Thermodynamics and phase equilibria in the A1-Ga system

As part of a programme to re-establish the thermodynamic properties of III V alloys and reassessment of the phase equilibria, the activities of aluminium in liquid A1-Ga alloys have been determined using a concentration cell of the type $Al(1)\vert NaCl + KCl + 3mol.$% $AlCl_3\vert Al_xGa_{1-x}$ The measurements were carried out over a wide temperature range from 925 to 1275 K and a compositional range $x_{Ga}= 0.1 -0.9$. The activities of A1 in the AI-Ga alloys exhibit positive deviation from ideality. The deviation is found to decrease progressively with increase in temperature and A1 content of the alloys. The phase equilibria in the system are evaluated using a five-parameter excess free energy function using the experimental data. The calculated solidus and liquidus boundaries of the system based on the present investigation are compared with those determined by the earlier evaluations and experimentally determined values available in the literature.