Identification of metastable phases in splat-quenched aluminium-germanium alloys

Abstract

Two AlGe alloys (6 at.% and 30 at.% Ge) were levitation-melted and quenched in the rotary splat-quencher designed at Sussex University. X-ray diffraction patterns were obtained with crystal-monochromatised CuKα in a precision Guinier camera, and further patterns were obtained after heating to various temperatures in a differential scanning calorimeter; the DSC was used to indicate when one of the metastable phases had completed its transformation. It was clear that there was more than one metastable phase in the concentrated (eutectic) alloy and possibly only one in the dilute alloy. Most of the lines matched those of the patterns reported by Rao et al. and by Köster, though these interpreted their patterns quite differently. Results published by other workers are completely at variance with ours. This study illustrates the difficulty of identifying metastable phases, especially when more than one is present.