Damping Capacity and Magnetomechanical Properties of Ni–Co–Nb–Si Alloys

Abstract

The effects of Nb and Si concentration on the internal friction, magnetic properties, and mechanical properties of Ni-25 mass%Co–Nb–Si alloys have been investigated, by furnace cooling or water quenching, or both. The measurements of internal friction, magnetic hysteresis and mechanical properties were carried out by an inverted torsion pendulum, an automatic recording fluxmeter and an Instron tensile testing machine, respectively. As the shear strain amplitude increased, the internal friction of these alloys first grew larger and then reached a maximum. The maximum internal friction and the shear strain amplitudes were defined as Qmax−1 and γc. The alloys containing no Nb showed the highest Qmax−1 value on furnace cooling for 3 mass%Si and on water quenching for 4 mass%Si. The alloys containing 1 mass%Nb showed the highest Qmax−1 value at 2 mass%Si on cooling by both methods. The strain amplitude, γc gradually decreased with decreasing Si concentration in these alloys. The alloys containing 3 mass%Nb had the highest Qmax−1 value and alloys with 2 mass%Si, the lowest γc value, on cooling by both procedures. The alloys containing 5 mass%Nb and 1 mass%Si had the highest Qmax−1 value when furnace-cooled, but for water quenching this occured for 2 mass%Si. The lowest γc value was recorded when 2 mass%Si cooling by both procedures. The coercive force Hc also varied with Si concentration much like γc. Both Hc and γc were small when Qmax−1 was large. These results indicate that there is a close relationship between the damping capacity and the magnetoelastic properties of the alloys. The larger the concentration of Nb and Si, the higher becomes the tensile strength and yield strength. The elongation was found to be independent of the Si concentration.