Experimental investigation and thermodynamic modeling of the Mg–Cu–Ca ternary system

Abstract The isothermal section in the Mg–Cu rich region of Mg–Cu–Ca ternary system at 300 °C was investigated in the present work. Two ternary compounds named as P1 and Mg25-xCu75Cax were observed. The solid solubility limit of the compound Mg25-xCu75Cax was found to be 8.29 ≤ xCa ≤ 15.71 with a constant value of about 75 at. % Cu at 300 °C. A narrow solid homogeneity range of the compound P1 was found to be Mg19Cu40Ca41 to Mg21Cu42Ca37 (in at. %). The maximum solid solubility of Ca in the terminal compound MgCu2 (C15) was determined to be 10.20 at. % at 300 °C. The maximum ternary solid solubility of binary terminal compounds Mg2Ca, Mg2Cu, Cu5Ca and CuCa were determined to be less than 2 at. %. For the more, thermodynamic modeling of the Cu–Ca binary and Mg–Cu–Ca ternary systems have been carried out by calculation of phase diagram (CALPHAD) method. The liquid solution was described using the modified quasi-chemical model (MQM). The compound energy formalism (CEF) was used for the solid phases. A self-consistent thermodynamic database of the Mg–Cu–Ca ternary system have been constructed in the present work.