Phenomenological and structural analysis of recovery-controlled creep, with special reference to the creep of single-crystal silver chloride

Abstract

The dislocation substructure has been studied in single-crystal samples of silver chloride, crept at high temperature (T⩾0·5 T _melt). It is shown that Hart's phenomenological analysis of plastic deformation in the absence of recovery is valid for high-temperature recovery-recontrolled creep of silver chloride, sodium chloride and aluminium. Hart's structural parameter, y, can be related to the average size of subgrains in secondary creep.

It has been shown experimentally that the average subgrain size decreases for an increase in applied stress but remains unchanged for a decrease in applied stress. Thus, the transient following a reduction in applied stress cannot be attributed to an increase in the subgrain size.

The two strain-rate sensitivities of the stress can be determined: v=1/n corresponds to a constant subgrain size and μ=1/m to the minimum creep-rate conditions with a variable subgrain size.

The secondary creep-rate _s is a function of the average subgrain size d, _s=Kd^n-mσⁿ with: