Semi-solid casting (SSC) of zinc alloy nanocomposites

An innovative casting method that combines semi-solid casting (SSC) and metal matrix nanocomposite (MMNC) technology was successfully demonstrated. The method uses the grain refining properties of the nanoparticles in the MMNC to produce slurry with the appropriate globular structure for semi-solid casting. In this way no additional material processing or mechanical agitation is necessary to achieve the desirable slurry microstructure. The grain refining attributes of the nanoparticles were shown to stem from the promotion of nucleation in the solidifying matrix alloy. Differential scanning calorimetry (DSC) showed a reduced undercooling necessary for nucleation owing to the nucleation catalytic potency of the nanoparticles. Using this method zinc alloy AC43A nanocomposite with 0.5 wt.% SiC β nanoparticle additions were cast at a 30% solid fraction. The resulting castings showed increased ductility, reduced shrinkage, and increased strength compared to their monolithic liquid cast counterparts.