FWF - BETI - Deformation-phases-strength interaction in ß-Ti alloys

1.) Wider research context Near beta titanium alloys are promising materials for structural applications due to their high specific strength, good hardenability, and good fatigue behaviour. The high performance of these alloys is mainly depending on the type of microstructure, which can be engineered by thermomechanical processing. 2.) Research questions /objectives Based on the assumption that the beta stabilizer elements affect the phase transformation and the plastic deformation, the description of the deformation behaviour and subsequent microstructural changes by thermal activation in binary Ti-Mo alloys with different Mo content is still unclear. The project aims to the analysis and detailed description of deformation mechanisms operating at moderate and large plastic deformations at high temperatures and the effect on subsequent heat treatments in selected near beta alloys from the Ti-Mo system. 3.) Methods Hot compression and torsion experiments are used to deform the microstructure in a wide range of temperature, strain, and strain rate. The characterization of the microstructural features during hot deformation will contribute to analyse the effect of the deformation on the phase transformation kinetics. The development and improvement of microstructure-based mesoscale models for near beta titanium alloys will describe the behaviour of the material under plastic deformation, restoration, and phase transformation. Phases and restoration of the microstructure will be analysed by high-resolution scanning and transmission electron microscopy, electrical resistivity, and thermal analysis techniques. High energy synchrotron diffraction will help to elucidate the effect of the kinetics of phase transformations in the bulk by the analysis of SAXS and WAXS signals. 4.) Level of originality The study of the effect of large deformation at high temperatures of the selected beta titanium alloys provides unique and original information about phase transformations and microstructural changes. It is expected that the refined microstructure will improve the mechanical properties of the material by both grain refinement and enhanced precipitation strengthening. The formation and evolution of metastable ω phase and stable α phase will be affected by the grain refinement and the energy stored during plastic deformation. 5.) Primary researchers involved Teams of the Charles University Prague and Graz University of Technology have extensive experience in the field of hot deformation and phase transformation in titanium alloys. The merged knowledge will contribute to elucidate the effect of the content of the beta stabilizer at larger deformation on the mechanisms of restoration during and after deformation and the phase transformation kinetics.