Process optimisation for a squeeze cast magnesium alloy metal matrix composite

The paper reports the influence of process variables on a zirconium-free (RZ5DF) magnesium alloy metal matrix composite (MMC) containing 14 vol.% Saffil fibres. The squeeze casting process was used to produce the composites and the process variables evaluated were applied pressure, from 0.1 MPa to 120 MPa, and preform temperature from 250 °C to 750 °C. The principal findings from this research were that a minimum applied pressure of 60 MPa is necessary to eliminate porosity and that applied pressures greater than 100 MPa cause fibre clustering and breakage. The optimum applied pressure was established to be 80 MPa. It was also established that to ensure successful preform infiltration a preform temperature of 600 °C or above was necessary. For the optimum combination of a preform preheat temperature of 600 °C and an applied pressure of 80 MPa, an UTS of 259 MPa was obtained for the composite. This represented an increase of 30% compared to the UTS for the squeeze cast base alloy.