Structural state and thermodynamic stability of Al–Cu alloys

Abstract

It is known that processes occurring in binary system melts affect the crystallization process and the phase composition of alloys. To predict these processes, we should determine the region of thermodynamic stability of the melt. In this paper, the structural properties of hypoeutectic and hypereutectic alloys in Al–Cu system are studied depending on the heating temperature above the liquidus line and aftercooling rate. It is shown that overheating of Al–Cu melts to 150 K above the liquidus line and further cooling leads to complete suppression of the process of formation of primary aluminum crystals in hypoeutectic alloys and [Formula: see text] phase in hypereutectic alloys. For the first time, by accounting in Gibbs energy of binary Al–Cu alloy for the first degree approximation of high-temperature expansion of thermodynamic potential, the dependence of temperature of line of the melt thermodynamic stability on copper content in alloy is obtained.