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hase Diagram Evaluations: Section II

Al-Cu-Fe-Si (Aluminum-Copper-Iron-Silicon) V. Raghavan

Since the early investigation of [1950Phr], Zakharov et al. [1989Zak, 1990Zak] have reported several polythermal and isothermal sections for this quaternary system.

Ternary Systems For recent updates on ternary systems, see [2005Rag] (Al-Cu-Fe), [2002Rag1] (Al-Fe-Si), [2002Rag2] (Cu-Fe-Si), and this issue (Al-Cu-Si).

Quaternary Phase Equilibria With starting metals of 99.995% Al, 99.99% Cu, 99.98% Si, and Al-Fe master alloys, [1989Zak] melted samples

(a)

(b)

under a protective layer of a flux. The phase equilibria were studied by differential thermal analysis, metallography, X-ray powder diffraction, and micro X-ray spectral analysis. The isothermal sections at 25 mass% Cu constructed by [1989Zak] at 850, 750, and 625 °C are shown in Fig. 1. At 850 °C (Fig. 1a), only one phase precipitates from the liquid: FeAl3, which dissolves up to 27 mass% Cu. The solubility of Si in FeAl3 was found not to exceed 0.9 mass%. At 750 °C (Fig. 1b), the second precipitate to form is aAlFeSi (Al7.4Fe2Si, denoted s5 by [2002Rag1]), which dissolves up to 22 mass% Cu. At 700 °C (Fig. 1c), Al7Cu2Fe is present as an additional phase in the section. Al7Cu2Fe dissolves less than 0.9 mass% Si. With starting metals of high purity, [1990Zak] melted alloys in a resistance furnace under a protective layer of a flux. The phase equilibria were studied by differential

(c)

Fig. 1 Al-Cu-Fe-Si isothermal sections at 25 mass% Cu and at (a) 850, (b) 750, and (c) 625 °C [1989Zak]

Fig. 2 Al-Cu-Fe-Si polythermal section at 5Fe-5Si (in mass%) [1990Zak]

Fig. 3 Al-Cu-Fe-Si polythermal section at 10Fe-11Si (in mass%) [1990Zak]

Journal of Phase Equilibria and Diffusion Vol. 28 No. 2 2007

209

Section II: Phase Diagram Evaluations thermal analysis (at a heating or cooling rate of 3-4 °C/min), metallography, and X-ray powder diffraction. The polythermal sections constructed by [1990Zak] at 5Fe-5Si and 10Fe11Si (in mass%) are shown in Fig. 2 and 3 respectively. The compound phases present are FeAl3 (with dissolved Cu), CuAl2, aAlFeSi, cAlFeSi (Al5Fe2Si2, denoted s4 by [2002Rag1]), dAlFeSi (Al2.7FeSi2.3 denoted s7 by [2002Rag1]) and Al7Cu2Fe. The following five-phase invariant reactions are seen in Fig. 3: at 620 °C, L + cAlFeSi M Al7Cu2Fe + aAlFeSi + (Si); at 567 °C, L + dAlFeSi M Al7Cu2Fe + CuAl2 + (Si); and at 520 °C, L M (Al) + Al7Cu2Fe + CuAl2 + (Si). [1990Zak] found that the liquidus temperature is increased by Fe, decreased by Si, with Cu having little effect.

1989Zak: A.M. Zakharov, I.T. Guldin, A.A. Arnold, and E.P. Chernova, Study of the Aluminum Corner in the Al-Cu-Fe-Si System, Metally, 1989, (2), p 216-218, in Russian; TR: Russ. Metall., 1989, (2), p 213-216 1990Zak: A.M. Zakharov, A.A. Arnold, and N.E. Ivanova, Certain Polythermal Sections of the Al-Cu-Fe-Si System, Metally, 1990, (5), p 220-222, in Russian; TR: Russ. Metall., 1990, (5), p 215-217 2002Rag1: V. Raghavan, Al-Fe-Si (Aluminum-Iron-Silicon), J. Phase Equilibria, 2002, 23(4), p 362-366 2002