In-situ electrochemical noise characterization on crack initiation and propagation during misorientation dependent stress corrosion cracking in AA2195 Al-Cu-Li alloys

Crack initiation and propagation behaviour of misorientation dependent stress corrosion cracking (SCC) of AA2195 alloy was investigated using slow strain rate tests in conjunction with in-situ electrochemical noise (EN) analysis. Grain misorientation and stress loading direction plays a critical role in governing differential SCC fracture modes. Rolling direction (RD) samples with small misorientation primarily activated layered geometric slip, resulting in wedge-shaped intergranular (IG) fractures, whereas transverse direction (TD) samples with high misorientation presented basal slip, producing V-shaped IG/transgranular (TG) mixed fracture morphologies. Crack initiation and propagation where regions with large strain were strongly associated with approximate (111) and (101) crystal plane. EN analysis, supported by Fourier transform statistical analysis of current and potential fluctuations, in-situ revealed distinct corrosion dynamics. RD samples underwent pitting corrosion during elastic stage, followed by prolonged IG cracking, and finally exhibited uniform corrosion behavior in fracture stage. TD samples exhibited multiple-sites pitting and significant passivation before undergoing rapid IG/TG mixed crack initiation and propagation in fracture stage. EN technique has been proved as a promising way to in-situ monitor corrosion transformation and crack propagation in different SCC stages.