Electronic origin of solid solution softening in bcc molybdenum alloys

The intrinsic mechanism of solid solution softening in bcc molybdenum alloys due to 5d transition metal additions is investigated on the basis of ab initio electronic-structure calculations that model the effect of alloying elements on the generalized stacking fault (GSF) energies. We demonstrate th...

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Bibliographic Details
Published in:Physical review letters 2005-04, Vol.94 (13), p.136402-136402, Article 136402
Main Authors: Medvedeva, N I, Gornostyrev, Yu N, Freeman, A J
Format: Article
Language:English
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Summary:The intrinsic mechanism of solid solution softening in bcc molybdenum alloys due to 5d transition metal additions is investigated on the basis of ab initio electronic-structure calculations that model the effect of alloying elements on the generalized stacking fault (GSF) energies. We demonstrate that additions with an excess of electrons (Re, Os, Ir, and Pt) lead to a decrease in the GSF energy and those with a lack of electrons (Hf and Ta) to its sharp increase. Using the generalized Peierls-Nabarro model for a nonplanar core, we associate the local reduction of the GSF energy with an enhancement of double kink nucleation and an increase of the dislocation mobility, and we reveal the electronic reasons for the observed dependence of the solution softening on the atomic number of the addition.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.94.136402