Effect of Homogenization Temperature and Soaking Time on the Microstructure and Corrosion Properties of a Twin Roll Casted AA3003

Abstract

The AA3003 alloy is widely used as fin material in heat exchangers. The lifetime of these heat exchangers is mostly determined by their corrosion properties. Twin roll casting (TRC) of AA3003 material is known to often result in the formation of a macrosegregation area of alloying elements toward the center plane of the casted strip (center line segregation = CLS). Considering the potential exposure of cross-sectional areas of TRC material in the heat exchanger fin application, and the relatively high corrosion susceptibility of the CLS, the study of this region is of key importance to understand the microstructural effects on the resulting corrosion mechanisms and kinetics for these materials. Typically the alloys are homogenized to bring the microstructures closer to an equilibrium state, but the impact of this heat treatment on the corrosion properties is insufficiently studied. Therefore, this study investigates the effect of different homogenization procedures on the corrosion properties of the CLS and the interaction of the intermetallic particles with the surrounding aluminum matrix. This work shows that the pitting corrosion resistance is greatly dependent on the homogenization temperature, with better corrosion resistance obtained with higher temperature, especially near the CLS. This difference in corrosion behavior is completely attributed to a difference in microstructure and not to an oxide layer effect. Furthermore, it is observed that not only temperature will have a large influence on the corrosion resistance, but duration of the heat treatment as well.