稀土镧对铝合金的去氢作用的机理分析

采用第一滴气泡法和减压凝固法 ,研究稀土镧对铝硅合金 (Al 11.2 %Si)中氢的作用 ,结果表明 :添加一定量的稀土镧 ,铝合金液体中溶氢量显著减少 ,铸件的针孔缺陷明显改善 ;稀土的去氢机理 ,认为稀土除氢效果不形成镧化氢 ,而主要是稀土镧减少氢在铝合金液体中的活度 ,降低铝合金液体中氢的析出压力 ,在凝固过程中增加氢在铝固溶体中有效分配系数。从热力学角度分析在铝液中形成镧化氢的条件。

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.