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Structural transformations and improved ductility in ordered FeCo and ZrCo intermetallics

Published online by Cambridge University Press:  26 February 2011

Maja Krcmar ,
Chong Long Fu  and
James R. Morris
Maja Krcmar
Affiliation:
krcmarm@ornl.gov, Grand Valley State University, Physics, One Campus Drive, PAD 144, Allendale, MI, 49401-9403, United States, (616)331-3004
Chong Long Fu
Affiliation:
cfu@ornl.gov, Oak Ridge National Laboratory, Materials Science and Technology Division, P.O.Box 2008, Oak Ridge, TN, 37831, United States
James R. Morris
Affiliation:
morrisj@ornl.gov, Oak Ridge National Laboratory, Materials Science and Technology Division, P.O.Box 2008, Oak Ridge, TN, 37831, United States
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Abstract

Using the first-principles calculations, we find that Fe-Co has a tendency for a structural transformation to a lower symmetry sheared L10 phase under the applied shear stresses. This tendency for structural transformation can have a significant influence on the mechanical properties of FeCo, as it might be closely connected with the intrinsic brittleness of Fe-rich and stoichiometric FeCo alloys and with the improved ductility of Co-rich FeCo alloys. We suggest that improved ductility in Co-rich FeCo alloys may originate from transformation toughening due to the B2→L10 structural transformation near the regions of high stress concentration, as the stress energy is fully dissipated by the decrease in the electronic energy due to the structural phase transformation into a lower energy structure. Similarly, in ZrCo, our first-principles calculations find that a B2→B33 martensitic phase transformation can occur under the applied shear stress, which may contribute to the good ductility of this alloy, despite the fact that ZrCo is a strongly ordered line compound.

Keywords

ductilityelectronic structurealloy
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 980: Symposium II – Advanced Intermetallic-Based Alloys , 2006 , 0980-II02-03
Copyright
Copyright © Materials Research Society 2007

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