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.

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It is a well-known fact that the magnetic properties of a reversible iron-nickel alloy, especially of 78.5% Ni, are largely modified by rapid cooling from 600°, namely, by the so-called permalloy treatment. Two theories have been advocated on the physical meaning of this treatment; one is the super lattice (Ni₃Fe) theory, and the other the plastic flow theory in magnetic domain. We carried out an experiment on the change of Young's modulus by the permalloy treatment and attempted to decide which theory is more reasonable of the two. By the lateral vibration method we measured the modulus of specimens cooled slowly after vacuum annealing at 1000_??_1100° for 20 hours, and then of specimens cooled rapidly from 600° in air after reheating to 1000°. Rapid cooling general, seems to decrease Young's modulus in both ranges reversible and irreversible. The marked decrease of the modulus occurs in the magnetically modifiable range of alloys (50_??_85% Ni). Moreover, the curve of the percentage decrease of the modulus to composition is quite similar to that of magneto-striction in longitudinal magnetic field. Similarity of these two curves suggests that some relation may exist between the change of Young's modulus by rapid cooling and the degree of plastic flow in magnetic domain. The decrease of magneto-striction by cooling in field was related directly to the degree of plastic flow of magnetic domains by Bozorsh and Dillinger, and afterwards was supplemented by Becker and During as a trans formation from cubic atom arrangement to somewhat tetragonal one. The decrease of Young's modulus by rapid cooling may be attributed to the degree of transfor-mation of atom arrangement from cubic to tetragonal.

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The corrosion test of 18% Cr steel was carried out by dip method. The corrosion resistance was examined in 5_??_98% HNO₃ at 30_??_70° by measuring the weight loss for 10 hours, and the corrosion rate was expressed as g/m²hr.
The results obtained were as follows (1) At 30°, this steel is not corroded. (2) At 50°, this steel is slightly corroded in conc. nitric acid. (3) At 70°, this steel is slightly corroded in above 50% nitric acid.

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The influences of magnesium on the mechanical properites of Al-Mg alloys were investigated. The tensile strength increases with magnesium up to 6%, and the elongation and the impact resistance decrease as rapidly as magnesium increases. The effect of heat-treatment on Al-Mg alloys and the influence of the structure of the casting before treatment on its properties after treatment are described.
The solution treatment consisted of a preliminary soaking for 0.5 or 24 hrs. at 420° followed by precipitation at 100_??_300° for 2_??_10 hrs. In the case of solution treatment, the hardness does not increase, but when the precipitation treatment were carried out, they show a marked increase of hardness. An appreciable amount of precipitation hardening is possible in alloys containing 8% or more magnesium. In any alloy, the maximum hardness is obtained by tempering at about 175°
The corrosion resistance in sea-water shows the maximum resistivity at 6% magnesium in cast or heat-treated condition. In case of thse alloys for which the solution treatment is for 3 hrs. at 420° followed by air cooling, the effect is more beneficial than water quenching, while in tempering the alloys of these series the corrosive resistance is recduced.
The mechanical properties of some of the more important Al-Mg alloys “Hydronalium” in the extruded condition, which contained 6_??_8% magnesium and 0.3_??_0.5% manganese, have been investigated. The mechanical properties of Hydronalium is barely affected by quenching up to 420°. But above 420°, the effect of temperatures is to decrease the mechanical properties markedly. When the extruded bars were quenched in water or air at 420° for 0.5_??_10 hrs., the heating time has a marked effect to improve the elongation up to 5_??_7 hrs. But after tempering the mechanical properties decrease as the tempering temperature increases.
Corrosion of Hydronalium in salt water was also investigated. In the case of quenching, it does not appreciably affect the corrssion resistance up to 420°. Above 420°, however, the corodibility is remarkably improved in air cooling, but in water quenching, the resistivity decreases progressively with the increase of quenching temperature. In the case of tempering, Hydronalium are more corrodible than in any other state.

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Fatigue properties of super duralumin plate (SDH) subjected to two different values of cyclic stress were investigated. The results obtained are summarised as follows:
(1) When the value of cyclic stress to be applied primarily is below the static yield point, the following relation has been found:
_??_
where Ni is the number of cycles of a stress applied alone at which the specimen shall be failed, and Ni' is the number of cycles of the same stress to be applied as a primary stress, or as a secondary one at which the specimen shall be failed. If the value of a primary cyclic stress is greater than of the subsequent cyclic stress, and the number of cycles of the former is relatively larger, the relation mentioned above becomes as follows:
_??_
(2) When the value of a primary cyclic stress is nearly the static yield point, the relation (1) changes as follows:
_??_
(3) When the value of a primary cyclic stress is about the altimete tensile strength, the relation has been obtained as follows:
_??_

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