The effect of atmospheric corrosion on metal fatigue

Abstract Polycrystalline specimens of copper, aluminium and gold were fatigued in, reversed bend in various pressures of air and in water vapour and inert gases. The ratio of life in atmosphere of air 60 that. in vacuum (∼ 10−6 mm Hg) at lives of about 106 cycles was 1:20 for copper, 1:5 for aluminium and about 1:1 for gold. Some specimens were examined at intervals during the test. Small cracks a few microns deep formed in the first few hundredths of the life in air and after the same number of cycles in vacuum. The effect of air was to speed the propagation of cracks in copper and aluminium but not gold. Electron micrographs showed that extrusions and intrusions can occur close to each other in the same slip band.