Development of dendrite array growth during alternately changing solidification condition

Abstract

To investigate competitive growth in a dendrite array a directional solidification study was carried out on a succinonitrile–acetone alloy. In the experiment the temperature gradient G applied is alternately altered over a wide range, increased from a lower to a higher limit, and then decreased back to the lower one. It was found that source dendrites, i.e. parent dendrites, are not superior to derived dendrites in terms of growth competition. The orientation deviation between neighbouring dendrites impacts both local dendrite creation and elimination. At lower gradients, the new dendrites grow out from the ternary arms, while at the higher gradients new dendrites originate directly from the secondary arms. During increasing and decreasing G, average primary dendrite spacing λ measured traces out different paths, revealing an unclosed hysteresis loop in the λ– G-diagram.