Growth of ω inclusions in Ti alloys: An X-ray diffraction study

We investigated the size and crystal structure of nanometer-sized omega inclusions in single crystals of beta-Ti alloys by X-ray diffraction pole-figure measurements and reciprocal space mapping. We studied the topotactical relation of the beta and omega crystal lattices, and from the positions and shapes of the diffraction maxima of the omega lattice determined the mean size of the omega inclusions and the misfit of the inclusion lattice with respect to the host lattice, as well as their changes during ageing. The lattice of the omega inclusions exhibits a large positive misfit already before ageing and the misfit is subsequently reduced during the ageing process. Using the theories of elasticity and X-ray scattering we simulated diffuse X-ray scattering around the beta diffraction maxima and demonstrated that the diffuse scattering is caused mainly by local elastic strains in the beta host phase around the omega inclusions. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.