Research on pressure loss and filling ability of semi-solid rheological behavior in squeeze casting

Abstract

The filling ability of semi-solid melt under pressure is significant for improving the dimensional integrity of thin-walled and thin-rod parts with complex structures via squeeze casting. The semi-solid rheological behavior involves many physical characteristics, e.g., heat conduction, phase change, apparent viscosity, pressure loss, and rheological shear, and has a crucial effect on the filling ability. In this study, Archimedes spiral samples of A356 alloy were used to investigate the filling length variation with the squeeze pressure and filling speed during squeeze casting. According to the calculation of the characteristic temperature distribution during the alloy melt filling process, the melt state was determined, and the spiral filling was confirmed to be a semi-solid rheological behavior. The stop filling of the semi-solid melt directly contributed to the pressure loss, which was mainly affected by the apparent viscosity determined by the alloy melt’s temperature distribution and filling speed in the channel. Prediction models of the pressure loss and filling length were established based on steady-state heat-fluid coupling rheological behavior to determine the minimum critical squeeze pressure and avoid insufficient filling. The agreement between the results of the theoretical calculations and experimental measurements demonstrated that the models could be used to quantitatively characterize the filling ability of alloy melt during the squeeze casting.