Effect Of Thermomagnetic Treatment Research Articles

Atomic Ordering of Soft Magnetic Fe–Si Alloys and Effect of Thermomagnetic Treatment

A mechanism of isotropic improvement of magnetic properties of soft magnetic Fe–Si alloys with a bcc crystal lattice upon thermomagnetic treatment in an ac magnetic field is proposed. The essence of the mechanism is the applied alternating-sign magnetic field, which reorients axes of neighboring Si atoms pairs (“directed atomic ordering”) in nanoclusters with the FeSi (В2 type) superstructure and transfers the silicon atoms from the stable equilibrium position at centers of cubic cells into nonequilibrium position. In this case, bonding forces between atoms weaken, and the possibility of their displacement by moving magnetic-domain walls appears. As a result, nanoclusters are destroyed, and the redistribution of weakly coupled silicon atoms over the volume and isotropic improvement of magnetic properties of Fe—Si alloys occur. The dependence of the effect of thermomagnetic treatment of the Fe–Si alloys on the strength of applied dc magnetic field is explained (the effect of thermomagnetic treatment in low and high magnetic fields is anisotropic and isotropic, respectively).

The influence of cold rolling and thermomagnetic treatment on the magnetic and mechanical properties of Fe-23Cr-9Co alloy

Abstract In this paper, the effect of thermomagnetic treatment (TMT) on the magnetic and mechanical properties of the cold-rolled Fe-Cr-Co alloy was investigated. For this purpose, an alloy with Fe-23Cr-9Co chemical composition was prepared by vacuum induction melting. Then, the cast ingots were subjected to hot forging. The homogenization treatments were performed on the forged samples at 1200 °C for 10, 60, 120, 240 min. Then, the homogenized samples were cold-rolled to 40% and 80% reduction in area. The cold-rolled samples were annealed under the magnetic field at different temperatures and holding times; subsequently, they were aged. The results showed that the best mechanical and magnetic properties could be achieved under these conditions: thermomagnetic treatment at 640 °C for 45 min and step-aging from 620 °C to 500 °C. Under these conditions, the samples had the coercivity and saturation magnetization of 77 Oe and 158 emu/gr, respectively; also, the ultimate tensile strength and elongation of them were 1050 MPa and 12%, respectively.

Effect of thermomagnetic treatment on magnetoresistive properties of trilayer thin films based on FexNi100-x and Cu

We investigated magnetoresistive properties of as-deposited and annealed in magnetic field at different temperatures F/N/F trilayer films based on ferromagnetic FexNi100-x (F-layer) and nonmagnetic Cu (N-layer). The results demonstrate that spin-dependent scattering is realized both in as-deposited and annealed at 400 K trilayer films within the range of thicknesses dF = 15–40 nm and dN = 6–15 nm and at the Ni concentration in magnetic layers cNi ≤ 90 wt %. The annealing at 550 K leads to the decrease of isotropic magnetoresistance value and to the appearance of anisotropy in thin films at the cNi ≥ 50 wt %. It was found that the maximum value of isotropic magnetoresistance has been observed for as-deposited Fe50Ni50(30 nm)/Cu(6 nm)/Fe50Ni50(30 nm)/S thin film at room temperature. The value of isotropic magnetoresistance increases in 1.3–2.2 times with the decline of the measurement temperature from 293 to 120 К depending on components concentration in magnetic layers.

Effect of thermomagnetic treatment on the magnetic properties of permalloy/manganese bilayer films

Formation of unidirectional exchange anisotropy has been studied during thermomagnetic treatment of permalloy-manganese bilayers. It has been found that, starting from the annealing temperature of 230°C, there is observed a shift of the hysteresis loop. The maximum value of the exchange bias field is achieved after annealing at 250°C for two hours and amounts to 155 Oe. Using electron microscopy, it has been demonstrated that the effects of the occurrence of unidirectional exchange anisotropy and of increase in the coercive force are due to the appearance of an ordered antiferromagnetic phase NiFeMn, which is formed as a result of diffusive interaction between permalloy and manganese upon annealing.

