A quaternary alloy (Al-5.0Cu-0.35Mn-0.25Ti, wt.%), having a similar chemical component with ZL205A, was prepared using a controlled diffusion solidification (CDS) process and a conventional casting process. The effect of the casting process on microstructure and hardness was investigated. The grain morphology and casting defects of the al oy prepared via the conventional casting and CDS were observed and compared at various pouring temperatures. Results show that the CDS process can al eviate the hot tearing defects and reduce the density of porosity, while getting rid of the riser that is general y used for feeding during conventional casting. Structure observations show that the grain morphology of the conventional cast al oy is mainly dendritic, and the grain size decreases when the pouring temperature is decreased, while the CDS cast al oy consists of a large number of spherical grains, which can decrease the thermal cracking tendency and segregation defect, and enhance the hardness of the al oy.