Pressure filtration tests of liquid Al–Si cast alloys: I. Flow behaviour

The flow behaviour during the Prifil Footprinter® tests of liquid Al–Si cast alloys has been investigated for the first time using the first and second derivative methods. The first derivative approach is recommended as the preferred method to determine the transitional points. At the initial transient stage flow rate decreases with filtration time. Higher quality liquid metal usually exhibits a shorter, or even no observable transient period. However, there remains some uncertainty of this conclusion, probably due to the variable waiting periods for the attainment of a designated temperature requirement prior to starting the filtration tests. During the steady state flow rate decreases linearly with filtration time and the second derivative values are around zero. At the initial and terminal transient states a periodic flow mode was also observed. The primary intermetallics possibly precipitated and sedimented prior to or during the tests may significantly influence the filtration behaviour.