Microstructure Evolution of the Near-Surface Deformed Layer and Corrosion Behavior of Hot Rolled AA7050 Aluminum Alloy

Abstract

The current study investigates the influence of hot rolling on the microstructure evolution of the near-surface region on AA7050 aluminum alloy and the corrosion performance of the alloy. It is revealed that hot rolling resulted in grain refinement in the near-surface region, caused by dynamic recrystallization, and equiaxed grains less than 500 nm can be clearly observed. Fibrous grains were evident in the hot rolled AA7050 aluminum alloy with relatively lower rolling temperature or larger rolling reduction, caused by the more severe elemental segregation at grain boundaries, which inhibited the progression of dynamic recrystallization. The density of the precipitates in the fibrous grain layer was higher, compared with those in the equiaxed grain layer, due to the increased dislocation density, combined with more severe elemental segregation, which significantly promoted the nucleation of precipitates. With the co-influence exerted by low density of precipitates and dislocations on the improvement of the corrosion performance of the alloy, the rolled AA7050 alloy with decreased density of precipitates and dislocations exhibited better corrosion resistance.

Investigation of Oxide Thickness on Technical Aluminium Alloys—A Comparison of Characterization Methods

“…Due to high shear forces during the rolling process the edges of the EDT craters often show distinctly different microstructure compared to the flatter regions, which account for the largest portion of the surface area. In addition, rolling and texturing affects the local surface properties due to the mechanical displacement during the production procedure and is often described as a surface near deformed layer (NSDL) [17][18][19]. As shown in Figure 2 the positions for the FIB preparation of the lamellae were chosen to be in a flatter and homogeneous area of the sample.…”

“…Since the investigated samples originate from industrial production and exhibit a surface texture with a certain roughness, local oxide thickness deviations may exist. In addition, the TEM lamellae, in the size of approximately 20 µm, were prepared from the flatter areas of the EDT imprints, giving values without influences from the surface texture, especially from the ridges and the deformed microstructure at the edges of the EDT imprints [17][18][19]24]. With an average spot size of 400 µm in diameter XPS is sensitive to every part of the textured aluminium surface.…”

The Effect of Cold Rolling on the Corrosion Behaviour of 5083 Aluminium Alloys

“…To conclude, complex corrosion phenomena can be significantly affected by various factors, such as heat treatment [16], surface treatments [17], forming processes [18], synergism between electrochemical phenomena and mechanical stresses (e.g., stress corrosion cracking) [19,20], etc. It is evident that any change in the microstructure of the surface or near surface layers [21][22][23] (e.g., grain structure, secondary phase composition and distribution, texturing etc. ), dislocation density, surface topography, generation of localized stresses and/or micro-defects can have a detrimental effect on the corrosion performance of a material that undergoes any forming process.…”