Magnetic field dependent elastic moduli and internal frictions in nickel alloy revealed by a quantitative electromechanical impedance method

Accurately and quickly determining the moduli and damping properties of ferromagnetic materials with bias magnetic fields is very important for vibration control and instrument design. In this work, the magnetoelastic properties of a nickel alloy were investigated by using a quantitative electromechanical impedance (Q-EMI) method under bias magnetic fields from 0 to 1364 Oe. Measurement results demonstrate that both the Young’s modulus and shear modulus of the nickel increase steadily with the bias magnetic field, tending to saturate under high fields. The internal friction of nickel initially increases and subsequently decrease with the magnetic field, exhibiting a pronounced peak. Meanwhile, it is found that the torsional internal friction is always considerably larger than the longitudinal internal friction. The amplitude dependent internal friction (ADIF) of the nickel alloy under bias magnetic fields was further studied using a dog-bone shaped specimen and a strain-amplifier horn. Results show that the specimen under zero field shows the most significant ADIF when the strain amplitude exceeds 2 ⅹ 10 ⁻⁵. While under a large bias field over 1000 Oe, the ADIF cannot appear until the strain amplitude is over 1 ⅹ 10 ⁻⁴ strain, indicating that the ferromagnetic domains had been stabilized by the large bias field. This study demonstrates the superiority of the Q-EMI method in probing the magnetomechanical properties of ferromagnetic materials.