Corrosion Mechanisms in Amorphous-Partially Nanocrystalline Alloys

该项目旨在从根本上理解纳米晶非晶合金的尺寸、成分和结构控制局部腐蚀和酸诱导去钝化性能的机制。所考虑的合金包括前过渡金属如锆、后过渡金属如铁和简单金属元素如铝。在不同温度下处理各种组合物以研究组合物和结构的影响。这类材料表现出比常规多晶合金更大的机械强度和弹性模量，同时只要纳米晶体的直径保持小于20 nm，就能保持完全非晶态的优异的宏观耐腐蚀性。该项目的一个主要目标是调查与尺寸相关的基本方面，这些方面决定了对酸中的一般腐蚀和局部腐蚀坑的形成的抵抗力。这项研究发展了新的基本认识，涉及保持耐腐蚀性沿着这些纳米材料的高机械强度。该项目包括广泛的电子显微镜建模和实验工作。腐蚀性能将与纳米尺度电化学性能以及纳米尺度组成和结构的理解联系起来。因此，这项研究将提供新的纳米尺度的结构，性能知识的腐蚀行为的一个通用类的材料的技术意义。这些新合金可用于需要高比强度和形状控制的部件，例如MEMS和NEMS，其中几乎不耐受腐蚀。这项研究的资助为研究生和本科生提供了一个机会，包括代表性不足的少数民族，以发展在腐蚀和材料科学的多学科领域的理解和经验。本研究对纳米晶-非晶合金的腐蚀机理有了新的认识，并努力避免这些新合金在高强度和良好的耐腐蚀性之间的权衡。除了科学进步，这项研究将有助于开发MEMS和NEMS技术所需的具有优异耐腐蚀性的高强度合金。

This project is aimed at fundamental understandings of the mechanisms by which nanocrystal size, composition and structure control both localized corrosion and acid-induced depassivation properties in nanocrystalline-amorphous alloys. The alloys being considered include early transition metals such as zirconium, late transition metals such as iron and simple metal elements such as aluminum. Various compositions are processed at different temperatures to investigate the influence of composition and structure. This generic class of materials exhibits greater mechanical strengths and elastic moduli than conventional polycrystalline alloys while simultaneously retaining the excellent macroscopic corrosion resistance of the fully amorphous state as long as nanocrystals remain smaller than 20 nm in diameter. A major goal of the project is to investigate the underlying aspects associated with nanocrystal size that govern the resistance to general corrosion in acids and the formation of localized corrosion pits. This study develops new fundamental understanding involved with preserving corrosion resistance along with high mechanical strength of these nanomaterials. The project includes both modeling and experimental efforts with extensive electron microscopy. Corrosion properties will be linked with understandings of nm-scale electrochemical properties as well as nm-scale composition and structure. Thus, this research will provide new nanometer-scale structure-property knowledge regarding the corrosion behavior of a generic class of materials of technological significance. These new alloys may be useful in components requiring high specific strength and shape control such as MEMS and NEMS where little corrosion can be tolerated. The funding of this research provides an opportunity for graduate and undergraduate students including underrepresented minorities to develop understanding and experience in the multi-disciplinary fields of corrosion and materials science. This research develops new understanding of the corrosion mechanisms in nanocrystalline-amorphous alloys and strives to avoid the trade-off between high strength and good corrosion resistance in these new alloys. In addition to scientific advances, this research will be useful in the development of high strength alloys with excellent corrosion resistance required in MEMS and NEMS technologies.