We studied the effect of friction stir processing (FSP) on the microstructure and properties of high-speed twin-roll cast strips made of an experimental Al–Mn–Cu–Be alloy. The samples were examined using light, scanning, and transmission electron microscopy, microchemical analysis, X-ray diffraction, and indentation testing. During FSP, the rotational speed varied, while other parameters remained constant. The uniformity of the microstructure increased with the growing rotational speed. In the stir zone, several processes took place, and the most important were: recrystallisation of the matrix grains, fragmentation of the primary intermetallic particles Al15Mn3Be2 and their more uniform distribution in the stir zone, fracture, and dispersion of the eutectic icosahedral quasicrystalline phase (IQC), transformation of tiny Al15Mn3Be2 and IQC particles into the τ1-Al26Mn6Cu4 phase and precipitation of Al–Mn–Cu precipitates. In the thermomechanically affected zone, new dislocations formed as well as dispersion of the IQC eutectic phase and recrystallisation of the matrix grains. In the heat-affected zone, dissolution of θ’-Al2Cu precipitates occurred. The hardness variation was not severe between the stir and heat-affected zones.

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.