Prediction Model of Rheological Feeding Distance Under Applied Pressure

Abstract

Semisolid rheological technology is an advanced casting process that can significantly refine the microstructure and improve the mechanical properties. However, the influences of fluid flow, solidification shrinkage and effective specific pressure on feeding distance during the semisolid forming process have not been investigated quantitatively. In this work, the one-dimensional (1D) model of limit feeding distance was developed for heterogeneous alloy melt with complex structures, and this alloy melt consisted of three phases including pure liquid phase, pure solid phase, and semisolid phase with the solid–liquid coexistence during pressurized rheoforming. The 1D model of limit feeding distance was derived from the semisolid rheological theory, and built on the basis of rheological feeding mechanism that the excess driving pressure caused sustained rheological feeding of alloy melts. Furthermore, the model covered three kinds of significant parameters including material property parameters, mold structure parameters and process parameters, so that it can be used to analyze the influence of various factors on the rheological feeding ability. In order to verify the theoretical model, the spiral samples of 6066 alloy were made at different velocities by squeeze casting. Moreover, the validity of theoretical model was verified through comparison of the numerical results and the length of samples without shrinkage porosity. The results showed that maximum relative deviation was only 6.8%. In addition, the effects of filling velocity, applied pressure, and the feeding channel initial diameter on the feeding distance were also discussed.