Nucleation catalysis potency of ceramic nanoparitlces in aluminum matrix nanocomposites

The nanoparticles in metal matrix nanocomposites (MMNCs) were shown to catalyze nucleation of solidification. Nanoparticles of SiC, TiC, and γ-Al₂O₃ were dispersed in an aluminum alloy A356 matrix using an ultrasonic processing technique. The droplet emulsion technique was used to examine the undercooling in each matrix-nanoparticle system. Despite their small sizes, the nanoparticles demonstrated the ability to significantly reduce the necessary undercooling for nucleation. In general, the degree of undercooling in the MMNCs containing SiC, TiC and γ-Al₂O ₃ was in agreement with the free growth undercooling. The nucleation catalysis by the nanoparticles resulted in significantly refined microstructures. The grain refining effectiveness of nanoparticles was also examined in pure Al and Al-10Mg using TiC_0.7N_0.3 nanoparticles. In both pure Al and Al-10Mg the nanoparticle addition significantly reduced the average grain size of the matrix. Comparison was made to the commonly used Al-5Ti-B grain refiner. At the addition levels used, the nanoparticles were more effective than the Al-5Ti-B grain refiner.