Effect of tin addition on the distribution of phosphorus and metallic impurities in Si–Al alloys

• The redistribution of P and metallic impurities were studied in Si–Al–Sn alloy.
• β-Al5SiFe compound was found accompanying with βSn phase.
• The Si–Al–Sn alloy with Sn addition had a higher impurity removal ratio than Al.

Metallurgical grade silicon was purified through solvent refining method by adding tin to the Si–Al alloy. The distribution of phosphorus and metallic impurities in the resulting Si–Al–Sn melts was investigated. Compared with the primary Si and the eutectic αAl+Si, the phosphorus and metallic impurities were more distinctly distributed in the βSn phase, which was always accompanied by needle-like intermetallic β-Al5SiFe compounds. To improve the phosphorus and metallic impurity removal ratios, Si–Al–Sn ternary alloys with different composition were investigated. The phosphorus removal ratio increased with the aluminum and tin content in the Si–Al–Sn ternary alloy. Compared to increasing the Al content and keeping the Si/Sn ratio fixed, the impurity removal ratios were higher when the Sn content was increased to the same mass percentage and the Si/Al ratio was kept fixed in the Si–Al–Sn melt.