Mushy State Behavior: Rheological Characterization and Influence on Air Gap Formation

Abstract

The literature survey about the thermomechanical behavior of the mushy state first demonstrates the lack of data about the rheological parameters for viscoplastic component. Then it shows discrepancies between experimental and modelling studies about the elastic component. In order to fill the gap underlined in the first point, we develop a new methodology which consists in associating a simple test geometry (needle indentation test), able to prduce the suitable strains and strain rates, with an FEM analysis of the induced flow. The thermal dependance of the power creep law (Norton-Hoff) can than be identified. The results obtained for the Al-4.5%Cu-Mg-Ti alloy are presented and applied to the thermomechanical prediction of air gap in permanent mold casting by comparisons of measurements and calculations.