Melting and casting characteristics of aluminum alloy A356-silicon carbide particulate reinforced cast composites

This thesis principally reports studies on melting and casting characteristics of aluminum A356 (Al 7% Si) alloy reinforced with 10, 15, and 20 volume percent silicon carbide particles. Remelting followed by holding and solidification of these aluminum based composites leads to settling of the SiC particles to the bottom of the mold. The height of the SiC particle-free zone formed at the top of the mold, as a result of settling, is referred to as the denuded zone. Aluminum A356 alloy with 20 volume percent silicon carbide ({dollar}sim{dollar}14 microns particle size) showed larger denuded zones for a given settling time compared to Al-A356 alloy system with 10 or 15 vol.% SiC. The latter contained smaller ({dollar}sim{dollar}9 microns) SiC particles, indicating a stronger influence of particle size on the hindered settling of particles than its volume fraction.; The permanent mold and sand mold spiral fluidities, and permanent mold casting fluidity of Al A356-SiC particle melt slurry generally decrease with increasing volume percent of a given size SiC. The fluidity values increase with temperature until a temperature range of 740-760{dollar}spcirc{dollar}C; above this temperature range the fluidity shows no significant increase. The fluidity test results indicate that the particle size, chemistry and shape influence the fluidity length of the composite slurry.; The heat transfer model developed to predict the length of fluidity spiral of monolithic metals has been applied to A356-SiC particulate composites. This model predicts a linear increase in fluidity with increasing temperature and a decrease in fluidity with increasing volume percentage of silicon carbide particles of a given size. The predictions are in qualitative agreement with the experimental observations at temperatures up to 760{dollar}spcirc{dollar}C for alloys containing SiC particles of a given size.; In addition, the solidification microstructures formed during static settling and during flow along the length of the casting fluidity for Aluminum-SiC particle composites have been analyzed in the context of particle settling during the flow of the slurry in the fluidity channels and particle pushing by dendrites during solidification. Influences of cooling rate, settling time, and oxide films on solidification microstructures of composites have been investigated. (Abstract shortened with permission of author.)...