A357 and 6082 aluminum alloys strengthened by aluminum nitride nanoparticles were obtained. The process of crystallization of the A357-0.5 wt% Al2O3 and 6082-0.5 wt% Al2O3 alloys was studied under conditions of varying the cooling rate. The A357 and 6082 aluminum alloy structure and hardness were analyzed for the Al2O3 content from 0 to 1 wt%.