Daihong Xiao

The effects of (Zn + Mg) total content (9.6–11.7 wt.%) combined with multi-directional forging (MDF) on the microstructure and properties of high-strength Al–Zn–Mg–Cu alloys were systematically investigated. Our results demonstrate that the alloy obtains significant grain refinement, which is attributed to the dynamic recrystallization in the MDF process. Specifically, Al-8.6Zn-1.55Mg-1.9Cu-0.11Zr (Zn + Mg = 10.15 wt.%) obtains the maximum recrystallization ratio (51.8%) and the weakest texture strength, and also forms the mortise and tenon nested grain structure. Increasing the total (Zn + Mg) content can achieve significant performance enhancement, which is attributed to the refinement of the η′ phase; however, a higher total (Zn + Mg) content will lead to the continuous distribution of coarse η-MgZn₂ phases formed along the grain boundary, accompanied by the broadening of precipitate-free precipitation zones (PFZs). Compared with other alloys, Al-8.6Zn-1.55Mg-1.9Cu-0.11Zr (Zn + Mg = 10.15 wt.%) maintains high strength while ensuring desirable plasticity due to its mortise and tenon nested grain structure. In addition, its desirable grain boundary precipitation behavior makes it exhibit the best corrosion resistance. These findings indicate that maintaining the total (Zn + Mg) content around 10 wt.% achieves a balance between strength and corrosion resistance, offering a theoretical foundation for the design of high-strength and corrosion-resistant Al–Zn–Mg–Cu alloys.

The existing Al-Ce heat-resistant alloys are not extensively utilized in high-temperature applications due to their poor room-temperature mechanical properties. In this study, the Al-10Ce-3Mg-5Zn alloy was enhanced using hot extrusion and heat treatment. The as-extruded alloy exhibited bimodal intermetallic compounds and grain structures. Additionally, high-density microcracks and twins were observed in the micron-sized intermetallic compounds. Compared with the as-cast state, the as-extruded alloy demonstrated a higher ultimate tensile strength (UTS) of 317 MPa and better elongation of 11.0%. Numerous nano-sized T phases precipitated in the α-Al matrix after the heat treatment, contributing to a further rise in UTS (365 MPa). The high strength of the alloy is primarily due to its strong strain hardening capacity, fine grain strengthening, and precipitation strengthening effect. The change in elongation mainly results from the expansion of pre-existing microcracks, twin deformation, and microstructural refinement. The heat-treated alloys exhibited superior strength retention ratios at elevated temperatures (64% at 200 °C) compared to conventional heat-resistant aluminum alloys. The results of this paper indicate that hot extrusion and heat treatment are effective for developing heat-resistant Al-Ce alloys with high room-temperature strength, offering a simple process suitable for industrial production.

This study systematically investigated the effects of the addition of the rare earth element yttrium (Y) on the microstructural evolution, mechanical properties, and corrosion behavior of as-extruded Al-5.6Zn-2.5Mg-1.6Cu-0.20Cr (wt.%) alloy through comprehensive characterization techniques, including X-ray diffraction (XRD), tensile testing, corrosion analysis, and electron microscopy. Microstructural characterization demonstrated that the incorporation of yttrium resulted in significant refinement of secondary phase particles within the as-extruded alloy matrix. Moreover, quantitative analysis revealed a substantial increase in low-angle grain boundary (LAGB) density, dislocation density, and the formation of subgrain structures. Notably, the volume fraction of η′ strengthening precipitates showed a marked increase, accompanied by a corresponding reduction in the width of precipitate-free zones (PFZs) along grain boundaries. Following the T74 aging treatment, the alloy with 0.1 wt.% yttrium addition exhibited a remarkable improvement in intergranular corrosion resistance, with the maximum corrosion depth reduced to 107.8 μm. However, it should be noted that the exfoliation corrosion resistance exhibited an inverse correlation with increasing yttrium content, suggesting a concentration-dependent behavior in corrosion performance.

Due to its high mechanical properties and low quench sensitivity, 7085 aluminum alloy is suitable for the aircraft industry. However, large cross-section forgings of 7085 alloy usually have over 40% anisotropy in mechanical behaviors, especially in the vertical direction. In this study, two-stage multi-directional forgings (MDFs) with different temperature combinations, isothermal medium-temperature composite MDF (MC-MDF) and isothermal hot MDF (H-MDF), were applied to 7085 aluminum alloy ingots. The results indicate that MC-MDF achieved anisotropy below 10% without losing ultimate tensile strength (UTS). Three-dimensional (3D) microstructure analysis suggested that the MC-MDF samples accumulated higher dislocation density and exhibited an enhanced recrystallization structure. The elongation of the vertical direction increased significantly, which lowered the directionality of MC-MDF and increased the effective utilization rate of forgings. Also, MC-MDF obtained a lower yield strength (YS) due to the forging temperature in exchange for higher work hardening and a ductility increase. The average 3D UTS, YS, and EL values of MC-MDF are 554 MPa, 472 MPa, and 13.4%, and the index value reflecting the anisotropy of EL decreased from 14.0% to 8.6% for H-MDF.

