Temperature Dependence of Heat Capacity and the Variation in Thermodynamic Function of the AZh 4.5 Alloy Doped with Tin

Abstract

It is known that technical aluminum with an elevated content of iron, silicon, and other impurities cannot find application in industry because of its low performance characteristics. Therefore, the development of new alloy compositions based on such a metal is very urgent. Eutectic (α-Al + Al₃Fe) in the Al–Fe diagram and hypereutectic alloys are promising because, having a minimal crystallization range, they correspond to an iron content of 2–5 wt %. The alloy of the composition Al + 4.5% Fe (AZh4.5) is accepted in this study as a model alloy and is subjected to modification with tin. The temperature dependence of heat capacity of the tin-doped AZh4.5 alloy is determined and the variation in its thermodynamic functions is calculated. Investigations are performed in the cooling mode using a computer and the Sigma Pilot program. The polynomials of the temperature dependence of heat capacity and varying the thermodynamic functions (enthalpy, entropy, and Gibbs energy) of the tin-doped AZh4.5 alloy and reference sample (Cu) are established with correlation coefficient R_corr = 0.999. It is established that the heat capacity of the initial alloy decreases with an increase in the tin content and increases with an increase in temperature. Enthalpy and entropy of the AZh4.5 alloy increase with an increase in the tin content and temperature, while the Gibbs energy decreases.