Nature of Surface Microcracks on Phosphorus Micro‐Alloyed Copper

The effect of plastic deformation and environment on the appearance of surface microcracks on phosphorus micro‐alloyed copper (Cu‐OFP) was studied by tensile test, scanning electron microscopy and focused ion beam milling (SEM‐FIB). Specimens tested in ambient conditions under tensile loading showed several thousand microcracks per mm 2 , with maximum length in the range of 15–20 µm and maximum depth of about 3 µm. Increasing plastic deformation resulted in a larger number of microcracks. While specimens tested in water with 80 mg/L sulfide showed a much smaller microcrack density, with no indication of growth due to the presence of sulfides. Tensile testing of three different batches of Cu‐OFP material showed similar results, suggesting that the results are batch‐independent. These results indicate that surface microcracks form on Cu‐OFP due to plastic straining both in air and in sulfide‐containing water. Furthermore, this study demonstrates that, under the tested conditions, sulfide exposure does not promote microcrack propagation through stress corrosion cracking.