Nanostructuring of the titanium alloy Ti-13Nb-13Zr (NanoTNZ) for osteosynthesis implants by continuous multidirectional swaging

Abstract

Musculoskeletal traumata involving damaged bones can reduce patients’ mobility and be life-threatening due to fracture-related infections. Osteosynthesis implants are increasingly vital for stabilizing fractures, especially with the growing prevalence of osteoporotic fractures in the aging population. However, advancements in manufacturing research are crucial for enhancing the biomechanical properties of these implants, improving healing outcomes, and enabling large-scale production. This study focuses on the development of a novel manufacturing process for the nanostructured titanium alloy Ti-13Nb-13Zr (NanoTNZ) using continuous multidirectional swaging (CMDS) followed by recrystallization and ageing. Various thermomechanical parameters were explored to ensure homogeneous strain and hardness distribution and fully nanostructure the alloy. Process limitations such as chevron cracks and shear bands were overcome by applying counter pressure for hydrostatic compression stress, enabling damage-free forming. Ageing of CMDS-TNZ leads to partial α''-martensite decomposition into finer structures of α_s and β phase resulting in a microstructure with substructures smaller than 100 nm. NanoTNZ exhibits a Young's modulus of 92 GPa, an ultimate tensile strength of 981 MPa, and 8 % elongation at rupture. A bone plate of NanoTNZ was manufactured to demonstrate the efficacy of this continuous thermomechanical nanostructuring technique to produce next generation osteosynthesis implants.