The cleavage surface energy of zinc

Abstract

Three different specimen geometries and analyses are employed to determine the cleavage surface energy of the basal plane of zinc. The simple beam technique used by Gilman produces a value ∼100 ergs cm⁻² whilst a modified beam technique gives a value of ∼400 ergs cm⁻². These results are rejected, however, since the specimen dimensions and manner of testing do not fulfil the requirements of the cantilever beam analysis. The third method is the tensile fracture technique in which a small cleavage crack, inserted by spark discharge, is propagated and the cleavage surface energy determined via the Griffith relation. The value obtained is 575 ergs cm⁻². This result is favoured because of the simplicity of the test and analysis and because this value is more rational than the others when general values of surface energy anisotropy are considered.