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Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy,Al-25Si-5Fe-3Cu(wt%,signed as 3C),fabricated by traditional cast(TC) and spray forming(SF) processes,were investigated by differential scanning calorimetry(DSC) and scanning electron microscopy(SEM) combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques.The results show that Al7Cu2Fe phase can be formed and transformed in TC-and SF-3C alloys between 802-813 K and 800-815 K,respectively.The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC-and SF-3C alloys,respectively.The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2→β-Al5FeSi is not detected in the present DSC experiments.Also,the mechanisms of the microstructural evolution and phase transformation are discussed.
Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminum-silicon alloy, Al-25Si-5Fe-3Cu (wt%, signed as 3C), fabricated by traditional cast (TC) and spray forming investigated by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The results show that Al7Cu2Fe phase can be formed and transformed in TC-and SF-3C alloys between 802-813 K and 800-815 K, respectively. The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC-and SF-3C alloys, respectively. The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2 → β-Al5FeSi is not detected in the present DSC experiments. Also, the mechanisms of the micros tructural evolution and phase transformation are discussed.