A NOVEL METHOD FOR THE DETERMINATION OF THE HYDROGEN SOLUBILITY IN ALUMINUM AND ALUMINUM-ALLOY MELTS

The CHAPEL method, which was developed for the direct and continuous d etermination of the hydrogen activity in aluminum melts by measuring t he equilibrium hydrogen pressure, has been modified for the determinat ion of the hydrogen solubility in aluminum and aluminum alloy melts. T he change of the hydrogen equilibrium pressure due to addition or remo val of a given amount of hydrogen from a melt of known mass yields dir ectly the Sieverts constant. Such experiments provide reliable data on ly if no additional gas exchange takes place between the melt and the gas phase. In the present work, a quasi-impermeable interface between the melt and the surrounding hydrogen atmosphere has been realized by maintaining the hydrogen pressure above the melt continuously at the l evel of the hydrogen equilibrium pressure. By this technique, which is performed by a relatively simple experimental setup, fast determinati on of the hydrogen solubility is possible. The main advantage of this novel method is the fact that it can be applied also for aluminum allo ys without protective oxide layer on the surface. Preliminary results on pure aluminum and Al-Cu alloy melts show good agreement with the da ta obtained by the classical method of Sieverts that is not well suite d for routine determinations on a wide range of alloy composition and temperature since it is very time-consuming. The method can also be ap plied for the investigation of other metal and alloy melts.