The formation, structure and crystallization of non-crystalline nickel produced by splat-quenching

Abstract

A non-crystalline phase has been formed in electron-transparent (0.1 to 0.5Μm thick) areas of splat-quenched foils of nickel. The positions in diffraction co-ordinates of the first two peaks and of a shoulder on the high-angle side of the second peak of the electron diffraction pattern agree closely with those for non-crystalline vapour-deposited Ni. The presence of the shoulder suggests that the structure is similar to that of dense random packed hard spheres, i.e. that it is amorphous rather than microcrystalline. The crystallization behaviour of the glassy phase studiedin situ in 1 MV electron microscope also supports this view. The crystallization temperature of about 150‡ C is unexpectedly high and suggests that stabilization by impurities (possibly up to 0.7 wt %) was occurring. The critical cooling rate for the formation of the glassy phase has been estimated from theories of homogeneous nucleation, crystal growth and transformation kinetics to be ∼10¹⁰ K sec⁻¹ which is in satisfactory agreement with experimentally derived estimates of the maximum cooling rate in electron-transparent areas of foils.