THE GROWTH OF SMALL CORROSION FATIGUE CRACKS IN ALLOY 7050

摘要

The corrosion fatigue crack growth characteristics of small (>35μm) surface and corner cracks in aluminum alloy 7075 is established. The early stage of crack growth is studied by performing in situ long focal length microscope (500X) crack length measurements in laboratory air and 1% NaCl environments. To quantify the "small crack effect" in the corrosive environment, the corrosion fatigue crack propagation behavior of small cracks is compared to long through-the-thickness cracks grown under identical experimental conditions. In salt water, long crack constant K_(max) growth rates are similar to small crack da/dN.