THE EFFECT OF THE DIFFUSION OF SOLUTE BETWEEN THE PARTICLE AND THE INTERFACE ON THE PARTICLE PUSHING PHENOMENA

Interaction between moving solid/liquid interfaces and particles durin g solidification of alloys has been analyzed. A particle pushing crite rion which incorporates the diffusion of the solute between the partic le and the interface is proposed. In addition, the stability of the in terface behind the particle is discussed. The shape of the interface b ehind the particle was obtained in terms of the ratio of the diffusion coefficient of the solute to the velocity of the interface (D/V). Bas ed on this, the critical interface velocity was calculated under stead y slate conditions. It was found that the concentration of the solute behind the particle increases with increasing the interface velocity; in addition at high interface velocity the curvature of the interface is independent of interface velocities. It was found that the critical interface velocity under steady state conditions is one order lower t han the critical interface velocity calculated numerically by Wu et al . in Al-Si alloy containing SiC particles. (C) 1998 Acta Metallurgica Inc.