T. S. Sycheva

Combined thermomagnetic and ion-beam treatments of anisotropic electrical materials

Problems of a substantial increase in the functional characteristics of soft magnetic Fe-3% Si- and Fe-70% Ni-based alloys have been studied. Variants of efficient combined thermomagnetic and ion-beam treatments have been developed. They ensure the optimization of the magnetic domain structure and a substantial decrease (to 15–20%) in magnetic losses for anisotropic transformer steels, a decrease (to 60%) in the coercive force of permalloys, and an increase in the linear saturation magnetostriction of the Fe-7% Al-1% Si and Fe-6% Al-2% Co alloys to a value of (40–60) × 10−6 corresponding to those of high-cobalt alloys.

On the structure formation in polycrystalline metals and alloys. I: Thermocycling

It has been found that the thermocycling of the Fe-3 wt % Si commercial alloy with a bcc lattice considerably changes its microstructure even in the absence of a temperature gradient over the cross section of the sample. This phenomenon is ascribed to the difference in the properties of grains and intergranular layers. These changes in the microstructure have been found to exert considerable influence on the structure and texture formation upon subsequent annealing.

Effects of ion irradiation and magnetic field on primary recrystallization of metals

On the example of a cold-rolled (110)[001] single-crystal Fe-3 wt % Si alloy, it has been shown that irradiation by accelerated Ar ions and application of an external magnetic field during annealing exert a substantial influence on the formation of structure and texture upon primary recrystallization.

On the structure formation in polycrystalline metals and alloys: II. Recrystallization

Effects of the difference in the thermal expansion coefficients of grains and intergranular interlayers on the process of recrystallization in metals and alloys are considered.

The Impact of the Strip Geometry on the Magnetic Properties of Anisotropic Electrical Sheet Steel

The impact of the geometry (mainly the surface roughness) of cold rolled strips of anisotropic electrical (transformer) steel of domestic production (technical soft magnetic bcc alloy Fe - 3 wt.% Si with an edge crystallographic texture (110)[001]) on the magnetic properties (particularly on electromagnetic induction B 800 and specific magnetic losses P 1 7/ 50 ) is studied. It is shown that corrugations are formed on the surface of steel strips during cold rolling to a final thickness of 0.23 - 0.30 mm with a reduction of 50 - 70%. As a rule, their ridges and valleys are perpendicular to the direction of rolling and have a wavy form. Formation of the relief is attributed to the gradient of the stress-strain state along the cross section of the strip and to the tightness of the flow of the surface layers at the end of the deformation region and inevitably accompanies the rolling process. The presence of corrugations like any other roughness on the strip surface reduces B 800 and increases P 1, 7/ 50 . We propose a method for elimination of the surface defects (including corrugations) of cold rolled steel strips after cold rolling, i.e., ironing, which can be carried out by drawing of strips with a small draft (~3%) in cold rolling mills with a disconnected work roll drive using coilers. Introduction of drawing into the transformer steel manufacture technology improves the magnetic properties of steel due to increased perfection of the crystallites (grains), increased sharpness of the edge(110)[001] texture and free movement of the boundaries of magnetic domains upon magnetic reversal. Ironing of the steel strips of nitride-copper melt (inhibitors - dispersed particles of AlN and CuMn 2 O 4 ) with a thickness of 0.30 mm increased B 800 up to 1.93 T and decreased P 1, 7/ 50 to 1.07 W/kg (thus improving the magnetic properties by 5.7 and 10%, respectively). The resulted properties of domestic steel production are not inferior to those of foreign steel.

Effect of tensile deformation rate on texture formation during subsequent rolling and recrystallization of electric steel

The paper deals with the study of the dependence of the number of the main components of the primary recrystallization texture on the deformation rate during uniaxial tension (with contraction) carried out before the cold rolling of an electric steel (bcc soft magnetic alloy Fe-3 wt % Si) stripe up to its final thickness. It is found that the maximum increase in the volume shares of the auspicious components {111}〈112〉, {112}〈351〉, and {113}〈361〉 in the primary recrystallization texture occurs during tension with a minimal deformation rate in the range of 0.00015–1.10 s−1.

Influence of mechanical and thermal actions on domain structure and magnetostriction of iron-based soft magnetic alloys

Certain mechanical and thermal actions are considered as sources of stresses in ferromagnetic materials, which generate 90-degree magnetic domains, thus increasing saturation magnetostriction. It is established that the value of internal residual stresses in crystallites (grains) depends significantly on the difference between the thermal expansion coefficients of phases generated upon thermal processing of ferromagnetic materials and the surrounding matrix.

Influence of temperature cycling near the curie point on the effects of thermomagnetic treatment in soft magnetic materials

It has been found that thermocycling near the Curie temperature improves magnetic properties of magnetically soft alloys and, in particular, decreases the coercive force of the Fe-70 wt % Ni by 15% in comparison with that observed after conventional thermomagnetic treatment.

Role of Thermal Expansion of Phases in Crystallization and Recrystallization of Metals

In this work, the effect of the difference between the thermal expansion coefficients of phases on the nucleation and growth of crystallites (grains) in the crystallization and recrystallization of metals is analyzed. This effect has not yet been taken into account when studying and using these processes.

Corrugation of grain boundaries during high-temperature thermomechanical treatment

A new mechanism is proposed for the formation of wavy grain (crystallite) boundaries in a metal subjected to high-temperature thermomechanical treatment (HTMT). It is based on the corrugation of certain atomic metallic layers during deformation.