Wydarzenia

Seminarium Oddziału Badań Strukturalnych

Anomalous x-ray diffraction and diffuse scattering from ω-Ti nanoparticles in β-Ti(Mo) single crystals

prof. Vaclav Holy

Department of Condensed Mater Physics, Faculty of Mathematics and Physics, Charles University in Prague

Structural transformation of cubic (bcc) Ti(Mo) alloy (β-phase) in hexagonal ω-phase is a diffusionless (shuffle) transformation, in which pairs of  cubic (111) planes collapse into single basal (0001) planes in the hexagonal system.  The growth of the nm-size ω-particles during subsequent annealing was observed in-situ by small-angle x-ray scattering and it has been found that the particle growth is accompanied by a local rearrangement of impurity atoms (Mo in our case). 

We performed anomalous x-ray diffraction and diffuse scattering measurements with various energies around the MoK absorption edge in particles after various stages of annealing, with the goal to investigate independently the chemical compositions of the ω and β phases during the growth. To our surprise, from the data it follows that the Mo content in the ω-particles increases during annealing. Further, from the analysis of the diffraction data collected around a reciprocal lattice point of the β-phase we determined the Mo content in given iso-strain volumes (volumes with the given strain values), from which the concentration profile of  Mo atoms and its change during annealing can be reconstructed.