Effect of phosphorus on modification of eutectic silicon in Al–7Si–0·3Mg alloy

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Abstract
The influence of the impurity element phosphorus on the modification of eutectic silicon by the addition of strontium was examined by the observation of microstructures, differential scanning calorimetric thermal analysis, a tension test, and fractographic observation. When the phosphorus content was 1·3 ppm, the eutectic morphology was the fine needle phase. Where the phosphorus content was 17·5 ppm, the eutectic silicon appeared as a coarse flake phase. Increasing the phosphorus content of the melt deteriorated the modification of the eutectic silicon and increased the eutectic temperature. Tensile strength and elongation decreased with increasing phosphorus content.