Primary dendrite spacing I. Experimental studies

Abstract

Directional solidification experiments have been carried out to study primary dendrite spacing of lead dendrites in Pb-Sn alloys over a very wide range of temperature gradient, G, solidification rate, V, and alloy composition. Based on these experiments, the primary dendrite spacings, λ, is found not to obey the correlation λ= KG - a V - b over a wide range of velocity and gradient values. For a constant V, λ is found to decrease as G is increased, and only for high velocity values is a correlation of the form λ= AG - a obtained. Even in this case the exponent a is found to be a function of velocity. Furthermore, for a given G, λ appears to go through a maximum as a function of velocity.