Plastic Behaviour of Thin Films of Gold Formed by Vacuum Evaporation

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Abstract
Plasticity of thin crystals has been studied on single crystalline films of gold of about 1000 Å in thickness, prepared by vacuum deposition. The deformation of films was made by stretching a substrate (Mylar) on which the films were fixed, and then examined in an electron microscope. When the stress was applied in direction, extension of stacking faults and/or of thin twins resulted. While, under the stress in direction, mechanical twins up to several microns in breadth were produced. In the broadened twin bands, slipping and secondary twinning were very active resulting in parting of the films, whereas slip in the matrix was only subsidiary. The mode of deformation is interpreted in terms of the resolved shear stress for each partial dislocation, which borders the fault, and in taking account of the effect of intersection between extended faults. The estimation of twinning stress does not conflict with the successive nucleation of twin dislocations.