Glass-forming ability of RE-Al-TM alloys (RE = Sm, Y; TM = Fe, Co, Cu)

The glass-forming ability (GFA) of RE-AI-TM (RE = Sm, Y; TM = Fe, Co, Cu) upon melt-spinning and die-casting into a copper mold has been studied. Melt-spun ribbons for both Sm- and Y-based alloys show a fully amorphous structure. However, die-casting revealed that Sm-based alloys exhibit a higher GFA than Y-based alloys. The as-cast Sm70Fe20Al10, Sm60Fe20Al10Co10 and Sm60Fe20Al10Co5Cu5 cylinders (3 mmx50 mm) contain a mixture of amorphous and crystalline phases after copper-mold casting. A new bulk metallic glass was obtained for the Sm60Fe10Al10Co15Cu5 alloy, which shows ferromagnetic behavior. In contrast, as-cast Y-based alloys are completely crystalline. Based on the data of the activation energy for crystallization of the amorphous phase, E-x, and the crystallization temperature, T-x, together with magnetic measurements, it is concluded that the as-cast Sm60Fe10Al10Co15Cu5 cylinder displays a tendency for clustering. The improved glass-forming ability of Sm-based alloys is interpreted in terms of classical nucleation theory. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.