Impol (Slovenia)

The present study investigates the accumulative roll bonding process applied to the EN AW 3003 aluminum alloy, serving as a composite material on both sides and consisting of the EN AW 4343 aluminum alloy. For the characterization of the optical microscopy, corrosion tests with saltwater acetic acid and mechanical properties before and after the braze test were employed. The numerical simulations accurately predicted the industrial cold rolling values for the rolling force and surface temperature. The most comprehensive understanding of the cold rolling parameters for both side-cladded materials was achieved by combining predictions for cladded and uncladded materials. The thickness of the cladded layer presented as a percentage after roll bonding was 18.7%. During the cold rolling and annealing, the cladded thickness was increased to 24.7% of the final 0.3 mm of the total cold-rolled product thickness. According to the performed braze test for final thickness, the ultimate tensile strength and yield strength were decreased, and the elongation increased to 18.1%. In addition to the described changes in mechanical properties, the material’s anisotropy improved from 5.4% in the cold-rolled condition to 2.0% after the braze test. After multiple re-meltings of the cladded material, the analyzed chemical compositions allow for recycling and reuse as different 4xxx, 5xxx, and 6xxx alloys.

Metallographic investigations are critical in research and materials’ quality control. Therefore, these methods are very present in scientific and industrial activities. In particular for quality control, metallographic analyses have an indirect correlation with quality, time and economic aspect in the metallurgical industry. Most of the metallographic methods used for aluminium alloys’ quality determination are non-standard and are required by customers. The suitability and effectiveness of these metallographic control methods are best determined by interlaboratory investigations. In this investigation, two metallographic laboratories with seven different operators using five different light microscopes with associated software were involved. The interlaboratory analyses covered a determination of the rim zone, dendritic arm space, intermetallic phases and non-metallic inclusions. From the calculated measurement uncertainty, where in the worst case results differ by 4.7 %, it is clear that all four metallographic methods are suitable for implementation in industrial quality laboratories, when correctly and accurately defined (with easy-to-follow instructions).

Aluminium alloys of group 2xxx contain copper as the main alloying element. Copper increases the strength and workability of the alloy, but also reduces the corrosion resistance and weldability. During casting, a nonequilibrium solidification occurs. Therefore, the cast alloy needs to be heat treated with a so-called homogenization process. Homogenization allows us to eliminate crystalline segregations and low-melting eutectics, and also causes changes in the morphology of intermetallic phases. The forming ability is in this way increased. In this research the subject of the investigations was the aluminium alloy with designation EN AW 2011 (AlCuBiPb), whereas the comparative analysis before and after homogenization annealing was made. Homogenization was conducted at 520 °C for 6 h. First, slices from two rods before and after homogenization were cut out, where three samples from each slice of the rod, namely in the middle, on D/4 and at the edge of the slice were prepared. Differential scanning calorimetry (DSC) was performed on all six samples, the results were compared with each other in order to establish the structure homogeneity before and after the homogenization process through the cross-section of the rod. Samples for light (LM) and scanning electron microscopy (SEM) were also prepared, whereas the phase composition and chemical homogeneity were analysed. Using the Thermo-Calc program, the nonequilibrium solidification was simulated and the phase formation during solidification was examined. From the obtained results, it was concluded that the homogenization was carried out successfully, due to a homogeneous chemical distribution in the examined phases and to a fairly homogeneous chemical composition throughout the cross-section of the rod slice.

A promising approach to the rapid inspection of inclusions in wrought aluminium alloys is optical emission spectroscopy (OES). However, in order to separate the peaks corresponding to particular inclusions from the peaks obtained from various microstructural features in the matrix, an advanced filtering of the OES spectrum is necessary. The methodology developed in this work is based on big-data-driven predictions of whether an on-line analysed sample is good or bad. A sufficient amount of relevant data, necessary for data-driven predictions, was established by the systematic quality control of samples of AA6082 using optical and scanning electron microscopy and by analysing the same surface using OES. By following a machine-learning process, an algorithm was developed to enable the on-line division of the samples into good and bad, based on criteria received from the casting house. Although the obtained results are promising, further improvements are necessary before this method can be validated for use in regular production.