The surface and internal defects of long cast rods made of a near-eutectic 84KKhSR Co alloy using nondestructive testing methods, namely, X-ray computed tomography and metal magnetic memory, and macrostructural and fractographic analyses are analyzed. The main defects in the rods are found to be gas pores and cavities. Zone melting is shown to eliminate these defects. Deep pores and cavities are eliminated during the first remelting, and the second remelting leads to complete elimination of defects and stabilization of geometric dimensions along the rod length.

The direct current (dc) heating effect of ferromagnetic amorphous wires (AW) on the electromagnetic properties of the serial Co-based alloy, Co – Fe – Cr – Si – B, is investigated. The Ulitovsky – Taylor method was used to produce AW with diameters D = 40, 70, 82, 98, 123, and 145 μm in a glass shell, that was removed mechanically by elastic bending on a laboratory bench. The developed in situ method of stepwise cyclic dc heating of AW of various diameters enables to choose the optimal values of the current (Ia) for carrying out the selected modes that maximize the magnetic properties. AW electromagnetic properties were monitored by registering the amplitude of the intrinsic electromagnetic signal of electromotive force (EMF) of the AW sample under study. Since reliable direct measurements of AW temperature (Ta) when passing the current (Ia) quite an undertakings, we used indirect method of AW heating temperature estimation by establishing the relationship Ta = f (Ia). For the AW specified diameters, the direct current values were experimentally determined, which ensure optimal heat treatment in the range of temperature stability of the amorphous phase, up to the crystallization temperature, Tx. A calibration curve was constructed using reference temperature points, i.e. Tx and the Curie temperature (Tc). The proposed technique for calibration graph construction I = f(D) may be used for different AWs that have different diameters and same composition; it allows one to determine the modes of current annealing required for the best EMF amplitude values of amorphous wires of the given diameter, up to 100 μm.

The study focuses on examining the impact of shell-induced stresses on the magnetic characteristics of Fe-based microwires encased in glass, with particular attention given to the critical fabrication parameters employed in the microwire production process utilizing the Taylor-Ulitovsky method. We systematically investigate how internal stresses affect magnetization reversal behaviors in both glass-coated and uncoated Fe77.5Si7.5B15 microwires through experimental analysis and compare these effects with those resulting from stress-annealing procedures. The simulation of stress distribution caused by the solidification process is based on thermo viscoelasticity theory considering a non-constant glass transition temperature. The analysis also includes the knowledge of the initial parameters of the microwires during the manufacturing.

Peculiarities of the fabrication and the physicomechanical properties of amorphous microwires and microspirals made from iron- and cobalt-based alloys, which determine advantages of these materials over available materials, are analyzed. Perspectives in their application in medicine and microelectronics and as parts and elements for promising technique are considered.

Abstract—To improve the quality of cast Co-alloy rod precursors used for manufacturing ferromagnetic amorphous wires by the Ulitovskii–Taylor method, it is suggested to apply zone melting. The manufacturing parameters of the process are determined. Tomography and fractography are performed and the mechanical properties of the rods are studied. Zone melting is shown to lead to complete disappearance of open and closed gas pores, stabilization of the geometric shape of the rods, and a substantial increase in the elastic and strength characteristics.

