The athermal omega transformation in Zr−Nb alloys

Abstract

The athermal ω reaction in Zr−Nb alloys has been investigated by transmission electron microscopy. In a 12 wt pct Nb alloy, ω forms periodic arrays of plates on {112} β planes. These plates are 10 to 40A thick and 150 to 200A in diam. The ω electron diffraction reflections are relatively sharp in the 12 pct Nb alloy but become diffuse as the solute content is increased. The diffuse intensity exists as sheets parallel to {111}β reciprocal lattice planes. It is proposed that this diffuse intensity results from a large amplitude lattice vibration rather than from small particle size effects,i.e. ω forms when the bee lattice becomes unstable to a transdiffraction effects identical to those in the Zr−Nb alloys.