The paper expounds the life journey and main scientific achievements of Boris Alexandrovich Kolachev, laureate of the USSR State Prize, honored worker of science and technology of the RSFSR, professor, doctor of engineering who in 2018 would have turned 90 years old.

The paper studies the statistical dependence of the mechanical properties of 218 forgings (15 types) made of VT3-1 and VT6 alloys in 2000–2014 on chemical composition (the content of alloying elements and admixtures, structural and strength equivalents of aluminum and molybdenum), structure types, subtypes and parameters after annealing, quenching and aging. It was found that the strength and plastic properties of one-type forgings vary quite widely. The share of variation of forging properties due to fluctuations in the content of main components and admixtures, as well as the influence of structure types and sizes of structural components was estimated.
Based on the correlation analysis it was revealed that the change of each alloying element or admixture content has a little or no effect on forging properties. This is caused by small increments of their change within the grade composition. However, their total content expressed in terms of aluminum and molybdenum equivalents can vary over a fairly wide range. It was statistically substantiated that the share of tensile strength variation of VT3-1 and VT6 forgings may be ~25÷65 % due to the influence of their chemical compositions (in terms of aluminum and molybdenum equivalents), and about 20 % due to only the influence of structure types and subtypes. When these two factors (composition + structure) are combined, the share of variation can reach ~50÷65 %. For plastic properties and impact toughness, this figure is less and ranges from 20 to 35 %. The mathematical models are offered to forecast the mechanical properties of forgings depending on the structure parameters and aluminum and molybdenum equivalents.

This paper is a continuation of studies on the effect of microalloying with gadolinium, a rare earth metal, on the structure formation and properties of a titanium alloy under thermal action. It was previously shown that the introduction of gadolinium into an experimental heat-resistant alloy promotes cast structure transformation and reduces the size of structural components, and affects the rate of growth and nucleation of particles. It has been established that additional alloying of gadolinium has no significant influence on the microstructure formation of hot-rolled sheets made of the heat-resistant experimental alloy after annealing at 950 °C. The structure is represented by equiaxial particles of the primary α-phase, secondary α-phase of lamellar morphology and a small amount of β-phase.
It has been established that the ordering processes occur in primary α-phase particles and α2-phase particles are formed during isothermal aging at 700 °C for 100 h with the formation of silicides at the α-β interface. It is shown that the α2 phase is formed in the body of the primary α-phase particles, and its border regions are free from precipitations that is due to their aluminum depletion as a result of β→α transformation. It has been established that the silicide particle size is reduced as the gadolinium content in the alloy increases. The average particle size is 0,2–0,3 μm in the alloy with 0 % Gd, and it is reduced to 0,05–0,1 μm in the alloy with 0,2 % Gd.
It was shown that the introduction of 0,2 % of gadolinium into the heat-resistant titanium alloy leads to a decrease in the gas-saturated layer depth, and to an increase in the cyclic durability and short-term strength at 700 °C by 30 %.

The article covers rheological properties of the EP742-ID alloy in high-temperature compression tests of cylindrical samples with different ratios of similar initial diameters and heights (d0 /h0). The results of experimental research in the temperature range t = 1000÷1150 °C and initial deformation rates ε · 0 = 3·10–2÷3·10–4 s–1 have shown that an increase in compression flow stress with the growth of the d0 /h0 ratio is observed at all temperatures and deformation rates with a linear dependence on the ε · 0 value and the d0 /h0 ratio. The method is proposed to recalculate deformation resistance indicators to the set ratio of similar sizes. Higher compression flow stress is connected with an increase in the coefficient of rigidity of samples and their specific contact surfaces. The dependence of apparent activation energy of alloy plastic deformation (Qdef), its relationship with the phase structure and conditions of the process of γ solid solution dynamic recrystallization is established. In the temperature conditions of the beginning of γ solid solution dynamic recrystallization process (1000–1050 °C) the Qdef value for d0 /h0 = 0,75 samples is 959 kJ/mol. The highest Qdef values for d0 /h0 =  0,75 samples of 1248 and 1790 kJ/mol are observed in the range of temperatures of intensive grain boundary γ ′-phase dissolution and coagulation (1050–1100 °C). Samples with d0 /h0 = 3,0 in this temperature range have Qdef up to 2277 kJ/mol. The apparent activation energy of plastic deformation decreases to 869 kJ/mol in the range of temperatures of homogeneous γ solid solution with grain-boundary primary and secondary carbides (1100–1150 °C). The paper provides the results of alloy sample compression at single and repeated consecutive loading with various times of pauses between deformations. It is shown that meta dynamic recrystallization under experimental conditions does not occur in the γ + γ ′-range, and occurs inertly in the γ-range.

