PREDICTION OF SOLIDIFICATION MICROSTRUCTURE OF ALNICO MAGNETS USING CAST CAE SYSTEM

摘要

Alnico magnets are well known for typical casting magnets having high remanence and good temperature stability. The excellent magnetic properties of these magnets arise from directional solidification using chill plates in a shell mold casting. We applied fluid flow analysis, solidification analysis and microstructure calculation for columnar Alnico-5 magnet (MK-5DG). The solidification microstructures were analyzed by coupling of a cellular automaton method and a finite differential method in 2-dimension. The heterogeneous nucleation rate was expressed as Gaussian distribution by a function of undercooling which has three kinds of parameters namely an average nucleation undercooling, a deviation of nucleation undercooling and a maximum nucleation density. By choosing the reliable parameters of bulk liquid and mold surface respectively, calculation of microstructures corresponded well to real casting magnets. The suitable mold casting design was determined by this CAE system.