Фазовая диаграмма системы Nb-Ti
К оглавлению: Другие диаграммы (Others phase diargams)
Nb-Ti (Niobium-Titanium)
J.L. Murray
The assessed Ti-Nb phase diagram does not differ qualitatively from previous
evaluations [Hansen, Elliott, Shunk]. The stable equilibrium diagram is
without invariant reactions, congruent transformations, or critical points.
[51Han] examined heat treated alloys microscopically for signs of incipient
melting; an uncertainty of с25 C was assigned to the data based on the
temperature interval examined. [69Rud] and [69Zak] made optical observations
of incipient melting: an uncertainty of с20 C is estimated for Ti-rich alloys
and somewhat more for the Nb-rich alloys. Experimental data are not available
for the liquidus because of the narrow melting range. The liquidus was
estimated by thermodynamic calculations, with an uncertainty of probably no
more than с2 at.%.
[64Bro] determined the (bTi,Nb) transus by resistivity measurements on cooling
and verified the results by rapid quenching experiments [66Bro]. The results
of [64Bro] and [66Bro] showed the transus to be lower in temperature than
previous determinations by as much as 150 C at 25 at.% Nb. Rapid quenching
methods have been shown to be necessary to determine the (bTi,Nb) transus. The
effect of sample contamination is also to raise the apparent temperature of
the transus.
The present assessment is therefore based primarily on the work of [64Bro] and
[66Bro]. The assessed phase boundary is placed somewhat above the resistivity (
cooling) results. The recent determination of the volume fractions of (aTi)
and (bTi,Nb) in equilibrium at 400 C [82Gus] supports placing the equilibrium
(bTi,Nb) transus somewhat above the resistivity results.
(bTi,Nb) can transform martensitically during quenching to the cph (a›Ti) form
for low Nb content or to an orthorhombic distortion of the cph form (a›Ti) for
higher Nb content.
The metastable w phase can form either during quenching from the (bTi,Nb)
field or during aging at temperatures below about 450 C. As-quenched w is
found in the approximate composition range 13 to 18 at.% Nb [58Bag, 69Hic]. [
69Hic] found w in the range 9 to 30 at.% Nb after aging at 450 C. [80Osa]
proposed a wider range on the Nb-side; w was found in a 36 at.% Nb alloy, but
the precipitation was very slow. During aging, the (bTi,Nb) matrix is depleted
in Nb, and a metastable two-phase equilibrium between w and (bTi,Nb) is
approached. Based on lattice parameter data, [69Hic] found compositions of 9
to 30 at.% Nb for w and (bTi,Nb), respectively, at 450 C.
[73Afo] studied w phase formation in 10 and 20 at.% Nb alloys under pressure;
w phase was formed at 30 and 50 kbar, respectively. Using a shock wave of
amplitude 320 с 20 kbar, [79Sik] also produced w in 10 and 20 at.% Nb alloys
previously annealed in the two-phase (bTi,Nb) + (aTi) region.
51Han: M. Hansen, E.L. Kamen, H.D. Kessler, and D.J. McPherson, Trans. AIME,
191, 881-888 (1951).
58Bag: Yu.A. Bagariatskii, G.I. Nosova, and T.V. Tagunova, Dokl. Akad. Nauk
SSSR, 122, 593-596 (1958) in Russian; TR: Sov. Phys. Dokl., 3, 1014-1018 (1958)
.
64Bro: A.R.G. Brown, D. Clark, J. Eastabrook, and J.S. Jepson, Nature, 201,
914-915 (1964).
66Bro: A.R.G. Brown and K.S. Jepson, Mem. Sci. Rev. Metall., 63(6), 575-584 (
1966) in French.
69Hic: B.S. Hickman, Trans. Metall. Soc. AIME, 245, 1329-1335 (1969).
69Rud: E. Rudy, Tech. Rep. AFML-TR-65-2, Part V, Wright Patterson Air Force
Base (1969).
69Zak: A.M. Zakharov, V.P. Pshokin, and A.I. Baikov, Izv. V.U.Z. Tsvetn.
Metall., (6), 104-108 (1969) in Russian.
73Afo: N.S. Afonikova, V.F. Degtyareva, Yu.A. Litvin, A.G. Rabin'kin, and Yu.A.
Skakov, Fiz. Tverd. Tela, 15, 1096-1101 (1972) in Russian; TR: Sov. Phys.
Solid State, 15(4), 746-749 (1973).
79Sik: V.N. Sikorov and V.F. Degtyareva, Fiz. Metal. Metalloved., 48(1), 211-
213 (1979) in Russian; TR: Phys. Met. Metallogr., 48(1), 181-182 (1979).
80Osa: K. Osamura, E. Matsubara, T. Miyatani, Y. Murakami, T. Horiuchi, and Y.
Monju, Titanium '80, Sci. Tech., Proc. 4th Int. Conf. Titanium, Kyoto, Japan,
1369-1377 (1980).
82Gus: L.N. Guseva and L.K. Dolinskaya, Dokl. Akad. Nauk SSSR, 266(3), 634-637
(1982) in Russian; TR: Dokl. Chem., 334-337 (1982).
Published in Phase Diagrams of Binary Titanium Alloys, 1987. Complete
evaluation contains 6 figures, 3 tables, and 44 references.
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