Change in microscopic surface profile during tensile plastic deformation of high purity aluminum polycrystals

Roughening on free surface in polycrystalline metal during plastic deformation is closely related to the inhomogeneous deformation in the respective grain at the surface. Uniaxial tensile tests were carried out on annealed pure aluminum sheet specimens with various grain sizes. The roughening was measured by a 3-dimensional stylus instrument in order to study the roughness change on both sides of specimen surface at each strain. The irregularities of surface shape on one side are found to be reversed on the backside, when the averaged grain size is as large as the thickness of the specimen. There are some deviations in the strains of the grains and their standard deviation increases with the applied strain.