Influence of Sc Addition and Rapid Solidification on the Microstructure and Mechanical Properties of Al-5Cu Alloys

In this study, to improve the mechanical properties of 2xxx series Al-5Cu alloy, 0.5% and 1.0% Sc doped Al-5Cu alloys were produced, and these alloys were processed by induction melting with a low cooling rate and melt spinning with a high cooling rate. The chemical compositions of the alloys were confirmed by XRF analysis, and XRD analysis showed the presence of α-Al and θ-Al2Cu phases in the ingot Al-5Cu alloy and Cu2Sc phase in the Sc-doped alloys. The same phases were observed in the ribbon alloys produced by rapid solidification, but the degree of crystallization and lattice stress were higher. SEM-EDX analysis revealed that the ribbon alloys have finer grain sizes, while Rietveld analysis showed that the Cu2Sc phase increases with the amount of Sc. DSC analyses confirmed the melting/solidification peak of the α-Al phase and the small peaks of the θ-Cu2Al phase, and it was also determined that the addition of Sc decreased the enthalpy of solidification of the α-Al phase. In the ribbon alloys produced by melt spinning, it was observed that the grain size was reduced, but the effect of Sc was limited to high cooling rates. The microstructure of the ribbon alloys showed finer grains on the disk surface, explaining the rapid heat removal from the melt. As a result, it is understood that Sc doping improves the mechanical properties of ribbon alloys obtained by rapid solidification, but its effect is limited in some cases.