A.M. Glenn

Improved Corrosion Resistance of Aluminum Brazing Sheet by a Post-Brazing Heat Treatment

This work studies the influence of the microstructure on the corrosion mechanism and susceptibility of as-brazed aluminum sheet. Various microstructures are obtained using postbrazing heat treatments developed to enhance the corrosion resistance of an AA4xxx/AA3xxx brazing sheet. The heat treatment results in a decrease of the matrix Si content within the heat affected zone and an increase of the Si fraction in the α-Al(Fe-Mn)Si phase. Additionally, the effect of the heat treatment on the local electrochemical activity and corrosion properties are studied. The results indicate that the corrosion susceptibility of the as-brazed structure is diminished resulting from of an amendment of the local electrochemical behavior of the outer clad surface after the post-brazing heat treatment. Moreover, the potential difference between the clad material and core is increased, resulting in an improved sacrificial cathodic protection of the core by the re-solidified clad layer.

Atom Probe Tomography Studies of the Initiation of Localized Corrosion in Aluminum Alloy 2024

Initiation of localized corrosion can compromise the durability of advanced light alloys and challenges the value of these materials in aerospace and automotive applications due to premature, sometimes catastrophic failure. The role of nanostructure in localized corrosion initiation is not well understood, which is due primarily to the difficulty of characterizing both chemistry and structure at the atomic scale. We address this difficulty by taking advantage of the high spatial resolution and chemical sensitivity of atom probe tomography (APT) to reconstruct a three-dimensional perspective of the electrochemical heterogeneities that are responsible for the early stages of corrosion of a typical high-strength aluminum alloy, AA2024 [1].