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A Dislocation Constriction, Pinning Point Model for the Flow Stress Anomaly in Iron Aluminides

Published online by Cambridge University Press:  10 February 2011

David G. Morris
David G. Morris*
Affiliation:
Institute of Structural Metallurgy, University of Neuchâtel, 2000 Neuchâtel, Switzerland
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Abstract

Iron aluminides with compositions from Fe3A1 to FeAl show an anomalous stress rise at temperatures about 600–800K. Many models have been suggested to explain this behaviour, with the suggestion of hardening by vacancies presently receiving much attention. An alternative model is suggested here, valid for those alloys where the simultaneous reduction of DO3order does not interfere, based on the density of constrictions produced on mobile <111> superdislocations and their subsequent pinning by decomposition or by their cross slip to produce jogs. The exponential increase in stress with temperature can be related to the pinning point density and the absolute values of strengthening correspond well with those predicted by this model. The orientation dependence of the stress anomaly and the tension-compression asymmetry can be related to the role of shear stresses in assisting constriction of the dislocation partials by modifying the core configuration and by assisting the expansion of the new, decomposed dislocations.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK4.3.1
Copyright
Copyright © Materials Research Society 1999

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