Distinct element simulation of grain alignment in mushy-state forging of magnets

Abstract

A method for simulating the motion of grains in mushy-state forming of magnets is proposed on the basis of the distinct element method. The grains of the magnet are modelled to be a lot of elliptical elements, and the effect of the liquid phase on the motion of the grains is treated as viscous resistance to the movement. The motion of individual grains is obtained by solving the equations of motion for a time increment under the action of the elastic repulsive, frictional and viscous forces. Macroscopic plastic deformation of a metallic capsule containing the magnet is calculated by the viscoplastic finite element method, and the obtained motion of the interface between the capsule and magnet is used as a boundary condition in the distinct element simulation. The motion of grains in mushy-state plane-strain upsetting of a rare earth magnet contained in a steel capsule is chosen as an example of the simulation. The degree of grain alignment due to the upsetting increases as the reduction in height increases. The calculated degree of grain alignment agrees well with that for a model experiment using acrylic resin grains and a plasticine capsule.