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Microstructure Control in Iron Aluminides by Phase Decomposition or by Mechanical Alloying for Improved Strength and Ductility

Published online by Cambridge University Press:  15 February 2011

D. G. Morris
Affiliation:
Institute of Structural Metallurgy, University of Neuchâtel, Avenue de Bellevaux 51, NEUCHATEL 2000, SWITZERLAND
S. Gunther
Affiliation:
Institute of Structural Metallurgy, University of Neuchâtel, Avenue de Bellevaux 51, NEUCHATEL 2000, SWITZERLAND
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Abstract

The iron aluminides based on Fe3Al or FeAl being developed for intermediate temperature applications suffer from mediocre room temperature strength and ductility and poor high temperature tensile and creep strength. Attempts to overcome these problems have been restricted by the limited possibilities of structure modification by, for example, precipitation of stable strengthening particles. The present study examines two approaches to obtaining two-phase mixtures for improved strength and ductility: by adjusting chemical compositions such that two-phase order-disorder (α-α″) mixtures are obtained, and by mechanical alloying. Two-phase α-α″ mixtures are obtained by heat treatment of Fe-Al alloys with Al content near 20–24% and in ternary Fe-Al-Si alloys with suitably adjusted Al and Si contents. Microstructures of such alloys can be modified during heat treatments by ordering, precipitation or decomposition, and two-phase mixtures similar to those in the γ-γ superalloys obtained. Such two-phase alloys show good high temperature tensile and creep strength with some indication of reasonable ductility and reduced environmental sensitivity. Mechanical alloying can easily produce FeAl alloys of fine grain size reinforced with stable oxide particles. These structures lead to high room temperature strength with some ductility: controlled recrystallization can significantly modify both strength and ductility.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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