Vol 57, No 11-12 (2016)

The effect of the temperature of heating for quenching on the content of retained austenite and its resistance to the deformation-induced martensitic transformation, the hardening capacity, and the resistance to abrasive wear are studied for high-carbon tool steels 150KhNML and Kh12MFL of pearlitic and ledeburitic classes.

The effect of compressive, tensile, and impact deformation on the mechanical and physical properties of a complexly alloyed austenitic-ferritic steel for making springs and elastic members is studied at room and negative temperatures. The structural changes and their interrelation with the mechanical properties are analyzed.

The mechanism of plastic straining and the structure of high-nitrogen austenitic steel 06Kh18AG19M2 (0.81% N) after a hardening treatment involving quenching, aging, and plastic deformation by equichannel angular pressing (ECAP) are studied. Electron microscope investigation is used to determine the mechanism of straining and fragmentation of the structure of the steel under the ECAP, i.e., twinning. The method of x-ray diffraction analysis is used to evaluate the contribution of the parameters of structural flaws into the broadening of austenite lines under the ECAP.

The microstructure and the post-aging hardness of an Al – Li – Cu – Mg alloy is studied by the methods of transmission electron microscopy. Tensile tests are performed. The volume fraction and the size of the particles of the δ′, S and T₁ phases are shown to be dependent on the aging temperature and time. The effect of the precipitates of the δ′, S and T₁ phases on the hardening of the Al – Li – Cu – Mg alloy during aging is determined.

Amethod and a scheme of a device for testing the fatigue endurance and dissolution of die steels in cast melts are presented. The laws of dissolution and the endurance of steel 4Kh5MFS in molten TsAM-4-1 are considered as a function of the mode of the heat treatment, the temperature of the melt, and the torsional deformations. The results of the metallographic studies are used to determine the dominant kinds of fracture of steel 4Kh5MFS in the process of fatigue testing in molten TsAM-4-1 upon variation of the amplitude of the torsional deformation and of the temperature of the melt.

The effect of the temperature of overheating in the range of 950 – 1250°C on the texture and grain size of steel 25KhN3MFA subjected to subsequent heating at 700 – 1100°C at a rate of 100 K/h is studied. The effect of the initial texture and grain size on the temperature of disappearance of large grains is determined. Recommendations are given on application of the results obtained for choosing heat treatment regimes for large forgings.

The effect of copper additives in an amount of up to 35 at.% on the structure and phase transformations in ternary Ti – Ni – Cu alloys in conventional microcrystalline, submicrocrystalline and nanocrystalline states is studied. Complete diagrams of thermoelastic martensitic transformations B2↔B19′, B2↔B19↔B19′ and B2 ↔ B19 are plotted as a function of the copper content. Special features of variation of the microstructure are determined. Tensile mechanical properties including the parameters of the shape memory effect are measured.

The cooling capacity of the Aqua-Quench 260 quenching medium with different concentrations of polyalkylene glycol (12, 15, 22 and 30%) is studied. Cooling curves and dependences of the cooling rate on the temperature of the polymer medium are plotted. The mechanical and corrosion properties of pilot pressings from the most widely used aluminum forging alloys V95pch, AK4-1ch, AK6ch and 1933 quenched in a solution of Aqua-Quench 260 with an additive of polyalkylene glycol are determined in comparison with quenching in hot and cold water.

The effect of volume-surface hardening (VSH) on the mechanical properties obtained in static and dynamic cyclic endurance tests of fragments of solebars from steel 20GL is studied. The VSH is shown the raise the mechanical properties of the fragments, i.e., the ultimate strength increases by a factor of 1.6 – 2, the conventional yield strength increases by a factor of 1.3 – 1.6, the bearing capacity increases by a factor of 2.6, the endurance limit increases by 10%, and the cyclic strength (durability) in the presence of a stress concentrator in the form of a notch increases by a factor of 3 at preserved high ductility.

The effect of the contents of aluminum, carbon and nitrogen on the production of thermally and mechanically stable austenitic alloys based on the Fe – (20 – 25)% Mn – (5 – 10)% Al – (0 – 10)% Ni – C – N system and the efficiency of the hardening of such alloys by nitrogen additives are studied computationally and experimentally. The experimental results confirm the adequacy of the computation of the phase composition and of the estimation of the solid-solution and precipitation hardening of these alloys.

The effect of microalloying with yttrium and zirconium in the amount of 0.06 and 0.07 wt.% respectively on the formation of structure, phase composition and measured hardness characteristics of a two-phase titanium alloy of the Ti – Al – Mo – V – Cr – Fe system is studied. The laws of variation of the phase composition and structure of the alloy with microadditives in the temperature range of 700 – 950°C and during subsequent cooling in water and air are determined. The diagram of variation of the phase composition of the alloy under water quenching is plotted.

Results of experimental studies of creep in a wide range of temperatures and stresses are presented for three modern single-crystal nickel-base alloys. A method for determining the creep characteristics by tests including step increase of the tension is suggested and tested. The effect of transition into plastic condition on the creep parameters, the influence of the chemical composition and loading conditions on the duration of creep stages I, II and III, and the conditions of appearance of crystallographic and not crystallographic modes of fracture are analyzed. Possible simple approximations of the creep curves are considered with allowance for the accumulation of damage and occurrence of unsteady creep stages.

The shape and size parameters of zones of plastic strain under fracture surfaces of quenched and tempered steel 09G2S are estimated. The shapes of the zones of plastic strain (PSZ) are studied after all the tested modes of heat treatment. Maps of distribution of the microhardness are plotted for complete PSZ of specimens standardized by GOST 9454–78 with relative crack length 0.55 and for specially prepared specimens with additional side V-notches with relative crack length 0.5.

Metallographic studies and mechanical tests of welded joints formed by a fiber laser in the mode beam scanning in two passes are performed. The laws of formation of the joint, the process of laser beam welding in the mode of scanning, and the effect of the thermal action of the second welding pass on the metal of the weld are described. The process of laser welding with beam scanning is shown to have advantages.