Permeability measurements of the flow of interdendritic liquid in equiaxed aluminum-silicon alloys

Abstract

A method developed recently for measuring instantaneous permeability in the mushy zone of aluminum-copper alloys is used to measure permeability in aluminum-silicon alloys. Permeability was also measured in packed glass beads using water, because measurements could be conducted in the absence of microstructural coarsening. Experimental data are compared with the Kozeny-Carman equation to determine the value of kC, the Kozeny-Carman constant. The results indicate that when kC=5.0, all the instantaneous permeability data agree well with the Kozeny-Carman equation. Factors affecting the accuracy of permeability measurements, such as surface oxidation of the sample, flow channeling during the test, microstructural coarsening, and liquid fraction reduction due to back diffusion in the solid are discussed. An experimental technique that minimizes errors due to these factors is outlined.