Mikio Yamamoto: Dynamical Measurement of the E-effect in Iron-Cobalt Alloys. The AE-effect (change in Young's modulus of elasticity with magnetization

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1 Mikio Yamamoto: Dynamical Measurement of the E-effect in Iron-Cobalt Alloys. The AE-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 E-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 E/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 a solid solution. The maximum measured values of the E-effect, ( E/E)max, are approximate to the saturation values, ( E/E)_??_,excluding only that for pure cobalt, and they are all positive in a whole composition range of the alloys. The ( E/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 percent, which is the highest value of the E-effect at ordinary temperatures ever observed. The course of the curve in the a-solid-solution range agrees qualitatively wellto the result of an approximate calculation. The results of the present dynamicalmeasurement 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. (Received July 16,1942)

3 Table 2 Composition and dimensions of specimens used, and miscellaneous measured data for iron-cobalt alloys. ( E./E)max and Imax denote, respectively, the relative change of Young's modulus with magnetization, and intensity of magnetization, measured at the highest magnetic field applied, Hmax. ( E/E)_ is the negative minimum value of the de-effect, KO the initial susceptibility, and E Young's modulus at a non-magnetized state. The data of saturation magnetostriction, _??_co, measured by Masiyama, are also tabulated. Fig. I Relation between the initial susceptibility, ko, and composition in iron-cobalt alloys. Fig. 2 Relation between the intensity of magnetization at the highest magnetic field applied, Imas, and composition in the a-solid-solution range of ironcobalt alloys.

4 Table 3 Experimental data of the E-effcct in iron-cobalt alloys. Hex denotes the external magnetic field, E/E the change of Young's modulus of elasticity with magnetization, relative to that at a non-magnetized state, and I the intensity of magnetization.

5 Fig. 3 Relative change of Young's modulus of elasticity, E/E, with magnetic field, H, in the a-solid-solution range of iron-cobalt alloys.

7 Fig.8 ( E/E-H) curves at weak fields of 0, 10, 20, and 30 percent cobalt-iron alloys. Fig. 10 ( E/E-I) curves of iron-cobalt alloys in the composition range of 80 `100 percent cobalt.

9 Fig. 13 Relation between the maximum measured values and calculated saturation values of the relative change of Young's modulus with magnetization, ( E/E)max and ( E/E)_??_, and composition in ironcobalt alloys. ( E/E)max measured statically by Honda and Tanaka is also shown for comparison.

10 Fig. 14 Relation between the negative minimum values of the relative change of Young's modulus with magnetization,( E/E)_, and composition in iron-cobalt alloys.

Mikio Yamamoto : Young's Modulus of Elasticity and Its Variation with Magnetization in Ferromagnetic Nickel-Copper Alloys. Young's modulus of elastici

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