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hase Diagram Evaluations: Section II

Al-Mg-Sb (Aluminum-Magnesium-Antimony) V. Raghavan

The early work on this ternary system was compiled by [1995Vil]. Recently, [2005Bal] optimized the thermodynamic parameters of the Al-Sb and Mg-Sb binary systems and combined the same with the well-established description of the Al-Mg system to calculate a liquidus projection and two vertical sections.

two crystal modifications: bMg3 Sb2 (D53, bMn2 O3 -type cubic) and aMg3 Sb2 (D52, La2O3-type hexagonal). On either side of Mg3Sb2, eutectic reactions L M (Mg) + aMg3 Sb2 and L $ aMg3 Sb2 þ ðSbÞ occur at 629 and 581 °C, respectively.

Computed Ternary Phase Equilibria Binary Systems The Al-Mg phase diagram [1998Lia] has the following intermediate phases: Mg2Al3 (cubic, labeled b), R or e (rhombohedral), and Mg17Al12 (A12, aMn-type cubic, denoted c). The phase diagram data and the thermochemical properties of the Al-Sb and Mg-Sb systems were reviewed in detail by [2005Bal]. The phase diagrams computed by [2005Bal] using the optimized interaction parameters agree well with the literature data. The Al-Sb system has one congruently melting stoichiometric compound AlSb (B3, ZnS-sphalerite type cubic, melting point 1055 °C). On either side of AlSb, eutectic reactions L M (Al) + AlSb and L M AlSb + (Sb) occur at 658 and 620 °C, respectively. The Mg-Sb system has one intermediate phase Mg3Sb2 with

Combining their optimized interaction parameters for the Al-Sb and Mg-Sb systems with the literature description of the Al-Mg system [1998Lia], [2005Bal] calculated the ternary phase equilibria, without introducing any ternary parameters. The liquidus projection computed by [2005Bal] is shown in Fig. 1. The temperatures and the compositions of the participating phases in the invariant reactions were listed by [2005Bal]. The closed loop formed by the liquidus lines in Fig. 1 is qualitatively consistent with the closed liquid miscibility gap reported in the early literature, see [1995Vil]. Along the Al-Mg side, a liquidus line runs just below the miscibility gap from the Mg end to the (Al) corner. Phases of primary crystallization are marked in Fig. 1. Two of the invariant reactions on the liquiudus

Fig. 1 Al-Mg-Sb computed liquidus projection [2005Bal]

Journal of Phase Equilibria and Diffusion Vol. 28 No. 6 2007

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Section II: Phase Diagram Evaluations

Fig. 3 Al-Mg-Sb computed vertical section along the AlMg3Sb2 join [2005Bal]

References Fig. 2 Al-Mg-Sb computed pseudobinary section along the AlSb-Mg3Sb2 join [2005Bal]

surface in Fig. 1 have been redesignated here as ternary monotectic reactions M1 and M2. The computed liquid miscibility gap disappears at 1112 °C. Computed vertical sections along the AlSb-Mg3Sb2 and Al-Mg3Sb2 joins are shown in Fig. 2 and 3 [2005Bal]. No experimental data are available for comparison.

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1995Vil: P. Villars, A. Prince, and H. Okamoto, Al-Mg-Sb, Handbook of Ternary Alloy Phase Diagrams, ASM International, Materials Park, OH, 1995, Vol 4, p 3899-3901 1998Lia: P. Liang, H.L. Su, P. Donnadieu, M. Harmelin