Damping Characteristics of Gentalloy in the Fe-Mo System

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  • Fe-Mo系吸振合金（Gentalloy）の減衰能特性
  • Fe Moケイ キュウシン ゴウキン Gentalloy ノ ゲンスイノウ ト

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Abstract

The relations of internal friction Q−1 with coercive force Hc, hysteresis loss Wh and magnetostriction λ for Fe-Mo alloys were studied by varying the heating temperature and cooling rate. Measurement of Q−1 was carried out by the inverted torsion pendulum method at a maximum shear strain amplitude of 1∼270×10−6 at a frequency of about 1 Hz. Both Hc and Wh were measured using the automatic recording fluxmeter, and λ by the optical roller method.<BR>The Q−1 value of Fe-Mo alloys became higher with increasing heating temperature. For the alloys with 0∼2%Mo, the Q−1 value was generally low, and in the furnace-cooled state Q−1 was higher than that in the rapidly cooled state. By contrast, for the alloys with 4∼8%Mo, Q−1 was generally high and showed a slight variation with cooling rate. Among the alloys the Fe-6%Mo alloy showed a maximum value of Q−1. For the alloys with 10∼16%Mo, Q−1 became higher by rapid cooling from high temperatures, suggesting that the precipitation of the non-ferromagnetic β phase in the matrix of ferromagnetic α phase was substantially reduced by quenching.<BR>The Hc value of the alloys with high Q−1 value was as small as about 0.05 kA/m, and consequently the magnetic rearrangement was readily caused by a small amplitude of strain when the vibrational stress applied. The Q−1 values of all the Fe-Mo alloys decrease with increasing magnetic field H. Further, the values of dWh⁄dH and dλ⁄dH, which are the slopes of the lines which connect the origin and each point on the Wh and λ vs Hc urves respectively, increase gradually with H, and then decrease after attaining the maxima. The strength of H for the most remarkable decrease in Q−1 with H is almost consistent with those for the maximum values of dWh⁄dH and dλ⁄dH. These gradients in weak magnetic fields are in proportion to the values of Q−1. The results indicate that the high damping capacity of Fe-Mo alloys is due largely to irreversible magnetization, and then is casued by the resultant large magnetic energy loss per cycle when the small vibrational energy applied.

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