LAUSR

ABSTRACT This paper reports on the characterisation of rapidly solidified Al-4.5 wt% Cu-xSc (x = 0.1, 0.2 or 0.4 wt %). The effect of micro-additions of Sc (up to 0.4 wt %) was examined through microstructural analysis of rapidly solidified, as well as aged samples, by means of electron microscopy, x-ray and neutron diffraction and microhardness measurements. The effect of micro-additions of Sc on the scale of the rapid solidified microstructure was negligible. The Sc additions were supersaturated mainly in the interdendritic regions. However, upon aging of the samples, directly after rapid solidification, nano-precipitates rich in Sc were observed in the matrix and some Sc was also associated with the θ phase. No W-phase was observed in either as atomised or aged samples. Furthermore, dramatic improvements in mechanical properties (specifically hardness) were achieved. This work highlights the use of various and complementary tools to characterise the effect of micro-additions of Sc to hypoeutectic Al-Cu alloys over a wide range of solidification thermal histories. It also demonstrates the capability of designing alloys and process strategies with unique microstructures and mechanical properties superior to age hardened Al-4.5 wt% Cu alloys.