Mechanism for the High Damping State in Alloys of the Fe-Al System

Abstract

Magnetic and crystalline structure as well as magnetic and damping properties of binary iron-aluminum (Fe-Al) alloys in the region from 3 to 12 wt.% aluminum have been investigated by using transmission electron microscopy (TEM), X-ray scattering, neutron scattering, magnetic hysteresis loops, and magnetostriction studies. It was found that independent of the impurity content (vacuum or air melting of alloys) the concentration dependence of damping capacity displays a pronounced maximum in the region of ̃5.5 wt.% aluminum, where the maximum value of the logarithmic decrement δ exceeds 25%. It was found that the magnetic domain structures in the bulk materials differ strongly for the alloys in the high damping state and for the alloys with the same composition after suppressing the high damping by heat treatment. The analysis of obtained magnetic data and microstructural analysis shows that the necessary condition for the appearance of the high damping state is the formation of a special magnetic domain structure with an enhanced fraction of movable 90-deg domain walls. An additional condition is the formation of a crystalline structure which provides a moderate value of magnetic hysteresis losses and coercive force. For the Fe-Al alloys investigated, it means that the most favorable structural condition for high δ-values is an intermediate stage of short-range ordering of the D03 structure.

Application of Neutron Refraction for Characterization and Optimization of High-Damping Iron-Based Alloys

“…It can be seen that the value of the logarithmic decrement 6 can be remarkably changed (~ 10 times) using the variation of the heat treatment regime. The drastic change of the damping capacity was found to be caused by essential modifications in the crystalline [2][3][4]8] and magnetic [7,8] structure of the material. In the present paper, let us briefly present the generalized data Heat treatment: 1 -water quenching from T = 10000°C; 2 -air-cooling; 3 -furnace cooling; 4 -cooling from T = 1000 to 600°C with the furnace, then cooling on the air.…”

“…Materials have been prepared using a standard metallurgical technology, including vacuum-melting from high-purity raw materials, forging and rolling [8]. Let us mention that the level of impurities and nonmetallic inclusions did not exceed the following limits: 0.009% C, 0.13% Si, 0.05% Mn, 0.01% Ti (wt.%).…”

Surface Treatment Effect on Bulk Magnetoelastic Properties of High Damping Fe-Based Alloys

“…Damping properties tests show that after slow cooling during heat treatment both Fe-Cr and Fe-Al high damping alloys possess the δ(ε) dependence in the shape of curve with a sharp maximum in the field of small amplitudes [6,7] (Fig. 2, initial state).…”

“…In the same time fast samples cooling (water quenching from T = 1000° C) leads to the effective suppression of damping capacity of the investigated alloys (δm < 4-5%). The reasons of such a behavior were discussed in the previous authors' papers [5][6][7][8]. It takes place, first of all, because of essential modifications in magnetic domain stucture of inaterials.…”

Low-frequency damping behavior of (Fe83Ga17)97.25Cr2B0.75 sheets

“…According to V. A. Udovenko [21], the high damping capacity of FeeAl at low frequency (Hz range) was induced mainly by energy loss upon the domain walls' irreversible jump. Since the phase and crystalline structure of FeeGa alloy is very similar to that of FeeAl alloy [11,22].…”