The Mechanism of Lanthanum Dehydrogenation on Al-Alloy
The effects of the rare earth La on the hydrogen in the Al Si alloy are analyzed by Degle method and the decompression solidification method. The results indicate that the content of the hydrogen and the defect of the needle holes in the aluminum alloy decreases apparently when La is added to the alloy. The principle of the dehydrogenation is discussed. The main reasons of the dehydrogenation are that La decreases the activity of the hydrogen in the aluminum melt, decreases the liberation pressure of the hydrogen, and increases the validity partition coefficient during solidification. The formation of the LaH x is not the reason of dehydrogenation. The authors also discuss the conditions of formation of the LaH x from the point of the thermodynamics.