Effects of Thermomagnetic Treatment on Microstructure and Mechanical Properties of Rolling Bearing Steel

The influence of the thermomagnetic treatment on metallurgical and mechanical properties of the rolling bearing steel was investigated. The heating and/or cooling and tempering processes of the samples occurred in a magnetic field having certain strengths. The X-ray diffraction (XRD) patterns of the rolling bearing (RUL 1) steel samples exhibited a beneficial effect of the magnetic field on the structure, phase transformation, and tension state. An increased fatigue reliability was found for the rolling tribomodel made from thermomagnetically treated steel.

Microstructure Evolution upon Thermomagnetic Treatment of Soft Magnetic Alloys

A new concept is suggested that serves to explain the effects of thermomagnetic treatment. Its validity is proved via measurements of magnetic properties and electron microscopy examination of structure of soft magnetic materials after different treatments. This concept allows one to consciously choose the treatment mode aiming on improvement of magnetic properties of alloys.

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.

Effect of thermomagnetic treatment on the damping properties of magnetically soft iron alloys

The effect of thermomagnetic treatment on the amplitude dependence of internal friction of magnetically soft Fe-Cr alloys and graphitized steels is investigated. The laws of variation of parameters of internal friction after thermomagnetic treatment of iron alloys with ferritic structure are determined. The effect of four structural characteristics (size of ferrite grains, graphite inclusions in ferrite matrix, content of impurities in alloys with ferritic structure, and content of vanadium and aluminum in alloys having no α-γ transformation) and of the composition on the variation of the damping properties of iron after thermomagnetic treatment is studied. The changes in the damping properties are analyzed depending on the changes in the crystal and magnetic structures.

Effect of thermomagnetic treatment on microstructure and tensile properties of aluminum borate whisker reinforced aluminum composite containing Fe3O4 particles

Effect of thermomagnetic treatment on microstructure and tensile properties of aluminum borate whisker reinforced aluminum composite containing Fe3O4 particles

Effect of thermomagnetic treatment on the magnetic state of a ferrofluid: a polarised neutron study

In magnetic colloids of sufficiently high particle concentration, frustration of dipolar interactions could arise as found in spin-glass systems. To understand this situation, a ferrofluid consisting of magnetite particles was frozen in either a horizontal or a vertical field and then 3D neutron-polarisation analysis was performed around the hysteresis loop in both field configurations. The same was done in the fluid state. A comparison of the data leads to the conclusion that frustration plays a key role in the self-organisation of nanoparticles in a frozen magnetic colloid.

Effect of Thermomagnetic Treatment on the Thermophysical and Mechanical Properties of Polymers

Effect of Thermomagnetic Treatment on the Thermophysical and Mechanical Properties of Polymers

Effect of thermomagnetic treatment on the structure and hardness of cast iron

Effect of thermomagnetic treatment on the structure and hardness of cast iron

Study of the effect of thermomagnetic treatment on the stability of the magnetic properties of an Fe?Co alloy

Results are presented from an experimental study of the stability of the magnetic properties of an iron-cobalt alloy with different regimes of thermomagnetic treatment.

Microstructure and magnetic properties of Fe-Cr-Co alloys

The microstructures of an Fe-31wt%Cr-23wt%Co ductile permanent magnet alloy after isothermal aging, thermomagnetic treatment, and step aging have been characterized by transmission electron microscopy and by measurement of the Curie temperature. Isothermal aging itself produces the undesirable microstructure. Aging at 600°C develops the magnetic chromium-rich phase. Aging at 600°C produces a nonmagnetic chromium-rich phase dispersed within the iron-rich phase. The effect of thermomagnetic treatment on the microstructure of the alloy is discussed in comparison with that of Alnico alloys. Step aging produces the deskable microstructure, viz., the elongated ferromagnetic phase imbedded in the paramagnetic phase.

Investigation of the effect of thermomagnetic treatment on structure changes and properties of alnico alloys

Investigation of the effect of thermomagnetic treatment on structure changes and properties of alnico alloys