Investigation of the interplay between deformation, phase transformations and mechanical properties in metastable β titanium alloys

Near beta titanium alloys are promising for structural applications due to their high specific strength, good hardenability and good fatigue behaviour. The performance of these alloys depends mainly on the type of microstructure, which can be engineered by thermomechanical processing. The use of nontoxic alloying elements can suit them as a good alternative for implant materials. Based on the assumption that the beta stabilizer elements affect phase transformation and plastic deformation, the description of deformation behaviour and subsequent microstructural changes by thermal activation in binary Ti-Mo alloys with different Mo content is still unclear.

The expertise of IMAT in hot deformation and microstructure modelling and the experience in phase transformation of titanium alloys of the Department of Physics of Materials at Charles University in Prague (Czech Republic) contributed to preparing and realising a unique research project. The project entitled “Deformation-phases-strength interaction in ß-Ti alloys” (BETI) was funded by Austrian Science Fund (FWF) and the Czech Science Foundation (GACR) for three years. The aim of BETI is 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 three high pure Ti Mo alloys: Ti-12Mo, Ti-15Mo and Ti-18Mo. Scientific activities in IMAT are:

• Deformation of Ti-Mo alloys by a wide range of strains at different temperatures and using various strain rates. These experiments help to describe the deformation behaviour depending on the stability of the β phase (i.e., on the Mo content) and the deformation parameters.
• Implementation of a microstructure-based model to gain insights into the mechanisms of restoration and how they affect the phase transformation kinetics of β-Ti alloys during subsequent heat treatment. The scientific group at Charles University concentrates their research on the characterization of the phase transformations and microstructural changes occurring depending on Mo content and the previous deformation state.