Microstructure and precipitation evolution of a (Sc, Zr, Er, Ti) multi-microalloyed Al–Li–Mg alloy from solution treatment to peak aging

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Al–Li–Mg alloys are crucial lightweight materials, but their properties are often compromised by excessive recrystallization and insufficient precipitation strengthening. This work demonstrates that multi-microalloying with Sc, Zr, Er, and Ti effectively addresses these challenges through systematically studying their effects on the microstructure and precipitation evolution of an Al–Li–Mg alloy from solution treatment to peak aging. Microstructural characterization reveals that the multi-microalloyed alloy exhibits a refined fibrous grain structure in the hot-rolled state and a strong inhibition of static recrystallization after solution treatment, retaining a deformed substructure with low-angle grain boundaries. This is attributed to the Zener pinning effect from thermally stable dispersoids like Al 3 (Sc, Zr, Ti). During aging at 160 °C, both the base and multi-microalloyed alloys precipitate fine δ′-Al 3 Li phases (∼10 nm), but the latter develops unique core-shell particles consisting of an Al 3 (Sc, Zr, Ti)–Er core and an epitaxial δ′-Al 3 Li shell. Consequently, the multi-microalloyed alloy achieves an approximately 15 % higher peak hardness, resulting from the synergistic effects of grain refinement, preserved substructure, and enhanced precipitation strengthening. This work demonstrates that multi-microalloying is an effective strategy for designing high-performance Al–Li–Mg alloys with enhanced microstructural stability and strengthening response.