A new-type nano-sized TiN/Ti composite grain refiner was prepared by high energy ball milling. Influences of the refiner on the as-cast microstructures and properties of Al-4Cu after solid solution and aging were investigated

and the grain refining mechanism was also discussed. The results show that TiN/Ti composite refiner exhibits the excellent grain refining effects on as-cast microstructure of Al-4Cu alloy. TiN/Ti composite refiner can refine significantly the α-phase

and with 0.2% addition

average grain size of α-phase in Al-4Cu sample is decreases from 161 μm to 131 μm

showing better grain refining effect than pure Ti refiner. The micro-hardness of the aged sample with 0.2% TiN/Ti refiner reaches hardness peak of 125 HV

increased by 19% than that of the sample without any refiners. Comparing with those of the sample without adding grain refiners

the tensile strength and yield strength of the sample with 0.2% TiN/Ti refiner are increased by 103.1% and by 155.42%

respectively. In addition

the fracture of the sample without any refiners is characterized by mixed-rupture of quasi-cleavage and dimples

while the fractured faces of the sample with 0.2% TiN/Ti refiner are characterized by ductile fracture with dimples.