The Model of Structure Refinement in Metals at Large Deformations and Factors Effecting Grain Sizes

摘要

The increase in the curvature of sample's bending and torsion at large cold deformation leads to the decrease in the sizes of the formed fragments and grains in pure metals, and to the increase of angular misorientations of their boundaries. Bending results in the change of the specific area of the deformation center surface ΔA_s, i.e. the parameter responsible for an average curvature of a sample and crystal lattice of grains. Extremely fine fragments are formed when the above parameter increases during deformation to the value equal to the maximum tensor density of dislocations β. This is provided by the increased value of the initial specific surface of the deformation center A_i/V - the ratio between area and volume. The peculiar features of deformation center and structure refinement in quasi-monotonic and non-monotonic processes are considered. It is shown that structure refinement is dependent not only on strain but also on the field of angular velocities of fragments' rotation in the deformation center.