Structure and Tensile Properties of High-Purity Al-Si Hypo-Eutectic Alloy

Structure and tensile properties of a high-purity Al-Si hypo-eutectic alloy, which was H-Alloy of 99.98 mass% purity, have been investigated comparing with a conventional one which was L-Alloy of 99.89 mass% purity. Although the base structure in both of the alloys was composed of proeutectic or-phase and eutectic structure, the eutectic structure of H-Alloy was finer than that of L-Alloy. Coarse crystals of plate-like silicon were observed in L-Alloy, while was not observed in H-Alloy. Based on the results of Brinell Hardness Test on the solidification structure, it was found that there was little difference of the hardness between the both alloys. Tensile tests were also performed in an atmosphere at room temperature. The elongation of H-Alloy was twice as large as that of L-Alloy, though the tensile strength of L-Alloy and H-Alloy were almost the same. Al-Fe-Si system compounds were observed at the interface between or-phase and eutectic silicon in L-Alloy.