Engineering the next-generation tin containing beta titanium alloys with high strength and low modulus for orthopedic applications

Metastable beta Ti alloys are the new emerging class of biomaterial for load bearing orthopedic applications. However, these alloys in the single beta phase microstructure have insufficient strength for use in load bearing applications. It is imperative to strengthen these alloys by carefully designed thermo-mechanical processing routes that typically involve aging treatment. In this investigation two newly designed Sn based beta Ti alloys of composition Ti-32Nb-(2, 4) Sn are evaluated. The effects of Sn content on the mechanical properties and biological performance of these alloys processed through designed thermo-mechanical processing route are investigated. The increase in the Sn content led to a reduction in the elastic modulus of the alloy. An increase in the Sn content increased the aspect ratio of the a precipitates, which led to a significant strengthening in the alloy while keeping the elastic modulus low. In addition, the corrosion behavior of the alloy was evaluated in simulated body fluid. The Sn containing beta alloys have an excellent corrosion resistance as desired for an implant material. The corrosion resistance improved with an increase in Sn content. These alloys were also observed to have excellent cytocompatibility as they not only supported the attachment and proliferation of human mesenchymal stem cells but also their osteogenic differentiation in vitro. The combination of high strength, low elastic modulus, superior corrosion resistance and biocompatibility underscores the promise of Sn containing beta Ti alloys for use in orthopedic applications