Deformation of Thin Copper Crystals

Abstract

Stress/strain curves of many number of copper crystals having various radii from 0.06 to 1 mm were measured. The range of easy glide increases considerably when the radius of crystal decreases. In the case of suitably oriented crystal the range of easy glide reaches to 50 per cent in shear, when the radius of crystal decreases less than 0.1 mm. The extrapolation of the range of easy glide to the infinitesimal radius gives a value between 40 to 80 per cent in shear irrespectively to the initial crystal orientation. The hardening rate in the easy glide region considerably decreases with the decreasing crystal radius. Meanwhile, the critical shear stress, the stress required for the transition from the easy glide to the rapid hardening region, the hardening rate in rapid hardening region reveal only slight dependence on the crystal radii, i.e. the former two slightly increase and the last slightly decreases with the decreasing crystal radii. These results are discussed qualitatively by introducing a concept ` mean free path of dislocations ' in a crystal.