Process for the grain refinement of primary silicon in eutectic and in hyper-eutectic aluminium silicon alloys

摘要

The primary Si in eutectic or hypereutectic Al-Si alloys is grain-refined by adding to an Al-Si melt a mixture of solid substances comprising one or more phosphates and Al and/or Mg. The phosphates are preferably Na-free, or contain less than three atoms of Na per atom of P, and may be AlPO4, Mg2P2O7, Na4P2O7 or NaPO3. The mixture preferably comprises a phosphate and Al powder in stoichiometric proportions corresponding to the formation of AlP, and it may be compressed into pellets or packaged in Al containers. Fluxes and small amounts of C or carbonaceous materials may be added to the mixture.