Three-dimensional injection molding simulation of AZ91D semi-solid magnesium alloy

Magnesium alloys are increasingly used in automotive, aeronautic and electronic applications to produce high performance, light weight parts. In the thixomolding process a semi-solid slurry is injected into a mold at controlled temperature such that the melt has specific flow behavior. This allows the fabrication of near net shape components with controlled microstructure and good mechanical properties. The numerical modeling of such applications present unusual challenges for both the physical modelling and the solution algorithm. This paper presents a 3D numerical solution algorithm for the simulation of the injection molding of semi-solid AZ91 magnesium alloys. The methodology deals with the shear thinning, temperature dependent viscosity behavior and is able to accurately solve the high velocity flows encountered during semi-solid magnesium molding. A segregated algorithm is used to solve the Navier–Stokes, energy and front tracking equations. The position of the flow front in the mold cavity is computed using a level set approach. Equations are integrated in time using an implicit Euler scheme and solved by stabilized finite element methods. The approach is applied to the injection of a tensile bar and the results compared with experimental data. The methodology presents the robustness and cost effectiveness needed to tackle complex industrial applications.