The Preparation And Properties Of TiNi Sharp Memory Alloy For Medical Application

TiNi alloy is currently a topic of notable interest for medical application because of its unique properties, such as shape memory effect, super-elasticity, corrosion resistance and biocompatibility. In this study, the development status of biomedical material was summarized firstly, then the medical application of TiNi shape memory alloy as well as its corrosion resistance and biocompatibility were reviewed. By research on the effect of annealing temperature on TiNi shape memory alloy's structure and mechanical properties, the process of annealing was ascertained. The biocompatibility of medical biomaterial is closely related to its surface properties. Surface modification technology will change the surface states of TiNi alloy and improve its biocompatibility. TiO2 thin film was prepared by magnetron bioactive engineering (MBE) on the surface of TiNi shape memory alloy. The super corrosion resistance and blood compatibility of tectorial TiNi shape memory alloy were validated through compare test. The following results were obtained:(1) It could be seen from the photo of TiNi shape memory alloy treated at different annealing temperature that the grain was isometric and distributing evenly. The grain degree of sample annealed at 650℃was maximal. This also showed that the grain was minimal;(2) It was verified that TiNi shape memory alloy was favorable in mechanical property according to its tensile curve. Under the optimal annealing temperature of 650℃, the TiNi shape memory alloy could obtain the maximal fracture strength of 937MPa, the maximal elongation coefficient of 44.5% and the maximal fracture surface contraction coefficient of 40.55%.It measured up to the require of medical biomaterial;(3) The cross-section micrographs of the TiO2 film was studied using SEM. The result showed that the oxidation film was distributing evenly and connected tight with basal body. The basis of this oxidation film was TiO2;(4) There was no desquamate on the film after 1000 times bending fatigue tests, it proved that the oxidation film had good adhesive force with basal body;(5) According to the contrastive test, the sample with a film was more preferable in corrosion resistance in simulative body liquid than the sample with no film.; Compared to the alloy which didn't make bending fatigue test, the corrosion potential of tectorial TiNi alloy which was treated by fatigue tests had nearly no change. They both indicated that this sample had satisfying corrosion resistance so it was appropriate for the application of biomedical.(6) At the same test mode, compared with the conventionally used medical 316L stainless steels, the tectorial TiNi shape memory alloy had longer thrombin time and plasma recalcification time, meanwhile the distortion and collective degree of the platelet adhered on its surface were less than 316L SS, which revealed that the activation extent of the latter on intrinsic coagulation factors is smaller than the former and the anticoagulant property of the latter is better.