Rearrangements of dislocations during continuous heating of deformed β-TiNb alloy observed by in-situ synchrotron X-ray diffraction

Heating of deformed metals always causes changes in their structure and properties. These changes are related to annihilation of the crystallographic defects and rearrangement of the dislocation structure. The currently existing knowledge on structural transformations occurring during the heating of deformed metals is mainly based on ex-situ metallographic observation of samples after they have been cooled to room temperature. In this study we attempted to observe defect annihilation and dislocations rearrangement in β-titanium alloy during heating by using in-situ synchrotron X-ray diffraction (SXRD). For this reason, a thorough peak profile analysis using modified Williamson-Hall (mWH) and modified Warren-Averbach (mWA) methods was applied to several hundreds of diffraction patterns obtained during continuous heating of cold rolled Ti45Nb alloy. Several stages of dislocation structure evolution were distinguished based on observation of changes in dislocation density, type of dislocation, energy of dislocations and crystallite size. Such analysis revealed several phenomena which haven't been reported in the literature so far. The results of synchrotron XRD analysis were in excellent agreement with measurements of mechanical properties. •The heat-induced rearrangements of dislocations in cold-worked Ti45Nb alloy were studied.•The synchrotron in-situ diffraction followed by peak-deconvolution profile analysis was used.•During the first steps of recovery a slight increase of dislocation density occurs.•Sharp increase of the energy of the system occurs during polygonization.•The last stage of polygonization is associated with increase of the fraction of screw dislocations.