Breaking the strength-ductility trade-off in nano-TiB2/Al–2Li–2Cu-0.2Sc metal-matrix composites

Conventional casting struggles to fabricate high-performance nanoparticle-reinforced Al-Li composites due to persistent agglomeration and casting defects. To overcome this, this study develops a novel multi-stage strategy integrating high-energy ball milling, vacuum melting, ultrasonic treatment, and squeeze casting. This innovative approach successfully achieves seamless nano-TiB 2 incorporation and uniform dispersion within Al-2Li-2Cu melts while eliminating casting defects. Crucially, the addition of Sc (0.2 wt.%) in combination with nano-TiB 2 has a synergistic effect in optimizing the solidification microstructure, such as refining α-Al grains to 20μm and promoting a more homogeneous distribution of TiB 2 . Consequently, the as-cast ultimate tensile strength (UTS), yield strength (YS) and elongation (El.) of the 0.5 wt.% nano-TiB 2 /Al-2Li-2Cu-0.2Sc composites by UT+SC were 266 MPa, 155 MPa and 16.0 %, respectively, which were 15.7 %, 23.0 % and 7.0 % higher than those of the composite without the addition of Sc element. Notably, the attained UTS×El. product (4.256 GPa·%) establishes a new benchmark for high-Li content composites, surpassing most previous reports and confirming an exceptional combination of strength and ductility.