Temperature Dependent Creep in Zinc Crystals

Abstract

Tensile creep measurements beginning in a tensile strain region of about 10⁻⁶ have been made upon a set of seven single crystals of zinc of 99.99⁺ percent purity. Measurements were made both by means of electrical resistance strain gauges and an optical lever system. Some of the measurements made in the latter apparatus lasted 100 hours or more, and in both systems, measurements were made at several temperatures. The creep results obtained in this work can be best described by the single empirical relation $${\mathrm{\eta =bt}}^m$$ in which η is the shear strain, t is the time after completion of the application of stress to the crystal, and b and m are constants for a given creep test under given experimental conditions. It is found that b increases with the stress but does not vary greatly with temperature. The values of m are practically independent of stress but vary with temperature, and appear to fit best the equation, $${\mathrm{m=m}}_0\exp {\mathrm{(-T}}_0\mathrm{/T)}$$ in the temperature interval investigated. For these crystals T₀ = 1580°K, m₀=120, and the temperature at which m=1 is 58°C. Values of m>1 are interesting in dislocation theory.