MODELING THE HOT CONSOLIDATION OF CERAMIC AND METAL POWDERS

Modeling of the consolidation of ceramic and metal powders by sinterin g, hot pressing, and hot-isostatic pressing (HIP) was conducted using a continuum yield function and associated-flow rule modified to incorp orate microstructure effects such as grain growth, pore size, and pore geometry. It was shown that consolidation behavior can be described o ver the entire range of densities through two parameters, the stress i ntensification factor and Poisson's ratio, which are readily measured using uniaxial upset tests. Both parameters are functions of relative density, whose exact dependence varies from one material to another. F urthermore, it was demonstrated that in sinter forging of ceramics, an ''apparent'' Poisson's ratio depending on stress level (relative to t he sintering stress) gives a quantitative measure of the competition b etween sintering and creep deformation. The accuracy of the microstruc ture-sensitive yield function was established through finite-element m odeling (FEM) simulations of the isothermal sintering of a soda-lime g lass, sinter forging of alumina, and die pressing of an alpha-two tita nium aluminide alloy.