Influence of the shape of the particles in the solidification of composite materials

The shape of a solidifying interface is generally affected when it encounters foreign inert particles. The degree of deformation depends on the morphology and physical properties of the particles, the melt, the solid and the external fields, affecting the pushing and capture process of the particles. The particle can be trapped by the interface at slower solidification velocity than that predicted by simple models which do not include any deformation of the interface. In all cases this interaction strongly determines the segregation of particles in the microstructure and therefore affecting the physical and physicochemical properties of the final material. In the present report the interaction between particle and interface is analyzed by means of a mathematical model employing the finite element method. The effect on interface shape of different particle shapes and relative thermal conductivities between particle and melt was studied. Thermal field results show that when the particle is more conductive than the melt, the interface is concave. Comparing the concave interfaces for different particle shapes it is observed that, when the particle is not spherical the separation particle-interface at the edge of the particle is the smallest. As a consequence of this phenomenon, which occurs in non-spherical particles, there is a remaining amount of melt between particle and solid which is the last in solidify. (C) 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of SAM/CONAMET 2011, Rosario, Argentina.