Acquiring Mg-Ag microalloying TiB2/Al-4.5Cu composite simultaneously with ultrahigh strength and ductility via optimized salt-metal reaction and multistage heat treatment

[Display omitted] •Mg-Ag microalloying ameliorates the detrimental agglomeration of TiB2 particles by segregating at the TiB2/α-Al interface.•Mg-Ag co-clusters act as favorable nucleation sites for the Ω-Al2Cu and σ-Al5Cu6Mg2 phases assisted by multistage heat treatment.•The acquired 5TiB2/Al-4.5Cu-0.5 Mg-0.6Ag composite yields an ultimate tensile strength of 496.3 ± 15.0 MPa and uniform elongation of 12.8 ± 1.4 %. The strength-ductility trade-off severely limits the extensive application of particle-reinforced aluminum matrix composites mainly owing to the critical issues of local particle agglomeration and poor interfacial characteristics. The present work concentrates on these intractable puzzles and proposes Mg-Ag microalloying TiB2/Al-4.5Cu composites fabricated by an optimized salt-metal reaction method and multistage heat treatment. The resulting microstructure evidence that this new tactic synergistically ameliorates the detrimental agglomeration of TiB2 particles by Mg and Ag doped at the TiB2/α-Al interface， meanwhile promoting the formation of nanosized Ω-Al2Cu and σ-Al5Cu6Mg2 phases. The mechanical property experimental results indicate that the Mg-Ag microalloyed TiB2/Al-4.5Cu composites exhibit an accredited combination of the tensile strength (ultimate tensile strength is 496.3 ± 15.0 MPa) and ductility (uniform elongation is 12.8 ± 1.4 %). We emphasize the reciprocal effect between TiB2 particles and the precipitated phase associated with unrelaxed misfit strains. Close attention is also paid to the interface binding characteristics and semi-coherent interphase boundary to evaluate their contribution to the ductility. The microalloying strategy can potentially be applied to many other metal matrix composites and boost analogous approaches for designing ultrahigh yet ductile materials for technological applications.