Ni-Fe-W-B非晶合金的晶化行为及其电化学腐蚀特性研究

Crystallization Behavior and Electrochemical Corrosion Characteristics of Amorphous Ni-Fe-W-B Alloy

采用单辊急冷法制备了57.5Ni-24.5Fe-14.5W-3.5B(质量分数,%)非晶薄带,并在不同温度下进行退火。用DSC和XRD分析了非晶薄带的晶化行为及析出相的演变过程;用电化学极化曲线及电化学阻抗法研究了试样在3.5%NaCl溶液中的电化学腐蚀行为;用SEM和EDS分析了试样腐蚀后的表面显微形貌及成分。结果表明:该非晶薄带的晶化过程分为3步,其晶化温度约为430,470和700℃;退火试样的耐腐蚀性整体优于非晶合金样,部分晶化试样的抗电化学腐蚀性能优于完全晶化试样;500℃退火试样表面形成致密钝化膜,抗腐蚀性能优异,而非晶薄带和720℃退火试样形成的钝化膜不稳定,易被点蚀和局部腐蚀。

57.5Ni-24.5Fe-14.5W-3.5B（wt%） amorphous ribbons were prepared by a melt spinning method, and then annealed at different temperatures. The crystallization process and evolution of phases were identified by differential scanning calorimeter and X-ray diffraction. A comparative study of the electrochemical corrosion behaviors of the samples was performed by the linear polarization method and electrochemical impedance spectroscopy in 3.5 wt% Na Cl solution. The morphologies and components of the samples after potentiodynamic polarization were analyzed by SEM and EDS, respectively. The results show that the crystallization process of the amorphous ribbons could be divided into three steps, and their crystallization temperature are about 430 °C, 470 °C and 700 °C. Compared with the completely amorphous alloy, the corrosion properties of the annealed amorphous sample increase obviously. A stable passive film is formed on the surface of the amorphous ribbon annealed at 500 °C, which contributes to its excellent corrosion resistance. However, the passive films on the surfaces of completely amorphous and amorphous samples annealed at 720 °C are not stable, which are susceptible to be attacked by pitting corrosion and localized corrosion.