Mechanical Properties and Behavior of the Ti-45Nb Alloy Subjected to Extreme Conditions

Mechanical properties and structure-property relationship of the Ti-45Nb (mass%) alloy with potential applications in biomedicine were investigated using a multidisciplinary approach. Because the biomechanical compatibility of metallic implant materials can be significantly improved by microstructural refinement and laser surface modification (LSM), the present study concentrates on the investigation of the mechanical properties of the Ti-45Nb alloy subjected to extreme processing conditions to evaluate their impact on the alloy improved applicability in the bio-environment. The alloy was therefore subjected to high-pressure torsion (HPT) and LSM processing to obtain favorable alloy characteristics. Crystal structure prediction was conducted using data mining (DM) and evolutionary algorithms (EA). All the obtained potential structure candidates were submitted to the local optimizations at the level of density functional theory (DFT); subsequently, the phonon lattice dynamics and mechanical properties were systematically investigated. The alloy structure progression and mechanical characteristics were examined under the influence of extremely high temperatures induced during the LSM processing and the extreme pressure achieved during the HPT treatment. XRD characterization was performed using experimental and theoretical methods showing the presence of bcc beta-Ti and orthorhombic Cmcm Ti4Nb phase. Mechanical properties such as Young's modulus, Vicker's hardness, and plasticity of the most relevant Ti4Nb modifications predicted after DM-EA-DFT were found to corroborate well with the experimental results of nanoindentation measurements. The present study reveals that the additional processing of the Ti-45Nb alloy under extreme conditions leads to significant improvement in the alloy's bio-mechanical compatibility. Ti-45Nb alloy biomechanical compatibility was evaluated by a multidisciplinary approach and improved by extreme condition processing. Ab initio calculations of mechanical properties are in very good agreement with experimental observations.