The Al-Si-Cr-Co-Ni High Entropy Alloy (HEA) with low density (about 5.4 g/cm³) and excellent performance had significant potential in the lightweight engineering material field. To further research and optimize the Al-Si-Cr-Co-Ni system HEA, the influences of element Cr on the microstructures and performances of lightweight AlSi_0.5Cr_xCo_0.2Ni (in mole ratio, x = 1.0, 1.2, 1.4, 1.6, and 1.8) HEAs were investigated. The experiment results manifested that AlSi_0.5Cr_xCo_0.2Ni HEAs were composed of A2 (Cr-rich), B2 (Ni-Al), and Cr₃Si phases, indicating that the addition of Cr did not result in the formation of a new phase. However, ample Cr increased the Cr₃Si phase composition, further ensuring the high hardness (average HV 981.2) of HEAs. Electrochemical tests demonstrated that HEAs with elevated Cr₃Si and A2 phases afforded greater corrosion resistance, and the improvement in corrosion was more pronounced when x > 1.6. This work is crucial in the development of lightweight engineering HEAs, which are of tremendous practical utility in the fields of cutting tools, hard coating, etc.

After the atmospheric hydrochloric acid leaching method is used to treat laterite ore and initially purify it, the extract that results often contains a significant amount of Fe²⁺ impurities. A novel metallurgical process has been proposed that utilizes microbubble aeration to oxidize Fe²⁺ ions in laterite hydrochloric acid lixivium, facilitating subsequent separation and capitalizing on the benefits of microbubble technology, including its expansive specific surface area, negatively charged surface attributes, prolonged stagnation duration, and its capacity to produce active oxygen. The study examined the impacts of aeration aperture, stirring speed, oxygen flow rate, pH value, and reaction temperature. Under optimized experimental conditions, which included an aeration aperture of 0.45 µm, stirring at 500 rpm, a bubbling flow rate of 0.4 L/min, pH level maintained at 3.5, and a temperature range of 75–85 °C, the oxidation efficiency of Fe²⁺ surpassed 99%. An analysis of the mass transfer process revealed that microbubble aeration markedly enhances the oxygen mass transfer coefficient, measured at 0.051 s⁻¹. The study also confirmed the self-catalytic properties of Fe²⁺ oxidation and conducted kinetic studies to determine an apparent activation energy of 399 kJ/mol. At pH values below 3.5, the reaction is solely governed by chemical reactions; however, at higher pH values (>3.5), both chemical reactions and oxygen dissolution jointly control the reaction.