FLUIDITY OF ALUMINUM-ALLOY ALSI7MG-SIC PARTICULATE COMPOSITE MELTS

A spiral test was used to evaluate the flowability of an AlSi7Mg0.6 al loy reinforced via 10-30 vol.-%SiC particles having average diameters of 9, 13, and 23 mu m. The results show that the composite melt has th e same ability to flow into long thin sections as unreinforced alumini um, when the particle contents is < 20 vol.-%. The flowability of the particulate metal matrix composite is significantly reduced for partic le volume fractions > 20 vol.-% and approaching 30 vol.-% as a result of increased viscosity. At these higher levels of SiC, an increase in pouring temperature cannot compensate for the reduced flowability. The particle distribution in the solidified material depends on the lengt h which the metal flows before solidification. After 150-200 mm of flo w, dendritic grains growing in the composite melt push the particles s o that the solidified microstructure consists of open areas without pa rticles. The particle free areas increase in diameter with the flow di stance. (C) 1994 The Institute of Materials.