Fe基非晶合金的微观非均匀性调控及其与腐蚀行为的关联研究

Owing to a series of merits, including the low cost, excellent corrosion resistance, high strength, and outstanding hardness, Fe-based amorphous alloys have a widespread application prospect in the corrosion protection and other fields. However, during the application process, the microstructure of amorphous alloys would inevitably be influenced by the external environment. Up to date, the response mechanism of heterogeneity to the external factors and the correlation between heterogeneity and corrosion behavior are still obscure. In this project, the novel Fe-Cr-Mo-W amorphous alloy system is selected as the model material. In order to modify the heterogeneity and corrosion behavior, heat and irradiation treatments are conducted. By analyzing the radial distribution functions, the quantitative parameters of the “liquid-like region”, the short/medium-range structure and composition characteristics of amorphous alloys, the response mechanism of heterogeneity to the heat and irradiation will be verified. Through the in-situ heat treatment tests, the relationship between microstructure evolution kinetics and microstructure morphology will be revealed. On this basis, considering the corrosion behaviors of Fe-based amorphous alloys, both of the correlation between heterogeneity and corrosion behavior, and the local corrosion mechanism will be ultimately clarified. Consequently, our project is expected to provide new insight into the modification of corrosion behavior and have great directive significance for the development of novel amorphous materials with excellent corrosion resistance or selective corrosion.

由于成本低、耐蚀性强、强度和硬度高等优点，Fe基非晶合金在腐蚀防护和其它领域有着广阔的应用前景。但在实际应用过程中非晶合金的微观结构不可避免会受到外场环境的干扰，目前非晶合金微观非均匀性对外场因素的响应机制以及与腐蚀行为的关联性仍不清晰。本项目以新开发的Fe-Cr-Mo-W系非晶合金为模型材料，拟采用热处理和辐照处理等方法调控合金的微观非均匀性和腐蚀行为，通过分析非晶合金的径向分布函数、“类液体区”的量化参数、短中程结构成分信息等，明确微观非均匀性对温度和辐照的响应机理；借助原位热加载试验，揭示非晶合金微观结构演变动力学与微观精细结构形貌间的关系。在此基础上，结合不同处理态非晶合金的腐蚀行为研究，最终确定Fe基非晶合金的微观非均匀性与腐蚀行为的内在关联，阐明局域腐蚀机理。本项目为优化和设计非晶合金的腐蚀行为提供了新思路，对发展高耐蚀性或选择性腐蚀非晶态材料具有重大的指导价值。

由于成本低、耐蚀性强、强度和硬度高等优点，Fe基非晶合金在腐蚀防护和其它领域有着广阔的应用前景。但在实际应用过程中非晶合金的微观结构不可避免会受到外场环境的干扰，目前非晶合金微观非均匀性对外场因素的响应机制以及与腐蚀行为的关联性仍不清晰。本项目以非晶合金的结构不均匀性和腐蚀行为的演变为桥梁，揭示Fe基非晶合金的微观非均匀性与腐蚀行为的内在关联，并阐明局域腐蚀机理。具体展开了如下研究工作：.(1) 分析了Fe基非晶合金在不同温度退火后的结构不均匀性、力学性能、电化学行为和钝化膜特性。通过对分布函数分析，发现在玻璃转变温度以下退火的非晶合金在1 mol/L HCl溶液中形成了一层致密的钝化膜，这主要是由于退火后非晶结构的自由体积减小和第一配位层收缩引起的。与之相反的，在过冷液体区退火后非晶合金的第一配位层变大，且非晶基体中生成了纳米级别的类晶体团簇，从而降低钝化膜的稳定性和保护性，最终恶化其耐腐蚀性。.(2) 探究了Ar+辐照下Fe基非晶合金的微观结构、电化学反应和钝化膜特性。在高辐照剂量下，非晶合金基本上保留了非晶结构，并在1 mol/L HCl溶液中表现出优异的耐蚀性。随着辐照量的增加，非晶相基质中逐渐析出越来越多的类固体区团簇，甚至析出了纳米晶。钝化膜的化学组成、价态分布和功函数等均表明纳米晶的析出破坏了钝化膜的均匀性和稳定性，从而降低了非晶合金的耐腐蚀性。这一发现表明了非晶合金在极端核辐照条件下的应用前景。.(3) 研究了低温弛豫对Fe基非晶涂层的显微结构、机械性能、润湿性和电化学性能的影响。由于自由体积的减少，低温弛豫可以提高非晶涂层的热稳定性、硬度和表面疏水性，进而提高其在3.5 wt.% NaCl溶液中的耐蚀性。这一发现阐明了低温弛豫与Fe基非晶涂层性能之间的关系，有利于改善非晶涂层的性能。.此外，从成分和结构的角度阐述了Fe基非晶涂层材料的腐蚀和其它性能，并总结了低温驰豫处理、刻蚀处理、封孔处理等改善措施，为后期相关工作的继续开展打下夯实的基础。