| Abstract Scope |
The role stress corrosion cracking (SCC) plays in accelerating corrosion fatigue (CF) kinetics (da/dN) of 5xxx series aluminum is investigated. 5xxx series alloys with as-fabricated microstructures are corrosion resistant. However, at temperatures 40 °C and higher, 5xxx series alloys containing greater than ~3 wt.% Mg precipitate anodic β-phase on α-aluminum grain boundaries. This phenomenon, called sensitization, increases environment assisted cracking susceptibility. Experiments on AA5456-H116 were conducted in 3.5 wt.% NaCl at different maximum stress intensities (K<sub>max</sub>), but same stress intensity range, to probe the effect of SCC on da/dN. Results establish that heavily sensitized microstructures exhibit da/dN with inverse <i>f</i>-dependence. The severity of this inverse <i>f</i>-dependence increases when K<sub>max</sub> values are within stage II for SCC. Conversely, increasing K<sub>max</sub> for lightly sensitized microstructures, which are SCC resistant, does not cause an inverse <i>f</i>-dependence. Findings support a hypothesis that strong inverse <i>f</i> dependent da/dN is driven by superposition of SCC. |