The ΔE-effect (change in Young's modulus of elasticity with magnetization) in the annealed state of iron-cobalt alloys has been measured at the room temperature by the method of magnetostrictive oscillation. The measured range of magnetic field is up to about 900 oersteds.
It was found that the negative ΔE-effect occurred at weak fields or at low magnetizations in alloys of the composition range excluding 45_??_50 and 100 percent cobalt. The negative minimum value of ΔE/E (change of Young's modulus, relative to that in a non-magnetized state) is, at most, of the order of -0.1 percent in a low-nickel-content range, while it amounts to -2 percent in a high-nickel-content range of α solid solution.
The maximum measured values of the ΔE-effect, (ΔE/E)max, are approximate to the saturation values, (ΔE/E)∞, excluding only that for pure cobalt, and they are all positive in a whole composition range of the alloys. The (ΔE/E)max vs. composition curve exhibits a very sharp and high peak at the composition of about 50 percent cobalt. The value at this composition is 22.10 percent, which is the highest value of the ΔE-effect at ordinary temperatures ever observed. The course of the curve in the α-solid-solution range agrees qualitatively well to the result of an approximate calculation.
The results of the present dynamical measurement were compared with those of a statical measurement by Honda and Tanaka, and it was concluded that marked differences discerned between them were due to differences impurities of specimen materials used and in the state of stress in specimens at the time of measurement.
Further, a secondary increase preceding to a saturation of Young's modulus of pure iron, and a maximum and minimum at weak fields of the modulus of pure cobalt, found previously by the present author, have been again confirmed by the present measurement.
Please do not copy without permission.