Damping Capacity, and Magnetic and Mechanical Properties of Ni–Co–Nb Alloys

Abstract

The internal friction Q−1, magnetic hysteresis loop and mechanical properties have been investigated for Ni–Co–Nb alloys with three different compositions of 25, 45 and 65% Co. Measurements of the Q−1 and the rigidity modulus G were carried out by an inverted torsion pendulum method. The coercive force Hc was measured by means of an automatic recording fluxmeter, and tensile tests were performed using an Instron-type machine.In both the furnace-cooled and the water-quenched state, the maximum internal friction against the maximum shear strain-amplitude, Qmax−1, was the highest at 3% Nb in the Ni-25% Co–Nb alloys and at 5% Nb in the Ni-45% Co–Nb alloys. Among the Ni-65% Co–Nb alloys, the highest value of Qmax−1 was attained at 1% Nb in the furnace-cooled state and at 5% Nb in the water-quenched state. The alloys with appropriately low Hc showed a fairly high value of Qmax−1, while the alloys with large Hc showed a very low value of Qmax−1 because of the precipitation of the compound Co2Nb or Co3Nb in the α phase matrix. The larger the ΔG effect, the higher the Qmax−1 became.The tensile strength and yield strength of the alloys in three different systems increased with increasing Nb concentration, while retaining a large value of elongation.