed, at which the work-hardening rate vanishes. The work-hardening rate decreases linearly with stress and can be described by a Voce equation. The data are represented by constitutive equations which were derived to describe the deformation of f.c.c. metals. The results are inconsistent with the Bailey-Orowan approach to simultaneous strain hardening and recovery. The equations are used to predict power-law creep behavior, which correlates very well with results obtained from steady-state tensile creep studies. A temperature-dependent stress exponent is measured. Finally, the activation parameters measured in this study are compared to those determined from creep, and the parameters in the constitutive equations for MgO are compared with those measured in f.c.c. metals. © 1979.