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Nucleation mechanism of the cubic σ phase in squeeze-cast aluminium matrix composites

Schueller, R. ; Wawner, F. ; Sachdev, A.

Journal of Materials Science, 1994, Vol.29(2), pp.424-435 [Tạp chí có phản biện]

ISSN: 0022-2461 ; E-ISSN: 1573-4803 ; DOI: 10.1007/BF01162502

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  • Nhan đề:
    Nucleation mechanism of the cubic σ phase in squeeze-cast aluminium matrix composites
  • Tác giả: Schueller, R. ; Wawner, F. ; Sachdev, A.
  • Chủ đề: Aluminiumlegierung ; Kupferzusatz ; Magnesiumzusatz ; Faserverstärkter Werkstoff ; Druckgießen ; Wärmebehandlung ; Ausscheidung (Metallurgie) ; Keimbildung ; Kristallwachstum ; Transmissionselektronenmikroskopie ; Mikrogefüge ; Phasenanalyse ; Sigma-Phase ; Squeeze Casting ; Engineering
  • Là 1 phần của: Journal of Materials Science, 1994, Vol.29(2), pp.424-435
  • Mô tả: An Al-4.3 wt% Cu-2.0 wt% Mg alloy reinforced with 20 vol% reinforcing fibres was examined after a T7 heat treatment. The expected precipitate phase was equilibrium S′ (Al 2 CuMg), which was confirmed to form in the monolithic alloy. However when this Al-Cu-Mg alloy was squeeze-cast into a fibre preform and given an identical T7 heat treatment a number of other phases also nucleated; these included θ′ (Al 2 Cu), β′ (Mg 2 Si) and the cubic σ phase (Al 5 Cu 6 Mg 2 ). These additional phases were determined to nucleate and grow rapidly during the water-quench following solution treatment. The existence of excess Si (approximately 0.5 wt%) in the matrix was determined to be responsible for nucleation of these additional phases. This extra Si entered the composite matrix during squeeze-casting through breakdown of an SiO 2 layer which existed at the fibre interfaces. During quenching Si clusters rapidly form and provide nucleation sites for the σ and θ′ phases. The Si clusters apparently created a compressive strain in the matrix which attracted a high concentration of small Cu atoms to their interface. The σ phase nucleated in this high-Cu region since, on a localized scale, σ became the equilibrium phase. This type of nucleation process may also explain the enhanced precipitate nucleation which occasionally takes place in other alloy systems when trace amounts of certain elements are added.
  • Ngôn ngữ: English
  • Số nhận dạng: ISSN: 0022-2461 ; E-ISSN: 1573-4803 ; DOI: 10.1007/BF01162502

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