Quantitative analysis on surface potentials of impurities and intermetallic compounds dispersed in Mg alloys using scanning Kelvin probe force microscopy and ultraviolet photoelectron spectroscopy

Abstract

It is well known that metallic impurities such as Fe, Cu, and Ni cause galvanic corrosion of Mg alloys because of the local cells formed at the interface between these impurities and the Mg matrix. The alloying elements of Mg alloys, such as Al, Mn, Si, and Ca, exist as intermetallic compounds (IMCs) to enhance their mechanical properties. On the other hand, some of these metallic impurities and IMCs influence the galvanic corrosion. In this study, the effects of secondary phases such as impurities and IMCs on the galvanic corrosion behavior of Mg alloys were quantitatively evaluated using the surface potential difference at the interface measured through scanning Kelvin probe force microscopy and ultraviolet photoelectron spectroscopy. Bulk IMC samples were successfully fabricated from the elemental mixture powder by solid-state sintering method based on powder metallurgy process. The correlation between the work functions and surface potentials of the impurities and IMCs was experimentally and theoretically investigated.