Stress corrosion cracking behavior of friction-stir-welded Al 6061-T651

In the present study, the stress corrosion cracking (SCC) behavior of friction-stir-welded Al 6061-T651 alloy was examined in 3.5 pet NaCl aqueous solution at an applied potential of -650 mV vs Ag/AgCI using a slow strain rate testing technique. The resistance to SCC was correlated to the percent change in tensile elongation with exposure to 3.5 pet NaCl aqueous solution with respect to the reference environment. It was demonstrated that the SCC resistance of friction-stir-welded Al 6061-T651 was considerably higher than that of parent material at an anodically applied potential. In friction-stir-welded Al 6061-T651 alloy, the stress corrosion cracks occur only locally in the boundary region between the dynamically recrystallized zone (DXZ) and the heat affected zone (HAZ) regions. However, the HAZ has much lower strength properties compared with the rest of the material, and thus, fracture occurs there despite the increase in stress intensity due to corrosion at the DXZ and HAZ boundary. Eventually, the tensile fracture in friction-stir-welded Al 6061-T651 was relatively unaffected by the SCCs formed in 3.5 pet NaCl aqueous solution.