Aluminum alloys based on the eutectic Al–Ni system are a promising class of lightweight materials for applications at elevated temperatures owing to the thermal stability of the eutectic Al₃Ni phase. In this study, the eutectic Al–Ni alloy was modified by the addition of 0.6 wt.% Zr to enhance the α_Al matrix by precipitation strengthening. The alloys were cast and subjected to T5 heat treatment followed by long-term isothermal aging at 350 °C. A comprehensive study was carried out to evaluate the evolution of microstructure, microhardness and mechanical performance over time. The formation of fine, coherent L1₂-Al₃Zr precipitates contributed to significant strengthening, as reflected by a ~60% increase in microhardness and an approximately twofold improvement in room temperature (RT) yield strength. A TEM analysis of the L1₂-Al₃Zr precipitates showed relatively good thermal stability after 30 days. Despite the improved mechanical properties at room temperature, the alloy did not retain this improvement when tested at 300 °C. Nevertheless, these results provide a comprehensive insight into the aging and thermal stability of Al–Ni–Zr alloys.

The main objective was to investigate and evaluate the influence of TiC and TiB₂ inoculants on the formation of not only the icosahedral quasicrystalline phase (IQC) but also the β-phase in our Al-Mn-Si-Cu-Mg alloy. First, the presence of both phases was confirmed using electron backscatter diffraction (EBSD), followed by microstructural segmentation and quantification using the open-source machine learning software ilastik and Fiji. The ilastik software was selected because it allowed us to use different parameters to distinguish between the IQC and β-AlMnSi phases, which otherwise have similar color/Z contrast and are difficult to distinguish in a timely manner using other methods. The analyses were performed on a total of 3662 images taken during optical light microscopy. The results show that TiC inoculants better promote the ability to form IQC compared to TiB₂. The use of TiC resulted in an increase of 40% compared to only 14% when TiB₂ was used. Exceeding the TiC threshold of 0.0224 wt.% resulted in a 571% increase in the amount of β-phase compared to our non-inoculated alloy. Microhardness measurements were carried out on the IQC phase using the Vickers method, and an average value of 680 HV0.01 was obtained.

In this work, the morphology of fractured surfaces and mechanical properties of four icosahedral quasicrystal (IQC) forming alloys from the Al-Mn-Si-Cu-Mg system were evaluated by tensile tests. The synthesized alloys contained varying amounts of TiC, a modifier with inoculant properties that promote heterogeneous nucleation of the primary IQC phase. This allowed us to synthesize alloys with different IQC phase fractions as well as other accompanying intermetallic compounds—mainly the β-AlMnSi phase—and thus obtain a correlation between the different phase fractions and the measured mechanical properties. Our results show that the ultimate tensile strength (UTS) of the gravitationally cast alloys mainly depends on the phase fraction of the hexagonal plate-like β-AlMnSi intermetallic compound, with high β-AlMnSi phase fractions leading to lower UTS and strain values. The fracture surfaces were analyzed by electron scanning microscopy (SEM) to determine possible decohesion between the IQC or other intermetallic phases and the surrounding aluminum matrix, all aiming to obtain a general impression of the morphology of the fracture regarding the matrix, IQC and β-AlMnSi phases. SEM images show an intact interface between both the IQC and β-AlMnSi phases and the surrounding matrix after tensile testing.

The phase equilibria of the ternary phase system Al-Cr-La were investigated in the Al-rich corner at 600°C, with minimum Al content of 98.77 at.%. The formed phases, transformation temperatures (specifically liquidus and solidus) and microstructure evolution were experimentally determined by isothermal annealing at 600°C for 600 hours and Differential Scanning Calorimetry (DSC) analysis. Scanning Electron Microscope (SEM) equipped with Energy-Dispersive X-ray Spectroscopy (EDXS) was employed to completely characterize the samples. The equilibrium microstructure state consists of the (Al), the binary phase \mathrm{Al_{45}} <![CDATA[ \mathrm{Cr_7} and the ternary phase \mathrm{LaCr_2} > \mathrm{Al_{20}} in the samples with increased Cr content (from 0.03 up to 1.12 at.%), while it consists of the (Al), the mixture (Al) + \mathrm{Al_{11}} <![CDATA[ \mathrm{La_3} and the ternary \mathrm{LaCr_2} > \mathrm{Al_{20}} phase in the samples with increased La content (from 0.03 up to 0.45 at.%). It was observed that even the small amount of alloying elements leads to the formation of ternary phase.