Desigh And Research On Properties Of New Type Metastable β Titanium Alloys With Room Temerature Martensite Transformation For Biomedical Applications

Titanium alloy has been widely used in repairing and displacement of human's hard tissue such as bones and teeth for it's good biocompatibility. Because of the stress-shield effect, which caused by the dismatch of the elastic modulus between metal and human's bone, a metal have a lower elastic modulus would be favored.β-type titanuim alloy has been found have a lower elastic modulus, further more, it is noticed that when the transformation fromβphase toα''martensite can been started in room temperature, not only a so called shape memory effect and supper elastic effect can be found but also a very low elastic modulus can be made.In this study, two new meta-stableβtitanuim alloy without toxic element has been designed based on the d-electron alloy design method. Alloy samples was prepared in WKII vacuum unconsumable electrode arc skull furnace, then alloy samples were cold rolled followed by hot forge. Heat treatment are also needed to improve the mechanical properties. Two new designed alloy samples were solution treatment finished by water quenched, then aged in two different process. The microstructure and phase structure of alloy samples in different heat treatment state s have been analysed by SEM, metalloscope and XRD, the relationship between mechanical properties and different heat treatment process were also studied. The results indicated that:1.β-phase can be reserved in room temperature in both alloy, and theβ-phase is metastable in room temperature, when stress added on it, martensite transformation could be induced.2. Both designed alloy have a extremity low elastic modulus in solution treat statement, it's about 40GPa. This caused by the stress-induced martensite transformation, meanwhile it also made a non-linear elastic deformation which appeared on the stress-stain curve. The supper-elastic effect was found in room temperature, but shape memory effect are not detected. It is because the martensite transformation temperature are lower than room temperature.3. The elastic modulus increased with the elongation of aging time, which made the volume ofαparticle rising. Tensile strength and hardness increased for the same reason.4. The biocompatibility test which include corrosion test, hemolysis test and simulated body fluid cultivation shows the fact that both new designed alloy have good biocompatibility, and the ability of corrosion resistance and anti-hemolysis are even better than NiTi.