Titanium in Biomedical Applications

  Médecine, Science

The good biocompatibility and high corrosion resistance of titanium (Ti) and its alloys makes them more suitable for biomedical applications compared to other commonly used metallic materials. However, various factors can cause health problems when Ti-based alloys are used for implants, due to the presence of elements such as Al and V that can be released as ions. Thus, research has focused on the development of new titanium alloys which contain only non-toxic elements, and more particularly titanium alloys of the β-metastable type which possess the specificities required for the envisaged applications.

Objective

In the present study, molybdenum, manganese and iron were selected as titanium alloying elements to obtain alloys for biomedical applications. Molybdenum in titanium alloys can improve corrosion resistance, help reduce Young\’s modulus and improve ductility, while adding iron to a titanium alloy can improve its strength. Since Mo, Mn and Fe are omnipresent and inexpensive, their use will lead to low cost alloys. Hypotheses Ti-Mn, Ti-Mo and Ti-Mo-Fe beta-type alloys have been tested to evaluate their compatibilities for biomedical applications. Pedro Fernandes Santos and his colleagues tried ,at first, to compare the mechanical properties of the same Ti-Mn alloy but produced according to various processes. Then, for a maximum of 13% weight of Mn in a Ti-Mn alloy, the tensile strength (938 to 1162 MPa) and the hardness (294 to 308 HV) of the alloys produced by the metal injection molding process are comparable to those of Ti-Mn alloys made by cold crucible levitation melting. Also, they found that Ti-9% Mn has the best balance between tensile strength (1046 MPa) and elongation (4.7%) among the 8-17% Mn alloys tested, and has a Young\’s modulus of (89 GPa ).

Niinomi compared the Ti-6Al-4V alloy with Ti-Mo-Fe alloys, which are not only less expensive, but also more compatible than Ti-6Al-4V considering many mechanical properties such as the Young\’s modulus. hardness and strength, and these properties are suitables for biomedical applications. Pedro Fernandes Santos and his colleagues said that the observed low ductility of alloys is attributed to the combined effects of high oxygen content, with the presence of interconnected pores and titanium carbides. As well as the elongation and the tensile strength of the alloys decrease with the increase of the Mn content. Yasser Abdelrhman and his colleagues have shown that the Ti-Mo-Fe alloy has a higher strength (949 MPa) and hardness (422 HV) and a lower Young\’s modulus (84.5 GPa) compared to an alloy Ti-Mo-Fe. 6Al-4V (900 MPa, 288 HV and 110 GPa, respectively). In addition, they have shown that the co-addition of molybdenum and iron as alloying elements in these new alloys increases resistance and reduces Young\’s modulus, making them more suitable for biomedical applications. Ti-Mo-Fe alloys showed higher corrosion resistance and low corrosion current densities (in the range of 10-9 A / cm 2) than the Ti-6Al-4V alloy. The oxide films formed on the surface of Ti-Mo-Fe alloys are passive protective films.

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