Effect of Mg loss on the kinetics of pressureless infiltration in the processing of Al-Si-Mg/SiCp composites

The effect of magnesium loss on the kinetics of infiltration of cylindrical SiCp porous preforms by an Al-Si-Mg alloy was investigated. Infiltration of SiCp preforms is preceded by an incubation period, which is significantly dependent on temperature, with incubation time decreasing as temperature increases. The activation energy required to initiate infiltration is 637.2 kJ/mol. The cross-sectional area of the cylindrical preform infiltrated can be predicted by a linear regression equation. Results also show that temperature is the process parameter that most significantly affects the degree of infiltration and that the combined effect of the parameters, time and temperature, is negligible. Magnesium is lost in significant amounts during the infiltration process; a plateau or arrest observed in the infiltration kinetics curves is attributed to Mg depletion at the infiltration front. At temperatures above 1050 degreesC, the beneficial effect of magnesium is diminished and the reactivation of infiltration in the final step is attributed only to the increase in temperature. (C) 2002 Elsevier Science B.V, All rights reserved.