Microstructural Evolution of Mg-4Al-2.5Ca Alloy during Solidification

Abstract:

In the present work, the microstructure evolution of Mg-4Al-2.5Ca alloy during solidification was investigated by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and differential scanning calorimetry (DSC). The results showed that the as-cast microstructure was typical dendritic structure, consisting of α-Mg and the Al₂Ca with a C15 structure formed at inter-dendritic regions. But during slow solidification, the sequence of phase formation of this alloy consisted of following stages: L→ L + α-Mg → L + α-Mg + (Mg, Al)₂Ca → α-Mg + (Mg, Al)₂Ca + Al₂Ca → α-Mg + Al₂Ca. Thermal analysis showed that the (Mg, Al)₂Ca and Al₂Ca phase separation temperature was about 520°C and 510°C respectively, which is different from thermodynamic calculation. With the temperature decreasing, the liquid (Mg, Al)₂Ca phase with thick and continuous morphology transformed into lamellar-shaped eutectic phase, and parts of (Mg, Al)₂Ca phase translated into Al₂Ca phase with bone-shaped and needle-like.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 486-491
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.486
• Online since: April 2015
• Authors: Zhong Tao Jiang, Bin Jiang, Jian Yue Zhang, Xiang Sheng Xia, Fu Sheng Pan
• Keywords: Mg-Al-Ca Alloy, Microstructural, Phase, Solidification

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