Effect of the presence of SiCp on dendritic coherency of Al-Si-based alloys during solidification

In order to explore the effect of the presence of SiC particles on dendritic coherency during solidification of Al-Si based metallic alloys, a factorial fractional two levels experimental design was implemented to allow an identification of the main effects of the particle content, silicon content, grain refinement, and cooling rate on the solid fraction at coherency. This solidification parameter was determined for Al-3wt%Si and Al-7%Si alloys, and Al-3%Si/SiCp and Al-7%Si/SiCp metal matrix composites. The cooling process during solidification was monitored by performing cooling curve measurements at two radial locations within samples poured into cylindrical molds at two cooling rates. The experimental cooling curves were numerically processed by the Fourier thermal analysis method to know the evolution of solid fraction as a function of time. The effect of grain size was included using samples with or without grain size refinement. The grain refinement was obtained by adding predetermined quantities of TiAlB master alloy. It was found that presence of SiC particles affects the coherency point of the metal matrix composites increasing the solid fraction at coherency. However this effect is relatively small when compared to the effect of grain refinement, cooling rate, and Si content on dendritic coherency of experimental probes.