Composition Undulation Induced Strain Hardening in Fine-Grained FCC Alloys

Abstract

A model is suggested that describes tensile plastic deformation of fine-grained FCC alloys with three-dimensional composition undulation. Within the model, composition undulation is approximated by spherical inclusions, which envelope the region of highest and lowest solute concentration. It is assumed that these inclusions can increase the yield strength due to their misfit stresses and, in addition, initiate the cross-slip of screw dislocations that otherwise tend to move in a planar mode. The initiation of additional dislocation slip systems reduces the dislocation mean slip path, which increases the dislocation density, enhances strain hardening and thereby increases the ultimate strength and ductility of alloys. It is demonstrated that the maximum ultimate strength can be achieved either at low or at high values of the composition undulation wavelength, while the uniform elongation slightly decreases with an increase in the composition undulation wavelength.