Influence of single and multiple slip conditions and temperature on the size effect in micro bending

The present work investigates the effect of crystal orientation and temperature on the size effect using micro-sized single-crystal bending beams of copper with thicknesses between 1 and 5 mu m. Two crystal orientations were studied: (111)<153> for single slip and (111)<001> for multiple slip. The bending tests were carried out with a nanoindenter installed in a scanning electron microscope at temperatures between room temperature and 200 degrees C. The results show clearly that, besides the phenomenon smaller is stronger, the size effect is influenced by temperature particularly in beams oriented for single slip. We demonstrated that, in the presence of strain gradients, the mechanical response is governed by dislocation pile-ups below a critical beam size, being more pronounced in single slip conditions. The pile-ups, however, collapse by temperature-induced cross-slip with increasing temperature, while in bigger samples, dislocation networks govern the strength. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.