Al-Ir-V (Aluminum-Iridium-Vanadium)

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Section II: Phase Diagram Evaluations

Al-Ir-V (Aluminum-Iridium-Vanadium) V. Raghavan

Recently, [2005Miu] determined a partial liquidus projection and an isothermal section at 1650 C for Ir-rich alloys of this system.

Binary Systems The Al-Ir phase diagram in the Ir-rich region determined by [2005Miu] depicts a eutectic reaction between (Ir) and IrAl (B2, CsCl-type cubic) at 30.5 at.% Al and 2020 C. The other Al-Ir phases are: Ir2Al5 (cubic, space group Pm 3n), IrAl3 (D018, Na3As-type hexagonal), Ir4Al13 (monoclinic), and Ir2Al9 (D8d, Co2Al9-type monoclinic). The Ir-V phase diagram [Massalski2] has the following intermediate phases: Ir3V (L12, AuCu3-type cubic), IrV1-x (L10, AuCutype tetragonal), IrV (orthorhombic), and IrV3 (A15, Cr3Sitype cubic).

alloys: 70Ir-24Al-6V, 72Ir-16Al-12V, and 80Ir-5Al-15V (at.%). The samples were annealed at 1650 C for 24 h. The phase equilibria were studied with scanning electron metallography, wavelength dispersive x-ray spectroscopy, and differential thermal analysis. The partial liquidus projection constructed by [2005Miu] is shown in Fig. 1. In the Ir-rich region, a U-type transition reaction L + (Ir) M Ir3V + IrAl occurs. Figure 2 shows the partial isothermal section at 1650 C. In the solid solution based on Ir3Ti, Al substitutes for V up to the solubility limit of 8 at.%. No ternary phases were found in this region.

Reference 2005Miu: S. Miura, K. Ohkubo, Y. Terada, Y. Kimura, Y. Mishima, Y. Yamabe-Mitarai, H. Harada, and T. Mohri, Phase Equilibria in the Ir-Rich Portion of the Ir-Al-X (X: V, Nb and Ta) Ternary Systems, J. Alloys Compd., 2005, 395, p 263-271

Ternary Phase Equilibria With starting metals of 99.99% Al, 99.9% Ir, and 99.7% V, [2005Miu] arc-melted under Ar atm three Ir-rich ternary

Fig. 1 Al-Ir-V partial liquidus projection for Ir-rich alloys [2005Miu]

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Fig. 2 Al-Ir-V partial isothermal section at 1650 C for Ir-rich alloys [2005Miu]

Journal of Phase Equilibria and Diffusion Vol. 29 No. 4 2008

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