Corrosion behaviour of four commercial aircraft materials, Al alloy 7075-T6, high strength steel AISI 4340, Ti alloy 9046 and Mg alloy RZ5, was studied in six commercial antiskid chemicals, one sodium acetate based, three potassium acetate based, one sodium formate based and one potassium formate based, using potentiodynamic polarisation measurements (polarisation curves) and chemical exposure tests (weight change data), combined with microstructural examinations (appearance of surfaces). The results show that among the four materials, the Ti alloy experiences least corrosion, showing pitting corrosion during the polarisation measurements and significant weight gains and discoloration in the exposure tests only in Safeway SF. In contrast to this, the Mg alloy and the high strength steel underwent corrosion in all chemicals, with severe pitting corrosion (polarisation measurements), significant weight changes and discoloration (exposure tests) being observed for the Mg alloy and discoloration (exposure tests) for the high strength steel. Accordingly, sodium formate based Safeway SF is the most corrosive of the chemicals, introducing some indications of corrosion on all materials, and potassium acetate based Safeway KA HOT and potassium formate based Meltium are the least corrosive chemicals: no signs of corrosion could be observed on the Al and Ti alloys. The results also show that based only on the salt, pH value and conductivity, corrosivity of the antiskid chemicals cannot be reliably evaluated. In this paper, explanations for these observations are presented and the similarities and differences between the results from the two types of corrosion tests are discussed.

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Mechanical fastening methods are used extensively to join aluminum alloys, particularly in the aerospace industries. Laser welding provides the possibility of a high productivity single-step process, with the added benefit of potential weight savings of about 10% in comparison with riveting. However, the weldability of many aluminum aerospace alloys is generally considered to be low, and little data are currently available. A procedure for CO2 laser welding of the alloy AA2024 is developed, with the use of 2319 filler wire. Weld property data are shown to achieve the requirements for the most stringent quality level of the current European workmanship standard for laser-welded joints in aluminum. Hardness and tensile strength properties are shown to be similar to those of gas tungsten arc (GTA) welds. The fatigue strength of GTA welds is superior to that of laser welds in the as-welded condition, but when the weld bead is machined flush with the plate surface the difference is reduced. The laser welds achieved the requirements of recommendations produced by the International Institute of Welding for single-sided welding of aluminum alloys. The quality of the weld toe is shown to have the greatest effect on fatigue strength.

Mechanical properties of most metallic materials can be improved by reducing their grain size. One of the methods used to reduce the grain size even to the nanometer level is the severe plastic deformation processing. Equal Channel Angular Pressing (ECAP) is one of the most promising severe plastic deformation processes for the nanocrystallization of ductile metals. Nanocrystalline and ultrafine grained metals usually have significantly higher strength properties but lower tensile ductility compared to the coarse grained metals. In this work, the torsion properties of ECAP processed ultrafine grained pure 1070 aluminum were studied in a wide range of strain rates using both servohydraulic materials testing machines and Hopkinson Split Bar techniques. The material exhibits extremely high ductility in torsion and the specimens did not fail even after 300% of strain. Pronounced yield point behavior was observed at strain rates 500 s −1 and higher, whereas at lower strain rates the yielding was continuous. The material showed slight strain softening at the strain rate of 10 −4 s −1 , almost ideally plastic behavior at strain rates between 10 −3 s −1 and 500 s −1 , and slight but increasing strain hardening at strain rates higher than that. The tests were monitored using digital cameras, and the strain distributions on the surface of the specimens were calculated using digital image correlation. The strain in the specimen localized very rapidly after yielding at all strain rates, and the localization lead to the development of a shear band. At high strain rates the shear band developed faster than at low strain rates.

Corrosion behaviour of four coating systems, which are commonly used in aircraft components; namely cadmium-coated and subsequently chromate-treated steel AISI 4340, aluminium-coated steel AISI 4340, anodised aluminium alloy 7075-T6 and chromatetreated aluminium alloy 7075-T6, were investigated in six commercial acetate-and formate-based de-icing chemicals. The results show that the aluminium-coated steel specimens experience least corrosion among the four coating systems; no corrosion is detected in potassium acetate-based de-icing chemicals (Safeway KA HOT, Safegrip and Safegripþ), although some corrosion is observed in the other three chemicals (Safeway SD, Safeway SF and Meltium). In contrast, the coatings in the other three coating systems are damaged in all six de-icing chemicals. The thickness of the coating does not necessarily predict how well the coating will protect the substrate; the thickest coating, several tens of micrometres, is apparent on the cadmium-and chromate-coated steel specimens, while only a few micrometres thin aluminium coating on the steel substrate is the only coating system that can survive the corrosion tests in some of the de-icing chemicals. Comparison of the results from the two test methods used in this research, polarisation measurements and chemical exposure tests, shows that, for each coating system, the extent of corrosion, as evaluated on the basis of weight changes calculated from corrosion current density values and those experienced during chemical exposure tests, is different: the weight changes that materialise during exposure tests are, at least, from one to two orders of magnitude higher than those predicted by calculations. In this paper, these observations are discussed and explanations for them are presented.