Examination and verification of the filtration mechanism of cake mode during the pressure filtration tests of liquid Al–Si cast alloys

The filtration equations at constant pressure were used to examine and verify the filtration mechanism of cake mode during the Prefil Footprinter® tests of liquid Al–Si cast alloys. Although cake mode is the dominant mechanism, the conventional equations have not well described the Prefil curves. The inverse mass flow rate deviates from the linearity with filtrate weight at the initial and terminal transient stages. The deviation at the initial transient stage is probably due to the lack of well-formed cakes. In the terminal transient stage the occurrences of partial and/or complete clogging may cause the deviation. If both the initial and terminal transient stages disappear, the linear relationship tends to hold true over the whole course. For some low filtrate weight melts, however, the deviations from the linearity occur at the steady stage probably due to the compressibility of the formed cake caused by oxide films and non-uniform cake thickness.