B-Nb (Boron-Niobium)

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Supplemental Literature Review: Section III

B-Nb (Boron-Niobium) H. Okamoto

The B-Nb phase diagram in [Massalski2] was redrawn from [Moffatt], which was based on [1959Now], with an additional phase B6Nb5 found later and minor modiﬁcations in phase boundaries for thermodynamic consistency. [2003Bor] reexamined the B-Nb system in the 50100 at.% Nb range and observed (1) no liquid formation during heat treatment of as-cast alloys at 1700 °C, (2) the existence of L = BNb + (Nb) eutectic reaction at 84 at.% Nb, and (3) the existence of BNb + (Nb) = B2Nb3 peritectoid reaction. This result is consistent with the B-Nb phase diagram reported by [1969Rud]. Figure 1 is drawn by compromising the data of [1959Now], [1969Rud],

and [2003Bor]. All invariant temperatures must be conﬁrmed experimentally. References 1959Now: H. Nowotny, F. Benesovsky, and Kieffer, Contribution to the Conﬁguration of the Niobium-Boron and Tantalum-Boron Systems, Z. Metallkd., 1959, 50, p 417-423 in German 1969Rud: E. Rudy, Compounds of Phase Diagram Data, AFML-TR-652, Part V, Air Force Materials Lab.. Wright Patterson AFB, OH, 1969 2003Bor: L.A. Borges, Jr., G.C. Coelho, C.A. Nunes, and P.A. Suzuki, New Data on Phase Equilibria in the Nb-rich Region of the Nb-B System, J. Phase Equilibria, 2003, 24(2), p 140-146

Weight Percent Niobium 0 20 40 50 60

70

80

90

100

3200 3000

L

2800

2469°C 2400 ? 2200

(Nb)

B2Nb3

BNb

(βB)

1600

B6Nb5

1800

B4Nb3

84

2092°C 2000 B2Nb

Temperature,°C

2600

1400 0

B

10

20

30

40

50

60

70

80

Atomic Percent Niobium

90

100

Nb

Fig. 1 B-Nb phase diagram

Journal of Phase Equilibria and Diffusion Vol. 29 No. 2 2008

201

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