Based on the earlier reported conceptions about the possibility to control the structure of liquid alloys by varying the heating temperature, we think that the use of optimized heat treatment of staring melts shows promise for stabilizing the properties of advanced liquid-metal coolants of nuclear reactors. This idea is confirmed by the results of studying the binary lead–bismuth, lead–tin, and gallium–indium liquid eutectics. Evidence about their metastable microheterogeneity, which can be retained in wide temperature ranges for a long time after melting a coolant, is obtained experimentally. Changing the preparation method of the melt is shown to weakly affect the degree of its heterogeneity and the temperature of transition into a homogeneous state. The main ways of eliminating the effect of the above microheterogeneity on the safe operation of a reactor are determined. The possibility to improve the quality of amorphous ribbons prepared by melt quenching and bulk amorphous alloys as a result of application of optimized temperature conditions of their melting is discussed. The effect of heat treatment of a starting melt on the structure and properties of amorphous samples prepared by traditional melt spinning is shown by examples of a number of systems. Heating of a liquid metal above the boundary of a metastable microheterogeneity is found to favor the formation of amorphous structure, which is more disordered as compared to that obtained by traditional melting technology, and to allow the concentration range of liquid metal amorphization to be substantially widened. Heating of a microheterogeneous melt to the temperatures of its intermediate structural transformations within two microheterogeneous states is also shown to be efficient not only in terms of laboratory experiments but also for full-scale production of amorphous ribbons. To understand the causes of the formation of bulk amorphous alloys, the correlation between the heating temperature of a starting melt and its capability toward deep supercooling is of key importance. The following specific temperature range is detected: after heating in this range, a melt can be subjected to deep supercooling, and the rate of decrease of the viscosity with increasing temperature and the activation energy of viscous flow decrease substantially in this temperature range. Our understanding of the causes of the correlation is reported.

The peculiarities of the gas release during melt solidification of cobalt alloy amorphous wires 50–80 μm in diameter, which are prepared by the Ulitovskii–Taylor, are considered. The results are compared with the pore-formation mechanism that takes place during the solidification of ingots fabricated by different technologies. The number of low-strength areas in a long amorphous wire, which are caused by local gas porosity, can be decreased using melt refining vacuum technologies.

The peculiarities of production and the physical-mechanical properties of amorphous microwires and microcoils made of alloys based on iron and cobalt, which determine advantages of such materials as compared with existing analogs, have been analyzed. The prospects of their application in medicine, microelectronics, as products and elements of promising technology are considered.

Typical local defects in long ductile amorphous Co-based alloy wires with a diameter from 50 to 110 μm obtained by the Ulitovsky–Taylor method in the process of continuous drawing of a melt jet in a glass shell are determined. It is shown that the defects are gas pores and necks. The impact of the gas dissolved in the molten metal and the state of the glass shell on the stability of the drawing process and the geometry of the wire are analyzed. The reason for formation of closed pores is liberation and distribution of the dissolved gas in the wire following the melt jet solidification. It is noted that gas porosity does not result in spontaneous breaks and changes in the wire geometry. Bending failure in the region of gas porosity has the characteristic form typical of brittle fracture of an amorphous wire. It is revealed that necking in the amorphous wire is caused by high-temperature transverse ring cracking of the glass shell upon contact with the quenching liquid. Plastic deformation of the amorphous wire in the region of the neck proceeds through the mechanism of formation and sliding of the transverse shear band. It is noted that longitudinal failure of the glass shell has no effect on the geometric parameters of the amorphous wire. The ways of eliminating local defects in production of ductile amorphous wires and possible prospects of practical implementation of wires with a variable diameter are proposed.

The mechanical properties of the wires made from the Co 69 Fe 4 Cr 4 Si 12 B 11 amorphous alloy, tungsten, molybdenum, and 40KKhNM steel and the microspirals made from the wires and the electromagnetic and tribological properties of the amorphous alloy wires, which are prepared with protective sheaths made in the form of a microspiral from the selected materials, are studied. All the wires are found to have a high tensile strength (2100–3100 MPa). Elastic compression ability of the microspirals is found. The friction is shown to be minimal in the amorphous alloy–amorphous spiral pair. As for a combination of the properties, an amorphous spiral containing a stress-sensitive amorphous wire can be recommended as a working element of an electromagnetic transducer.

