Abstract:
Composite materials with their well-known advantages have found widespread usage in various engineering applications. The metal matrix composites are, perhaps, the most important class among composites for automobile and aerospace applications because of their excellent mechanical and lubricating properties especially at high temperatures. During centrifugal casting of Aluminum melts containing suspended ceramic particles, segregation of the particles occurs either to the outer or to the inner periphery of the casting depending on their relative density compared to that of the melt. An one dimensional heat transfer model coupled with equations for force balance on particles is developed to predict the temperature distribution in the casting and mold regions, solidification time of the casting and particle distribution in the casting region. The model takes into consideration propagation of solid-liquid interface and movement of particles due to centrifugal acceleration which takes place either in opposite or in the same direction as the solidification front depending on the relative density difference between particles and melt. The solution of the model equations has been obtained by pure implicit finite difference technique with modified variable time step (MVTS) approach.
The effects of various parameters like particle size, mold rotational speed, relative density difference between melt and particle, etc. on segregation of particles and solidification time have been studied. It is noted that for a given set of operating conditions, the thickness of the particle rich region decreases with the increase in rotational speed of the mold, particle size, relative density difference between the particle and melt, and the melt superheat. When the interfacial heat transfer coefficient at the metal-mold interface is considered, the solidification time increases with decrease in heat transfer coefficient. Consequently, the thickness of the particle rich region decreases and hence, more intense particle segregation obtained in metal matrix.
