The fatigue of zinc single crystals

Abstract

Zinc single crystals with 30°<χ{1010}, was observed. Cyclic stressing produced considerable hardening with flow stresses in the range 1•5—3•5 Kg mm⁻² r.s.s. (corresponding to fatigue failures in 10⁶—10³ cycles at 100 c/s). It is considered that this hardening results from a dynamic equilibrium between the continuous generation by fatigue of defects (vacancies, dislocation loops) and their disappearance by annealing. Crystals fatigued at 78°K did not achieve such high stresses because crystallographic notching was severe and readily initiated cleavage. Crystals with an initial flow stress of 1•3 Kg mm⁻² r.s.s. produced by fatigue at 78°K were hardened by resting at 195°K. This supports the view that a dynamic hardening mechanism is appropriate to describe fatigue of zinc crystals at room temperature (0•4T _m).