Typical local defects were identified in extended ductile amorphous Co-based alloy wires, having 50 – 110 µm in diameter, obtained by Ulitovsky – Taylor in a continuous process of drawing a jet of melt in a glass shell. The studies found that gas pores and necks are local defects of glass-coated wires. The paper analyses the impact of the dissolved in the metal melt gas and glass-coating stress on the drawing process stability and the geometric parameters of the wire. The formation of hidden pores is due to gas expelling and redistribution of gas following the melt stream solidification. It is noted that gas porosity would not result in spontaneous breaks and changes in wire geometry. The characteristic form of a brittle rupture of an amorphous wire was observed upon fracture by bending in the region of gas porosity. It was in the studies revealing that amorphous wire neck formation was caused by high temperature transverse ring cracking of the glass-coating in contact with quenching liquid. Elastic deformation of amorphous wire in the vicinity of neck flows through the mechanism of formation and sliding transverse shear band. It is noted that the longitudinal destruction of the glass shell does not affect the geometric parameters of the amorphous wire. The procedures for local defects eliminating while producing ductile amorphous wires and the possible prospects for the variable diameter wires manufacturing are proposed.

The existing methods for obtaining amorphous wires of large diameters from a melt are considered. The advantages of the Ulitovsky–Taylor method for obtaining amorphous wires in a wide range of diameters with stable geometric characteristics are underlined. The factors that affect the process of obtaining “thick” amorphous wires by a continuous version of the Ulitovsky–Taylor method are analyzed. It is demonstrated why it is necessary to use alloys with a high glass-forming ability and with melting temperatures of 950–1150°C. The practicability of introducing technological additives (Nb, Mo, Cr, etc.) is justified. It is noted that, to ensure a continuous process of producing a “thick” wire, it is necessary to use a high-purity precursor with stable geometric parameters. A variant of a quenching device is proposed for cooling a melt jet with a counterflow of water. The technique for removing the glass cover is based on elastic bending of the metal core and brittle cracking of glass. The technology for producing “thick” wires was tested. Long wires with diameter of 50–200 μm with a high set of properties were manufactured.

The effect of the wire diameter and tensile and torsion loads on the remagnetization ability and the stress sensitivity of amorphous Co-alloy wires is investigated. It is shown that amorphous wires have a high magnetic softness to the applied external field in a wide range of diameters of 20–300 μm. The amplitude of the electromagnetic signal of electromotive force (EMF) increases with increasing wire diameter. It is established that amorphous wires with diameter in the range of 50–140 μm are sensitive to applied elastic tensile stresses. Increase in stresses to 300 MPa is accompanied by a fourfold decrease in the amplitude of the EMF signal. These wires are also sensitive to torsion stresses in a weakly and strongly stretched state. The first stage is accompanied by an intense increase in the amplitude of the EMF signal to values near to the amplitude of the original unloaded wire. At the second stage, the amplitude value achieved is preserved. It is established that an optimum interval of recording torsion stresses is determined by the wire diameter and values of applied tensile load. It is concluded that amorphous wires in a wide range of diameters can be used as highly sensitive noncontact sensors of field and tensile and torsion load detectors.

Abstract—The bending-deformation behavior of rapidly quenched Co69Fe4Cr4Si12B11 alloy wires 0.1–1 mm in diameter, which are fabricated by the Ulitovskii–Taylor method, are studied. A correlation between the failure mechanism of a wire and its diameter and bending loading conditions is shown. It is found that wires up to 0.2 mm in diameter exhibit no bending failure. The wedge-type fracture is observed for wires 0.2–0.35 mm in diameter; wires more that 0.35 mm in diameter exhibit steplike fracture. The wedge-type fracture, a dense regular shear-band network, and vein- and corallike fracture are shown to correspond to the 100% amorphous state of wires. This combination of signs is observed for wires up to 0.4 mm in diameter.

Results are presented from investigating the structural and magnetic characteristics of Co 69 Fe 4 Cr 4 Si 12 B 11 amorphous microwires with magnetic core diameters of 35–360 µm, obtained using an updated Ulitovskii–Taylor approach. It is found that the microwires have stable geometric dimensions along their lengths and almost defect-free surfaces. They are characterized by high plasticity and strength, and their magnetic characteristics depend on their diameter. The possibility of the microwires’ practical application is shown.