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

Abstract

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.

On the Corrosion Behaviour of Low Modulus Titanium Alloys for Medical Implant Applications: A Review

“…In order to address the issues associated with the most commonly used alloy of Ti-6Al-4V, there have been many efforts to develop a new class of titanium alloys (known as β-type titanium alloys) with reduced levels of stiffness. Any alteration in the chemical composition of Ti alloys may lead to stabilization of a certain phase and crystal structure: the high temperature Ti has a body-centered cubic (BCC) crystal structure, β-phase, while the low temperature phase (α) displays a hexagonal close-packed (HCP) structure (e.g., CP Ti) and the combination of the two phases (α + β) (e.g., Ti-6Al-4V) [18]. The β-type titanium alloys containing beta-stabilizing elements (e.g., Nb, Ta and Zr) exhibit many advantages such as lower Young's moduli that are closer to that of the human bone (which can mitigate bone loss and implant loosening due to stress shielding), non-allergic and non-toxic elements such as Nb, Ta and Zr, excellent corrosion resistance due to the formation of more stable oxide layers and good biocompatibility [19,20].…”

Biomaterials Used in Orthopedic Implants

“…Al ve V iyonlarının salınması Alzheimer ve nöropati hastalıkları ile ilişkilendirilmiştir [38]. Bu nedenle Mo, Ta, Zr, Nb ve Sn gibi bazı β-stabilize edici alaşım elementleri ilave edilerek β-titanyum alaşımları geliştirilmiştir [44]. Bu alaşım elementlerinin V ve Al ile karşılaştırıldığında daha güvenli oldukları düşünülmektedir ve alaşımlar insan kemiğininkine yakın elastik modül, mükemmel korozyon direnci ve yüksek özgül dayanım gibi avantajlara sahiptir [44], [45].…”

“…Bu nedenle Mo, Ta, Zr, Nb ve Sn gibi bazı β-stabilize edici alaşım elementleri ilave edilerek β-titanyum alaşımları geliştirilmiştir [44]. Bu alaşım elementlerinin V ve Al ile karşılaştırıldığında daha güvenli oldukları düşünülmektedir ve alaşımlar insan kemiğininkine yakın elastik modül, mükemmel korozyon direnci ve yüksek özgül dayanım gibi avantajlara sahiptir [44], [45]. Ancak, β-titanyum alaşımlarının biyouyumluluğuna ilişkin şimdiye kadar elde edilen uzun vadeli klinik uygulama verileri ve takip raporları sınırlı sayıdadır [46].…”

Fabrication of a Promising Hierarchical Porous Surface on Titanium for Promoting Biocompatibility

“…Metallic materials have been extensively applied in surgical implants [1][2][3][4][5]. Among them, titanium (Ti) and its alloys are widely adopted as metallic implants owing to their superior physical and chemical properties [6][7][8][9][10][11][12][13][14][15]. Ti and its alloys exhibit excellent corrosion (crevice corrosion and pitting) resistance.…”