3D Surface Topography And Its Corrosion-resistant Research Of Milling Aeronautic Aluminum Alloy

The aviation manufacture industry is a high-tech intensive industry, which represents the level of national manufacturing technology. Aerial aluminum alloy is widely used in aviation industry for its low density, high strength, and many other excellent performances. New machining processes such as high-speed machining, hard machining, dry machining and precision machining have been widely employed. Lots of researches focus on mechanism, process, etc, while less focus on the corrosion resistance of machined parts.Corrosion problem is very important in the aviation industry.The marine environment will accelerate the corrosion of the metal. Aircraft corrosion problems, especially the structure of the stress corrosion and corrosion fatigue often result in catastrophic accidents, which affect the reliability and security of aircraft.Surface integrity such as surface morphology, residual stress, physical damage, play an important role in corrosion resistance of parts. In this paper, the effects of surface morphology on corrosion are mainly investigated. The objective of this research is to reveal the relationship among cutting process, surface morphology characteristics and component corrosion resistance.End milling and side milling have been condcuted to reveal the influence of the cutting parameters (cutting speed and per tooth feed) on surface roughness and residual stress. The results show that high-quality machined surface was achieved when cutting speed is1500m/min and per tooth feed is0.2mm. Surface residual stress is compressive stress in low speed milling and with the increase of cutting speed, it transition to the tensile stress.Three-dimentional surface topography has been characterized by parameter characterization method. Three-dimensional surface roughness has been studied by separating roughness from reference surface with Fourier-Gauss filter, to calculate the amplitude parameters related to the peak and valley. Root mean square deviation Sq can be used to describe the degree of surface roughness. That is, Sq is larger when surfce is rougher. Partial slope Ssk and kurtosis5ku are related to the distribution of peaks and valleys and theirsteep degree, which can be used as reference parameters to measure the surface corrosion resistance. When cutting speed is too high or too low, it is easy to generate pits or pinnacles on surface, which corrosion solution is easy to accumulate. It is bad to the corrosion resistance.The salt mist corrosion experiment of aluminum alloy7050-T7451has been conduted to simulate the corrosion mechanism in the marine environment. The main corrosion pattern was pitting accompanied with local denudation. With the increase of corrosion cycle, the length, width, surface area, depth and number of the corrosion pits increased. The pits of irregular or triangles shape in the plane are gradually evolved into round or oval shapes and the pits are mostly distributed along the cutting marks. Corrosion damage degree and average corrosion depth were used for corrosion damage evaluation.The influence of surface texture on the corrosion resistance has been researched through electrochemical experiments and self-corrosion potential and corrosion rate were used for the quantitative evaluation of its corrosion resistance. The results reveal that corrosion resistance is related to processing texture in some extent.Polished surface texture present the best corrosion resistance performance.This paper is supported by National Natural Science Foundation of China (grant number51175306) and Natural Science Foundation of Shandong Province (grant number ZR2010EQ041).