The second part of this paper compares modeling and experimental results with the Huber–Mises plasticity theory during the axisymmetric settlement of EP742-ID alloy samples with various ratios of initial d0/h0 sizes. The influence of initial sizes on the strain-stress state of model experimental samples and virtual workpieces is estimated. Settlement modeling results are given for ∅15 mm cylindrical samples and ∅300 mm workpieces made of EP742-ID heat-resistant nickel alloy with various ratios of initial similar sizes with the substantiation of choosing average stress and equivalent deformation as internal factors that determine microstructure formation. It is shown that compression axial tension component values in the center of samples under initial plastic deformation of 0,2 % are increased by more than 1,5 times with the higher d0/h0 ratio. Experimental and calculated values of offset yield strength, axial and radial stresses are obtained at a compression temperature of 1050 °C depending on d0/h0. The paper reviews the influence of the degree of deformation and the ratio of initial sizes on the distribution of average stress and equivalent deformation along the radius of the mid-height of meridian sections of the ∅15 mm settled (experimental) samples and ∅300 mm virtual workpieces. The paper describes general microstructure forecasting principles for applications that use process modeling software packages when developing settlement modes for disk workpieces made of heat-resistant nickel alloys. Special attention is paid to the fact that modeling methods must be theoretically proved and experimentally confirmed.

This paper considers the possibility and efficiency of thermohydrogen processing of the high-modulus Ti–8,7Al–1,5Zr–2,0Mo titanium alloy with aluminum content exceeding its solubility limit in α-titanium. Experimental data on the effect of hydrogen on the alloy phase composition and structure are obtained. Regularities of phase transformations in the hydrogen-containing alloy are analyzed under different thermal effects. An alloy–hydrogen system is diagramed in the hydrogen concentration range from the initial content up to 1,0 wt.% and temperature range from 20 up to 1100 °C. It is shown that a β single-phase structure forms in the alloy via quenching from the temperatures of β range at a hydrogen content of 0,6 wt.% or more. Hydrogen saturation up to 0,8–1,0 wt.% causes β → δ hydride shear transformation during quenching from the temperatures below 750 °C and results in partial eutectoidal β phase transformation at slow cooling. It is stated that hydrogen extends the region of β phase stability by decreasing the temperature of β / (α + β) transition by 210 °C (at 1,0 wt.% of hydrogen) and increases the temperature of α2 phase stability by 50 °C. Technological schemes and modes of thermohydrogen processing are developed and tested using the alloy specimens in order to form the two types of structure – submicrocrystalline and bimodal, and formation mechanisms of these structures under thermohydrogen processing are analyzed as well. Mechanical properties of the alloy specimens are determined. It is stated that thermohydrogen processing results in growth of strength and hardness as compared with the initial state. The thermohydrogen processing forming submicrocrystalline structure leads to decrease of plasticity characteristics at maximum hardness.

This paper examines the ZK51A (ML12) alloy samples with the content of Zn from 3.5 to 5.5 wt.% and Zr from 0.5 to 0.8 wt.%.
The influence of the Zn and Zr content on phase transition temperatures and phase composition in equilibrium conditions and with the Scheil-Gulliver solidification model was determined using the phase diagram calculation in Thermo-Calc software. It is shown that the Zr content of 0.8–0.9 wt.% leads to a significant increase in the alloy liquidus temperature and requires raising the melting temperature over 800 °С. This is undesirable when using steel crucibles. The equilibrium content of alloying elements in the magnesium solid solution was calculated at different temperatures. Scanning electron microscopy was used to study the microstructures of ascast and heat-treated alloys with different alloying elements content. The distribution of Zn and Zr in a dendritic cell of the alloy in as-cast and heat-treated conditions was investigated. Zinc in an as-cast condition is accumulated on the dendritic cell boundary, but after the heat treatment its concentration in the center of the dendritic cell became higher than concentration on the cell boundary.
Zirconium is accumulated in the center of the dendritic cell. We determined the effect of the solution heat treatment conditions on the alloy hardness. The maximum hardness gain was achieved using a two-step treatment at 330 °С for 5 h and then at 400 °С for 5 h. We studied the effect of aging heat treatment (150 and 200 °C) on the alloy hardness. The better hardness was achieved after aging at 200 °С. The maximum value was reached after 8–10 h of aging. The tensile strength 285 ± 13.5 MPa and elongation 11.4 ± 1 % were achieved after the two-step heat treatment consisting of isothermal holding at 330 °С for 5 h and then at 400 °С for 5 h with quenching and aging at 200 °С for 8 h.