Vol 2019, No 11 (2019)

The formation of the structure and the phase composition of a heat-resistant titanium VTI-4 orthorhombic-intermetallic-based alloy is studied in the course of its alloying with hydrogen to different hydrogen contents. The laws of the changes in the phase composition of the hydrogen-containing alloy upon heating to different temperatures are determined. A portion of the VTI-4 alloy–hydrogen phase diagram under the conditions under study is constructed; it demonstrates the location of phase regions as a function of temperature and hydrogen content.

The oxidation resistance of cast β-NiAl + γ'-Ni₃Al + γ-Ni alloys of the Ni–Al–Co system in air at 1100, 1200, and 1300°C for 100 h is studied. An increase in the cobalt content from ≤5 at % (in complexly alloyed high-temperature γ' + γ VKNA alloys with ~17 at % Al and Cr, Mo, and W) to 10 at % in chromium-free β + γ' + γ alloys with 26–29 at % Al and 0.26 at % Ta, Re, Hf, and Y is shown to increase the heat resistance due to an increase in the aluminum content, an increase in the plasticity of scale, and the prevention of its exfoliation. The oxidation resistance of the base alloy decreases because of an increase in the cobalt content in the base NIAL-1 alloy from 10 to 16 at % and the introduction of 4.25 at % Cr and 0.16 at % Y of Hf. Its oxidation resistance at 1300°C, which was estimated from the weight increment per unit surface in 100 h corresponds to that of the well-known VKNA/VIN γ' + γ alloys at 1100°C. The oxidation resistance of the alloys with 16 at % Co or 4.25 at % Cr at 1100 and 1200°C is at the level of the VKNA/VIN alloys at 1000°C. The new β + γ' + γ alloys, which have higher oxidation resistance than structural high-temperature γ' + γ alloys and lower high-temperature strength, can be considered as heat- and oxidation-resistant coating-free alloys for short-term operation at 1100°C.

The hardness of a ferritic–martensitic steel EK-181 after ion irradiation to a maximum damaging dose of ~50 dpa in the temperature range 250–400°C is investigated. Nanoindentation is used to measure the mechanical properties. The hardnesses of the layer damaged by ions and that of the undamaged bulk material are found. At temperatures below 300°C, softening at a dose below 10 dpa and hardening at high doses of ~50 dpa are observed. Hardening is detected over the entire dose range at 400°C. The maximum hardness of the sample irradiated to ~50 dpa at 400°C is 1.7 GPa.

The influence of the strain (24, 30, 40%) during the pressure welding (PW) of an EP975 alloy in a superplasticity state and subsequent high-temperature heat treatment of welded joints on their structure and room-temperature mechanical properties is studied to find the conditions of PW of a single-crystal [001] Ni₃Al-based VKNA-25 blade alloy and an EP975 disk alloy in order to fabricate a blisk. The tensile strength of the welded samples is found to be maximal after PW of the EP975 alloy at a strain of ~40%, and the strength reached at lower strains is also sufficiently high, 0.7–0.8 of the strength of the VKNA-25 blade alloy. To optimize the technology of solid-phase joining, it is reasonable to decrease the PW strain to 20% and to increase the welding temperature to 1175°C.

The phase composition and the magnetic characteristics of 20 as-cast of Cu–Mn–Bi alloy samples have been studied experimentally. The samples have been studied using scanning electron microscopy, electron-probe microanalysis, atomic emission with inductive-coupled plasma, and X-ray diffraction analysis. The magnetic characteristics of the alloys are studied by a vibration method at room temperature. The samples contain the α-MnBi and Mn₃Cu₄Bi₄ intermetallic compounds along with a copper-based solid solution and bismuth precipitates. The α-Mn phase can precipitate at high manganese contents in the sample compositions. The magnetic characteristics of the alloys are dependent on the volume proportion of the phases. A high of intermetallic compound content leads to an increase in the magnetic susceptibility of the samples up to the manifestation of their ferromagnetic properties. In addition, Vickers microhardness HV_0.1 is measured.

The principles of monitoring the laser processing of metals are considered; the design and the main parameters of the spectrophotometer designed on the base of an optical-fiber AvaSpec 2048 spectrometer with the spectral range 380–1050 nm are presented. The technique of its calibration is discussed and the obtained spectral sensitivity is reported. The measured spectra of optical and near IR radiation that forms in the contact region of CO₂ laser radiation (wavelength 10.2 μm, power 1 kW) with the steel surface are presented. The problems of selecting the spectral portion in which the uncertainty of measuring temperature during contactless technological monitoring of high-temperature laser processes using thermographic devices will be minimal are discussed.