A rheological assessment of the effect of trace level Ni additions on the solidification of Sn-0.7Cu

The influence of trace level Ni additions on the eutectic solidification mode of Sn-0.7Cu has been studied using continuous torque experiments during solidification. The solid fraction at which resistance to paddle rotation at the thermal centre of the sample occurs is related to the spatial distribution of solid during solidification. The results indicate that a transition in solidification mode occurs in the range 0-300 ppm Ni. Growth occurs antiparallel to heat flow from near the mould walls in the Ni-free alloy, while equiaxed growth from distributed centres dominates in alloys containing at least 300 ppm Ni. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.