Vol 60, No 11-12 (2019)

Processes of structure and texture formation in hot rolling of electrical anisotropic steel are studied. It is shown that the structure of the surface layers of hot-rolled strips forms as a result of the joint action of γ → α phase transformation and dynamic recrystallization. The structure of the central layers forms as a result of recovery of deformed grains.

A method for assessing the effect of the temperature of friction stir welding on the microstructure and mechanical properties of welded joints of aluminum alloy D16AT is suggested. The temperature cycles in different zones of a welded joint are determined by mathematical simulation. The computed temperature cycles are implemented in a Gleeble-3800 system. It is shown that the welding temperature affects little the evolution of the microstructure in different zones of the welded joints of alloy D16AT.

Results of a study of the production of spherical-shape powder from shavings of high-alloy high-temperature steel 13Kh11N2V2MF (ÉI961) are presented. It is shown that the rate of feeding of the powder into the flow of thermal plasma affects the process of spheroidization of the particles. The chemical composition of the powder is compared to that required by the GOST standard.

The interrelation between the fine structure and the cold resistance of forgings and rolled sheets from ferritic-pearlitic steel 09G2SA-A after heat hardening and additional tempering at 450°C is studied. The additional medium-temperature tempering is shown to raise effectively the cold resistance of the steel due to coagulation and spheroidization of the cementite-type carbides, which make the structure of the steel more equilibrium.

Friction-stir-welded joints of commercial-purity copper and aluminum alloy AMg5 are studied. The effect of the process parameters on the microstructure and mechanical properties of the joints is analyzed. The results of temperature measurements during the welding made with the help of thermocouples are presented. A mathematical model is suggested for computing the temperature field of a weld. The computed and experimental data are compared.

The structure and mechanical properties of specimens produced by selective laser melting of a plasma-atomized powder of alloy VT6 are studied. The effect of annealing at 800 – 1050°C on the microstructure represented after the selective laser melting by a fine dispersed martensitic α′-phase and primary β-grains is considered.

Formation of a quasi-crystalline phase under rapid solidification and heat treatment of alloys of the Al – Cu – Fe – Cr system is studied. The study is performed by x-ray diffractometry, optical, scanning and transmission electron microscopy and differential scanning calorimetry. It is shown that the quasi-crystalline Al₆₅Cu₂₀Fe₁₀Cr₅ phase is a mixture of icosahedral and decagonal phases. The substitution of iron with chromium destabilizes the icosahedral I-phase and promotes formation of a decagonal d-phase. After quenching from 880°C, the Al₆₄Cu₂₄Fe₁₀Cr₂ alloy acquires a pure I-phase, and the Al₆₄Cu₂₄Fe₈Cr₄ alloy acquires a d-phase.

Nonmetallic inclusions in magnetic alloys of the Fe – Co – Ni – Cu – Al – Ti system with additions of niobium and hafnium used in the production of single-crystal permanent magnets are studied. The kinds of inclusions in magnetic alloys are determined with the help of rapid analysis of the chemical composition, optical and electron microscopy, quantitative microscopic x-ray spectrum analysis, and electron back-scatter diffraction. The phase compositions are computed with the help of the Thermo-Calc software.

An alternative for the traditional free-cutting steels, i.e., a graphitized steel, is suggested with allowance for the tendencies in design of free-cutting steels connected with reduction of the sulfur content and transfer to unleaded steels. The graphitization process due to inoculation of the steel with boron nitride (BN) is studied by metallography. Electron microscopy is used to determine the interaction between the boron nitride substrate and the graphite. The statistical relation between the content of the graphite phase and the duration of the graphitization process is used to show that the degree of graphitization is describable by the Avrami equation.

Special features of structure and phase formation in deposited metal based on alloyed Ni₃ Al nickel aluminide formed due to high-gradient crystallization under the conditions of the thermal cycle of arc surfacing are studied. The effect of microalloying with ultrafine WC carbides on the resistance to thermal fatigue and plastic straining at elevated temperatures (up to 1200°C) is considered.

A high-strength aluminum alloy based on the Al – Zn – Mg – Ni – Fe system is studied in deformed condition after radial shear rolling with reduction 2.78 and 8.16. The microstructure and the hardness are shown to change in the process of the thermal deformation involving quenching and aging by modes T and T1. The bars deformed with reduction 8.16 have a dense gradient structure containing a surface layer with a thickness of bout 300 μm, in which the size of the fine dispersed equiaxed grains ranges within 15 – 25 μm. The high accumulated strain combined with the precipitation hardening of the alloy in state T1 is shown to provide competitive mechanical properties, i.e., an ultimate strength of 605 MPa, a yield strength of 551 MPa, and an elongation of 5.5%.

The effect of hot rotary swaging and subsequent annealing on the microstructure and mechanical properties of magnesium alloy WE43 of the Mg – Y – Nd – Zr system is studied. The optimum temperature of rotary swaging providing refinement of the microstructure, change in the preferential grain orientation, strain hardening and growth in the strength is determined. It is shown that subsequent annealing at 400°C for 60 min raises the ductility, causes the appearance of equiaxed grains, and removes the strain hardening, which makes it possible to perform further deformation.

The crystallographic structure, the phase composition, and the microstructure of refractory nickel alloy ZhS32-VI fabricated by selective laser melting of a powder composition on single-crystal stub substrates with crystallographic orientations 〈001〉 and 〈111〉 are studied.

Results of a study of billets from steel 30KhGSA after a volume laser treatment, which consists of high-speed (20 mm/sec) remelting of a metallic plate with a thickness of 10 mm by a laser beam, are presented. It has been expected that this treatment process should yield a laser-beam-remelted gradient layer with changed microstructure due to the high cooling rate.

The crack resistance of railroad rails with transverse internal and external cracks in the head formed in operation is determined. The ultimate crack resistance I_c, the values of which coincide with the critical values of the stress intensity factor KIc under the brittle fracture typical for rails, is determined.