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Formation and Thermal Stability of Quasi Crystalline and Other Metastable Al-RICH Al-Mn Phases

Published online by Cambridge University Press:  25 February 2011

M.X. Quan  and
B.C. Giessen
M.X. Quan
Affiliation:
Materials Science Division, Barnett Institute, Northeastern University, Boston, MA 02115
B.C. Giessen
Affiliation:
Materials Science Division, Barnett Institute, Northeastern University, Boston, MA 02115
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Abstract

RSP of Al-rich Al-Mn alloys is known to produce several metastable phases, including (with increasing Mn content) supersaturated Al solid solution and two non-crystallographic phases, identified in the literature as an icosahedral phase (I) and a (probably) decagonal phase (T) with translational symmetry in one direction. The formation of these phases in the composition range from 8 to 30 at. pct. Mn has been studied in melt-spun and arc-furnace quenched alloys. The thermal transformation characteristics of all metastable phases were measured by DSC; transformation temperatures, enthalpies and activation energies were determined. At compositions from 17 to 20 at. pct. Mn, two transformations were observed. Noteworthy results include: smeared out (slow-onset) reactions, transformation temperatures dropping sharply toward lower Mn contents, transformation enthalpies rising steeply in the same range, and activation energies ranging from ~40 kcal/gmol for the low-temperature process (at ~763 K) to ~80 kcal/gmol for the high temperature process (~883 K).

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 58 , 1985 , 241
Copyright
Copyright © Materials Research Society 1986

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Footnotes

*

Communication No.280 from the Barnett Institute

References

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