Thermodynamic properties and phase equilibria in alloys of Bi—Tm system

V. A. Shevchuk 1,
Kudin V.G 2,

1 I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Kyiv
2 Taras Shevchenko National University of Kyiv, Kyiv

Usp. materialozn. 2021, 3:93-101


The thermochemical properties of the melts of the Bi—Tm system at a temperature of 1100 K in the range of compositions 0 ≤ xTm ≤ 0,2 were determined for the first time by the calorimetry method. It is established that the minimum value of the enthalpy of mixing of these liquid alloys is equal to –75,7 ± 0,5 kJ / mol at xTm = 0,65. = –150,7 ± 16,7 kJ / mol, = –230,9 ± 21,8 kJ / mol. The activities of the components and molar particles of associates were calculated according to the model of an ideal associated solution (IAR), using data on the thermochemical properties of melts of the Bi—Tm system. It was found that the activities of the components in these metallic solutions show very large negative deviations from ideal solutions with a high content of TmBi and Tm2Bi associates. The obtained dependences of the first i melts of the Bi—Tm system on temperature showed a large steepness of the Bi curve in contrast to the gradual decrease of exothermic values of Tm. This indicates large changes in the structure of the Bi atom with increasing temperature. Excess integral and partial Gibbs energies of Bi-Tm system melt mixing calculated from component activities The absolute values of ΔG in the whole concentration range are smaller than ΔH (ΔG min = –41,8 kJ / mol at xTm = 0,58), and the function ΔG of is more asymmetric, which is caused by the entropy contribution (entropy of mixing of the studied melts is negative, and ΔSmin  = −30,5 J / mol • K at xTm = 0,65).

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