Strengthening effect of Mo in biocompatible titanium alloys

Metastable titanium alloys containing molybdenum (Mo) are promising for biomedical applications due to their superior mechanical properties. To investigate the influence of Mo content on thermomechanical processing, the deformation mechanisms in Ti-Mo alloys were analysed using hot compression experiments performed on Ti-12Mo and Ti-18Mo. Tests were carried out in both the α+β- and β-phase regions over a temperature range of 610 °C–910 °C and at strain rates from 0.01 s −1 –10 s −1 , up to a true strain of 0.80, followed by immediate water quenching. Microstructural characterisation of samples tested in the α+β- and β-phase regions was performed using scanning electron microscopy images and electron backscatter diffraction measurements, respectively. Flow curves in the β-phase region display pronounced work hardening, a behaviour rarely observed in β-Ti alloys, which is likely attributed to suppressed dynamic recovery influenced by Mo. In α+β-phase deformation, flow curves exhibit softening after reaching peak values, corresponding to morphological changes in the α phase. Due to the slow diffusivity of Mo, subgrain formation and α-phase globularisation were primarily confined to prior β grain boundaries, resulting in a heterogeneous deformed microstructure. The extent of dynamic recovery, subgrain size, and dynamic α-phase globularisation were quantified and compared between the investigated alloys. Mo retards dynamic recovery and α-phase globularisation, increasing strength in the β-phase region but reducing it in the α+β region. • Mo slows dynamic recovery and refines subgrains, revealed by EBSD analysis. • Mo confines subgrain formation and α globularisation to prior β grain boundaries. • Higher Mo content strengthens the alloy in the β region but softens it in α+β. • Extent of α globularisation quantified through SEM image analysis. • Higher Mo reduces α-phase content and slows dynamic α globularisation.