Recently, the high-temperature resistant aluminum alloy team of the National Key Laboratory of Metal Material Strength at Xi'an Jiaotong University collaborated with Shanghai Jiao Tong University and the University of Grenoble in France to jointly tackle a research problem. They made significant progress in the study of high-temperature resistant and high-strength aluminum alloys at 500°C levels by using additive manufacturing methods. The research team proposed a new design strategy called "thermal stability dual interlocking stabilization", allowing two types of high-temperature resistant nanoparticles to grow in pairs and "lock" each other within a three-dimensional space, achieving a high-temperature organizational stabilization effect that is greater than the sum of its parts (1+1>2). The related research results were published in "Today's Materials".
The research team utilized the solute retention effect of non-equilibrium solidification in additive manufacturing, by adding trace amounts of scandium and zirconium elements, to form a dense aluminum-vanadium-scandium-zirconium (Al-V-Sc-Zr) nano-amorphous structure around the unit cell-like structure; after a short 400°C heat treatment, an in-situ coupling phase transformation occurred between the cellular structure and the surrounding amorphous structure, dominated by the diffusion of V atoms. The two phases were tightly combined and distributed in pairs, forming a composite nano-precipitate phase. The overall volume fraction reached approximately 37.7 vol%, with an average size of only 56 nanometers. The content and refinement degree of the precipitate phase were far superior to those of traditional process-prepared heat-resistant aluminum alloys.
The demand for the dual performance indicators of lightweight structure materials and high-temperature service capability, which are usually difficult to achieve simultaneously in key fields such as aerospace, advanced energy, and high-end equipment manufacturing, is becoming increasingly urgent. Lightweight, high-strength, and heat-resistant aluminum alloys are one of the core candidate materials for achieving structural weight reduction. In recent years, heat-resistant aluminum alloys have become a research hotspot in the industry, and new types of aluminum alloy materials with a service temperature exceeding 200℃ have been gradually developed. The team proposed a design strategy of coupling fast-diffusing solute atoms with slow-diffusing atoms, developed a series of heat-resistant high-strength aluminum alloys at temperatures ranging from 300 to 400℃, and achieved breakthroughs in engineering application.
To meet higher temperature requirements, 500℃ (approximately 0.83 Tm, where Tm is the absolute melting point temperature) has been recognized as the insurmountable ceiling temperature for aluminum alloys in service - this means that the high-temperature areas such as those around the engine can only use denser titanium alloys or high-temperature alloys to date, and the potential for weight reduction cannot be further exploited. 500℃ grade heat-resistant aluminum alloys will be a disruptive material and technological breakthrough in the field of aluminum alloys.
The research further revealed that this dual-phase symbiotic structure has formed a unique "growth mutual restraint" effect: the interfaces between the two nano-phase particles are mutually interlocked, which from the dynamic perspective inhibits the high-temperature coarsening of the precipitated phase. This stabilization mechanism based on dynamic constraints is different from the traditional ideas of thermodynamic-dominated stabilization such as solute segregation at the interface and strengthening of lattice bond energy. It endows the composite precipitated phase with an unprecedented anti-coarsening ability. The extraordinary microstructure thermal stability has brought about breakthrough high-temperature mechanical properties. This alloy has a tensile strength of up to 230 megapascals at 400°C and still maintains a high strength of approximately 120 megapascals at 500°C, significantly surpassing the high-temperature strength levels of existing cast and additive manufacturing aluminum alloys. The ability to resist long-term slow deformation (steady-state creep rate) at 400°C and 500°C is 2-3 orders of magnitude higher than that of existing heat-resistant aluminum alloys. Its creep resistance at 500°C even outperforms the performance of most traditional heat-resistant aluminum alloys at 400°C.
This research is the first to raise the service temperature of additive-manufactured aluminum alloys with near-net-shape forming (printing results close to the final shape of the part and requiring almost no further processing) to the 500℃ range. It has broken the traditional perception that "high-temperature and high-strength aluminum alloys cannot exceed the 500℃ service limit", providing a new paradigm of "dynamic constraint stabilization" for the design of high-temperature microstructures of light alloys. It is expected to achieve significant weight reduction and energy efficiency improvement in aerospace high-temperature structural components and heat exchange parts of new energy equipment, etc.
