P. P. Umnov

Effect of the state of a melt on the glass-forming ability, structure, and properties of a melt-quenched bulk amorphous nickel-based alloy

The glass-forming ability, viscosity, phase composition, and microhardness of a melt-quenched Ni64.4Fe4Cr4.9Mn2B16.2C0.5Si8 bulk amorphous alloy quenched from various melt temperatures at near-critical rates are studied. The melt-quenching temperature ensuring the maximum glass-forming ability and microhardness (HV= 13 GPa) of the alloy is found to be 1200–1230°C. The melt viscosity is shown to behave anomalously near the solidification temperature, and the related factors favoring this anomalous behavior are detected.

Strength and plastic properties of amorphous cobalt alloy wires produced by various melt quenching methods

The strength and plastic properties of amorphous wires produced by melt spinning, in-rotatingwater spinning (INROWASP), and the Taylor-Ulitovskii method are studied. The wire produced by the Taylor-Ulitovskii method is found to have the highest level of strength and plasticity. The fracture and lateral surfaces of the amorphous wires are subjected to fractographic analysis. The high plasticity of this wire is shown to be caused by sequential formation of various families of shear bands and their interaction. The structure of the surface layer in an amorphous wire is assumed to be controlled by thermomechanical treatment to form a one-dimensional nanoamorphous composite material.

Mechanical properties of “Thick” amorphous metallic wires produced by the Ulitovskii-Taylor method

The strength and plastic characteristics of thick (d = 40–120 μm) amorphous wires made of a model Co-based alloy and fabricated by the Ulitovskii-Taylor method are studied. They are found to have stable strength and plastic characteristics along the length. The plasticity of the thick wires is high, and they can form a full knot and undergo a load of 0.5 ultimate tensile strength in this state. The surface state and fracture surfaces of the amorphous wires are analyzed by scanning electron and optical microscopy. The wires are found to have a smooth lustrous lateral surface almost free of defects and to retain stable geometrical parameters along their length. Zones with different positions and frequencies of shear bands can form on the wire surface depending on the type of deformation action. The fracture surfaces of the thick amorphous wires are specific: a venous zone consists of several large pronounced principal “veins” and a rare network of adjoining secondary veins.

“Thick” amorphous wires in the Fe75Si10B15–Co75Si10B15–Ni75Si10B15 system: Fabrication, structure, properties

Samples of rapidly -quenched ribbons and wires with a diameter of metal core of dс= 50–200 μm within the ternary eutectic system Fe75Si10B15–Co75Si10B15–Ni75Si10B15 were obtained by the melt spinning and Ulitovsky–Taylor methods. The liquidus surface and crystallization surface of the amorphous alloys were constructed on the basis of the results of investigations of the thermal, mechanical and magnetic properties of the system alloys; the concentration ranges of amorphous alloys with various crystallization mechanisms and the ranges of amorphous alloys with the positive and negative Villari effect were determined. The concentration range of compositions favorable for obtaining amorphous wires with high glass-forming ability was determined. The comparative study of the structure and properties of the “thick” wires samples was carried out for two models alloys: Co71Fe4Si10B15 and Fe31Co34Ni10Si10B15. It was found that the wires possess a new complex of high strength, ductile, elastic, and soft magnetic properties. The prospects for application of “thick” ferromagnetic amorphous wires associated with the development of new types of structural and functional materials were considered.

Effect of quenching conditions on the structure and properties of a “thick” microwire fabricated by the Ulitovskii-Taylor method

The effect of quenching conditions on the mechanical and magnetic properties of a meltquenched wire with a core diameter of 50 μm, which is made of a model soft magnetic Co69Fe4Cr4Si12B11 alloy and is fabricated by the Ulitovskii-Taylor method, is studied. The highest set of mechanical and soft magnetic properties of a wire is achieved when it is quenched from the upper position of a quenching stream. The lowering of the position of the quenching stream degrades the mechanical and magnetic properties of the wire at a retained amorphous structure in it.

Application of thermal analysis technique for development of technology of melt preparation to obtain “thick” amorphous Co-alloy microwires

The thermal analysis technique of estimating the ability of a melt to overcool is used to determine the optimum technological regimes of melt preparation in all the production stages of amorphous wires. The temperature range of high-temperature melt homogenization and the regimes of precursor extraction and melting are defined for the model Co69Fe4Cr4Si12B11 alloy. With use of the established regimes of heat treatment, the precursor melting is conducted and the samples of high-ductile amorphous microwires with a diameter 200 μm are produced by the Ulitovsky–Taylor method.

Structure and properties of amorphous finemet alloy microwires produced by the Ulitovskii-Taylor method

Amorphous Fe73.5Si13.5B9Nb3Cu1 alloy microwires 19–50 μm in diameter are fabricated by the Ulitovskii-Taylor method. The mechanism of crystallization of the amorphous microwires is shown to be analogous to the mechanism of crystallization of an amorphous ribbon made of the same alloy. Microwires up to 30 μm in diameter are found to exhibit ductility upon bending. The near-surface magnetic properties of the microwires are shown to depend on the microwire diameter. The magnetic properties of the amorphous microwires are highly sensitive to elastic tensile and torsional strains in an ac magnetic field.

Conditions of formation of “thick” plastic amorphous Fe-Co microwires in Fe 75 Si 10 B 15 -Co 75 Si 10 B 15 system

Equilibrium and rapidly quenched Fe-Co-Si-B alloys are studied in Fe75Si10B15-Co75Si10B15 cross section. The polythermal cross section is developed in the range of melting and crystallization temperatures. Amorphous ribbons of alloys are produced by melt spinning, and rapidly quenched microwires in a glass sleeve with diameter of the metal core dcore = 10–100 μm are obtained by the Ulitovskii-Taylor technique. The structure and physical and mechanical properties of the alloys are studied. The concentration range of stability of “thick” amorphous plastic microwires with core diameter dcore ≥ 50 μm is determined using analysis of the phase diagram and content-property diagram. A special two-stage crystallization mechanism responsible for high glass-forming ability of microwires is established.

Conditions of formation of “thick” plastic amorphous Fe-Co microwires in Fe75

Equilibrium and rapidly quenched Fe-Co-Si-B alloys are studied in Fe75Si10B15-Co75Si10B15 cross section. The polythermal cross section is developed in the range of melting and crystallization temperatures. Amorphous ribbons of alloys are produced by melt spinning, and rapidly quenched microwires in a glass sleeve with diameter of the metal core dcore = 10–100 μm are obtained by the Ulitovskii-Taylor technique. The structure and physical and mechanical properties of the alloys are studied. The concentration range of stability of “thick” amorphous plastic microwires with core diameter dcore ≥ 50 μm is determined using analysis of the phase diagram and content-property diagram. A special two-stage crystallization mechanism responsible for high glass-forming ability of microwires is established.

Conditions of formation of “thick” plastic amorphous Fe-Co microwires in Fe75Si10B15-Co75Si10B15 system

Equilibrium and rapidly quenched Fe-Co-Si-B alloys are studied in Fe75Si10B15-Co75Si10B15 cross section. The polythermal cross section is developed in the range of melting and crystallization temperatures. Amorphous ribbons of alloys are produced by melt spinning, and rapidly quenched microwires in a glass sleeve with diameter of the metal core dcore = 10–100 μm are obtained by the Ulitovskii-Taylor technique. The structure and physical and mechanical properties of the alloys are studied. The concentration range of stability of “thick” amorphous plastic microwires with core diameter dcore ≥ 50 μm is determined using analysis of the phase diagram and content-property diagram. A special two-stage crystallization mechanism responsible for high glass-forming ability of microwires is established.