journal article·2024-12-27Open access

Mechanisms of corrosive freeze-thaw damage in AA7075 using time-resolved x-ray microtomography and correlative electron microscopy

Ankit Kumar, Eshan Ganju, Daniel Sinclair, Nikhilesh Chawla

npj Materials Degradation· Volume 8· Issue 1

Abstract

Aluminum aircraft structures experience severe corrosion from exposure to aggressive chloride environments, including cyclic freezing and thawing of residual water during ascent and descent, introducing a cyclic freeze-thaw component to the corrosion process. While corrosion mechanisms in aircraft structures are well studied at constant temperatures, the microstructural and mechanistic behavior under freeze-and-thaw conditions remains unclear. To understand transformations induced by cyclic temperature, we used three-dimensional (3D) x-ray computed tomography (XCT) with scanning electron microscopy (SEM) to study the behavior of AA7075-T651 in a simulated seawater environment undergoing freezing and thawing cycles. Rods immersed in saltwater were thermally cycled above and below freezing, and structural changes were intermittently characterized in 3D. Under freeze-thaw conditions, cracks initiated within corrosion pits through ice expansion, causing progressive crevice growth and spalling along inclusions and grain boundaries with intermediate misorientation angles. Damage mechanisms in freeze-thaw and conventional corrosion environments are compared, with correlations to microstructural evolution.
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Research context

OpenAlex topics: Aluminum Alloy Microstructure Properties · Advanced Welding Techniques Analysis · Aluminum Alloys Composites Properties

SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.

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