The advantages of the anisotropic properties of α-uranium for the study of plasticity

The development of dislocation cells and texture during the plastic deformation of metals remains unresolved in many details. The relation between the overall plastic.. strain, s'v'... and the plastic strain f* induced on the individual active slip system s is expressed in equation (1): where ys is the magnitude of slip on the s~ slip system. The yield condition on any slip system is expressed in the 6-dimensional yield surface by the intersection of the stress tensor with the hyper-plane representing that system. Usually the stress intersects a (multi-slip) corner of the surface where n hyper-planes intersect. Due to their high crystallographic symmetry all multi-slip corners in FCC metals of contain 8 or 12 slip systems ie «= 8 or 12 [1]. Shear deformation has only five degrees of freedom, therefore in those multi-slip corners have no one-to-one correspondence between the overall plastic deformation and the individual slip activities [2]. The lack of one-to-one correspondence between the plastic strain and the activity of the slip systems sets a major problem in the analysis of texture development and the formation of dislocation cells. Here rests a potential advantage of low symmetry metals, when trying to relate macroscopic plasticity experiments with the microscopic dislocation behavior. We calculated the yield surface of a-uranium at high temperatures and found that most multi-slip corners of uranium contain only 5 slip systems.