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Relating Mechanical Properties with Dislocation Cores in Ni3Ge-Fe3Ge Intermetallic Alloys

Published online by Cambridge University Press:  15 February 2011

T. John Balk ,
Mukul Kumar  and
Kevin J. Hemker
T. John Balk
Affiliation:
Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, MD 21218–2686
Mukul Kumar
Affiliation:
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218–2686
Kevin J. Hemker
Affiliation:
Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD 21218–2686
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Abstract

The transition from positive to negative temperature dependence of 0.2% yield stress is investigated m the model pseudo-binary Ni3Ge-Fe3Ge system. Ni3Ge and Fe3Ge, both Ll2 intermetallic alloys, show complete solid solubility as Fe is continuously substituted for Ni across the composition range. However, Ni3Ge exhibits the yield stress anomaly, whereas the yield stress of Fe3Ge shows a normal decline with temperature. Mechanical testing has verified this behavior, with the anomalous behavior gradually disappearing with increasing Fe content. It is proposed that this transition results from changes in the structure of dissociated superdislocation cores. Alloys with anomalous behavior from this system are characterized by the presence of screw superdislocations locked in the Kear-Wilsdorf (KW) configuration. Conversely, alloys with normal yield stress dependence are observed to contain curvilinear superdislocations that glide on the cube planes. Results from mechanical testing are presented and correlated with TEM observations of deformation structures. These results are discussed in light of planar fault energies determined through computer simulations of images.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 460: Symposium Z – High-Temperature Ordered Intermetallic Alloys VII , 1996 , 641
Copyright
Copyright © Materials Research Society 1997

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References

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