Degradation Of Sic Particles In The Composite With AlMg5 Alloy Matrix
Andrzej Zyska, Janusz Braszczyński, Zbigniew Konopka Politechnika Częstochowska, Katedra Odlewnictwa, al. Armii Krajowej 19, 42-200 Częstochowa
Annals 1 No. 1, 2001 pages 114-117
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abstract There have been both thermodynamic and experimental analyses of a reaction resulting in Al4C3 creation within a composite of AlMg5 matrix containing mechanically introduced SiC particles. It has been revealed (Table 1) that this is a three-stage reaction proceeding on the AlMg/SiC interface. First, SiC is dissolved and intermediate compounds of Al-C-Si type are created in situ. This is followed by Al4C3 nucleation on the SiC/Al-C-Si interface. Then the growth of Al4C3 nuclei occurs along with the decaying of Al-C-Si precipitates. The thickness of observed Al4C3 and Al-C-Si (or Al-C-Si-Mg) precipitates has varied in the range 0.5 to 2.5 μm, what proves that the process is non-homogeneous and indicates the preferred regions of reaction proceeding. The occurrence of SiO2 layers on the particle surfaces has also caused precipitating of MgO and Mg2Si compounds on the matrix/particle boundaries (Fig. 2). Remelting of the composite has resulted in degradation of SiC particles and formation of a stable aluminium carbide of characteristic jagged morphology (Fig. 3).