Grain boundary sliding and deformation mechanism maps

The influence of grain boundary sliding (GBS) on the nature of deformation maps for aluminum and nickel is considered. Phenomenological equations for GBS (which can lead to fine-structure superplastic flow) are used to illustrate how they modify the two types of deformation mechanism maps now used (Ashby-Frost and Langdon-Mohamed maps). Specifically the map of Ashby is re-examined for the modulus-compensated stress versus homologous temperature at constant grain size for the case of pure nickel. Also, the Langdon-Mohamed map is re-examined for normalized grain size versus reciprocal of the homologous temperature at a high constant normalized stress for the case of pure aluminum. It is shown that large portions of such deformation maps are dominated by GBS.