Effect of particle size and Mg content on the processing parameters of Al-Si-Mg/SiCp composites processed by pressureless infiltration

The effect of the following processing parameters, namely SiC particle size (20 and 75 mu m) and Mg content (3 and 6 wt.%), on residual porosity and on the degree of infiltration for SiCr, preforms by Al-Si-Mg alloys were investigated and quantified (here the subscript p means particles). The contribution of each of these parameters to the infiltration mechanism was determined employing an analysis of variance (ANOVA), and the effect of the levels of each parameter was examined using a surface response analysis. ANOVA results show that particle size is the parameter that most significantly affects the degree of infiltration and residual porosity. A surface response analysis shows that the degree of infiltration increases with an increase in magnesium content. The increasing rate in the degree of infiltration is higher for 20 mu m than for 75 p.m of SiC, whereas residual porosity diminishes with decreasing particle size; these two effects occur for both Mg concentrations in the alloy. Accordingly, the optimum parameters for a maximum degree of infiltration as well as for a minimum residual porosity are 20 mu m SiC powders and 6 wt.% Mg in the alloy.