Phase equlibria
in the {Y, Gd}–Ni–Al ternary systems in the 65-100 at.% Al range at 773 K: a reinvestigation
Chem.
Met. Alloys 3
(2010) 208-219
https://doi.org/10.30970/cma3.0171
Taras MIKA,
Bogdan KOTUR
The phase equilibria
in the Al-rich region of the {Y, Gd}–Ni–Al
ternary systems at 773 K have been reinvestigated using XRD, microstructure and X-ray microprobe analysis. Four intermetallic compounds: 1 - R3Ni5Al19 (structure type Gd3Ni5Al19),
2 - R4Ni6Al23
(Y4Ni6Al23), 3 - RNi3Al9 (YNi3Al9) and 4
- RNiAl4 (YNiAl4),
exist in both systems. It was shown that the thermodynamic equilibrium state of
the samples could be reached after a relatively long heat treatment (up to four
months). This is probably the main reason for some contradictions in the
literature on the {Y, Gd}–Ni–Al phase diagrams.
The crystal structure of the Y3Ni5Al19 ternary
compound (Gd3Ni5Al19 type, space group Cmcm) was refined
by the Rietveld method from powder X‑ray
diffraction data. The refined cell parameters are a = 0.40713(1) nm, b = 1.5957(3) nm, c = 2.7052(6) nm.
Isothermal cross-section of the Y–Ni–Al ternary system at 773 K, nominal composition of some alloys and their numbers are according to [10]. Ternary compounds: 1 – Y4Ni6Al23, 2 – YNiAl4, 3 – YNi3Al9.
Keywords
Rare-earth ternary systems / Phase equilibria / Intermetallic
compounds