Vol 58, No 3-4 (2016)

The effect of dendritic segregation on mechanical properties of specimens cut from templates of two different batches of hot-deformed pipes from steel 38KhN3MFAis investigated. Comparative analysis of the results of mechanical tests and metallographic and x-ray spectrum studies of specimens with satisfactory and unsatisfactory macrostructures are performed, and the results are used to estimate the influence of intracrystalline inhomogeneity on the mechanical properties of ready articles from steel 38KhN3MFA.

The effect of the temperature and degree of deformation during warm swaging on the evolution of the microstructure and mechanical properties of preliminarily quenched medium-carbon steel 40KhGNM is studied. It is shown that the deformation produces an ultrafine-grained structure with ferrite grains elongated over the longitudinal direction and fine distributed nanocarbides.

The effect of gas laser sawing on the properties of the cut edges of aluminum alloys is studied. Recommendations on application of gas laser sawing are developed. The main criteria for estimating the optimum speed of gas laser sawing of aluminum alloys are determined.

The prospects of industrial application of the process of electron beam synthesis for fabricating powder and composite materials for the production of critical parts are proved experimentally. The new process is tested on titanium and titanium-molybdenum alloys and is shown to provide materials with homogeneous structure and high operating properties.

The structure and mechanical properties of magnesium alloy AZ31 are studied after conventional and deformation aging under conditions corresponding to the thermal cycle of polymerization in paint coating of cars. The aging is conducted after 3-h solution treatment at 400°C, water quenching, and aging at 180°C for from 10 min to 6 h. Some of the specimens are deformed by 0.5% right after the solution treatment and then aged by the same regime.

The effect of heat treatment of aluminum alloy 01570 on the microstructure, phase composition and mechanical properties of an ingot at elevated temperatures is studied. An optimum mode of heat treatment raising the strength properties of alloy 01570 at good ductility in the range of elevated temperatures is suggested.

The interrelation of the parameters of microplastic strain, the slope of the left-hand branch of the fatigue curve, and the fatigue limit of a maraging steel is studied. The growth in the microplastic strain is shown to match the growth in the fatigue limit and the decrease in the slope of the left-hand branch of the fatigue curve. The strength of the steel decreases with decrease in the temperature of post-quenching aging.

The tensile strength and fatigue properties of alloy 1575 of the Al – Mg – Sc system are studied after hot deformation (at 360°C) and subsequent cold rolling with different reduction ratios. The effect of the deformed structure on the properties and mechanisms of fracture of the alloy under cyclic tests is determined.

Quantitative analysis of the phase composition of the Ti – Al – Mo – V – Zr system is performed as applied to a standard titanium alloy VT20L. Polythermal and isothermal sections of the phase diagram are plotted, the solidus and liquidus temperatures and the temperature of transition to the β-range under heating (T_pt) are determined. The methods of light and scanning electron microscopy are used to study the effect of heat treatment on the structure of alloy VT20L.

The microstructure and strength properties of hot-pressed alloy IMV7-1 of the Mg – Y – Gd – Zr system are studied after additional cold and hot rolling deformation. It is shown that the strength properties of the pressed alloy can be elevated by cold deformation at an admissible level of ductility.

Computer and experimental studies of the effect of admixtures of Te and H₂ surface-active elements (s.a.e.) on the kinetics of nucleation of crystallization centers and phase growth under accelerated crystallization of eutectic cast iron are performed. It is shown that under quenching cooling with decelerated diffusion processes the admixtures of s.a.e. in the melt play the role of initiators of diffusion redistribution of elements in formation and growth of new phase fragments affecting the structure and properties of the formed material.

A method of preparation of samples and quantitative analysis of the structure of in-situ nanocomposite conductors is developed. The microstructure of specimens of in-situ nanocomposites of the Cu – Fe and Cu – V systems with diameter 0.44 – 0.80 mm is analyzed by the methods of transmission and scanning electron microscopyΩ. Both specimens are shown to have a grain-subgrain structure with grain size about 200 nm and precipitates of second phase (Fe/V fibers) with a length of 100 – 400 nm and a thickness of 10 – 80 nm (in cross section).

The effect of annealing on the microstructure of foils of alloy Bi₅₀Sn₃₅In₁₅ is studied. It is shown that prolongation of the annealing time is accompanied by coarsening of the structure, which reduces the specific surface of the interfaces virtually without changing the volume fractions of the phases.

Results of experimental studies of low-carbon steel 20 and high-carbon steels of types 70 and 65G after carburizing, heat treatment and laser hardening are presented. The variation of the microhardness of the surface layers of the steels and of their wear resistance due to different variants of hardening is determined. Optimum modes of treatment aimed at raising the strength and wear resistance are suggested for the steels used for working members of cultivating machines.

Amodel of the elastoplastic behavior of commercial titanium is developed with allowance for the evolution of the microstructure of Ti Grade-4 Ti under equal channel angular pressing with application of the Conform process. The evolution of the mean dislocation density, of the dislocation density in the body and on the boundaries of grains, and of the density of mobile dislocations is studied. The concentrations of strain-induced vacancies, the speeds of gliding dislocations, and the angles of off-orientation between neighbor grains are determined, which widens substantially the understanding of the mechanisms of the elastoplastic behavior of Ti Grade-4 under severe plastic deformation.