In-situ tailoring microstructure by directly synthesized TiC–TiB2 nanoparticles to achieve well-balanced strength and ductility in Al–Cu alloy

Incorporating and dispersing trace manipulated agents into Al alloy melt is a longstanding challenge that hinders the balance of strength-ductility in cast Al alloys. A delicate strategy of in-situ fabrication and effective incorporation of the tuned agents was put forward in this study to achieve a better-optimized microstructure of Al-5.5Cu alloys with superior room-temperature and high-temperature mechanical performance. The tailored microstructure effects and optimized mechanical properties under room temperature and elevated temperature (220 °C) by varying mole ratios of dispersed TiC–TiB2 particles were investigated. The in-situ TiC–TiB2 nanoparticles with the mole ratio in 1 : 2 (TiC: TiB2) performed the best microstructure tailoring capacity for Al–Cu-based alloy, which the manipulated alloys shows the most refined and homogeneous grain microstructure with a size of 40.4 μm, compared with the based Al–Cu alloy, refined by 73.8%. Also, the segregation of Cu was mitigated and after heat treatment, the transformation of θ″ → θ′ was accelerated. Thanks to the contribution of TiC–TiB2 particles, Al–Cu alloys perform excellent strength and ductility synergy both at room temperature and elevated temperature, and the strengthening mechanism was also discussed. It is believed that this work can give an optimized strategy from the in-situ synthesis, incorporation and dispersion of manipulated agents to the alloy microstructure tailoring and strength-ductility balancing.