Thermodynamic assessment of the Al-P system based on original experimental data

All directly measured experimental data on phase equilibria and thermodynamic data of the Al-P system are critically reviewed, based on meticulous analysis of original sources. Confusion in the literature, especially regarding the reference state of phosphorous, is clarified. Based on these digested original data a consistent thermodynamic description is developed using the Calphad method. For the first time verified calculations of the vapor pressure, heat capacity and absolute entropy of AlP are included, together with directly measured heat of formation and reliable data on the solubility of P in liquid Al. Evidence is given that this work is necessary because published thermodynamic descriptions of the Al-P system are not acceptable. For example, negative values of Cp are produced for AlP from a most frequently cited dataset published in 1994. Other serious flaws are revealed in two more recently published works which, in our opinion, did not follow the true Calphad spirit.