Study On SCC Of The 2A12 Hard Aluminum Alloy Used In Aircraft

SCC (stress corrosion cracking) of 2A12cz aluminum alloy in the 3.5% NaCl solution was approached in this paper. The aim of this paper was to clear the effect of temperature, strain and loading direction on SCC of 2A12cz aluminum alloy in the 3.5% NaCl solution. And SEM (scanning electronic microscope) was employed to test the crack morphology of SCC.With increasing of the plane's active time, stress corrosion has been a serious problem which can severely effect on and restrict in safe working, regular maintenance and repair of the plane. The paper summed up the general situation and problems of the similar studies at home and abroad. In order to solve these problems, the electric stress corrosion equipment was made. SCC of 2A12cz aluminum alloy in the 3.5% NaCl solution was studied and the reason for SCC was discussed. The V-t curve achieved was changed into a-t curve, K_I value was calculated and K_ISCC and da/dt value were gained on each experimental condition. As a result, the K_I-V curve and da/dt-K_I curve were achieved on each experimental condition. The SCC fracture morphology under different experimental conditions and the cracking mechanism was discussed.The conclusion was that the temperature increased leading to da/dt value increased, K_ISCC value decreased, so SCC life-span became smaller. The strain increased leading to da/dt value of 2A12cz aluminum alloys in 3.5% NaCl solution increased, K_ISCC value decreased, so SCC life-span became smaller. When the loading direction was 45°angle with rolling direction, da/dt value of 2A12cz aluminum alloys in 3.5% NaCl solution was biggest and K_ISCC was smallest. In short, the direction of 45°was the most sensitive direction of 2A12cz aluminum alloy SCC. The direction of 90°was less sensitive. From the analysis to fracture section, it was known that the fracture morphology of the SCC of 2A12cz aluminum alloys in 3.5% NaCl solution was mainly intergranular fracture and it was rock candy structure. The fracture belonged to brittleness fracture on macroscopic. On microcosmic, the fracture partly had characteristics of ductile fracture. The SCC of 2A12cz aluminium alloy was mainly resulted from anodic dissolution, hydrogen and brittleness in action together. Hydrogen and brittleness is very important in stress corrosion cracking and expanding. Anodic dissolution is the mainly fracture mechanism of SCC of 2A12cz aluminum alloy.