Corrosion Mechanisms in Amorphous-Partially Nanocrystalline Alloys

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

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.