Numerical simulation of die filling in semisolid metal processing

Abstract

Semisolid Metal Processing offers distinct advantages over other near-net-shape technologies, such as a more homogeneous microstructure, less porosity and thus excellent mechanical properties. A perfect control of die filling during processing is however necessary, especially in the case of semisolid forming of aluminum, where a non-controlled die filling can lead to oxide inclusions. Numerical simulation can be used to predict die filling, and hence used to optimize the die design. However, the constitutive behavior of semisolid metals is quite complex. The non-Newtonian behavior depends not only on the volume fraction of liquid, but also on the metal's history prior to processing, and the processing conditions. In this paper, a `Bingham type', or Herschel-Bulkley constitutive relation is presented, capable of describing correctly the bulk rheological behavior of the semisolid slurry. This constitutive equation is introduced in a modified version of the casting simulation package SIMULOR. Simulations for the filling of 2-D and 3-D cavities under various processing conditions are shown. Issues related to die design using numerical simulation are also addressed.