Microstructure and mechanical properties of hot rolled TiNbSn alloys

Microstructure and mechanical properties of additive manufactured porous Ti-33Nb-4Sn scaffolds for orthopaedic applications

Customized porous titanium alloys have become the emerging materials for orthopaedic implant applications. In this work, diamond and rhombic dodecahedron porous Ti-33Nb-4Sn scaffolds were fabricated by selective laser melting (SLM). The phase, microstructure and defects characteristics were investigated systematically and correlated to the effects of pore structure, unit cell size and processing parameter on the mechanical properties of the scaffolds. Fine β phase dendrites were obtained in Ti-33Nb-4Sn scaffolds due to the fast solidification velocity in SLM process. The compressive and bending strength of the scaffolds decrease with the decrease of strut size and diamond structures showed both higher compressive and bending strength than the dodecahedron structures. Diamond Ti-33Nb-4Sn scaffold with compressive strength of 76 MPa, bending strength of 127 MPa and elastic modulus of 2.3 GPa was achieved by SLM, revealing the potential of Ti-33Nb-4Sn scaffolds for applications on orthopaedic implant.

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

Metastable β Ti alloys are the new emerging class of biomaterial for load bearing orthopedic applications. However, these alloys in the single β 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 β 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 α 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 β 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 β Ti alloys for use in orthopedic applications.

The mechanical behavior of TiNbSn alloys according to alloying contents, cold rolling and aging

The present study is focused on mechanical properties that result from cold rolling and aging treatments applied to TiNbSn alloys comprising different Nb (35% and 42%) and Sn (0% and 2.5%) contents. The alloys were arc melted, homogenized, solubilized, cold rolled and aged at 400°C for different aging times. A set of characterization tests performed, included microstructural analysis, X-ray diffraction, microhardness, tensile tests and fracture analysis. The alloys contained all three β, α" and ω phases after cold rolling, regardless of the alloying content. The solid solution effect led to changes in the alloys' mechanical behavior. Furthermore, the alloys presented α phase precipitation, and it led to a peak-aged stage after different aging times due to the Nb content. The alloys containing 42% and 35% Nb content reached the peak-aged stage within 48 and 72h, respectively. The α phase precipitation in the alloys at peak-aged stage increased the hardness, tensile strength and elastic modulus of the alloys; however, it also caused ductility to decrease. The fine dispersed precipitates of the α phase generated small and shallow dimples, which are a characteristic fracture micromechanism of peak-aged alloys.