Nanoparticle additions promote outstanding fracture toughness and fatigue strength in a cast Al–Cu alloy

Fatigue resistance and fracture toughness are essential to the reliability of castings during service. Reducing microporosity in cast alloys is a crucial issue for improving their fatigue strength and fracture toughness. Here we report a significant reduction in microporosity of a cast aluminum-copper alloy developed using in situ TiC nanoparticle additions coupled with a stir-casting method. The addition of TiC nanoparticles is found to improve the interdendritic feedability of liquid metal and as a result reduces the volume fraction of microporosity by two orders of magnitude compared to a conventionally cast Al–Cu alloy. This method, which is mechanistically associated with a pore-dominated process, acts to significantly improve the fatigue strength, fracture toughness and uniform elongation of the cast Al–Cu alloy to values which, to the best of our knowledge, represent the highest ever achieved for a cast aluminum alloy.