A further step towards an understanding of size-dependent crystal plasticity: In situ tenison experiments of miniaturized single-crystal copper samples

A method for in situ testing of miniaturized tension specimen was developed. The size effects of the plastic deformation behavior of copper single crystals loaded along the Æ234æ direction were investigated. The diameter was varied between 0.5 lm and 8 lm, and the aspect ratio, gauge length to side length, between 1:1 and 13.5:1. At high aspect ratios hardening was negligible. However, an increase of the flow stress with decreasing diameter was observed. This increase was small for diameters above 2 lm, and somewhat larger below 2 lm. These findings are explained by individual dislocation sources which govern the plastic deformation. For low aspect ratios the behavior is significantly different. A pronounced hardening and a very strong size effect was observed. Both are a result of dislocation pile-ups due to the constrained glide of the dislocations caused by the sample geometry