Zeyu Li

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.

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.

In this study, the effects of the combined addition of CeLa and GdY on the microstructure and mechanical properties of as-cast Al-4Cu-1Mn alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile testing. The results show that the minor addition of CeLa and GdY leads to a refinement of grain size. The addition of CeLa results in the formation of supersaturated vacancies in the Al matrix, whereas the addition of GdY leads to a decrease in the precipitation temperature of the Al₂Cu phase. The combined CeLa and GdY additions can significantly increase ultimate tensile strength (UTS) while losing only a small amount of elongation (EL). Compared with the unmodified alloy, the grain size and SDAS of the alloy (0.2 wt.% CeLa + 0.1 wt.% GdY) were diminished by 67.2% and 58.7%, respectively, while maximum hardness and UTS rose by 31.2% and 36.9%, respectively.

In this study, the effects of combined addition of CeLa and GdY on microstructure and mechanical properties of as-cast Al-4Cu-1Mn alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopies (TEM) and tensile testing. The results show that the minor addition of CeLa and GdY leads to the refinement of grain size. The addition of CeLa results in the formation of supersaturated vacancies in the Al matrix, whereas the addition of GdY leads to a decrease in the precipitation temperature of the Al2Cu phase. The combined CeLa and GdY addition can significantly increase ultimate tensile strength (UTS) while losing only a small amount of elongation (EL). Compared with the unmodified alloy, the grain size and SDAS of the alloy (0.2 wt% CeLa + 0.1 wt% GdY) were diminished by 67.2% and 58.7%, respectively, while maximum hardness and UTS rose by 31.2% and 36.9%, correspondingly.