Abstract: Heat-resistant aluminum alloys are widely used in aerospace and automotive fields for manufacturing hot components due to their advantages in lightweight design and energy conservation. However, the high-temperature strength of existing cast aluminum alloys is always limited to about 100 MPa at 350 °C due to coarsening and transformation of strengthening phases. Here, we reveal that the yield strength and ultimate tensile strength of the T6 state Al-8.4Cu-2.3Ce-1.0Mn-0.5Ni-0.2Zr alloy at 400 ℃ increase by 34% and 44% after re-aging at 300 °C for 100 h, and its thermal strength exhibits distinguished advantage over traditional heat-resistant aluminum alloys. The enhanced elevated-temperature strength is attributed to the reprecipitation of the Ni-bearing T-Al₂₀Cu₂Mn₃ phase, whose number density increases over one time. The significant segregation of Ni, Ce, and Zr elements at the interfaces helps improve the thermal stability of the T phase. The thermostable T phase effectively strengthens the matrix by inhibiting dislocation motion. Meanwhile, a highly interconnected 3D intermetallic network along the grain boundaries can still remain after long-term re-aging at 300 °C, which is conducive to imposing a drag on the grain boundaries at high temperatures. This finding offers a viable route for enhancing the elevated-temperature strength of heat-resistant aluminum alloys, which could provide expanded opportunities for higher-temperature applications.

Key words: Aluminum alloys, Precipitation, Thermally reinforcement phase, Re-aging treatment, High-temperature strength