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Vol 2018, No 9 (2018)
- Year: 2018
- Articles: 10
- URL: https://journal-vniispk.ru/0036-0295/issue/view/10484
Article
Structure and Properties of the Metal in the Laser Welding Joints of an Austenitic Steel Containing ~0.5% N in the As-Cast and Deformed States
Abstract
The microstructure, the chemical and the phase compositions, and the mechanical properties of the welded-joint metal of sheet (hot-rolled) and as-cast austenitic 0.05% C–(21–23)% Cr–8% Ni–15% Mn–(1–2)% Mo–(0.2–0.5)% N steels butt welded with a laser beam have been studied. Welding is carried out without a welding additive using a fiber ytterbium laser developed by IPG IRE–Polus. It is shown that defect-free welds from 350 to 1200 μm wide without δ-ferrite and σ phase can be formed over the entire welding regime range. Laser welding is found to affect the manganese and nitrogen contents in the weld metal. The mechanical properties of the weld metal are estimated. In welding the hot-rolled and the as-cast steels, the ultimate strength of the weld metal is shown to be almost the same as that of the base metal, which correlates with the microhardness measured in the base metal and the weld metal, and to be higher than the ultimate strength of traditional corrosion-resistant nitrogen-free steels.
795-802
Thermodynamics of the Oxygen Solutions in the Titanium-Containing Ni–Cr Melts
Abstract
A thermodynamic analysis of the oxygen solutions in the titanium-containing Ni–Cr melts at 1873 K has been performed. The oxygen solubility in the Ni–Cr melts is shown to be higher than that in pure nickel. The higher the chromium content, the higher the oxygen solubility. Low titanium contents weakly affect the oxygen concentration in a melt, which is determined by the chromium content. At titanium contents of above 0.020–0.035%, titanium determines the oxygen solubility in a melt depending on the alloy composition. The titanium contents at the minima in oxygen solubility curves and the oxygen concentrations corresponding to the titanium contents have been determined.
803-807
Thermomechanical Behavior of Titanium Nickelide-Based Alloys at a Constant Counteraction
Abstract
The influence of a constant counteraction on the shape recovery and the specific shape recovery energy in a titanium nickelide-based alloy is considered. This energy is shown to be maximal after preliminary deformation of the material to a critical value and the external counteraction of shape recovery that corresponds to critical stresses. The specific shape recovery energy is maximal in a titanium nickelide-based alloy with the structure recrystallized at an annealing temperature of 570°C.
808-814
Resistance of the Contact Welding Electrodes Made of a Cu–0.7% Cr–0.9% Hf Alloy with an Ultrafine-Grained Structure
Abstract
The structure, the mechanical properties, and the electrical conductivity of the Cu–0.7% Cr–0.9% Hf alloy subjected to equal-channel angular pressing (ECAP) followed by aging are studied. The treatment that consists of ECAP and aging at 450°C for 2.5 h is shown to result in a high strength (σu = 605 MPa) and a high electrical conductivity (78% IACS) of the alloy. This combination of properties increases the resistance of the contact welding electrodes made of an ultrafine-grained Cu–0.7% Cr–0.9% Hf alloy as compared to its initial coarse-grained state.
815-819
Influence of Tungsten Carbide and Titanium Carbide Nanoparticles on the Structure and Properties of the Weld Metal
Abstract
The influence of nanoparticles introduced into a molten weld pool using a flux-cored wire on the structure and impact toughness of the weld metal is considered. The use of a flux-cored wire with tungsten carbide particles is shown to decrease the scatter of the impact toughnesses of the weld metal. The use of titanium carbide allows one to increase the average impact toughness.
820-825
Effect of Pulsed Helium Ion Fluxes and Helium Plasma on the Inconel 718 Alloy
Abstract
The results of the irradiation of the Inconel 718 alloy with pulsed helium ion and helium plasma fluxes at a power density q = 107 W/cm2 and a pulse duration τ ≈ 100 ns in the Vikhr Plasma Focus setup are presented. The surface layer is not melted under the irradiation conditions. However, a slight increase in q causes melting of local regions in the surface and the formation of a wavy relief. Beam–plasma irradiation results in structural and phase changes in the irradiated surface layer, namely, the precipitation of microinclusions (complex niobium carbides), a redistribution of alloy elements, a slight decrease in the microhardness, and, accordingly, slight softening. These changes in the microstructure and the properties are determined by the melting of the irradiated surface in local regions, partial sputtering of solid-phase regions, and recrystallization in the near-surface layer during pulsed heating for each beam–plasma action.
826-834
On the Superconductivity Mechanism in Yttrium Ceramic Used as an Example
Abstract
The nature of the superconducting state of the yttrium high-temperature superconductor is discussed, and the causes and mechanism of superconductivity are considered. A perovskite structure is used as an example to calculate the bond length and the lengths of elastic and electron waves. The Fermi energy and the charge density sphere radius are calculated. The first ionization potential of copper is, in essence, the kinetic energy of an elastic longitudinal wave. A hypothesis is advanced to explain the origin of superconductivity in this superconductor.
835-853
Composite Membranes Based on Pd–Cu and Pd–Pb Solid Solutions
Abstract
Composite membranes with a thin selective layer based on the Pd–46 at % Cu or Pd–5 at % Pb solid solution on the surface of a bilayer heterostructure with two-level porosity in the form of Kh18N10T steel/nanoporous titanium oxide (steel/rutile) are fabricated. The structure of the selective 4-μm-thick layer is found to have no through pores, and a metal does not penetrate into the nanopores in titanium oxide. The selective layer in both versions has a fine submicrocrystalline granular structure, which is caused by the presence of a second component in the Pd–Pb layer and by a two-phase composition of the Pd–Cu layer. In the temperature range 200–300°C, the hydrogen permeability of the membrane based on the two-phase Pd–Cu solid solution is higher than the membrane based on the Pd–Pb solid solution by a factor of 1.7–2.0.
854-858
Atomic-Force Microscopic Study of the Surface Morphology of the Nd2Fe14B Alloys Prepared by Various Techniques
Abstract
Atomic force microscopy is used to study the nanostructured state of a number of Nd2Fe14B alloys. The starting alloys are synthesized in an argon atmosphere using an induction furnace. The nanostructured state of the Nd2Fe14B alloys is reached by two techniques, namely, severe plastic deformation and melt quenching; combined treatment, which includes severe plastic deformation of melt-quenched ribbons and subsequent annealing, is also used. The surface morphology of all studied samples is studied. These are used to interpret the magnetic hysteretic properties of the samples prepared by the different techniques.
859-866
Effect of Recovery and Recrystallization on the Hall–Petch Relation Parameters in Submicrocrystalline Metals: III. Model for the Effect of Recovery and Recrystallization on the Hall–Petch Relation Parameters
Abstract
A theoretical model is developed to describe the influence of recovery and recrystallization on the macroelastic limit, the yield strength, and the grain-boundary hardening coefficient of the submicrocrystalline (SMC) metals fabricated by severe plastic deformation. The anomalous hardening and the increase in the grain-boundary hardening coefficient upon annealing of the SMC metals are shown to be related to defect accumulation in migrating grain boundaries in them. Equations are derived to relate the Hall–Petch relation parameters to the grain-boundary migration velocity, the nonequilibrium state of grain boundaries, the lattice dislocation density, and the annealing temperature and time. The results of the numerical calculations performed using the developed model are compared with the experimental results obtained in part I of this work.
867-879