Effect of Cooling Rate on Microstructure and Grain Refining Behavior of In Situ CeB6/Al Composite Inoculant in Aluminum

Abstract

Melt spinning was performed to process an in situ CeB6/Al inoculant at different rotating speeds to investigate the influence of cooling rate on the grain refining behavior of inoculants. It has been found that a high cooling rate caused two obvious changes in the inoculant: the supersaturated solid solution of Ce in the α-Al matrix and the miniaturization of CeB6 particles. At high cooling rates of ~108 K/s, the Ce content is largely beyond the theoretical solid solubility of Ce in Al, and the size of the CeB6 particles in ribbons is reduced to ~100 nm. The grain refining effect of melt-spun CeB6/Al composite inoculant shows significant dependence on holding time of which the best value should be no more than 2 min. The excellent grain refinement of the inoculant can be attributed to the combined effect of the nano-sized refiner particles and the large undercooling caused by the sudden melting of supersaturated Al–Ce solution.