Grain boundary contribution to the bauschinger effect in beta-brass bicrystals

Abstract

A set of shear-incompatible bicrystals of 48.5 wt pct zinc β-brass was made by diffusion bonding and was then cyclically deformed in tension and compression to study the effect of the grain boundary on the Bauschinger effect. The presence of the secondary stresses near the grain boundary, arising out of compatibility requirements, was confirmed by the increased flow stresses of the bicrystal compared to the single crystal and by the presence of secondary slip systems. The Bauschinger stress in the bicrystals was larger than that in the single crystals, and the amount of the Bauschinger effect depended on the amount of cumulative strain and bicrystal size. It is deduced from extensive slip band observation that the degree of plastic incompatibility compensation by the compatibility slip controls the reverse slip behavior and thus the Bauschinger effect in bicrystals. The Bauschinger effect increases as the degree of incompatibility compensation decreases.