Analysis of Dislocation Mobility under Concentrated Loads at Indentations of Single Crystals

Abstract

An approximate solution is given for the dependence of the dislocation track length, l, around a microhardness indentation in single crystals on the load applied to the indenter (P), the temperature (T), and the duration under load (t): l ∼ Pm/(2m+1)t1/(2m+1) [exp −U/kT(2m+1)]. The assumption is made that dislocations move from the indenter in plane arrays and that the dislocation velocity is v ∼ τm exp (− U/kT), where τ is an effective stress, U is the activation energy. In a definite range of parameters the equation agrees satisfactorily with the literature data and those obtained in the present work, and may be used to estimate the dislocation mobility from the dislocation track length. The value of the ratio l/d (d is the indentation diagonal) is constant for ionic crystals but depends on the temperature and the load in the case of covalent crystals. l is connected with the yield strength τs as lτs ≈ const for covalent crystals (m ≈ 1), but l2τs ≈ const for ionic crystals (m ≫ 2). Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA