Achieving multi-scale synergistic modification of Al-Zn-Mg-Cu alloy through spray forming and Sc, Zr microalloying

Al-Zn-Mg-Cu alloys are widely applied in key components across multiple fields, but the preparation of ultra-high strength Al-Zn-Mg-Cu alloys remains a challenge in the industry. The Al-Zn-Mg-Cu alloy in 800MPa level was fabricated by spray forming in present work, and the synergistic effects of spray forming and Sc, Zr microalloying on the microstructure and mechanical properties were systematically clarified. Approximately uniform microstructure with fine grains and precipitates is developed due to rapid solidification during the spray forming, and the metastable microstructure is stabilized by coherent Al3(Sc, Zr) particles with Sc, Zr modification. The synergistic modification significantly enhances the comprehensive properties of Al-Zn-Mg-Cu alloys, with the yield strength, tensile strength and elongation achieving 805±4MPa, 833±5MPa and 7.9±1.0%, respectively. Quantitative analysis of reinforcement contribution indicates the ultra-high strength results from the synergistic effects of grain boundaries strengthening, Orowan strengthening and dislocation strengthening. The mechanisms of Sc, Zr modification are clarified as hindering the recrystallization by Zener pinning effect during the solid solution treatment, which retains more deformation microstructure and geometrically necessary dislocations (GND) developed in extrusion. This study provides a technical approach for the design and multi-scale modification of ultra-high strength aluminum alloys.