Is Ashby grain-boundary hardening model applicable for high strains?

This work was undertaken to evaluate the applicability of the Ashby grain-boundary hardening model for a high strain range. To this end, Al−Mg alloy with distinctly different grain sizes (~100 μm vs ~1 μm) was cold-rolled to a true strain of ~1.6 and the resulting dislocation densities were compared by using transmission electron microscopy. A minor difference revealed by the measurements suggested a violation of the Ashby’s model. This effect was attributed to a partial relaxation of strain constraints due to significant change of grain shape, development of texture and formation of pronounced substructur