SPS烧结Ti-25Ta-3Ag合金的组织演变与腐蚀行为研究

Microstructure Evolution and Corrosion Behavior of Ti-25Ta-3Ag Alloy via Spark Plasma Sintering

采用XRD、SEM等测试手段对SPS烧结的Ti-25Ta-3Ag生物合金的物相、形貌和微观结构进行表征:采用开路电位、动电位极化曲线和电化学阻抗谱等方法研究了不同烧结温度制备的合金在人工模拟体液(Hank's溶液)中的电化学腐蚀行为。结果表明:Ti-25Ta-3Ag烧结产物中存在α相(不规则多边形)、马氏体α"相(针状)和β相(片层状),同时在晶界处有单质Ag(白色颗粒)析出。电化学实验结果表明:随着烧结温升高,合金的耐腐蚀性能增强。该合金在人工模拟体液中耐腐蚀性能优异的主要原因是:Ag提高了合金的腐蚀电位,且在晶界析出,由于Ag的高耐腐蚀性,使得晶界不易发生腐蚀;另一方面合金表面形成的钝化膜主要由TiO2和Ta2O5氧化物、Ti和Ta的低价态氧化物以及金属Ag组成,且钝化膜与基体钛结合紧密,其稳定性和保护性更强。

Biomedical Ti-25Ta-3Ag alloys were prepared by spark plasma sintering(SPS).The microstructure,morphology and phases of the alloy were characterized by XRD and SEM.The effects of sintering temperature on the electrochemical corrosion properties were investigated in artificial simulated body fluid(Hank's solution)by open-circuit potential,potentiodynamic polarization and electrochemical impedance spectroscopy.The results show that there are a phase(irregular polygon),martensite α"phase(needle)and β phase(platelets)in the sintering product of Ti-25Ta-3Ag.and the elemental Ag(white particle)precipitates at the grain boundary.Electrochemical experiments show that the corrosion resistance of the alloy is improved with the increase of the sintering temperature.The excellent corrosion resistance of the alloy in Hank's solution is attributed to the fact that Ag addition in the alloy improves the corrosion potential as well as Ag precipitates at the grain boundary;due to the high corrosion resistance of Ag,the grain boundary is less prone to corrosion.On the other hand,the passivation film formed on the surface of the alloy consists of TiO2 and Ta2Os oxides,low ionic oxides of Ti and Ta as well as metal Ag precipitations,and the films bond tightly with the substrate,whose stability and protection are enforced.