Crack Propagation behavior Under Low-Cycle Corrosion Fatigue of A7003-T6 Aluminum Alloy

Abstract

Crack propagation behavior has been observed in A7003- T6 aluminum alloy under low cyclic loading with hold time over the frequency range 4×10^-31 Hz in 3.0% saline solution. From the experimental results, the effect of cyclic frequency on crack propagation rates was found to be exemplified by two different regimes. One has a positive dependency on the frequency below a critical frequency, f_crit, at which point maximum environmental attack occurs in terms of da/dN, and the other is negative above f_crit. The behavior of crack propagation below f_crit was explained by the concept of stress assisted dissolution which tends to inhibit mechanical failure by crack blunting and microbranching. The number and depth of secondary cracks occurring under the fracture surface were measured by metallographic examination, and the actual crack tip stress intensity factor was estimated.