Residual quenching stresses in glass-coated amorphous ferromagnetic microwires

Abstract

The calculation of the residual stress tensor components in glass-coated amorphous ferromagnetic microwire is carried out on the basis of the theory of viscoelasticity. The approach takes into account the relaxation of the stresses both in a metallic core and a glass shell of the wire within a certain temperature interval near the point of the wire's vitrification. The distribution of the residual stresses is investigated as function of mechanical characteristics of metallic core and glass shell at different ratios of the metallic core radius to the total wire radius. The magnetic behaviour of a glass-coated amorphous microwire with small negative magnetostriction is analysed and is shown to be consistent with the experimental data.

Technology, Preparation and Properties of the Cast Glass-Coated Magnetic Microwires

“…The origin of the residual stresses is a difference in the thermal expansion coefficients of a metal and of glass. A simple theory for the distribution of the residual stresses in the metallic core of the microwire was proposed in the works [4][5][6][7][8][9][10][11].…”

Tailoring of Magnetic Properties and Magnetoimpedance Effect in Thin Amorphous Wires

“…Similarly to recently observed changes induced by annealing we can assume that the stress relaxation induced by annealing can change the sign of the magnetostriction constant. Indeed the reported internal stresses values inside the metallic nucleus are between 200 MPa and 5 GPa [10][11][12]. Experimentally measured values of the B-coefficient from Eq.…”

“…Consequently both thermal stresses induced by the solidification of the metallic nucleus from the surface layer as well as the internal stresses associated to the difference in the thermal expansion coefficients between the glass coating and the ferromagnetic nucleus affect the magnetoelastic anisotropy [10][11][12]. The strength of the internal stresses induced by the difference of thermal expansion coefficients depends on the ρ-ratio between the metallic nucleus diameter, d, and total microwire diameter, [10][11][12] increasing with decreasing the ρ-ratio, i.e. with increasing of the relative volume of the glass coating.…”

Development of Ultra-Thin Glass-Coated Amorphous Microwires for High Frequency Magnetic Sensors Applications

“…The magnetostriction constant depends on the chemical composition and nearly vanishes in amorphous FeCo based alloys with Co/Fe 70/5 [4,16]. On the other hand, the estimated values of the internal stresses in these amorphous microwires arising from the difference in the thermal expansion coefficients of metallic nucleus and glass coating are of the order of 100-1000 MPa, depending strongly on the thickness of glass coating and metallic core diameter [17]. It was established that the strength of such internal stresses increases with the increasing glass coating thickness.…”

“…Such critical diameter is predicted to be of order of a few μm. On the other hand, with the decreasing glass-coated microwires diameter the strength of the internal stresses drastically increases [17][18][19], giving rise to the growth of the magnetoelastic energy. Therefore, it is not an easy task to produce magnetically soft thin glasscoated microwires, and the nearly-zero magnetostrictive composition should be selected with a high precision.…”