Effect of Al-3 wt% Al2O3 master alloy fabricated by calcined kaolin on grain refinement and mechanical properties of A356 alloy

In the present study, Al-3 wt% Al2O3 master alloy was successfully prepared by the reaction between calcined kaolin and aluminum melt, combined with mechanical stirring and high-energy ultrasonic dispersion technology. The gamma-Al2O3 particles produced by the reaction are uniformly dispersed in the matrix, and the average size of gamma-Al2O3 is about 65 nm. The refinement effect of Al-3 wt% Al2O3 master alloy on A356 alloy was studied. It was found that the a-Al grain size in A356 alloy refined by Al-3 wt% Al2O3 master alloy was decreased from 980 +/- 155 mu m to 337 +/- 95 mu m. Compared with the Al-5Ti-1B master alloy, Al-3 wt% Al2O3 has a higher refinement efficiency. In addition, the refinement efficiency of the Al-3 wt% Al2O3 master alloy will not fade within 60 min. Transmission electron microscope analysis showed that the orientation relationship between gamma-Al(2)O(3 )and Al was (22-2)(gamma-Al2O3)[011](gamma-Al2O3)//(11-1)(Al)[011](Al), which demonstrated that gamma-Al2O3 could be used as heterogeneous nucleation sites to refine alpha-Al grains. Moreover, the tensile properties of A356 alloy had been significantly improved. (C) 2021 Elsevier B.V. All rights reserved.