Abstract
A computer simulation was used to study the influence of particles on microsegregation during solidification. Particles in the melt can affect the solidification microstructure by changing the cooling curves, acting as barriers to solute diffusion, reducing the metal volume, affecting the coarsening process, etc. The computer simulation model used in the present work calculates the effect of particles of different thermal properties on the cooling curves and the consequent changes to microsegregation and dendrite arm spacing. The microsegregation calculations are valid for cases where the interparticle spacing is much smaller than the dendrite arm spacing. By using the simulation, it was possible to study various contributing factors in isolation as well as in combination so that the relative significance of each factor could be evaluated. It was observed that the reduction of liquid volume by the presence of the particles was the largest contributing factor to the influence of particles on the solidification microstructure. Thus, the changes in matrix microstructure of cast metal matrix composites depend more on the volume fraction of the reinforcing particles than on the properties of the particles themselves. Irrespective of the thermal properties of the particles, the dendrite arm spacing and microsegregation in the composite matrix was seen to be less than in the unreinforced alloy solidified under the same external conditions.
MST/3405
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