The local displacement field around Co and Nb solutes in ω-phase forming bcc-Zr at high temperatures

In order to determine the displacement field around Co and Nb solutes in high temperature bcc-Zr the diffuse scattering intensity was measured in Zr_0.985Co_0.015 and Zr_0.92Nb_0.08. Strong diffuse intensities were found in the (110) and in the (001) reciprocal planes. The comparison of these results with model calculations shows that Co as well as Nb atoms cause radial symmetric displacement fields in the high temperature bcc phase of Zr. ω-phase like displacements around these defects, on the other hand, can explain the measured diffuse intensities less well. It is concluded, that the resulting displacement field is a superposition of all displacements for which low energy phonons exist. These low energy phonons are related to the martensitic transitions of the bcc structure to the hcp and ω-structure.