Al-Mg-Sm (Aluminum-Magnesium-Samarium)

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Phase Diagram Evaluations: Section II

Al-Mg-Sm (Aluminum-Magnesium-Samarium) V. Raghavan

The previous study of this system by [1987Zhe] presented an isothermal section at 400 C, which depicts no ternary compounds. Recently, [2008Jia] carried out a thermodynamic assessment of this system and computed the isothermal section at 400 C and a tentative liquidus projection.

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 Al-Sm system [1989Gsc, 2007Del] depicts the following intermediate phases: Sm3Al11 (D13, Al-deficient Al4Ba-type tetragonal), SmAl3 (D019, Ni3Sn-type hexagonal), SmAl2 (C15, MgCu2-type cubic), SmAl (ErAl-type orthorhombic) and Sm2Al (C23, Co2Si-type orthorhombic). The Mg-Sm phase diagram [Massalski2] depicts the following compounds: Mg41Sm5 (tetragonal), Mg5Sm (cubic), Mg3Sm (D03, BiF3-type cubic), Mg2Sm (C15, MgCu2-type cubic), and MgSm (B2, CsCl-type

cubic). The computed phase diagrams of the above binaries were given by [2008Jia].

Computed Ternary Phase Equilibria The optimized binary interaction parameters of the Al-Sm and Mg-Sm systems were listed by [2008Jia] along with those adopted from the literature. As there are no ternary compounds in this system, [2008Jia] calculated the ternary phase equilibria by extrapolation of the binary data without introducing any ternary interaction parameters. The computed isothermal section at 400 C shown in Fig. 1 was found to agree well with that determined by [1987Zhe]. The liquidus projection computed by [2008Jia] is shown in Fig. 2. In the binary Al-Sm phase diagram updated by [2007Del], there is only one modification of Sm3Al11 (Al-deficient Al4Ba-type). Accordingly, the ternary peritectic reaction P2: L + SmAl3 + Sm3Al11(HT) fi Sm3Al11(LT) computed by [2008Jia] is omitted in Fig. 2. The reactions close to the Al-Mg side are shown schematically in the lower part of Fig. 2. An enlarged view of the Mg corner is

Fig. 1 Al-Mg-Sm computed isothermal section at 400 C [2008Jia]

Journal of Phase Equilibria and Diffusion Vol. 30 No. 1 2009

69

Section II: Phase Diagram Evaluations

Fig. 2 Al-Mg-Sm computed liquidus projection [2008Jia]

shown in Fig. 3. The liquidus projection may be considered tentative, as there are no experimental data for comparison.

References

Fig. 3 Al-Mg-Sm computed liquidus projection near the Mg corner [2008Jia]

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1987Zhe: C. Zheng, L. Chen, and Y. Ye, Phase Equilibria in Al-Mg-Sm System at 400C, Acta Metall. Sinica., 1987, 23(3), p B117-B120 1989Gsc: K.A. Gschneidner, Jr. and F.W. Calderwood, The Al-Sm (Aluminum-Samarium) System, Bull. Alloy Phase Diagrams, 1989, 10(1), p 37-39 1998Lia: P. Liang, H.L. Su, P. Donnadieu, M. Harmelin, A. Quivy, P. Ochin, G. Effenberg, H.J. Seifert, H.L. Lukas, and F. Aldinger, Experimental Investigation and Thermodynamic Calculation of the Central Part of the Mg-Al Phase Diagram, Z. Metallkd., 1998, 89, p 536-540 2007Del: S. Delsante, R. Raggio, G. Borzone, and

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