Characterization of direct laser deposited low modulus Ti-26Nb alloy on Ti-6Al-4V for biomedical applications

Abstract

After a joint replacement, a stress-shielding phenomenon often appears resulting from Young’s modulus mismatch between the implant and the cortical bone. In accordance with Wolff’s law, it will result in bone resorption and could lead to loosening of the implant.Ti-Nb beta metastable alloys are excellent candidates for biomedical applications because of their very low elastic modulus close to that of cortical bone and their high strength. This material, associated with the direct laser deposition or CLAD® process allows the fabrication of biomimetic implants. Nevertheless, Ti-Nb powders are still rather uncommon, thus the alloy could be utilized as a replacement material for Ti-6Al-4V on the implant surface only, this configuration creating an elasticity gradient.Microstructure and phase analysis of a direct laser deposited Ti-26(at%)Nb wall revealed a fully beta microstructure. Micro-hardness tests refuted the anisotropy of the deposited alloy and tensile tests showed that the elastic properties of the CLAD® material are not far from those of the cast material. EDS analysis of a CLAD® build of Ti-26Nb on a Ti-6Al-4V substrate highlighted the diffusion of the elements of the substrate towards the deposit. Grain growth was studied with EBSD. Moreover, nanoindentation tests highlight an evolution of the elastic modulus from the substrate to the deposit.After a joint replacement, a stress-shielding phenomenon often appears resulting from Young’s modulus mismatch between the implant and the cortical bone. In accordance with Wolff’s law, it will result in bone resorption and could lead to loosening of the implant.Ti-Nb beta metastable alloys are excellent candidates for biomedical applications because of their very low elastic modulus close to that of cortical bone and their high strength. This material, associated with the direct laser deposition or CLAD® process allows the fabrication of biomimetic implants. Nevertheless, Ti-Nb powders are still rather uncommon, thus the alloy could be utilized as a replacement material for Ti-6Al-4V on the implant surface only, this configuration creating an elasticity gradient.Microstructure and phase analysis of a direct laser deposited Ti-26(at%)Nb wall revealed a fully beta microstructure. Micro-hardness tests refuted the anisotropy of the deposited alloy and tensile tests showed that the elastic properties of the C...