An electron microscopy study of the metastable structures in splat-cooled erbium-zirconium alloys

Abstract

The metastable structures produced by splat-cooling in Er-Zr alloys were investigated by using transmission electron microscopy and X ray analysis in order to deduce the mechanism by which a continuous series of supersaturated solid solutions are formed between Er and Zr in their low temperature h c p allotropic form. The study revealed that the microstructure of alloys with extended solid solubility consisted of an h c p phase exhibiting predominantly martensitic character together with small amounts of a metastable beta phase. The volume fraction of the martensitic phase increased and that of the beta phase decreased with increase in Zr content of the alloy. The phase transformations involved in the formation of the various metastable phases in the Er-Zr system during splat cooling and the stability of these phases during subsequent ageing treatments are discussed in relation to the equilibrium phase diagram for this system.