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

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 β phase. The volume fraction of the martensitic phase increased and that of the β 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. (author)