The measurement of stacking-fault energies of pure face-centred cubic metals

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Abstract
Using standard imaging techniques of electron microscopy it is not possible to resolve the partial dislocations having the equilibrium separation for dissociated dislocations in the pure face-centred cubic metals. Consequently the stacking-fault energy γ cannot be determined from direct measurements of the separations of the partials. In this paper it is demonstrated that such determinations are possible using the weak-beam method of electron microscopy. The separations of Shockley partial dislocations in silver and copper have been measured, as a function of dislocation line orientation, using this method. From these measurements, the values γsilver= 16·3+1·7 erg cm−2 and γcopper= 41±9 erg cm−2 have been obtained from analyses based on anisotropic elasticity theory.