Orientation dependence of slip band formation in single-crystal aluminum studied by photoelectron emission

We report the application of a photoemission technique to study slip band formation in single-crystal aluminum (99.995%) during uniaxial tensile deformation. Light with a single 253 nm wavelength was isolated from a mercury lamp and used as the source for photoemission experiments. Deformation of aluminum single crystals with three orientations (near [1 1 2], near [2 1 5] and near [2 3¯3¯]) was conducted with a tensile stage in ultrahigh vacuum at an initial strain rate of about 5 × 10−4 s−1. We show that photoelectron emission is sensitive to the changes in the surface morphology accompanying deformation, including slip line and slip band formation, and that the photoemission intensity both increases with strain and exhibits a strong orientation dependence. Moreover, some time-resolved photoelectron measurements show discontinuous increases in intensity that are consistent with the heterogeneous nucleation and growth of slip bands during tensile deformation. The in situ photoelectron data and real-time stress vs. strain from the three single crystals validate the classical crystallographic relationships governing slip band formation and suggest that dislocation dynamics during deformation of aluminum may demonstrate a percolation-like behavior. The slip bands on the deformed surfaces were examined with both optical microscopy and atomic force microscopy.