The evolution of electrochemical, microstructural, and mechanical properties of aluminium alloy 2024-T4 (D16AT) during fatigue cycling

Abstract

Coupons of fuselage skin made from the aluminium alloy D16AT (the Russian equivalent of 2024-Ò4) were obtained from several Russian TU-154 passenger aircraft after different numbers of flight cycles and different lengths of operation. The coupons were subjected to electrochemical, microstructural, and mechanical testing with the aim of identifying any trends indicating fatigue damage accumulation and residual fatigue lifetime reduction during service. Alongside this investigation, laboratory fatigue test specimens were machined from the same alloy and subjected to cyclic fatigue loading to simulate the service conditions for the coupons. Electrochemical testing was used in order to determine the evolution of the corrosion potential of the near-surface layers. X-ray diffraction analysis was also carried out to characterize residual stress and texture evolution, while microstructural investigations were made using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and secondary ion mass spectroscopy. The suitability of using electrochemical, microscopic, and diffraction characterization methods for the detection of surface structural state modification and its connection with the mechanical performance of this alloy are discussed.

Identification of the metallurgical parameters explaining the corrosion susceptibility in a 2050 aluminium alloy

“…This result was in agreement with the data obtained for the AA 2050-T34 sample for corrosion at subgrain boundaries and was better explained by the presence of many subgrain boundaries and dislocations inside the large polygonized grains, leading to a significant amount of stored energy and consequently, a strong reactivity. The literature reports an evolution of the corrosion potential with the dislocation density but without any identified trends [25]. It was assumed in the present work that the grains with the highest dislocation density have the most negative corrosion potential.…”

“…This result means that in the AA 2050-T34 sample, intergranular corrosion developed mainly between grains with disparate areas: a galvanic coupling between a small grain and a large grain should explain this result because there is a stronger reactivity at their shared interface. Indeed, several works have shown that the corrosion potential of a metal varied with the dislocation density [24,25] and the grain size [26,27]. It was possible to transpose this result on the polycrystal scale by considering the galvanic coupling between grains of different sizes and possessing different dislocation densities.…”

The propagation of localized corrosion in Al‐Cu‐Li alloy

“…First, the higher population density of dislocation leads to the higher level of thermodynamic instability, which results in the higher corrosion susceptibility. Previous research revealed that with dislocation density difference, electrochemical potential difference around 20 mV can be generated . Therefore, the boundary and interior of the grain with higher level of defects have higher corrosion susceptibility than those of the grains with lower stored energy.…”

Experimental Study on the Effects of Coolants on Surface Quality and Mechanical Properties of Micromilled Thin-Walled Elgiloy

“…As the influence of RS on tensile strength is obvious [ 27 ] and the mechanical properties are the key indexes, the mechanical properties of the machined work piece are analyzed directly. The main mechanical properties [ 37 ], which include Young’s module E , yield strength , tensile strength , and breaking elongation , are calculated from engineering the stress-engineering strain curve of the test component. An original component is tested for calibrating related calculation parameters.…”