Ti基金属玻璃复合材料的腐蚀行为

Corrosion Behaviour of Ti-based Bulk Metallic Glass Matrix Composites

采用水冷铜坩埚悬浮熔炼-铜模吸铸法制备了直径为3mm的(Ti0.5Ni0.5)80Cu20金属玻璃复合材料试样,对合金的组织结构进行表征,用电化学工作站三电极体系测试了不同腐蚀介质中的动电位极化曲线,并分析表征电化学腐蚀后的形貌和腐蚀产物。结果表明:合金组织由非晶基体+形状记忆晶体相组成,在铸造过程的温度梯度下呈现梯度组织,边缘为快冷形成的无序密堆非晶结构,心部主要析出相为过冷奥氏体相。在人工海水和模拟人体的PBS溶液中,合金均表现出良好的耐蚀性。与晶态TC4合金相比,自腐蚀电位高,腐蚀的热力学倾向小;自腐蚀电流密度低,极化电阻高,腐蚀的动力学速率低。合金在PBS溶液中由于介质中活性阴离子浓度低,比在人工海水中表现出更优异的抗蚀性。在腐蚀形貌中未发现点蚀坑,边缘区的氧化膜较心部区域更为致密均匀。

（Ti0.5Ni0.5）80Cu20 metallic glass composite samples with 3mm diameter were prepared by the levitation suspend melting-water cooled Cu mold process, microstructure of the alloy was character-ized. The potential dynamic polarization curves in the different media were tested by electrochemical workstation in a three-electrode system, meanwhile, the electrochemical corrosion morphology and corrosion products were analyzed and characterized. The results show that the microstructure consists of amorphous matrix and shape memory crystal phase, exhibits gradient microstructure in casting process of temperature gradient, random dense pile of amorphous structure is formed in the edge area due to fast cooling rate, the main precipitation phase is overcooling austenite phase in the core area. In artificial seawater and simulated body solution （PBS）, the alloy exhibits good corrosion resistance. Compared with crystalline TC4 alloy, the alloy exhibits high free corrosion potential that shows low corrosion thermodynamics tendency and has low corrosion current density as well as high polarization resistance that indicates low dynamic corrosion rate. Due to the low activity anion concentration in PBS solution, the alloy exhibits more excellent corrosion resistance than in artificial seawater. No pit-ting corrosion pits and corrosion products were found after electrochemical corrosion. The oxide film in the edge area is more compact and uniform than in the core area as well.