Azimov Kh.Kh., Ganiev I.N., Amonov I.T., Ibrohimov N.F. Effect produced by lithium on the heat capacity and the changing thermodynamic functions of the AZh2.18 aluminium alloy

Abstract

It is known that unalloyed aluminium with a high content of iron, silicon and other impurities cannot be used in industry because of its low performance characteristics. Hence, the development of new aluminium alloys sets an important task. One of the promising compositions in the aluminium-iron diagram is the eutectic (α-Al + Al3Fe), which, having a minimum crystallization interval, corresponds to the iron content of 2.18 wt%. This composition was taken as a model alloy and was inoculated with lithium. Heat capacity is the most important characteristic of substances. By analysing how heat capacity changes as the temperature changes one can determine the type of phase transformation, the Debye temperature, the energy of vacancy formation, the electronic specific heat and other properties. For the purposes of this research, the heat capacity of the AZh2.18 alloy with lithium was determined in the "cooling" mode against the known heat capacity of the reference copper sample. For this purpose, the cooling rate curves for the AZh2.18 alloy with lithium sample and the reference sample were analysed and polynomials were yielded that describe the cooling rates of the samples. After that, using the experimentally determined values of the cooling rates of the reference sample and the samples made from the alloys and knowing their weights, polynomials were established for the temperature dependence of the specific heat of the alloys and the reference sample, which are described with a four-term equation. With the help of integrals and based on the specific heat, temperature dependence models were established for changing enthalpy, entropy, and Gibbs energy. The obtained dependences show that as the temperature rises, the heat capacity, enthalpy and entropy of the alloys tend to increase. At the same time, Gibbs energy tends to decrease. The addition of lithium does not cause any significant increase in the heat capacity, enthalpy and entropy of the initial AZh2.18 alloy and does not change the Gibbs energy value.

Keywords

АZh2.18, lithium, heat capacity, heat transfer factor, enthalpy, entropy, Gibbs energy.

Kholiknazar Kh. Azimov – Postgraduate Student

Nikitin Institute of Chemistry, Academy of Sciences of the Republic of Tajikistan, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Izatullo N. Ganiev – D.Sc. (Chemistry), Professor, Academician

Academy of Science of the Republic of Tajikistan, Head of Laboratory at the Nikitin Institute of Chemistry, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Ilkhom T. Amonov – Ph.D. (Eng.), Associate Professor, Rector

Technological University of Tajikistan, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Nasim F. Ibrohimov – Research fellow

Nikitin Institute of Chemistry, Academy of Sciences of the Republic of Tajikistan, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..

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