Material modeling for the hot consolidation of metal powders and metal-matrix composites

The modeling of the deformation and densification behavior of metal powders during hot consolidation processes was treated through the application of a continuum yield function and associated flow rule modified to incorporate microstructure effects such as grain growth, pore size, and pore geometry. The material-dependent parameters in the yield function/flow rule were the constitutive behavior of the fully dense metal, the stress intensification factor, and Poisson's ratio. Methods to measure the various material parameters were developed and applied for two titanium aluminide alloys (Ti-24Al-11Nb and Ti-48Al-2.5Nb-0.3Ta, in atomic percent). The accuracy of the material modeling approach was validated through a comparison of predicted and observed densification behavior during die-pressing of monolithic alpha-two powder and hot-isostatic pressing of tapecast monotape composite layups comprising Ti-24Al-11Nb powder end continuous silicon carbide fibers.