EFFECT OF MELT, SOLIDIFICATION AND HEAT-TREATMENT PROCESSING PARAMETERS ON THE PROPERTIES OF AL-SI-MG SIC(P) COMPOSITES/

With the recent renovations in casting technology and foundry procedur es, Al-Si-Mg alloys reinforced with SiC particulates are being increas ingly employed in automotive and aerospace applications. The SiC reinf orcement particles influence the solidification process in various way s, affecting the fluidity and castability of these composites. This ar ticles reviews the results of an extensive study carried out on differ ent aspects of Al-Si-Mg/SiC(p)-type metal-matrix composites containing 7 or 10 wt % Si, reinforced with either 10 or 20 vol% SiC particulate s. Aspects investigated include the castability and soundness in terms of melt fluidity, the effect of the solidification rate and of inclus ions on the mechanical properties, and optimization of the heat-treatm ent parameters with regard to these properties. The influence of the p rocessing parameters on the mechanical properties was determined by mo nitoring the microstructural changes taking place during the various s tages of processing, by measurements of the dendrite arm spacing, poro sity and SiC-particle content and distribution in the castings obtaine d, as well as the amount of oxide inclusions and other harmful reactio n products such as Al4C3 present therein. The effect of employing the fluxing procedure commonly used in Al-Si-Mg alloys on the mechanical p roperties of one of the four composites studied is also reported.