A mesoscale model to predict the effect of microstructural heterogeneitieson superplastic deformation

A two-dimensional approach is proposed to describe superplastic deformation at a mesoscopic scale in order to predict the effect on the mechanical beh aviour of microstructural heterogeneities, like grain size distribution or spatial distribution of grains. The grains in the microstructure may slide and plastically deform, the extent of each mechanism depending on the appli ed conditions. The degree of homogeneity of deformation through the materia l is estimated by the predictions of differences in shear rates along bands specifically oriented in reference to the stress axis. It is shown that th e superplastic behaviour not only depends on the grain size distribution bu t also on the degree of dispersion of the large grains through the microstr ucture, despite a same mean grain size. This dependence may concern the mac roscopic behaviour as well as the extent of localisation of deformation thr ough the sample. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Scie nce Ltd. All rights reserved.