The effect of environment on fatigue crack growth behavior of aluminum alloy 5456

The effect of laboratory air, water vapor and oxygen on fatigue crack propagation behavior of aluminum alloy 5456 has been investigated over a range of growth rates spanning five orders of magnitude. Environmental interactions in the intermediate region are found to be associated with microscopic fracture features and mechanisms governing degradation. The alloy shows significantly enhanced crack growth rates in the environments of laboratory air and water vapor than in the oxygen environment. Mechanisms contributing to the enhanced crack growth rate are examined and discussed in light of constituents in the environment, fracture surface features and microstructure.