Some aspects of splat-quenching in an inert atmosphere and of the formation of non-crystalline phases in Al-17.3 at. % Cu, germanium and tellurium

Abstract

An apparatus for splat-quenching by the gun technique in a sealed, inert atmosphere is described. The importance of a low-oxygen quenching atmosphere in promoting efficient spreading of liquid particles and good thermal contact with the quenching surface is shown. A cooling rate of ∼10¹⁰ K sec⁻¹ was estimated from the interlamellar spacing in a quenched Al-17.3 at. % Cu alloy. The process mechanisms of the gun technique are discussed with particular reference to the atomized droplet size and the effective specimen thickness for heat transfer.

New non-crystalline phases are reported in electron-transparent areas of splat-quenched foils of Al-17.3 at. % Cu (eutectic composition) pure Ge and pure Te. The glassy Al-Cu phase was also observed in specimens which were chemically thinned from the thicker regions of foils; lattice image studies by high-resolution electron microscopy tentatively suggest that this phase has an amorphous, liquid-like atomic configuration. The peak positions in the electron diffraction patterns of the Ge and Te phases were compared, where possible, with those for the corresponding liquid and vapour-deposited phases. The results for Ge suggest that significant structural rearrangement took place during cooling and freezing from the liquid to give a paracrystalline, tetrahedral short-range order whereas, for Te, the liquid structure was probably largely preserved on freezing.