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A Calorimetric Evaluation of the Role of Impurities in the Nucleation of Secondary Phases in 1xxx Al Alloys

Published online by Cambridge University Press:  10 February 2011

C. M. Allen
Affiliation:
Oxford Centre for Advanced Materials and Composites, Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
K. A. Q. O'Reilly
Affiliation:
Oxford Centre for Advanced Materials and Composites, Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
P. V. Evans
Affiliation:
Alcan International Limited, Banbury Laboratory, Southam Road, Banbury, Oxon. OX16 7SP, U.K.
B. Cantor
Affiliation:
Oxford Centre for Advanced Materials and Composites, Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
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Abstract

Superpurity (> 99.995wt% pure) lxxx series Al-0.3wt%Fe-0.lwt% Si alloys with different impurity additions have been melt spun to produce ribbons with microstructures of fine scale ∼0.1–0.2μm diameter secondary phase particles entrained in a higher melting point Al matrix. The melting and resolidification behaviour at 2Kmin−1 of the secondary phase particles while entrained in the solid matrix was monitored using differential scanning calorimetry, to simulate the nucleation of secondary phases in liquid interdendritic regions during the final stages of solidification in casting. The melting and resolidification behaviour of 500ppm V and Zr doped superpurity ribbons is the same as that of a commercial purity ribbon. This indicates that V is responsible for the promotion of the metastable FeAlm phase in the commercial purity ribbon. The presence of FeAlm in direct chill (DC) cast commercial purity alloys indicates that V also influences phase selection in the faster cooled (∼5-10Ks−1) regions of these alloys.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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