Refinement of Primary Silicon Crystals by Novel P-Doped γ-Al₂O₃ Particles in Solidification of Hypereutectic Al-Si Alloys

Abstract

P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities. The optical micrographs show that the morphologies of primary silicon crystals in solidification of Al-18Si alloy are changed from irregular coarse morphologies to fine regular particles. The average particle size of primary Si decreased from 52 μm to 25 μm and 22 μm in adding P-doped α-Al2O3 and P-doped γ-Al2O3 respectively. It was clear that P-doped γ-Al2O3 led to good refinement of primary Si and the modification effect on eutectic Si was retained in solidification of commercial purity Al-18Si alloy. Adding P-doped γ-Al2O3 give a good primary Si refinement to Al-18Si alloy if compared with the addition of P and using finer P doped γ-Al2O3 powder give narrower particle size range similar to that of adding P.

Functional and Environmental Advantage of Cleaning Ti5B1 Master Alloy

“…The presence of oxide films in master alloys causes various opinions among experts. While some view a reasonable amount of oxide films as excellent nucleation sites [28,29] the other reason that oxides have a little contribution in instigating crystallization but have a detrimental effect on mechanical properties in the final structure [30][31][32]. In current work, the commercial master alloy has an order of magnitude more oxide agglomerates than clean master alloy, but it didn't change liquidus, primary undercooling, or recalescence temperatures in a favorable direction.…”