Aluminum alloys of the 7XXX series are widely used in aircraft applications. During the manufacturing of aeronautic components, the parts pass through four production phases (milling/drilling, deburring/adjustment, non‐destructive testing, and surface treatment) and come into contact with several kinds of fluids such as degreasing and cleaning solutions, which can lead to the occurence of surface defects due to localized corrosion, then requiring reworking or scrapping. The present study aimed at studying the influence of process parameters in the deburring/adjustment stage on the development of surface defects in 7075 alloy parts. The methodology consisted of design of experiments, immersion and drying tests, and surface analysis for quantification of corrosion damage. The results showed that the degreasing bath concentration and temperature, the immersion time of the aluminum parts in the degreasing solution, and the use of solvent pre‐cleaning had no significant influence on the quantity of surface defects. Therefore, these factors do not need to be rigorously controlled in the process. Clean washing water must be preferred and the parts must be dried in the stove at 110 °C in order to ensure a surface free of defects. The immersion and electrochemical tests showed that the occurrence of surface defects is lower in aged degreasing solution than in recently prepared solution.

The 7xxx alloys are mainly used in high stress applications, such as aircrafts structural parts, due to their great mechanical properties and low density compared to steel. Depending on the intermetallics in the alloys, they may suffer pitting which reduces the materiaĺs fatigue life time. The objective of the study was to identify what factors during the manufacture of AA7075 alloy parts are significant and how they should be controlled to minimize the occurrence of corrosion. Three steps of the production cycle were considered, machining, deburring and liquid penetrant test. After the definition of the significant factors at each step separately, a design of experiment based on a fractional factorial type was built for the whole manufacture line. The response variable was the amount of corrosion obtained by image analysis. The most significant factors were found at the machining stage: state of the bench vice jaw material (device which holds the aluminum part at the CNC lathe) and chloride concentration in the cooling fluid.

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Subregions of CA6NM (ASTM 743) heat-affected zones-HAZ, were investigated in a microstructural and mechanical perspective. Those subregions suffer microstructural changes in welded joints, being considered the most critical regions in welded components. As the HAZ subregions possess very small volume, base metal was submitted to a welding simulation in the physical Gleeble simulator, which allows to reproduce the same microstructures found in real welding, allowing characterization of the different subregions in HAZ. Simulated samples were analyzed by optical microscopy (OM), scanning electron microscopy and X-ray diffraction measurements. For mechanical properties, evaluation samples were submitted to impact and hardness measurements. Microstructural and mechanical analysis for the experiments showed that d-ferrite is found in all HAZ subregions, being related to higher microhardness and higher absorbed energy in impact. Higher heat inputs promoted higher hardness levels and higher d-phase amounts.

The aim of this work was to evaluate the porosity, microstructure, hardness, and electrochemical behavior of AISI 316 steel layers deposited on an AISI 347 steel substrate using the LMD process. Depositions of two, four, and six layers with a 0.5 mm height for each layer were performed at a speed of 375 mm/min, a power of 250 W, a focal distance of 5 mm, and without overlapping laser tracks. The results showed epitaxial growth of the deposited layers in relation to the substrate and a predominantly austenitic microstructure with ferrite as the substrate. The deposited layers presented a dendritic microstructure with a mean porosity of 4.5%. The porosity decreased as the number of deposited layers increased, affecting the pitting corrosion resistance. The sample with six deposited layers showed greater pitting corrosion resistance, whereas the corrosion current speeds were similar for the studied samples. Vickers hardness tests showed that the hardness decreased as the distance from the substrate increased, and the hardness decreased close to the remelted regions.