Effect of solute convection on the primary arm spacings of Pb–Sn binary alloys during upward directional solidification

In this article, in order to investigate the effect of solute convection on the primary arm spacings of Pb–Sn binary alloys, upward directional solidification experiments have been carried out under the condition of 1×g. The primary arm spacings have been measured with the increase of fraction solidified. Results show that the primary arm spacings of hypoeutectic Pb–Sn binary alloy changed with increase of fraction solidified and the peak of distribution of primary arm spacings was shifted to the field of the narrower spacings with the increase of fraction solidified. It has been noted that the average of spacings decreased with the increase of fraction solidified. Mechanism of tip splitting of primary dendrite arm was found to be responsible for the change of the primary arm spacings with the increase of fraction solidified.