Yu. V. Khlebnikova

Perfect cubic texture, structure, and mechanical properties of nonmagnetic copper-based alloy ribbon substrates

A sharp cubic texture is formed in a number of copper alloys subjected to cold deformation by rolling by 98.6–99% followed by recrystallization annealing, which opens up fresh opportunities for long thin ribbons made of these alloys to be used as substrates in the production of second-generation high-Tc superconductor (2G HTSC) cables. The possibility of creating ternary alloys based on a binary Cu-30 at % Ni alloy with additional elements that harden its fcc matrix (iron, chromium) is shown. The measurements of the mechanical properties of textured ribbons made of these alloys demonstrate that their yield strength is higher than that of a textured ribbon made of pure copper by a factor of 2.5–4.5.

Choice of copper-based alloys for ribbon substrates with a sharp cube texture

It has been shown that, in some copper-based alloys subjected to cold deformation by rolling to 98.6–99% followed by recrystallization annealing, a sharp cube texture can be produced. Optimum conditions of annealing have been determined, which make it possible to produce a sharp biaxial texture in Cu-Ni, Cu-Fe, and Cu-Cr alloys with the fraction of cube grains of more than 95%; this opens a possibility of using thin ribbons made of these alloys as substrates for multilayer film compositions, in particular when developing second-generation high-temperature superconductors.

Formation of cube texture during annealing of rolled tapes from alloys Ni95.3Mo4.7 and Ni48.8Fe51.2

The paper deals with the study of the process of the formation of the primary recrystallization texture in Ni95.3Mo4.7 and Ni48.8Fe51.2 nickel alloys during annealing after deformation by rolling to large reduction. The electron backscatter diffraction method is used to show the effect of the temperature and the heating rate during annealing on the structure and texture in alloys that differ in the temperature of the beginning of primary recristallization. The majority of attention is focused on investigating the possibility of estimating the temperature range of primary recrystallization from the dilatometry anomaly on the temperature dependence of the thermal expansion coefficient. Variations in the relief of the rolled tapes after recrystallization are studied.

Creating textured substrate tapes of Cu-Fe alloys for second-generation high-temperature superconductors

It is established that Cu-1.6 at % Fe alloy tapes obtained through cold rolling to 98.9% followed by recrystallization annealing possess a sharp cube texture, which opens prospects of using thin tapes of this alloy as substrates for second-generation high-temperature superconductors. The optimum regime of annealing is determined that allows an alloy with sharp biaxial texture containing more than 97% cubic grains to be obtained. The yield stress of a 90-μm-thick Cu-1.6 at % Fe alloy tape upon recrystallization annealing at 800°C for 1 h amounts to 78 MPa, which is about three times higher than the value for a pure copper tape with sharp cube texture.

Creation of ternary Ni-Cr-W alloys with a sharp cube texture and a curie temperature below 77 K to produce epitaxial substrates for superconducting compositions

The texture, structure, and magnetic and mechanical properties of thin tape substrates fabricated of nickel alloys with chromium and tungsten have been investigated. It has been shown that in Ni89.6Cr8.6W1.8 and Ni89.6Cr7.8W2.6 alloys a sharp cube texture can be formed, which is stable up to high annealing temperatures. In the Ni89.2Cr7.2W3.6 alloy, other orientations are present along with a cube component. The possibility of obtaining a sharp cube texture after primary recrystallization is connected with the quantitative relationship between the texture components in a cold-rolled tape, which is determined by the method of orientation-distribution functions. The alloys studied are paramagnetic at 77 K.

Effect of recrystallization annealing on the formation of a perfect cube texture in FCC nickel alloys

Based on the data of X-ray diffraction, dilatometry, transmission electron microscopy, and electron backscatter diffraction, the optimum regimes of heat treatment of cold-rolled (to 98.5–99%) tapes made of binary Ni-W, Ni-Cr, Ni-Fe and ternary tungsten-containing Ni-Pd-W and Ni-Cr-W alloys that are widely utilized in the world practice for the fabrication of high-temperature superconducting cables of the second generation, which make it possible to obtain a perfect cube texture. In all five alloys, the spreed of the texture upon slow heating and two-step annealing decreases by 0.2°–1.5° around the RD and by 0.1°–0.6° around the RD in comparison with the single-stage high-temperature annealing.

