Effects of boron and lanthanum on the impurity iron in aluminium melts

Abstract

Effects of boron and lanthanum on the impurity iron in aluminium melt with 0·12 wt-% and 0·78 wt-% Fe were studied. The Al melts were held for enough time at 720°C with the addition of La, B, or both of La and B. La or B had no effects on the iron phases in purity aluminium when they were added solely. Only AlB₂ phases formed after the addition of boron in the Al melts at 720°C, and precipitated to the bottom. AlB₂ and Al–Fe phases were found after solidification. No phases formed with the addition of lanthanum in Al melt at 720°C, only α-Al₁₁La₃ and Al–Fe phases formed in aluminium samples after solidification. LaB₆ formed in the Al melt at 720°C and settled down to the bottom of melt with the addition of La and B. LaB₆ showed 3–5 at-% solubility for Fe when the initial Fe content was 0·78 wt-%, which caused iron content slightly decreased to 0·76 wt-%. However, LaB₆ did not dissolve Fe atoms when the Fe content was as low as 0·15 wt-%.