Vol 119, No 10 (2018)

The effect of selective thermomagnetic treatment on the exchange interaction between magnetic layers in Fe₁₁Ni₈₉/Tb₃₀Co₇₀/Ti films has been investigated. Dependencies of the exchange bias field induced in the Fe₁₁Ni₈₉ layer on the annealing temperature have been obtained and interpreted. We consider structural modifications of the interface and stress-relaxation processes in the Fe₁₁Ni₈₉ layer to be the main reasons for the observed modifications of hysteresis properties.

In the current work, a diffusion model was suggested to estimate the boron activation energies for FeB and Fe₂B layers on the gas-borided Armco iron at temperatures of 1073, 1173, and 1273 K for a treatment time varying between 1.33 and 4 h. This model takes into account the effect of boride incubation times during the formation of the FeB and Fe₂B phases. The mass balance equations were reformulated to describe the evolution of boride layers after applying the diffusion annealing process. In addition, the time needed to completely dissolve the FeB phase in the boride layer was also predicted. This predicted time was influenced by the boriding parameters during the diffusion annealing process.

Two Cu/Mg-composite rods of different content of components were produced by hydrostatic extrusion. The volume proportion of the copper sheath and magnesium core was almost equal in one of the two composite samples. Seven thin magnesium fibers were located in the copper matrix of another composite. Estimate calculations of the strength properties and electrical resistance of deformed composites were carried out and compared with the experimental results. The influence of anneals on the microstructure and electrical and mechanical properties of composites was also studied. This work has shown that a temperature rise causes sequential formation of the intermetallic compounds CuMg₂ and Cu₂Mg at the Cu/Mg interface, which, according to the phase diagram, results in eutectic reactions. The results of this work can be used in the development of high-strength composite conductors.

In the present study, the Chou’s general solution model (GSM) has been used to predict the excess Gibbs enthalpy of the liquid Co–Sb–Sn ternary alloys with three selected sections x_Sb/x_Sn = 1/3, x_Co/x_Sb = 1/5, and x_Co/x_Sn = 1/4, of Ag₁₀–In₈₀–Pd–Sn₁₀, Ag₂₀–In₆₀–Pd–Sn₂₀, and Ag–In₄₀–Pd₂₀–Sn₄₀ quaternary alloys and the excess Gibbs energy of Ni–Cr–Co–Al–Mo–Ti–Cu with seven component alloys with selected sections, namely, x_Ni = x_Cu, x_Cr = x_Ti, x_Co = x_Ti, x_Al = x_Ti, x_Mo = rx_Ti, x_Ti = (1 – x_Cu)/(r + 5), and r = 0.1 at temperatures 1273, 1173, and 2000 K, respectively. However, any information in the literature regarding the application of GSM to the alloys mentioned above could not be found, the other geometric models such as Kohler, Muggianu, and Toop are also included in present calculations. Using standard deviation formula, it is seen that some reasonable agreements exist between the results of the geometric models and those of related experiments.

Computer simulation was used to study the relaxation of disordered systems of dislocations in the stress field of nonequilibrium grain boundaries upon ultrasonic treatment (UST). The effect of ultrasound is simulated by an oscillatory shear stress applied to the crystal. Edge dislocations in a model grain with three nonparallel slip systems located at an angle of 60° to each other were examined. The nonequilibrium state of grain boundaries is simulated with the aid of a quadrupole of wedge disclinations located at its junctions. This study showed that the UST caused a rearrangement of the dislocation structure and led to a reduction of internal stresses. The amplitude of ultrasound and the degree of the nonequilibrium state of grain boundaries (strength of the disclination quadrupole) significantly affect the relaxation of the dislocation structure. There are optimum values of the UST amplitude, at which a maximum reduction of the internal stresses is achieved. This study also investigated the dependence of the degree of relaxation of internal stresses on the amount of dislocations in the grain.

This paper presents the results of our study of the contact endurance of laser-clad chromium–nickel coatings of the NiCrBSi system with different contents of chromium, boron, and carbon (PG-SR2, containing 0.48% C, 14.8% Cr, 2.1% B wt %; and PG-10N-01, containing 0.92% C, 18.2% Cr, 3.3% B wt %) and with additions of carbides of titanium TiC (15 and 25 wt %) and chromium Cr₃C₂ (15 wt %) upon contact fatigue loading according to the scheme of the pulsing non-impact “sphere-to-surface” contact. It has been established that the contact endurance of chromium–nickel coatings with different chemical compositions and different dispersity of structure is determined by their ability to resist plastic deformation under the conditions of repeated elastic–plastic deformation upon the mechanical non-impact contact action. This study has shown that composite coatings can be created, which contain large (50–150 μm) particles of the strengthening phases, whose contact endurance will not be substantially inferior to the contact endurance of coatings with fine (1–10 μm) strengthening phases. An estimation of the ability of the surface of the coatings to resist the mechanical contact action was made with the use of the data on microindentation. It has been shown that the method of microindentation (single loading) can be used for determining the ability of chromium–nickel coatings to withstand repeated contact loadings.