The Y–Ni–Cu ternary system at 600°C

The isothermal section of the Y–Ni–Cu phase diagram at 600°C has been investigated by means of X-ray diffraction and microstructure analyses. The homoge neity ranges of the solid solutions YNi 5-хCuх (0 ≤ х ≤ 4.6) (structure type CaCu5, space group P6/mmm a = 0.48861(2)–0.50080(4), c = 0.39592(2)–0.40740(4) nm), Y2Ni17-хCuх (0 ≤ х ≤ 7.8) (structure type Th2Ni17, space group P63/mmc, a = 0.8314(1)–0.8387(1), c = 0.8042(1)– 0.8117(1) nm), YCu6–7Nix (0 ≤ х ≤ 0.28) (structure type TbCu7, space group P6/mmm, a = 0.49470(4)– 0.49540(4), c = 0.4133(4)–0.4227(4) nm) were refined. It was fou nd that the maximal solubility of the third component does not exceed 3.8 at.% in Y 2Cu7 and less than 1 at.% in Y2Ni7, YCu, and YCu4. The crystal structure of a single crystal of composition YNi 4Cu (YNi5-хCuх solid solution) was investigated by X-ray diffraction: a = 0.4899(2), c = 0.3979(3) nm, R1 = 0.028 for 57 independent reflections with Io ≥ 2σ(Io), wR2 = 0.058. A new ternary compound, YNi 2.85–0.75Cu1.15–3.25, of unknown structure with an extended homogeneity range, was found.