Effect of Sn content on microstructure and boron distribution in Si–Al alloy

Abstract

Abstract Si–Al and Si–Al–Sn alloy melts were used for silicon purification by alloy solidification refining method. The effects of Sn addition on alloy microstructure, eutectic Si morphology, as well as B distribution were investigated using optical microscopy, scanning electron microscopy, electron probe microanalyzer and inductively coupled plasma mass spectrometer. Primary Si and αAl + Si structures with flake-like eutectic Si were found in Si–Al alloy; while an additional structure of αAl + βSn + Si in Si–Al–Sn alloy was found. Si in αAl + Si eutectic had a globular shape, whereas some Si in αAl + βSn + Si eutectic had an octahedral shape. Compared with primary Si, more boron was found to distribute in final solidified phase during the solidification, i.e. αAl + Si for Si–Al system and αAl + βSn + Si for Si–Al–Sn system. The refining ratio of B decreased with increasing Al content in Si–Al alloy melt, while increased with Sn addition using Si–Al–Sn alloy melt.