Vol 61, No 5-6 (2019)

A method for rapid determination of former austenite grains in bainitic-martensitic steels employing standard software for processing the results of mapping of crystallographic orientations obtained by electron back-scatter diffraction analysis in a scanning electron microscope is proposed. The method is verified for orientations of retained austenite in steel 09KhN2MD.

Nonuniformity of texture component and microstructure parameter distribution in the cross section of an alloy 8011 billet during hot rolling in a continuous group is studied. The study is performed by optical microscopy and x-ray diffraction analysis of microsections taken from hot-rolled strip in all stages of rolling in a hot-rolling mill continuous group. It is established that at first the texture is inhomogeneous over the thickness of a specimen, but it levels out in the hot rolling finishing passes. The results obtained are in good agreement with the theoretical concept of O. Engler in which the ratio of the components of the strain rate tensor I₁₃/I₁₁ is used to estimate the probability of appearance of a friction texture. Finite modeling using DEFORM 2D/3D software is used for theoretical analysis of the strain tensor components.

We study the influence of 1 wt.% Ti, In and Sn additions on the microstructure, mechanical properties and corrosion resistance of the as-cast and hot-rolled AM60 magnesium alloys. The analysis of microstructure was performed by using optical and scanning electron microscopes The phase composition of the alloys and grain sizes are analyzed. We also determine the ultimate strength, yield limit, relative elongation, and corrosion resistance of the alloys. The efficiency of alloying of AM60 alloy with titanium and tin (for the improvement of the mechanical characteristics) and with indium (for the improvement of corrosion resistance) is demonstrated.

Mechanically synthesized hybrid powders of the AMg2/graphite + Al₂O₃ system and coatings deposited by cold gas dynamic spraying from these powders are studied. The effect of Al₂O₃ concentration in the powder on surface morphology, structure and microhardness of the coatings formed is determined.

Friction-stir-welded joints of 16-mm-thick plates of AA7075 aluminum alloy have been studied. The macrostructure of the weld region over the thickness of the plates and microstructures of various regions of the welded joint were determined using optical and transmission electron microscopes. Tensile testing of the welded samples was conducted, and the average values of the ultimate strength and yield point, as well as relative elongation were calculated. The Vickers hardness profiles in the middle of the cross-section of the welded joint were measured. Friction stir welding with forced cooling (by a compressed air flow or water immersion) was tested to reduce heat damage and improve mechanical properties. The efficiency of such welding has been demonstrated.

Deformation behavior of finely-lamellar pearlite in steel with 0.78% C during multiple cold plastic deformation by drawing is considered. It is revealed that during deformation apart from ferrite platelet thinning with an increase in overall reduction cementite phase behavior starts to play a more important role. The change in distance between pearlite platelets in relation to the degree of deformation is evaluated. The connection between microstructure transformation and changes in mechanical properties during drawing is established.

A composite material based on alloy V95 containing 10% silicon carbide and prepared by powder metallurgy is studied. Composite granules are fabricated by mechanical alloying in a planetary mill in an inert gas atmosphere. It is shown that the structure of the composite granules affects the structure of the billets obtained after deformation treatment by extrusion, i.e., the more homogeneous the structure of the granules, the more homogeneous is the bar structure.

We study the microstructure and mechanical properties of friction stir processed AZ91D cast magnesium alloy under various conditions of heat treatment. It is shown that, in the initial as-cast state, the structure of the alloy contained a continuously networked β-phase with an average grain size of 150 μm. The friction stir processed (FSP) specimens had an average grain size of 12 μm and smooth grain boundaries. The subsequent heat treatment of the FSP specimens at various temperatures between 150°C and 250°C led to the appearance of numerous particles of the β-phase. The FSP specimens heat-treated at 200°C had finer grains, a larger number of fine particles of the β-phase, and better mechanical properties than any other specimens.

Ti – Zr-based alloys with a high zirconium content prepared by vacuum-arc remelting with nonconsumable tungsten electrode are studied. The optimum number of remelting operations and melting conditions in order to achieve a highly uniform distribution of components and low content of impurities in the alloy are determined. Optimum thermomechanical treatment (cold rolling) and post-deformation annealing regimes are proposed. X-ray studies are conducted at room temperature and after thorough cooling in order to determine the crystallographic resource of alloy reversible deformability. Alloy susceptibility towards superelastic behavior at room temperature, cyclic endurance and its dependence on annealing atmosphere are evaluated in the course of tension-compression mechanical tests.

The effect of homogenizing heating on the structural state (titanium sulfide morphology, δ-ferrite shape and content, grain size, excess phase precipitates, etc.) and impact strength of corrosion-resistant rolled product of steels 08Kh18N10T and 10Kh17N13M2T with 0.015 – 0.030% sulfur is studied.

An original method is proposed for the description of a nitriding mixture obtained from a two-component input mixture with nitrogen either under a low pressure or under the atmospheric pressure. In this method, the dissociation rate of ammonia is used as a parameter alternative to the nitriding potential.

Mechanical properties and structure of butt welded pseudo-α-(VT41) and (α + β)-(VT8-1) refractory titanium alloys are studied as applied to electron-beam welding of rotor parts of gas turbine engine compressors. Welded joints of VT8-1 + VT8-1, VT8-1 + VT41 and VT41 + VT41 are studied. The effect of post weld annealing on the short-term and long-term strength and impact strength of matrix metal is studied in the operating temperature range. Partial annealing of welded joints is shown to have a favorable effect on matrix metal and weld material strength properties without a substantial reduction in high-temperature strength. Weld metal ductility remains at a low level, while that of the matrix metal hardly decreases.

We study composites with copper matrix reinforced by plates of graphene oxide produced by the method of repeated pressing and sintering. We determine the hardness, relative density, ultimate strength, elongation, and conductivity of composites made by applying different modes of pressing and sintering. The influence of the modes of treatment on the properties of composite is analyzed by the method of design of orthogonal experiments L₁₆ (4⁵). The optimal parameters of double pressing and sintering are proposed.