Abstract
In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase during solidification. The strips were characterised by light microscopy, scanning and transmission electron microscopy, microchemical analysis, and X-ray diffraction. Indentation testing was used to determine the mechanical responses of the strips in different areas. A smooth surface was achieved on both sides of the twin-roll-cast strip, while the free surface of the single-roll-cast strip was rough. The microstructures in both strips consisted of an Al-rich solid solution matrix embedding several intermetallic phases Θ-Al2Cu, Be4Al (Mn, Cu), Al15Mn3Be2 and icosahedral quasicrystalline phase (IQC). The microstructure of the single-roll-cast strip was more uniform than that of the twin-roll-cast strip. Coarse Al15Mn3Be2 particles appeared in both alloys, especially at the centre of the twin-roll strip. These coarse particles adversely affected the strength and ductility. Nevertheless, both casting methods provided high-cooling rates, enabling the formation of metastable phases, such as quasicrystals. However, improvements in alloy composition and casting procedure are required to obtain enhanced microstructures and properties.
Highlights
Accepted: 18 January 2022Quasicrystals belong to crystals having long-range order without periodicity [1].Generally, they are hard and brittle at room temperature
Quasicrystals are metastable in numerous Al alloys and can predominantly be obtained by rapid solidification
The surfaces formed in contact with the the rolls were relatively smooth, with lines parallel to the casting direction (Figure rolls were relatively smooth, with lines parallel to the casting direction (Figure 2b). 2b)
Summary
Quasicrystals belong to crystals having long-range order without periodicity [1] They are hard and brittle at room temperature. Song et al [10] discovered that the addition of Be sharply reduced the critical cooling rate for the formation of quasicrystals during solidification and the required Mn content in Al-Mn alloys. They established that quasicrystals could be formed using conventional casting methods, e.g., by die-casting. Improved versions of their alloys were developed by Rozman et al [11].
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