Abstract
A procedure based on nucleation theory has been developed to predict the formation of primary phases in liquid quenched Al–Cr and Al–Zr alloys as a function of powder size, heat extraction, and cooling rate in an idealised gas atomiser. The theory predicts that (i) with decreasing powder size/increasing cooling rate there will be a preferential suppression of the intermetallic compounds in favour of α-Al and (ii) there will be a hierarchy for the suppression of the various intermetallic phases. Both effects arise from differences in entropy of fusion of the competing phases and are in agreement with experiment. Maps of predicted rate limiting phase versus composition and powder diameter are presented.
MST/718
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