Influence of lithium on the temperature dependence of heat capacity and thermodynamic functions changes in AK1 alloy based on high-purity aluminum

Abstract

The heat capacity of the AK1 alloy based on high-purity aluminum with lithium was determined in the cooling mode using the known heat capacity of the reference aluminum sample. By means of mathematical processing of cooling rate curves of samples from AK1 alloy with lithium and the reference sample, polynomials describing their cooling rates were obtained. Further, the polynomials of the temperature dependence of the heat capacity of alloys, described by a four-member equation, were established using the experimentally found values of the cooling rates of samples from alloys and the standard, taking into account their mass. Using integrals from specific heat capacity, models of temperature dependence of enthalpy, entropy and Gibbs energy changes were established. It was found that the heat capacity of the alloys increases with rising temperature. The addition of lithium when the temperature is up to 600 K significantly increases the heat capacity, and at temperatures above 600 K lithium in amounts of 0.5 wt. % reduces the heat capacity of the initial alloy AK1. It is shown that lithium addition increases the enthalpy and entropy of the initial AK1 alloy and decreases the Gibbs energy value.