The ΔE-Effect, Young\u27s Modulus, and Magnetic Properties in Ferromagnetic Nickel-Copper Alloys

The results of the dynamic measurements of Young\u27s modulus and its change with magnetization (the ΔE-effect) as well as of the ballistic measurements of the ferromagnetic characteristics made at ordinary temperatures on annealed ferromagnetic nickel-copper alloys are described. The ΔE-effect in alloys containing 5 to 20 percent copper shows a negative small minimum at low fields or at low magnetization. It is shown that the observed values of the saturation ΔE-effect are in a quantitatively fairly good agreement with values computed from a formula : - (ΔE/E_0)_s=0.7×κ_0E_0λ_s^2/I_s^2/(1-0.7×κ_0E_0λ_s^2/I_s^2), where κ_0 is the initial susceptibility, I_s the saturation magnetization, and λ_s the saturation magnetostriction. Young\u27s moduli at unmagnetized state as well as at magnetically saturated state reveal minima at 15 to 20 percent copper. Some new information is also given of the magnetic properties

Young\u27s Modulus and Its Variation with Magnetization in Annealed Iron-Cobalt Alloys

With annealed iron-cobalt alloys covering the whole composition range, Young\u27s moduli and their changes with magnetization (the ΔE effect) in magnetic fields up to 900 Oe have been measured at ordinary temperatures using the method of magneto-strictively excited longitudinal vibration. In this connection, the density and some ferromagnetic properties have also been determined. It has been found that the negative ΔE effect occurs at weak magnetic fields in most alloys excluding 45~50 and 100%Co. The absolute magnitude of the negative minimum of the ΔE effect is, at most, of the order of 0.1 % in alloys containing less than 45%Co, while it amounts to more than 2% in alloys containing 65~70%Co. The maximum measured values of the ΔE effect, (ΔE/E_0)_, which are approximate to the saturation values, (ΔE/E_0)_s excepting only for pure cobalt, are all positive in the whole composition range of the alloys. The (ΔE/E_0)_ vs. composition curve exhibits a very sharp and high peak of 22.10% at about 50%Co. The trend of the curve in the α (body-centered cubic) phase range agrees qualitatively very well and quantitatively-fairly well with the results of calculation by a formula (ΔE/E_0)_s=(0.7χ_0λ_s^2E_0/I_s^2)/(1-0.7χ_0λ_s^2E_0/I_s^2), where χ_0λ_s, I_s, and E_0 are the initial magnetic susceptibility, saturation magnetostriction, saturation magnetization, and Young\u27s modulus at unmagnetized state, respectively. The Young\u27s modulus at unmagnetized state vs. composition curve shows two maxima at about 25~30 and 60%Co and one minimum at about 50%Co in the α phase range, and then falls considerably up to its boundary (at about 80%Co). The modulus recovers in the α+γ phase range, but it decreases again in the narrow ε (hexagonal close-packed) phase range. The marked discrepancies found between the results of the present dynamical measurements and those of the previous statical measurements by Honda and Tanaka on the ΔE effect and Young\u27s modulus at unmagnetized state are shown to be due to differences in purity and in treatments of the specimens as well as to differences in the state of stress at the time of measurements of the specimens. It is also shown that, with an addition of cobalt to iron, the density increases approximately hyperbolically up to cobalt, except for a small discontinuity near 80%Co, and the initial magnetic susceptibility exhibits a sharp maximum near 50%Co and a flat minimum at 65~75%Co

A Note on the Formation of Etch Pits on Crystals

It is shown that an etch pit on a crystal may be originated from one of the two causes. The first cause is a microscopic pit or an easily soluble minute portion or inclusion which exists accidentally and locally on the crystal surface, and the other is a dislocation existing in the crystal. In the etch pit originated from the first cause its depth is unchanged but its calibre increases as dissolution or etching proceeds (the temporary or short-time etch pit), while both the depth and calibre of the etch pit originated from the second cause increase in proportion to the etching time (the permanent or dislocation etch pit). A brief consideration is also made of the mulitiplicated etch pit as a variation of the dislocation etch pit. Experimental evidences for the considerations are presented

