Phenomenological analysis of recovery-controlled transient creep supported by substructural observations in single crystals of sodium chloride and silver chloride

Abstract

Single crystalline samples of sodium and silver chloride, have been crept at high temperature ( T > 0.5 T m ). It is shown that Hart's analysis of plastic deformation without recovery, can be extended in the case of transient, recovery-controlled creep of sodium and silver chloride. The region on the right of the minimum creep rate curve on the log σ — log ⋗e diagram corresponds to transient creep states with unstable substructure. It has been found theoretically and verified experimentally that the initial strain rate. ge i , of a sample precept at σ 1 after a stress increase σ 0 = σ 2 − σ 1, is a function of the stress σ 1 and the associated secondary strain rate ge s1 : ge i = ( σ 2 σ 1 ) nge s1 The exponent n, is the strain rate sensitivity of the stress at constant structure introduced by Hart. We found: n = 7.3 ± 0.3 for sodium chloride: n = 6.1 ± 0.3 for silver chloride.