Microstructure modification and quasicrystalline phase formation in Al–Mn–Si–Be cast alloys

In this paper, we report the formation of the new quaternary icosahedral quasicrystal in the Al–Mn–Si–Be system, which has a primitive icosahedral structure and has a significant lower cooling rate at the time of its formation. The icosahedral quasicrystalline phase was found to form in the Al-rich composition of Al–Mn–Si–Be alloy by conventional casting technique as well as by rapid quenching technique, indicating that the addition of Be to Al–Mn–Si alloys improves the quasicrystal forming ability. The icosahedral phase in conventionally cast Al–Mn–Si–Be alloys forms as a dendritic phase in the under-cooled melt showing five well-developed branches indicating the five-fold symmetry structure. At the later stage of the growth of the icosahedral phase, 1/1 approximant phase forms heterogeneously from the icosahedral phase. The Al–Mn–Si–Be icosahedral phase is metastable, and transforms into the 1/1 cubic approximant phase at high temperature.