Theory of the Wiedemann Effect

As regards the classical problem of the Wiedemann effect in polycrystalline ferromagnetics, any satisfactory theory has not yet been proposed, except Fromy\u27s theory for the case of thin-walled circular tube specimens. We derive, in a simple way, a general expression for the Wiedemann effect or the torsion angle per unit length, θ_γ, of a cylindrical layer of the radius γ in cylindrical rod of ferromagnetic substance, fixed at its one end and magnetized by a longitudinal magnetic field, H_l, parallel to, and by circular field, H_, arround, its rod axis, and show that, when the elastic energy is negligible as compared with the magnetic field energy as in normal ferromagnetics, the general expression is reduced to θ_γ= (2/γ){λ_l(H_γ) - λ_t(H_γ)}(H_lH_/H_γ^2) where H_γ= (H_l^2+H_^2)^ and λ_l(H_γ) and λ_t(H_γ) are the longitudinal and transverse magnetostrictions accompanied with H_γ. This expression may be written, for the surface of the rod of the radius a, as θ_α = (2/α){λ_l(H_α) - λ_t(H_α)}( H_lH_/H_α^2), which holds also for a thin-walled tube and is the expression derived already by Fromy. This expression is further reduced to θ_α = (3/α)・{λ_l(H_α)・( H_lH_/H_α^2) when the volume magnetostriction may be negligible as in normal ferromagnetics. It is shown that the above expressions can explain, qualitatively completely and also to a considerable extent quantitatively, all of the available experimental facts concerning the Wiedemann effect

Ferromagnetic Behavior and Its Dependence on the Crystal Orientation and on the Method of Demagnetization in Single Crystals and a Polycrystal of 0.5 Percent Aluminium Iron

The magnetization curve, ballistic demagnetizing factor (as defined with respect to the break point of the descending hysteresis curve), N, domain distribution, magnetocrystalline anisotropy constants, K_1 and K_2, as well as K_0, saturation magnetic field, H_s, residual magnetization (as the magnetization at the break point of the descending hysteresis curve), I_k, coercive force, H_c, and initial magnetic susceptibility, X_0, and their dependence on the crystal orientation have been studied at ordinary temperatures, using the ballistic method, with single crystals and a polycrystal of iron containing 0.53% Al in thermally demagnetized (TD) state and in alternating-current demagnetized (AD) state. It has been discovered that, irrespective of either single crystal or polycrystal and of crystal orientation, N_>N_>N_a, where N_a is Shuddemagen\u27s demagnetization factor. This fact suggests that the domain distributions in TD and in AD states are different in such a way that, in TD state, the volume of domains magnetized along a direction of easy magnetization far from the rod axis of the specimen is larger than that of domains magnetized along a direction of easy magnetization nearest to the rod axis, as compared with AD state. This may be interpreted by an idea that TD and AD induce additional small uniaxial magnetic anisotropies with positive and negative anisotropy constants, respectively, the former anisotropy being due to directional ordering (the self magnetic-anneal effect), and the latter due to the re-distribution of interstitial foreign atoms. It has been found that (K_0)_>(K_0)_ and (K_1)_>(K_1)_, and that, irrespective of either single crystals or polycrystal and of crystal orientation, A_>A_ (A=∫^I_s_0HdI), (H_s)_>(H_s)_, (I_k)_, (H_c) _=(H_c)_, and (X_0)_> (X_0)_. It has also been found that, in single crystals, (H_-H_)_>(H_-H_)_>0, and (H_-H_)_> (H_-H_)_>0, and (I_k)_> (I_k)_>I_s/Σβ_i (Kaya\u27s rule), where β_i\u27s (i=1, 2, 3) are the direction cosines, referred to the tetragonal axes, of the rod axis of the single crystal specimen. We have found, further, that (K_2)_ , and that, irrespective of the method of demagnetization, 3/2 > K_2/K_1>-3, H_>H_> H_, (H_s)_>(H_s)_, (I_k)_>I_s/Σβ_i, H_>(H_c)_, X_>X_>X_, and (X_0)_>(X_0)_. It is shown that the measured facts concerning the difference in the method of demagnetization may be explained by the above-mentioned idea of small uniaxial ferromagnetic anisotropies with negative and positive anisotropy constants, induced, respectively, by TD and AD, and that the observed relations between the polycrystal and single crystal data may be interpreted in terms of the magnetic interaction between crystal grains. It is also shown, for both of TD and AD states, that the observed anisotropy of H_c coincides well with a formula H_c=H_(Σβ_i/Σβ_i^3), which is derived from Kondorsky-Vonsovsky\u27s theory for the case where the 180°domains are grouped and I_k=I_s/Σβ_i (Kaya\u27s rule) and that the observed anisotropy of X_0 accords well with a formula X_0=X_ [2(Σβ_i^3/Σβ_i)-Σβ_i^4/(Σβ_i)^2], which are derived from Brown\u27s theory of the domain wall displacements for the case where 180°domain are grouped and the relative volumes of domains in unmagnetized state are expressed as v_=(1/2) ( β_i/Σβ_i). Furthermore, it has been found that a formula |K_1|=αI_s(H_s)_, where α=1/3～1/4, holds for cubic ferromagnetics

