EFFECT OF IMPURITY OF HYDROGEN ATOMS ON THE ENERGY CHARACTERISTICS OF Ni, Al AND Ni₃Al CRYSTAL LATTICES UNDER ELASTIC DEFORMATION

The effect of elastic deformation (compression and stretching up to ±5 %) and the incorporation of hydrogen atoms (concentration from 1 to 50 atoms) on the internal energy of crystal lattices of nickel, aluminum and Ni₃al intermetallic compounds has been studied by the method of molecular dynamics at a temperature of 0 K. The simulation was performed using a reliable interatomic potential EAM, which adequately describes the interaction in the metal‒hydrogen system. The placement of hydrogen in tetrahedral and octahedral interstices, as well as deformation along one, two, and three axes, was analyzed, which made it possible to evaluate the contribution of various types of stress states. It is shown that both the deformation and the introduction of hydrogen lead to an increase in the internal energy of the systems, reducing their thermodynamic stability. The greatest increase in energy is observed with a combination of compression (‒5 %) and high carbon concentrations in tetrahedral pores, which is especially typical for Ni₃Al intermetallic. It was found that the bond strength of hydrogen with the lattice depends on the nature of the metal: the Ni – H bond turns out to be stronger than Al – H due to the electronic structure of nickel. Ni₃Al intermetallic compound is characterized by a synergistic effect leading to increased affinity with hydrogen in the absence of deformation. When deformed, its sensitivity to hydrogen incorporation weakens, approaching the average value between nickel and aluminum. The results are consistent with the laws of thermodynamics and the theory of elasticity, and explain the mechanism of hydrogen embrittlement caused by local lattice distortions and changes in electron density. The results obtained are important for predicting the durability and reliability of materials in conditions of hydrogen-containing media and mechanical loads.

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