The electrochemical corrosion and stress corrosion crack growth properties of untextured and textured 2014 Al-Cu-Mg-Si alloys were studied related to ageing conditions in aqueous solutions of 53 g NaCl and 9 ml 30% $H_2O_2$/1 $H_2O$ (pH=5.5-5.6) at 30℃ and of 3.5 wt.% NaCl solution (pH=2.0-2.2) at 27℃, respectively. The compositions of the alloy tested were Al-4.65 Cu-0.46Mg-1.00Si-0.93Mn-0.18Fe in weight percentage.
Electrochemical corrosion potential and corrosion rate were measured by means of potentiostatic method. The relation between stress corrosion crack growth rate V and the plane strain stress intensity factor $K_I$ was obtained by using Manjoine's WOL (Wedge-Opening-Loading) specimen under constant tension loading and in the NaCl test medium.
Corrosion potential decreased with ageing time for both untextured and textured specimens, showing that the untextured specimen was more cathodic than the textured specimen in the initial stage of ageing. Corrosion rate increased and then decreased for textured specimens with ageing time. However, it decreased with ageing time for untextured specimens.
Critical plane strain fracture toughness for stress corrosion cracking (SCC) K$_{\mbox{ISCC}}$, J$_{\mbox{ISCC}}$ and (K$_{\mbox{ISCC}}$/K_${\mbox{IC}})^2$ decreased and then increased for both untextured and textured specimens with ageing time. However, relative change in plane strain fracture toughness due to SCC K$_{\mbox{IC}}$-K$_{\mbox{ISCC}}$/K$_{\mbox{IC}}$ showed an increase and then decrease with ageing time for both untextured and textured specimens.
Thus in the present study, the value of (K$_{ISCC}}/\sigma{\mbox{ys}})^2$ was considered as a measure of resistivity of SCC in the linear-elastic range and relative change in plane strain fracture toughness due to SCC, K$_{\mbox{IC}}$-K$_{\mbox{ISCC}}$/K_{\mbox{IC}}$ as a measure of susceptibility to SCC. The untextured specimen was shown to be more resistant to SCC than the textured specimen.
