Stress corrosion cracking behaviour of conventional and innovative aluminium alloys for aeronautic applications

Research on the Improvement Effect and Mechanism of Micro-Scale Structures Treated by Laser Micro-Engraving on 7075 Al Alloy Tribological Properties

During various applications in aerospace, ships, autos, and aircraft, 7075 Al alloy will frequently contact other materials, and therefore suffer from slight abrasion. However, the poor tribological properties of 7075 Al alloy greatly affect its performance and life length, leading to limitations in its application. Preparing roughness structures on the surface is regarded as a promising method to improve the properties of materials. However, the tribological properties of 7075 Al alloy cannot be enhanced significantly by roughness structures in complex dynamic changeable environments, owing to the incomplete understanding of the effect of roughness structures. Given the above issues, in this paper, micro-scale structures (linear grooves, gridding grooves, and arc grooves) were designed and prepared on 7075 Al alloy surfaces by a surface treatment (laser micro-engraving), which provides excellent controllability of the morphology and dimensions of as-prepared roughness structures. The tribological properties of the as-prepared surfaces were investigated systemically. The effect of micro-scale structures on the tribological properties was studied. The wear mechanism and tribological properties improvement mechanism of the surfaces were clarified. Furthermore, the effect degree of the enhancement factors of the micro-scale structures on the tribological properties was explored under different conditions. The results indicate that the micro-scale structures play an important role in improving the tribological properties of Al alloy under different sliding speeds. The improvement mechanism can be summarized by four factors. However, the effect degrees of these factors on the tribological properties exhibit considerable differences. This study not only develops specific micro-scale structures that can dramatically improve the tribological properties of 7075 Al alloy under different conditions, but also offers guidance for the construction of appropriate roughness structures that can dramatically improve the tribological properties of Al alloy according to the friction conditions.

Influence of Temperature on Corrosion Behavior of 2A02 Al Alloy in Marine Atmospheric Environments

The corrosion behavior of 2A02 Al alloy under 4 mg/cm² NaCl deposition at different temperatures (from 30 to 80 °C) has been studied. This corrosion behavior was researched using mass-gain, scanning electron microscopy-SEM, laser scanning confocal microscopy-LSCM, X-ray photoelectron spectroscopy-XPS and other techniques. The results showed and revealed that the corrosion was maximal at 60 °C after 200 h of exposure. The increase of temperature not only affected the solubility of oxygen gas in the thin film, but also promoted the transport of ions (such as Cl⁻), and the formation of protective AlO(OH), which further affects the corrosion speed.

A universal laser marking approach for treating aluminum alloy surfaces with enhanced anticorrosion, hardness and reduced friction

Through a simple laser marking approach, microstructures on a large scale AA7075 Al alloy surface have been fabricated. The corrosion resistance, hardness and wear resistance of the surface could be simultaneously improved by this method.

Laser Cutting of Aluminium Sheets with a Superficial Cold Spray Titanium Coating

In the manufacturing of metal components both wear and corrosion have to be considered. In particular, corrosion is a primary problem in the aeronautic field, where the aluminium alloys are affected by several corrosion typologies. Furthermore, nowadays carbon fibre reinforced plastics (CFRP) are finding an increasing use, but they can induce galvanic corrosion phenomena when coupled with aluminium alloys. To overcome this problem, corrosion resistant coatings are used on aluminium components. On these premises, the realization of a titanium coating on aluminium components could allow the coupling of CFRP and aluminium alloys, improving the corrosion resistance. Cold Spray Deposition is a recent technology to realize these coatings. This technology allows the production of near fully dense coatings on metallic surfaces. In many applications the coated aluminium sheets have to be machined (cut or drilled). Machining with conventional cutting methods leads to both tool wear and damages in the coating. Laser cutting represents a promising alternative: it does not involve any mechanical cutting force or tool wear and, thanks to the small laser beam spot, it allows to realize complex shapes. In this paper, laser cutting of an Al alloy sheet (0.6 mm thick) coated with Ti Alloy, was studied. The adopted laser source was a 150 W, lamp pumped Nd:YAG, specifically developed for micro-machining operations on metals. During the tests, the process parameters (cutting speed, pulse duration and entrance side) were changed and the kerf geometry was analysed as a function of the process parameters.