Aluminum alloy 7050-T74 with varying zinc-to-magnesium (Zn/Mg) mass fractions was synthesized using melt casting and hot extrusion techniques. This study investigated the influence of different Zn/Mg ratios on the microstructure, mechanical properties, and corrosion resistance of the alloy. Light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile testing, and corrosion testing were employed as analytical methods. The findings indicate that as the Zn/Mg ratio increases from 2.36 to 3.84, the proportion of low-angle boundaries (LABs) within the alloys initially rises and then decreases, achieving a balance between high strength and favorable elongation. Specifically, at a Zn/Mg ratio of 2.72, the alloy exhibits a tensile strength of 641 MPa, a yield strength of 609 MPa, and an elongation of 10.1%. Additionally, increasing the Zn/Mg ratio to 2.90 slightly reduces intergranular corrosion resistance while enhancing exfoliation corrosion resistance.

The microstructure and mechanical properties of as-cast Al-10Ce-3Mg-xZn (x = 0, 1, 3, 5 wt.%) alloys were systematically investigated, with a focus on the effect of Zn on the Al₁₁Ce₃ reinforcing phase in the alloy. The results showed that the Al-10Ce-3Mg alloy consists of α-Al, a Chinese-script Al₁₁Ce₃ eutectic phase, and a massive Al₁₁Ce₃ primary phase. With the addition of Zn content, most of the Zn atoms are enriched in the Al₁₁Ce₃ phase to form the acicular-like Al₂CeZn₂ phase within the Al₁₁Ce₃ phase. Increasing the Zn content can increase the volume fraction of the Al₁₁Ce₃ phase. Compared to the alloy without Zn addition, the microhardness and elastic modulus of the Al₂CeZn₂-reinforced Al₁₁Ce₃ phase in the alloy with 5 wt.% Zn increased by 18.9% and 9.0%, respectively. Moreover, the room-temperature mechanical properties of Al-10Ce-3Mg alloys were significantly improved due to the addition of Zn element. The alloy containing 5 wt.% Zn had the best tensile properties with an ultimate tensile strength of 210 MPa and a yield strength of 171MPa, which were 21% and 77% higher than those of the alloy without Zn, respectively. The alloy containing 5 wt.% Zn demonstrated a superior retention ratio of tensile strength at 200–300 °C, indicating that the alloy has excellent heat resistance. The improvement in the mechanical properties is primarily attributed to second-phase strengthening and solid solution strengthening.

The large-scale ingot of the 7xxx-series aluminum alloys fabricated by direct chill (DC) casting often suffers from foundry defects such as cracks and cold shut due to the formidable challenges in the precise controlling of casting parameters. In this manuscript, by using the integrated computational method combining numerical simulations with machine learning, we systematically estimated the evolution of multi-physical fields and grain structures during the solidification processes. The numerical simulation results quantified the influences of key casting parameters including pouring temperature, casting speed, primary cooling intensity, and secondary cooling water flow rate on the shape of the mushy zone, heat transport, residual stress, and grain structure of DC casting ingots. Then, based on the data of numerical simulations, we established a novel model for the relationship between casting parameters and solidification characteristics through machine learning. By comparing it with experimental measurements, the model showed reasonable accuracy in predicting the sump profile, microstructure evolution, and solidification kinetics under the complicated influences of casting parameters. The integrated computational method and predicting model could be used to efficiently and accurately determine the DC casting parameters to decrease the casting defects.

A novel high-efficiency industrialized clean production technology based on multi-stage gradient batching and smelting was proposed for the production of high-quality ferrovanadium. The thermodynamic mechanism of aluminothermic reduction equilibrium, alloy settlement and raw material impurity distribution were confirmed, and a multi-stage double-gradient aluminum addition pattern (DG-ADP), the highly efficient separation of molten slag and alloy, and typical impurity control standards of raw materials were achieved on the basis of a self-propagating high-temperature synthesis with an electric auxiliary heating (SHS-EAH) process. The reduction efficiency, separation efficiency and the comprehensive utilization rate of the secondary resources were significantly improved, as the whole total vanadium (T.V) content in the industrially produced residue slag reduced from 2.34 wt.% to 0.60 wt.%, while the corresponding smelting yield increased from 93.7 wt.% to 98.7 wt.% and the aluminum consumption decreased from 510 kg·t⁻¹ to 400 kg·t⁻¹. The multi-stage DG-ADP process enabled the internal circulation of vanadium-bearing materials in the ferrovanadium smelting system, as well as the external circulation of iron and residue slag in the same system, and finally achieved the zero discharge of solid and liquid waste from the ferrovanadium production line, which provides a brand-new perspective for the cleaner production of ferrovanadium alloy.