Microstructure And Biological Properties Of Ti-Ag Based Alloys For Biomedical Applications

Titanium and its alloys have been widely used as biomaterials due to its light weight, high corrosion resistance and excellent biocompatibility. Commercially pure Ti and Ti-6Al-4V alloy are most commonly used titanium materials for implant applications. However, the insufficient strength and poor wear resistance of unalloyed titanium was often complained. Furthermore, more and more concerns are raised due to the toxicity of aluminum and vanadium released from Ti-6A1-4V alloy. In addition, it has been reported that corrosion resistance of titanium and its alloys may be significantly reduced in environments containing fluoride ions, and fluoride ions often exist in oral environments.In this study, the optical microsturcture, phase constitution, mechanical properties, corrosion resistance, and biocompatilbity of the three series of Ti-Ag, Ti-Ag-Fe, and Ti-Ni-Ag alloys are systematically investigated. The influence of the alloying elements and the heat treatment on these properties is revealed by optical microsope, X-ray diffrictation, scanning electron microscope (SEM), Transmission electron microscope (TEM), tensile and compression test, wear test, electrochemical measurments and biocompatibility evaluations. Moreover, the antibacterial activity of Ti-Ni-Ag alloys is investigated.Ti-Ag alloys consist of single a phase at room temperature. Ti-Ag alloys show slightly higer strength and hardness values than that of CP Ti. Moreover, the wear resistance of Ti-Ag could be largely improved. The lower corrosion current and higher open circuit potential indicate that Ti-Ag alloys have better corrosion resistance in artificial saliva solution with and without NaF. They are corrosion-resistant metal and exhibit very low ion release amount in 1% lactic acid solution and 0.1 mol/1 H2O2+0.9% NaCl+de-ionized water solution. In vitro cytotoxicity tests indicate that these alloys do not present any cytotoxic effect and exhibite as excellent biocompatibility as CP Ti. The homogeneous single-phase nature of the Ti-Ag alloys leads to the formation of a uniform passive film which is able to separate the bulk of the alloy from an aggressive environment and, hence, is responsible for the low ion release rate and excellent cellular response.Ti-5Ag-xFe alloys are prepared andβphase could be retained by Fe addition. Ti-5Ag-xFe alloys show much larger compression strength and hardness values than that of CP Ti. Moreover, the wear resistance of Ti-5Ag-xFe could be largely improved by Fe addition. They also exhibit similar or improved corrosion resistance compared to that of CP Ti. The excellent corrosion resistance and low ion release rate can be mainly attributed to the TiO2 film on the surface. The cytocompatibility tests show that Ti-5Ag-xFe alloys indicate similar cell viability than that of CP Ti. Therefore, Ti-5Ag-xFe alloys may be good candidate as dental materials because of their superior mechanical properties, excellent corrosion resistance, low ion release rate and good biocompatibility.Ti-Ni-Ag ternarys alloy are successfully fabricated with arc-melting method with water cooling Cu bath. The Ag particles precipitated within the Ti-Ni alloy matrix, with the size ranging from several tens of nanometers to several micrometers. The tensile tests show that Ti-Ni-Ag alloy has higher strength than that of Ti-Ni binary alloy. Compared with Ti-Ni alloy, Ti-Ni-Ag alloy possesses similar corrosion resistance and cyto-biocompatibility. Moreover, Ti-Ni-Ag alloy exhibits reduced bacteria adhesion when compared with Ti-Ni binary alloy. The antibacterial effect is attributed to the release of Ag ions from the tiny Ag precipitates. Therefore Ti-Ni-Ag alloy is believed to be a functional biomaterial which combines antibacterial activity and shape memory effect, and is likely to broaden the range of the biomedical application of Ti-Ni alloy system.