Reactive two-phase flow model for materials in the semi-solid state

摘要

Semi-solid metal alloys have a special microstructure of globular grains suspended in a liquid metal matrix. This particular physical state of the matter can be exploited to produce near-net-shape parts with improved mechanical properties. However, the flow of solidifying metal is complex and associated data are difficult to obtain from experiments, which complicated the understanding of the material for application in the casting industry. This paper describes a reactive two-phase mixture model for semi-solid slurries, which accounts for phase relative motion and phase conversion. It assumes that the processing material can be regarded as a solidifying binary alloy in a state of local equilibrium. The coupling force between the phase is derived on the assumption that the slurry is a fluid saturated isotropic media. The proposed methodology is implemented in a finite element code. The constitutive equation is derived from a set of experimental rheological data. The model is then used in a simple test case, The resulting flow and associated segregation patterns obtained are encouraging. However, further numerical experiments, to enhance the stability of the solution, as well as a thorough validation procedure are required before the model can be used properly to predict the real process.