Ma. Easton et Dh. Stjohn, A model of grain refinement incorporating alloy constitution and potency of heterogeneous nucleant particles, ACT MATER, 49(10), 2001, pp. 1867-1878
A model for the determination of relative grain size is developed based on
the assumption that nucleant substrates are activated by constitutional und
ercooling generated by growth of an adjacent grain. The initial rate of dev
elopment of constitutional undercooling is shown to be equivalent to the gr
owth restriction factor and is a useful approximation for the effect of sol
ute on grain size when potent nucleant substrates are present. However, whe
n the nucleants are of a poor potency then a calculation of the fraction so
lid necessary to develop the constitutional undercooling required for nucle
ation needs to be performed. Using the model, trends in grain size observed
experimentally by the addition of titanium to pure aluminium and to a typi
cal casting alloy, AlSi7Mg0.3, can be predicted. II was also found that sum
ming the individual growth restriction factors of each solute element in a
multi-component alloy can grossly overestimate the actual value of the grow
th restriction factor for the alloy. (C) 2001 Acta Materialia Inc. Publishe
d by Elsevier Science Ltd. All rights reserved.