A numerical study of solidification in powder injection molding process

Thermal analysis of mold filling and post-filing solidification has been carried out for the powder injection molding process. The filling material comprised alumina powder and polymeric binder was used to fill a rectangular cavity. The interphase momentum transfer was accounted for using a momentum exchange model due to Wang et al. [Y. Wang, S. Ahuja, C.Beckerman, H.C. de GROH III, Multiparticle interfacial drag in equiaxed solidification, Metall. Mater. Trans. B 26B (1995) 111–119]. Though both the alumina powder and polymeric binder are treated as fluids, as the alumina powder does not undergo a phase change, only the solidification of the binder has to be considered. The liquid fraction of the binder was assumed to follow a linear rule between the liquidus and solidus temperature. An iterative latent heat recovery formulation has been developed to obtain the liquid fraction during solidification. It was found that the predictions for pressure rise at the inlet compares favorably with the results from the single-phase mixture model. However, the multi-phase model could predict the powder segregation unlike the mixture model. The multi-phase model predicts higher temperature compared to mixture model due to powder particle migration.