A NEW COMBINATORIAL APPROACH TO PROPERTY-DRIVEN DESIGN OF Ti ALLOYS FOR BIOMEDICAL APPLICATIONS

Abstract

Ti and Ti based alloys containing nontoxic elements, such as Nb, Mo, Ta, and Zr have been proposed as prospective candidates for biomedical applications, due to their excellent corrosion resistance, biocompatibility, high strength, toughness and wear resistance. However, stress shielding has become a major setback to their application.  When elastically soft bone tissue (~E=20-40GPa) is replaced by a stiffer implant, the implant takes over a considerable amount of the load, shielding the surrounding parts of the skeleton.  Reducing the physiological loads on the bone induces re-sorption processes that give rise to a drop in bone density, mineralization state and strength.  Stress shielding can finally promote contact loosening, implant failure, or debris-induced infections. For this, the aim of this study is to develop a new biomaterial to use in the load transfer implant field.  An ab initio theoretical calculation was used to couple elastic properties from homogenised multiphase elastic parameters for the design of new Ti-Mo-Nb-Zr alloys with bone matching modulus. The agreement between the predictions and detailed experimental characterization, sheds light on the decisive influence of the multi-phase character of the polycrystalline composites on their structural and mechanical properties. An attempt is also made to highlight the influence of heat treatment and cold work in enhancing the modulus of the alloys. The study shows that the novel combinatorial approach can be highly beneficial as it may lead to something of a breakthrough with respect to reducing the Young’s modulus of metallic biomaterials, which is pertinent to preventing stress shielding and bone resorption in orthopedic implants.