On The Correlation Between Surface/Interface Microstructures And Electron Work Function Of Light Alloys

Light alloys have been used in the fields of aerospace, transportation, petrochemical and so on due to their advantages, such as light weight, high strength, strong corrosion resistance, etc. With the development of modern society, more and more requirments are added to the quality of alloys and their joints. The surface and interface behaviors are one of the mot important factors affecting the surface corrosion and joint strength of alloys and their joints. Therefore, it is very necessary and significant to investigate the correlation between surface/interface microstructures and electron work function of light alloys.This thesis investigated the correlation between surface/interface microstructures and electron work function of aluminum and titanium alloys as well as their joints, and evaluated the effect of surface/interface microstructures on the corrosive mechanisms of light alloys. The surface and interface work function of light alloys were measured using a scanning kelvin probe system, and their morphology was monitored using a scanning electron microscopy in order to build up the correlation between the work function and surface morphology and obtain th information associating with the surface corrosion and mechanical properties.Our results indicated that the electron work increased with the increase of the thickness of the oxidation layers on the surface of light alloys because the thick oxidation layers effectively limited the escape of free electron. The surface roughness of alloy surface had an important effect on the work function, and the large roughness corresponded to a high work function. During the surface corrosion, the surface work function was dependent on the corrosive process. Generally, the resistant to corrosion was weak when the corrosive current and the fluctuation of work function were high. In addition, we found that the work function of alloy joints at the interfacial region was strongly depended on the surface morphology and grain size, and the mechanical properties was almost linear with the change of work function. Based on these facts, a method of evaluating the joint strength using the scanning kelvin probe technique was found.