Abstract
A phase diagram of Al-Si system in the hypoeutectic region at 28kb has been composed. A girdle-type high pressure device was used to press and heat the specimens, and an electric resistance method to detect the phase transitions. The characteristic figures obtained are as follows;
(1) The melting point of pure Al has been elevated to 840°C at 28kb from 560°C at 0kb giving 6.4°C/kb as for the pressure derivative. The fiqures are very close to the experimental value of Jayaraman and also agrees approximately with a value 5.5°C/kb calculated from the Clausius-Clapeyron's thermodynamical relation.
(2) The eutectic temperature of this system has been elevated from 577°C at 0kb to 660°C at 28kb giving 3.0°C/kb as for the pressure derivative. This value agrees fairly well with the calculated value 2.5°C kb.
(3) The solid solubility of Si at the eutectic temperature has been broadened to 7.0 at.% at 28kb from 1.6 at.% at 0kb, This value is comparable to the solubility 8.5 at.% calculated under the assumption of the dilute solid solution model using-5.5×10-24cm3/atom as the change of molar volume per solute atom.