Light-Figure Phenomena Revealed and Crystal Faces Developed by Chemically Etched Nickel-Copper Alloy Crystals

The light-figure phenomena have been observed with single crystals of nickel-copper alloys containing 5～95 percent copper, etched with various chemical reagents, in order to obtain information regarding crystal faces developed by etching and to examine the suitability of the observed light figures to the orientation determination. The etching with boiling saturated aqueous solution of ferric chloride produces distinct light figures, suitable for the orientation determination, for all of alloy crystals, while any other reagent reveals only indistinct or no light figure. The main crystal faces developed by etching with ferric chloride solution are the {hk0}. {110} and {111}-vicinal faces, hk0 varying from 910 for nickel crystals over 610 for 20%Cu alloy crystals to 210 for 95%Cu alloy crystals

On the Solution-Body Phenomenon and Anisotropy of Solution Rate in Bismuth Crystals

The solution-body phenomenon has been investigated with bismuth single crystals, of circular-rod and sphere forms, etched with various reagents and some information concerning the anisotropy of solution rate has been obtained. It has been found that 31.6 percent nitric acid is only one reagent that produced clear-cut solution-bodies characteristic to the trigonal symmetry of bismuth crystal and that the rates of solution along various crystallographic directions in this reagent are in the order of V_>V_>V_V_>V_, V_ where h+k+l = 0 and m and n = any rational number. It is also shown that solution rates in 50 percent aqueous solution of 1 : 2 mixture of hydrochloric acid and nitric acid are in the same order as in 31.6 percent nitric acid, though the anisortopy is far smaller

Work-hardening of Foil Crystals of Copper

An investigation has been made on the plastic properties of recrystallized copper foil crystals of which thicknesses are down to 6.6 microns. It has been found that stress-strain curves of single crystal and pseudo-single crystal (crystal having the cube-texture) specimens thicker than 50 microns consist of three deformation stages in a quite similar way to those of bulk single crystals and that the value of the work-hardening rate in the stage II of deformation decreases very sensitively with decreasing specimens thickness. Pseudo-single crystal specimens thinner than about 10 microns do not reveal the stage II of deformation, but the work-hardening rate takes a very high value when the tensile axis approaches to the [001] direction. The work-hardening rate of the well-developed stage II in 50.8 microns thick specimens elongated in directions near [011] is much lower than that observed in the specimens elongated in directions near [001]. A large fraction of slip lines observed on (100) surfaces of the foil crystals are clustered in early stages of deformation. This clustered distribution of slip lines becomes more remarkable with increasing strain when the tensile direction of the specimens is near [001]. On the contrary, when the specimens are elongated in directions near [011], the distribution of slip lines tends to be uniform as the deformation becomes larger. Some considerations are made on the mechanism of work-hardening on the basis of possible interactions between dislocations operating during deformation

Direct Measurements of Densities of Nickel-rich Nickel-Manganese Alloys

The present short note reports the density data measured at room temperature on face-centered cubic nickel-rich Ni-Mn alloys. The specimens were cylindrical rods, about 2mm in diameter and about 140mm long, prepared from electrolytic nickel and electrolytic manganese. The nominal manganese compositions were 6.0, 11.0, 17.0, 22.0 and 27.0 weight percent. The density measurements were made, by using the weighing-in water method, at room temperature (13~14℃) after quenching from 600℃. The results of the measurements show that the density of nickel decreases linearly and rapidly with increasing addition of manganese. The density values calculated from the data of lattice constants of Ni-Mn specimens quenched from 1000℃, as measured by Koster and Rauscher, are in good agreement with the measured data within the limits of experimental error