Том 120, № 12 (2019)

The structure of the Fe_63.5Ni₁₀Cu₁Nb₃Si_13.5B₉ alloy, which is a classic alloy of the FINEMET type with 10 at % Ni substituted for Fe, has been studied after crystallization in the presence of tensile stresses. It has been shown that, upon the crystallization of the alloy (520°C) both in the presence of a tensile load and without it, nanocrystals of an α-(Fe, Ni)Si solid solution and of the Fe₃Si phase are formed with an increase in the duration of annealing from 10 min to 1 hour. When the length of the annealing is further increased from 1 to 4 hours, a tetragonal phase Fe₃NiSi_1.5 appears in the alloy. A relationship between the structural state (phase composition) of the Fe_63.5Ni₁₀Cu₁Nb₃Si_13.5B₉ alloy and its magnetic properties and the type of the induced magnetic anisotropy has been shown. The growth of the coercive force, which was previously observed in samples of this alloy as the duration of the annealing was increased to 4 hours, is therefore associated with the appearance of a tetragonal phase in the alloy. The transverse magnetic anisotropy, which is induced in the alloy in the process of nanocrystallizing annealing in the presence of a tensile load, is associated with the formation of nanocrystals of the α-(Fe, Ni)Si solid solution and of the Fe₃Si phase with a negative magnetostriction.

This work proposes an approach for the calculation of equilibrium solubility limits in binary alloys, which is an alternative to approaches based on gradient expansions. The proposed approach rests on the description of alloys in terms of a weak nonlocality, which generalizes the classical local equilibrium hypothesis. This results in a theory that can be used to derive the explicit concentration dependence of all used parameters solely from knowledge of the concentration dependence of free energy density, which is impossible within the framework of existing approaches.

The electron back-scatter diffraction (EBSD) method was used to study the structural and textural states of low-carbon low-alloy steel after thermomechanical controlled processing (TMCP) and subsequent heat treatment (HT) including austenitization, holding at the temperature of the decomposition of the γ phase by the diffusion mechanism for different times, and quenching. As a result of the HT, structures were obtained consisting of polygonal ferrite and martensite in various ratios. The crystallographic textures of both martensite and ferrite after HT reproduced the texture of bainite formed as a result of the TMCP. The orientations that form this texture are related to the main orientations of deformed austenite grains upon the TMCP via the orientation relationships (ORs) intermediate between the Kurdjumov–Sachs and Nishiyama–Wassermann ORs. In the case of both ferrite and martensite, the orientational connection between the components of the texture components is explained by the onset of the realization of the phase transformation on crystallographically stipulated (including special) boundaries.

Transmission electron microscopy and scanning electron microscopy were used to study the evolution of the structure of iron (of 99.97% purity) in the course of deformation at 250°С by torsion under pressure. Electron back-scattered diffraction analysis was used to determine the size of recrystallized grains, their orientation, angular range of grain-boundary misorientation, and fraction of recrystallized structure. It was found that, upon deformation at 250°С by torsion under a pressure, the dynamic recrystallization of iron starts on reaching the true strain е = 2.4. At the steady stage of deformation, the structure with an average grain size of 0.5 µm forms, which is characterized by the absence of any preferential orientation.

The accelerated Ar⁺ ion irradiation at a fluence of 1.2 × 10¹⁵ cm^–2 for 4 seconds formed 6.2% austenite in a cold-worked Fe–6.29 at % Mn alloy with a structure of α ferrite. The related ion beam heating of a foil 25 μm thick is 299 ± 5°C, according to temperature monitoring. The content of manganese calculated from Mössbauer spectroscopy data in α and γ phases after irradiation is 5.5 and 17.1 at %, respectively. Grounds for the activation of low-temperature atomic mobility in the alloy are discussed in this paper. The mobility was shown to not be caused by the formation of radiation defects and radiation-enhanced diffusion. Nanoscale dynamic effects, resulting in the possible viscous flow of material at the front of post-cascade shock waves propagating in a undamped mode, play a vital role.

Based on the results of compression tests in temperature ranges of 1100–1250°С and strain rates of 0.1–10 s^–1, a rheological model of the deformation behavior of the 13CrMoNbV ferritic-martensitic steel is constructed. A fracture criterion for the 13CrMoNbV steel in the process of hot plastic deformation and a method for determining its critical value, based on tensile tests at a Gleeble 3800 complex for physical modeling of thermomechanical processes and the results of modeling using the finite element method,—are proposed. The rheological model and the fracture criterion showed satisfactory accuracy when calculating the deformation process under conditions of a complex stress–strain tension–torsion state at the Gleeble 3800 complex at a temperature of 1100°C.