Transmission electron microscopy studies of a vapour-deposited AlZr Alloy

Abstract

Thin films of an Al-9.4wt.%Zr alloy have been produced using the flash evaporation technique onto Formvar-coated copper grids. The as-deposited thin films constitute a supersaturated solid solution of zirconium in aluminium. The microstructure and crystal structure of the phases in the as-quenched state as well as those formed on subsequent decomposition of the supersaturated solid solution have been characterized using transmission electron microscopy and electron diffraction techniques. When annealing was carried out at about 773 K, two metastable intermediate phases were found to form. Electron diffraction evidence suggested that these phases have a cubic structure with a = 0.85 nm for the Al 11Zr 2 phase and an orthorhombic structure with a = 0.7489 nm, b = 0.6556 nm and c = 0.8961 nm for the Al 6Zr phase. When annealing was performed for a long time, the equilibrium constitution (i.e. a mixture of aluminium solid solution and the tetragonal Al 3Zr phases) was achieved. Details of the transformation behaviour and morphology of the metastable transformation products are discussed.