Effect of alloying elements on stationary concentration of hydrogen in molten aluminum

The effect of such principal alloying elements to aluminum as Si, Cu, Mg and Zn on the stationary concentration of hydrogen in molten aluminum was studied. The hydrogen concentration in binary alloys of Al-Si, Al-Cu, Al-Mg and Al-Zn in the molten state in the air was measured at proper intervals and the stationary concentrations of hydrogen (Hs) were evaluated. The results are summarized as follows. (1) Hs increased slightly by the addition of Si when the amount of Si was less than 12%. However, when 19% of Si was present in the melt, Hs showed a marked increase. (2) The presence of Cu resulted in a slight increase of Hs when the amount of Cu was less than 10%. (3) The presence of a small amount of Mg, approximately 1%, remarkably decreased Hs. However, when the amounts of Mg in the melt were 2.5% and 5%, the hydrogen concentration changed with the lapse of time, and thus, Hs was not clearly determined. (4) Hs decreased considerably when less than 10% of Zn was present in the melt.