Effect of different organization states on corrosion resistance of Cu-7Ni-3Al-1Fe-1Mn alloy

Enhancing the corrosion resistance of copper-nickel alloys is crucial for extending their service life in marine engineering applications. This study employed an extrusion-annealing process to prepare Cu-7Ni-3Al-1Fe-1Mn alloys with different microstructural states. Comprehensive characterization methods including electrochemical testing, XPS, SEM, EBSD, and TEM were utilized to reveal the intrinsic mechanism by which heat treatment enhances alloy corrosion resistance through microstructural regulation. The results indicate that: (1) The formation of a homogeneous single-phase solid solution with strong (111) texture promotes the uniform and dense growth of a protective Cu 2 O film; (2) Grain clusters composed of a high density of triple junctions and low Σ CSL grain boundaries effectively block the connectivity of random high-angle grain boundaries, significantly inhibiting intergranular corrosion propagation; (3) Selective oxidation of Al at corrosion film defects leads to in situ formation of Al 2 O 3 /Al(OH) 3 , enabling dynamic repair of film defects and enhancing film stability. Furthermore, this study clarifies that the corrosion film growth mechanism follows the evolution pattern of “dissolution-precipitation → spontaneous inward oxidation.”