Abstract
Effect of arsenic added to hyper-eutectic Al-Si, Sn-Si and Ag-Si alloys on the microstructure and line scanning analysis by X-ray microanalyser were studied.
The results of experiment are summarized as follows :
(1) When arsenic was added to molten aluminum and Al-Si alloy, a compound was formed which has been identified with AlAs. When As and Al were added to molten Sn-Si alloy or Ag-Si alloy, a compound identified with AlAs was formed in these alloys.
(2) With the addition of As or As and Al, the grain size of primary silicon in hyper-eutectic Al-Si alloy or Sn-Si and Ag-Si alloys was refined.
(3) The excess AlAs were retained in the matrix of alloy, free from the primary and eutectic silicon crystals, but the greater part of AlAs was included in the refined primary silicon crystals.
(4) The grain size of primary silicon and the size of AlAs in the silicon particles of the specimen cast into a metal mold were smaller than those in the specimen of the sand mold, and the number of grians in the metal mold specimen was larger than the number in the sand mold.
The results of the experiment seem to suport the ‘foreign neucleus theory’ which has been believed to be an appropriate explanation of the refining mechanism of AlAs.
