In the early 1940's, the development of titanium alloy was gradually carried out, and Bothe et al applied titanium to the rat bone, and found that the compatibility of rat bone with titanium was good, and no adverse reactions occurred. 50 ~ 60 s of the 20th century, the development of the titanium alloy with high temperature resistant properties, in the early 70 s, a group of corrosion resistant titanium alloy have been developed, in the mid - 80 - s phase, the second generation of type a + beta without vanadium titanium (Ti - 6, 7 nb and Ti - 5 Al - 2.5 - Fe) has been developed, in a certain clinical application, but this kind of toxic elements in alloy Al and Fe can bring certain harm to human body, and the elastic modulus of the alloy is still not up to the standard of the real femur, produces the stress shielding around the implant appear the phenomenon of bone resorption, implant rupture caused by loose or leading to implant failure. At the beginning of 1990, the United States and Japan began to work on the third generation of new medical titanium alloys, which were dominated by beta titanium alloys.
Although titanium alloy has good biocompatibility, it belongs to biological inert material. Wear resistance is low, under the condition of wear easy to generate a large number of chip, containing titanium may induce inflammation, even lead to bone tissue around implant dissolved, reduce its service life. On titanium alloy surface modification can retain the original on the basis of the excellent properties of titanium alloy, make its biocompatibility, wear resistance, corrosion resistance, etc, to strengthen and improve its clinical use performance in order to better play its use value. There are many methods for surface modification of titanium alloy, including oxidation modification, gas phase deposition, ion implantation, plasma spraying and laser surface modification.
When choosing to adapt to medical materials, the elastic modulus, toughness, strength and corrosion resistance of materials are the necessary factors for different parts. Yu zhentao et al. compared the different metal elements in the experiment, and their results were shown as follows: V, Co, Cd, Cr, Ni, Hg and other elements were more virulence, Fe and Al elements were secondary. In the body of the spleen, liver, kidney and other parts of the organism, the ionic precipitates of V were found, and its biological toxicity was relatively large. Al elements also accumulate in the body in the form of Al salt, resulting in nervous system disorders and damaged organs. Ta, Mo, Zr, Sn, Pd, Hf, Nb and other elements have good biocompatibility and can be used as addition elements of alloy. Mo, Sn, Zr, TaHf, Nb, Pd have good chemical stability, and Ta, Nb, Zr, Mo can reduce the elastic modulus of alloy, so it can effectively improve the stability of the alloy. To sum up, the ideal alloys for biomedical titanium alloys include ti-mo-nb, ti-zr-nb, ti-zr-mo-nb and ti-zr-sn-mo-nb, etc.
In the design process of titanium alloy, d electronic design theory is the basic method of alloy design. The basic idea is: based on Ti and add elements of the electron orbital parameters calculation, get the corresponding value and Bo, Md, in turn, elastic modulus and tensile strength of alloy and related parameters were analyzed. The experimental results show that the lower Md value is favorable for phase stabilization, and the higher Bo value is conducive to enhancing the strengthening effect of solid solution. The Md value of 2.35~2.45 and the Bo value of 2.75~2.85 should be controlled in the design of the meso-stabilized titanium alloy. The thermal stability of the titanium alloy can slip and deform during the process of plastic processing, while the stability of the titanium alloy can occur slip, martensite or twin deformation. Therefore, the properties of materials can be improved by controlling the microstructure of different alloys.
