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Insufficient performance, especially at high temperatures, limits the extensive application of cast Al–Cu alloys. This study proposes a novel method of direct reaction synthesis (DRS) for the simultaneous synthesis and dispersion of hybrid-sized in situ TiC–TiB 2 particles in the melt to prepare a trace-particle-reinforced high-performance cast Al–Cu 5.5 –Mn 0.45 –Ti 0.3 –V 0.3 –Cr 0.2 –Zr 0.14 –B 0.04 alloy. The particulate-reinforced alloy achieved strength–ductility synergetic enhancement at room and high temperatures. In comparison to the Al–Cu matrix alloy, the yield strength of 0.7 wt% (TiC–TiB 2)/Al–Cu alloy at 298 K (529 MPa), 493 K (214 MPa), and 533 K (183 MPa) had an increase of 28%, 18% and 35%, meanwhile their elongation increased by 4%, 50% and 62%, respectively. The yield strength enhancement primarily benefited from the thermal mismatch between the particles and matrix, and Orowan strengthening. The strength–ductility performance improvement is due to the optimization of the microstructure: significantly refined α-Al grains with smaller and more dispersed θʹ precipitates. Further, the improvement mechanism of the microstructure is due to the action of the nanoparticles on the heterogeneous nucleation stimulation and dendrite growth inhibition of α-Al during the solidification process. Meanwhile, the segregation of the Cu atoms was inhibited by the particles. The precipitation was significantly promoted because of more uniformly distributed Cu atoms, and more defects induced by particles improved diffusion of the Cu atoms the number and density of the precipitation sites. The results of this study provide an economical and accessible synthesis strategy for industrial manufacturing. [ABSTRACT FROM AUTHOR]

At high temperatures, the weakened strength and decreased ductility of Al alloys limit their industrial applications. (TiB 2 –TiC)/Al–Cu–Mg–Si composites were synthesized by adding in situ dual-phased and bimodal-sized (TiB 2 –TiC)/Al master alloys to molten Al–Cu–Mg–Si alloys. The addition of minor amounts of TiB 2 and TiC particles (0.05 and 0.1 wt%, respectively) effectively refined the α-Al grains and θ′ and Q′ precipitates and increased the elevated-temperature strength and uniform elongation of the Al–Cu–Mg–Si alloys. The 0.1 wt% (TiB 2 –TiC)/Al–Cu–Mg–Si composite showed the best yield strength (279 MPa), ultimate tensile strength (366 MPa), and uniform elongation (10.6%) at 493 K, with enhancements of 9.4%, 15.1%, and 24.7% compared to the Al–Cu–Mg–Si matrix alloy (255 MPa, 318 MPa, and 8.5%). The simultaneous increases in the elevated temperature strength and ductility of the composites were attributed to the strengthening effects of the bimodal-sized TiB 2 and TiC particles, θ′ and Q′ precipitation strengthening, and the refined partial recrystallization microstructure. [ABSTRACT FROM AUTHOR]