Study of the structure of cobalt single crystals during the β → α transformation

Methods of metallography, transmission electron microscopy, and X-ray diffraction have been used to study the specific features of the structure formation during the fcc → hcp transformation occurring under different thermokinetic conditions in a single crystal of cobalt. It is shown that only one of four possible versions of hcp-phase crystal orientations is predominantly realized upon the β → α transformation occurring in the single crystal at a low cooling rate (Vcool ∼ 1–2 K/min). It has been established that several cycles of slow heating to temperatures of 600, 800 and 1000°C and subsequent cooling of the single crystal do not increase the number of α-phase orientations. The restoration of the initial fcc-phase single-crystal orientation was observed after each heating cycle of the oriented sample, while after cooling the restoration of the preferred hcp-martensite orientation was observed; in this case, the quantity of the retained β phase fixed in the structure at room temperature increases with increasing number of cycles. After rapid quenching from 530°C into salt water (Vcool ∼ 600–700 K/min), α-phase crystals of all four possible orientations are formed in the structure. Upon high-temperature quenching from 1000°C, the volume of crystal is divided into packets each containing martensite plates of predominantly one orientation. The transformation-induced recrystallization of the cobalt pseudo-single crystal quenched in salt water has been observed during repeated heating to temperatures above the β → α transformation temperature.

Possibilities of Nondestructive Testing of Physico-Mechanical Characteristics of Hypereutectoid Carbon Steels with the Structures of Isothermal Austenite Decomposition

The possibilities of estimating the hardness, the wear resistance under abrasive action and sliding friction, the impact strength, and the internal stresses of the U9 steel (with 0.94% of carbon) with the initial fine-lamellar pearlite structure annealed at 650°C during 2–600 min on the basis of magnetic and electrical characteristics, readings of an eddy-current instrument, and parameters of electromagnetic-acoustic conversion are studied. A comparative analysis of the magnetic, electromagnetic, strength, and tribological characteristics of the U10 and U15 hypereutectoid steels (with 1% and 1.53% of carbon, respectively) subjected both to isothermal treatment at 330–650°C (with formation of pearlite and bainite structures) and to additional short-time annealing at 650°C is carried out.

Evolution of the structure of an α-titanium single crystal during high-pressure torsion

The microstructure of an iodide titanium single crystal subjected to severe plastic deformation in Bridgman anvils at a pressure of 8 GPa and room temperature or the liquid-nitrogen temperature is studied by electron microscopy and X-ray diffraction. The initial α-titanium single crystal undergoes the baric α→ω transformation during compression and deformation under pressure. A decrease in the deformation temperature to 80 K is found to activate twinning. Upon deformation up to a strain e = 6, the strain hardening at room temperature exceeds the low-temperature strain hardening. At higher strains, the room-temperature strain hardening begins to decrease as compared to the low-temperature strain hardening due to the development of dynamic and postdynamic recrystallization. A decrease in the deformation temperature to 80 K suppresses recrystallization; correspondingly, titanium deformed in liquid nitrogen exhibits a larger microhardness increment in the strain range 6 < e < 10.

Investigation of the structure and magnetic and mechanical properties of textured substrates of an Ni-Cr-W alloy

Based on the data of X-ray diffraction, electron-backscatter diffraction, dilatometry, thermal analysis, and scanning electron microscopy, we determined the optimum regimes of heat treatment of cold-rolled tape substrates of an alloy Ni88.4Cr9.2W2.4 that permit obtaining a perfect cube texture. It has been shown that the use of two-stage annealings makes it possible to obtain in this ternary nickel alloy a cube texture in which the scatter about the rolling direction (RD) and the transverse direction (TD) of the substrates varied within 6.75°–7.20° and 4.8°–5.4°, respectively.