Martensitic phase transformation and lattice dynamics of fcc cobalt

The phonon dispersion of the high-temperature fcc phase of pure cobalt has been measured by inelastic neutron scattering at 833 K. Transverse phonon branches were measured above and below the Martensitic hcp-fcc transformation in order to learn about an influence of lattice dynamics, if any. No new anomalies could be observed, except those confirming an anomalous decrease of the (Formula presented) (hcp) shear constant when approaching the transformation from below and those confirming a transverse (Formula presented) and (Formula presented) branch of relative low energy. The small shear constant and results from an analysis of elastic diffuse and Bragg data can be understood in the framework of a dislocation-driven transformation mechanism proposed by Seeger.