In:
MRS Proceedings, Springer Science and Business Media LLC, Vol. 1128 ( 2008)
Kurzfassung:
The ternary Nb-Cr-Al phase diagram exhibits extended phase fields of the cubic C15 and the hexagonal C14 Laves phases Nb(Al x Cr 1-x ) 2 . A number of Nb-Cr-Al alloys were prepared by levitation melting and annealed at temperatures between 1150 and 1450 °C for up to 1500 h. Isothermal sections of the ternary Nb-Cr-Al phase diagram at 1150, 1300 and 1450 °C were obtained from electron probe microanalysis, X-ray powder diffraction and metallographic investigations in order to study the effect of Al on the stability and structure of the Laves phases. The C14 Laves phase in the Nb-Cr-Al system can dissolve up to 45 at.% Al by substituting Cr with Al on the two different crystallographic B -sites 2a and 6h of the C14 AB 2 unit cell. The site occupations of the Al and Cr atoms on these two B -sites were determined by Rietveld analysis using the program FullProf. The experimental site occupation factors were compared to site occupation factors computed by a statistical mechanics approach based on first-principles electronic structure calculations. The experimental as well as the calculated site occupation factors indicate a preferred occupation of the 2a site by Al.
Materialart:
Online-Ressource
ISSN:
0272-9172
,
1946-4274
DOI:
10.1557/PROC-1128-U08-11
Sprache:
Englisch
Verlag:
Springer Science and Business Media LLC
Publikationsdatum:
2008