Vol 120, No 6 (2019)

The theme of this survey is the application of new ideas of uncommon quantum states to the physics of the condensed state, in particular, of solids, in the context of the contemporary field theory. A comparison is performed with the classical works on the many-electron theory, including the formalism of many-electron operators. Principally, the many-particle nature of the ground state, individual and collective excitations, and quantum fluctuations in the systems in question are discussed, as well as quantum phase transitions (mainly, the topological aspects considering the effects of frustration). The variational approaches and the concepts of auxiliary particles, the corresponding mean-field approximations, the theory of gauge fields, the problem of confinement–deconfinement, the breakdown of the Fermi-liquid behavior, and exotic non-Fermi liquid states are considered. A survey of the contemporary theory of the entangled topological states, formation of spin liquid, strings, and string networks is given.

The double electromagnetoacoustic transformation method is used to study the dynamic magnetoelastic properties of the Fe₈₁Si₇B₁₂ amorphous alloy depending on the temperature of crystallization annealing. Changes found in the velocity of sound, its damping, and differential magnetostriction are related to the relaxation of quenching stresses and the surface crystallization.

The influence of the polymer coating used in the manufacture of magnetic shields and of the conditions of its formation on the distribution of the magnetization and on the magnetic properties of shields has been studied. Samples of a ribbon of the Co-based soft-magnetic amorphous alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) with a saturation magnetostriction close to zero were used in the study. The coating was deposited in the temperature range of 90–130°C on the ribbon subjected to heat treatments in air that form a state with a negative saturation magnetostriction. The change of magnetic characteristics was investigated over a two year period. It has been shown that there is a temperature range in which a change in the sign of the saturation magnetostriction occurs upon the formation of the coating. This change is due to a change in the structural-phase state of the ribbon because of the diffusion processes that occur upon heating. The formation of the coating leads to a reduction in the maximum magnetic permeability; nevertheless, over a two year period, no decrease in μ_max is observed in the ribbon with a coating formed in the 110–130°C temperature range.

The microstructure and crystal orientation of Ni–5 at % W (Ni5W) long tapes during recovery and recrystallization processes under various tensile stresses are studied systematically by using a tensile stress annealing equipment designed in our University. Comparing these two processes with and without tensile stresses, it is found that tensile stresses can promote recrystallization, for example: the cube orientation fractions under a tensile stress of 20 MPa is twice as high as without tensile stress at 650°C. In the complete recrystallization process, tensile stresses below 10 MPa have little effect on the microstructure and crystal orientation. When the tensile stress is increased to 25 MPa, the grain boundary grooves are obviously deepened into cracks, while the fractions of both low angle grain boundaries and cube texture decreased. This is in contrast to an increase of the fractions of Σ3 twin boundaries showing a more abnormal grain growth. The effects of tensile stresses on the annealing process of Ni5W long tapes are investigated experimentally. They are expected to guide the reel-to-reel dynamic recrystallization annealing of Ni5W long tapes and to promote the transition from laboratory to industrialization.

Grain size and its distribution is the dominant microstructure feature of austenitic stainless steels. These characteristics considerably affect the mechanical properties of the steels. The distribution of grain size during preheating prior to the hot deformation has the main effect on the uniform distribution of the strain interior of the grains and, consequently, on the homogeneous development of processes such as static, dynamic, and metadynamic recrystallization in the material. The grain size distribution can be expressed using the Jensen–Gundersen point method along with the commonly-cited distribution functions such as the lognormal, gamma, Weibull, Louat, or Hilert relations. In this study, 3D Monte Carlo Potts method was employed for predicting grain growth kinetics and relevant grain size distribution during annealing process to describe which distribution function is dominant. To validate simulation results, the serial sectioning procedure was performed on AISI 316L cylindrical samples annealed at 1200°C for 5, 10, and 15 min. Results show that grain number densities (GND) affect the grain size distribution, in which at the relatively low GNDs, the lognormal function and at the higher ones, the gamma function are realized. Moreover, a new method for the grain size standard deviation statement via the lognormal distribution is introduced.

The role of volume changes on the structural rearrangements of dislocation pileups accompanied by the formation of the intercrystallite boundaries, pores, and microcracks upon the plastic deformation of materials is analyzed. The results of this analysis are applied to the study of the microscopic mechanisms of the effect of pressure on processes of the formation and fracture of the nanostructure of metals and alloys.

The evolution of the microstructure and mechanical properties of deformed sheets made of a new Al–4Cu–2.7Er alloy has been studied in the course of homogenization and annealing. The structure of the cast alloy consists of a dispersed eutectic ((Al) + Al₈Cu₄Er), Al₃Er-phase inclusions located along the dendritic-cell boundaries, and a nonequilibrium AlCu phase. During annealing at 605°C before quenching, the intermetallic phases have high thermal stability: the particle size of Al₈Cu₄Er and Al₃Er phases does not exceed 1–4 µm. The annealing of deformed sheets at temperatures below 300°C leads to a slight decrease in the hardness; grains elongated along the rolling direction are observed in the structure. With an increase in the annealing temperature from 350 to 550°C, the recrystallized grain size increases from 8 ± 1 to 14.5 ± 1.5 μm. The uniaxial tensile tests showed that the annealed alloy possesses sufficiently high strength characteristics: yield stress of 260–280 MPa, ultimate tensile strength of 291–312 MPa, and relative elongation of 5.5–6.1%.