Homogenization heat treatment is the first step in the processing of aluminium alloys, which for most alloys is carried out before any deformation process. Homogenization is performed to counteract ...microsegregation, which is the result of non-equilibrium solidification caused by diffusion rate differences between solid and liquid states during solidification. Special attention must also be paid to the impact of homogenization on changes in the morphology of iron-based constituents which are known to adversely affect formability. For the purpose of this work, a hypoeutectic Al–Fe alloy containing 1.1 mass/% Fe was homogenized at 600 °C for up to 12 h in an electric furnace. After the homogenization heat treatment, differential scanning calorimetry (DSC) was performed, comparing the homogenized samples with the sample in the as-cast state. The results were compared with thermodynamic calculations using Thermo-Calc software in order to determine the differences between the microstructure in the equilibrium and non-equilibrium state. All samples were analysed by optical and electron microscopy, and the intermetallic phases were qualitatively evaluated by both methods. In addition, energy-dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) were required to determine the type of phases present in all experimental samples and a difference between the as-cast and homogenized state was found. The presence of metastable phases in the as-cast state and the transformation of such phases during the homogenization process was confirmed. A homogenization process, which lasted 12 h at 600 °C, was also performed with a DSC instrument. The experiment confirmed a greater heat transfer at the beginning of the homogenization process, which is consistent with all previous analyses. All results showed that after 10 h of homogenization the effects of non-equilibrium solidification in this alloy were sufficiently counteracted.
The industrial production of products, such as foil and aluminium alloy strips, begins with the production of semi-finished products in the form of slabs. These are produced by the continuous casting ...process, which is quick and does not allow the equilibrium conditions of solidification. Non-homogeneity—such as micro and macro segregation, non-equilibrium phases and microstructural constituents, as well as stresses arising during non-equilibrium solidification—are eliminated by means of homogenization annealing. In this way, a number of technological difficulties in the further processing of semi-finished products can be avoided. The aim of this research was the optimization of the homogenization annealing of the EN AW 8006 alloy. With the Thermo-Calc software, a thermodynamic simulation of equilibrium and non-equilibrium solidification was performed. Differential scanning calorimetry (DSC) was performed on selected samples in as-cast state and after various regimes of homogenization annealing and was used for the simulation of homogenization annealing. Using an optical microscope (OM), a scanning electron microscope (SEM) and an energy dispersion spectrometer (EDS), the microstructure of the samples was examined. Based on the results, it was concluded that homogenization annealing has already taken place after 8 h at 580 °C to the extent, that the material is then suitable for further processing.
The effect of various neodymium additions on the characteristic solidification temperatures and on the microstructure development of the laboratory-prepared binary alloy AlCu5.5 was investigated. The ...aluminium corner of ternary system Al–Cu with various Nd additions was investigated using thermal analysis, differential scanning calorimetry and optical and scanning electron microscopy. The presence of Nd phases was confirmed using X-ray diffractometer. Microhardness of α-Al in AlCu5.5 alloy containing various Nd additions was analysed. The results show that the addition of neodymium raises eutectic (α-Al + Al
2
Cu) solidification temperature and solidus temperature, which leads to a narrower solidification interval. It was also confirmed that Nd formed two binary eutectics (α-Al + Al
2
Cu(Nd)) and (α-Al + Al
8
Cu
4
Nd). The addition of Nd also caused the increase in microhardness of α-Al phase.
The influence of chemical composition and heat treatment on the mechanical properties and formability of the selected commercial aluminium alloy EN AW 5454 was investigated. The main properties of ...alloy 5454 from the AA 5xxx series are very good corrosion resistant and has good formability. From the cast slab a 50 mm thick slice was taken in the width cross section in the slab centre. One half of the slice was homogenised for 10 hours at a temperature of 530 °C. The cast and homogenised samples were investigated using light and scanning electron microscopy. For the study of the influence of the heat treatment, samples in the as-cast state were annealed in the laboratory furnace at a temperature of 530 °C for 4, 6, 8, 10 and 12 hours. To study the influence of chemical composition, four different samples were prepared: the first without additions, the second with an addition of 1 wt% Mn, the third with 3 wt% Mg and the fourth with an addition of both elements, Mn and Mg. The XRF analyses confirmed the desired chemical composition of all four produced alloys. Half of each alloy’s sample was homogenised at the same temperature and time as the base alloy in the as-cast state. The hot deformation behaviour of the different alloys was investigated using cylindrical hot compression tests performed on a Gleeble 1500D thermo-mechanical simulator. By comparing flow curves a high influence of the thermo-mechanical parameters on the alloy formability can be seen. The alloy has good workability and with the addition of Mn and Mg, the stress values are higher than those of the base alloy.
In this research enthalpy balance analysis of the EN AW 5182 aluminium alloys during entire process path of sheet production was made, whereas samples after every step of sheet production process ...path were obtained. Using Thermo-Calc computer program thermodynamic simulation of equilibrium and nonequilibrium solidification was made. Differential scanning calorimetry was made on every sample, whereas the melting characteristic temperatures and the melting enthalpies from the results were obtained. Optical microscopy and scanning electron microscope with energy-dispersive X-ray spectroscopy were used to analyse microstructure and microstructural components. It was found that each step of the process, involving different processing temperatures and deformation, has a significant effect on the reaction/melting enthalpy and cannot be uniquely described. Homogenization reduces and intermediate annealing of the hardened sheet increases the melting enthalpy. Hot rolling has a significant effect on the melting enthalpy, while cold rolling has only a minor effect.
In the whole manufacturing chain of aluminium products, hot rolling significantly impacts the obtaining of favourable microstructures and desired mechanical properties of final products. The ...determination of crucial differences between the reverse hot rolling on a single-stand mill and the tandem hot rolling on a tandem-stand mill presented a major challenge. Besides the grain-size distribution in the microstructure’s cross-section, the crystallographic textures of hot-rolled strips were also determined and compared. The alternating band areas of a coarse-grained microstructure and fine-grained microstructure due to reverse hot rolling and, especially, the appearance of extremely fine grains on the surfaces present limitations compared to the tandem hot rolling. For subsequently cold-rolled foils, classical mechanical properties were measured. Besides, the usefulness of EN AW-8021B foils with a thickness of 60 µm for pharmaceutical-packaging applications was tested with a burst test. A minor but important difference of 1 % in the elongation is shown for the convex height increased by 1 mm.
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