Influence of Thermomagnetic Treatment on the Damping Properties and Structure of Iron-Based Alloys

The paper describes the influence of thermomagnetic treatment on the parameters of the amplitude dependence of internal friction, the crystal and magneto-crystalline structure of Fe alloys with ferrite structure: Fe – 8%Cr, Fe – 16%Cr, Fe – 19%Cr, Fe – 4%Cr – 2%V, Fe – 3%Cr – 3%Al, and Fe–1.2%C–2% Si–2%Al graphitic steel with graphite and ferrite structure. The thermomagnetic treatment was carried out at a temperature of 450ºС. The structure was studied by means of metallography, X-ray crystal structure analysis, ferromagnetic resonance, and nuclear gamma resonance spectroscopy. It is shown that, the larger the ferrite grain in alloys with ferrite structure is, the greater an increase in internal friction is, in the amplitude range up to approximately the amplitude of its maximum owing to thermomagnetic treatment. The change of the damping properties of graphitic steel caused by thermomagnetic treatment is relatively small, due to a large number of diamagnetic inclusions of graphite and quite fine-grained ferrite matrix. The results of the X-ray crystal structure analysis, the ferromagnetic resonance and nuclear gamma resonance spectroscopy have shown that, in the case of thermomagnetic treatment, diffusion redistribution of atoms of alloying elements, combined with the change of structural anisotropy, takes place in Fe-Cr alloys.

Phase transformations and properties of concentration-inhomogeneous magnetic materials based on the Fe–30%Cr–27%Co system

The phase and structural transformations of a powder magnetically hard alloy of the system Fe–30%Cr–27%Co–1%Si–0,07%B with a metastable α1+α2 phase composition, a high content of cobalt, and a high level of magnetic properties were studied. The density and coefficient of variation of the concentration of the main elements of the sintered blanks at the level of deformable analogs are achieved by sintering in the α-phase with contact melting in the presence of a «vanishing» liquid phase formed due to the addition of silicon and boron ferroalloys. A kinetic approach to the development of a competitive hard magnetic alloy with a high proportion of the strongly magnetic phase is proposed. The effect of boron additions on the incubation period of the formation of an undesirable σ-phase and the temperature range of the concentration stratification of the α-solid solution on the strongly magnetic α1-phase and the weakly magnetic α2-phase were established. Optical microscopy, X-ray phase analysis and differential scanning calorimetry were used to determine temperature and time parameters of heat treatment of the alloy, including hardening, thermomagnetic treatment (TMT) and final aging, providing the required combination of Hc and Br by increasing the stability of the metastable α-phase up to 20 minutes in the interval temperatures of spinodal decomposition α → α1 + α2. The greatest increase in magnetic properties after TMT, observed at the 1st and 2nd steps of final aging, is related to the decomposition of the α-solid solution and the formation of subgrain boundaries. Elements of the obtained structure are characterized by submicron and nanometric sizes, which correlate with the research results on deformable alloys based on the Fe – Cr – Co system. The anisotropic α1+α2-structural state achieved by thermomagnetic treatment provided an increase in the magnetic properties of the studied 30H27KSR powder alloy to 30 % and the squareness coefficient of the magnetic hysteresis loop equal to 0,82 .

Manifestation of Magnetoplastic Effect in Some Metallic Alloys

A brief review of the magnetoplastic effect during aging of quenched aluminum, copper, titanium and magnesium alloys in constant magnetic field is presented. We report the effect of thermomagnetic treatment on the composition and microstructure of the studied alloys, and on their mechanical properties, which constitutes the core of the magnetoplastic effect.

Effect of Thermal and Thermal Magnetic Treatment on Damping Properties of Fe-Cr-Al Alloys

The authors studied the effect of the pre–heat treatment and subsequent thermomagnetic treatment on the damping and magnetic properties of the Fe–Cr–Al alloy system. This article reveals the dependences of influence of chromium and aluminum on the thermomagnetic treatment effect. As a result, the study identified the optimal modes of treatment of the alloys to maximize the damping capacity.