Metastable phase formation during mechanical alloying of Al-Ge and Al-Si alloys

Abstract

In this paper we report the mechanical alloying behaviour of elemental aluminium with diamond cubic elements Ge and Si. A metastable crystalline phase with rhombohedral crystal structure forms in Al₇₀Ge₃₀ and Al₆₀Ge₄₀ alloy compositions. The phase always coexists with elemental constituents and decomposes over a broad temperature range. No such metastable phase could be observed in the Al-Si system. We also report X-ray diffractometry and differential scanning calorimetry results suggestive of amorphization. Finally a comparison was made of the present result with that obtained in rapid solidification.