Transmission electron microscopic studies of rapidly solidified Al-Cu-Gd alloys

Abstract

We report the results of the synthesis and structural explorations of the rapidly solidified Al-Cu-Gd alloys. Interesting structural phases have been observed for Al33.3Cu33.3Gd33.3, Al25Cu25Gd50, Al30Cu30Gd40, Al65Cu20Gd15 and Al42Cu50Gd8. For the Gd-rich compositions Al33.3Cu33.3Gd33.3, Al30Cu30Gd40 and Al25Cu25Gd50 the observed phases have been found to be dominantly amorphous and glassy. The metallic-glass nature of these phases has been confirmed through the occurrence of glass-transition observed in differential thermal analysis measurements. On the other hand, the Al65Cu20Gd15 and Al42Cu50Gd8 alloys exhibit some ordered crystalline phases. The Al65Cu20Gd15 alloy exhibits a tetragonal phase (a = 6.2±0.1 Å and c = 10.1±0.1 Å) and a monoclinic phase (a = 6.499±0.002 Å, b = 5.028±0.002 Å, c = 4.372±0.002 Å and β = 108.43±0.01°). After preliminary analysis of electron diffraction patterns it appears that these phases may correspond to the vacancy ordered phases based on CsCl-type structure. In the case of Al42Cu50Gd8 alloy, we have observed a cubic phase (a = 8.742± 0.005Å) which is a τ3 modulated phase based on the CsCl-type structure. © 2001 Elsevier Science B.V. All rights reserved.