Density functional theory was employed to investigate the grain boundary (GB) property of W-TM alloys (TM: fifth and sixth row transition metals). GB strengthening was found for Hf, Ta, Nb, Ru, Re, Os and Ir for S27{525} and to a lesser degree for S11{323}. Lower valence solutes strengthen the GB at certain substitutional sites, while higher valence elements enforce it at other positions. For S3{112}, the alloys exhibit reduced cleavage energies. Hence, allowing with TMs increases the GB cohesion more effectively for large-angle GBs whose cleavage energy is, in general, inherently lower than the low-angle ones. Electron density analysis elucidates the mechanism of charge addition or depletion of the GB bonding region upon TM substitution at various positions leading to stronger or weaker intergranular cohesion, respectively.
Revised: August 28, 2012 |
Published: April 17, 2012
Citation
Setyawan W., and R.J. Kurtz. 2012.AB INITIO STUDY OF GRAIN BOUNDARY PROPERTIES OF TUNGSTEN ALLOYS. In Fusion Reactor Materials Semiannual Progress Report for the Period Ending December 31, 2011. 59-63. Oak Ridge, Tennessee:Fusion Reactor Materials Program, US Department of Energy.PNNL-SA-85573.