Takao Kino

Deviations form Matthiessen's Rule in Dilute Aluminum Alloys

The electrical resistivity of dilute alloys of aluminum with Mg, Si, Cu, Zn and Ag as solute, respectively, has been measured together with the resistivity of pure aluminum from 4.2 to 300 K as a function of the solute concentration (0.001∼1 at%), to determine the deviation Δ from Matthiessens rule. At intermediate temperatures, the humps have been observed in the curves of Δ/ρ 0 (ρ 0 : residual resistivity) versus temperature. The hump moves toward lower temperature and becomes more sharp and higher as the solute content decreases. These behaviors can be explained in terms of the anisotropy of the nonequilibrium electron distribution function. At lower temperatures, Δ does not follow a well defined T n law and it is attributed to simultaneous scattering by at least two processes. At high temperatures above about 100 K, Δ increases or decreases linearly with temperature.

A New Low-Temperature Dislocation-Relaxation Peak in Aluminum

Amplitude-independent internal friction measurement is made on a zone-refined aluminum single crystal between 2–240 K by a composite oscillator method. In the lightly deformed state \(({\lesssim}10^{-4})\), a new relaxation peak is clearly found at 11 K. The activation energy of this peak is derived to be about 0.01 eV by assuming the attack frequency f 0 =10 10 s -1 , and if the peak is due to the kink pair formation of the dislocation on the Peierls potential valley, the Peierls stress is estimated to be about 10 -5 µ (µ: shear modulus), which does not conflict with the yield stress of low-temperature plastic deformation measurements.

Deviations from Matthiessen's Rule of the Electrical Resistivity of Dislocations in Aluminum

The electrical resistivities have been measured in temperature range from 4.2 K to 300 K on both deformed and quenched aluminum, and the deviations from Matthiessens rule have been observed in both the resistivity of dislocations and of the faulted loops formed by quenched-in vacancies. The deviations show comparatively similar behavior as the whole, but in detail show somewhat different profile. The results were compared with data published by the other investigators. It is concluded that the origin of the deviation for the dislocation resistivity comes from the anisotropy in scattering mechanism. Furthermore the specific electrical resistivity of dislocation and stacking fault in aluminum were estimated as 1.2×10 -19 ohm-cm 3 and 3.7×10 -13 ohm-cm 2 , respectively.

Migration Energy of Mono-Vacancy in Aluminum at High Temperature

A vacancy generation kinetics from dislocations has been studied by a pulse-heating method and residual resistance measurement on zone refiend aluminum. From the generation curve of vacancies, the migration energy of mono-vacancy, E m , was determined as 0.66±0.05 eV in the temperature range from 310 to 400°C. Furthermore, it was concluded that the temperature dependence of E m is small in aluminum.

Orientation Dependence of Flaking of Ion Irradiated Aluminum Single Crystals

Surface erosion on mono- and poly-crystalline aluminum, irradiated with 300-500 keV He+ or Ne+ ions at room temperature along the axial or off-axial directions, has been examined by SEM and TEM. The critical fluence at which flaking appears on the surface increased according to the order of the poly-crystalline sample, mono-crystals with surface normals of [111], [100] and [110]. On the contrary, flaking over multiple layers first appeared on a (110) surface. Results of skin-thickness measurements and microstructure observations suggest that flaking is basically caused by the coalescence of small bubbles which are created in a layer close to the projected ion range. The orientation dependence of the flaking was interpreted in terms of a difference in the depth profile of the bubble distribution associated with channelled ions. Some discussions are made concerning blisterling.

Thermomigration of Scandium in Aluminum

The redistribution of scandium in polycrystalline A1-0.04 at ppm Sc dilute alloy which was annealed under a temperature gradient was investigated by means of the neutron activation analysis. The remarkable result is that the concentration of scandium increased at both the hot and the cold sides of specimen. Such a distribution is caused by a movement of scandium toward the both ends through the specimen. The movement of scandium toward the cold end is explained qualitatively in terms of the scandium flow associated with vacancy flow. It is pointed out that such an induced solute flow plays an important role on the thermomigration in substitutional alloys, and that the vacancy distribution under a temperature gradient should be investigated quantitatively to establish a well understanding of thermomigration in substitutional alloys.

Vacancy Source in Nearly Perfect Crystals

Vacancy generation process in nearly perfect aluminum single crystals was investigated by X-ray diffraction topography technique of Lang. A lot of small black dots were observed in the topograph taken after the temperature rise from room temperature to 200°C, and these dots are confirmed to be small interstitial type dislocation loops. It was concluded that the thermal generation process of vacancies in nearly perfect crystals consists of the following two steps. Small interstitial clusters are formed in the perfect lattice first, and then these grow to interstitial type dislocation loops emitting vacancies into lattice.

Deviations from Matthiessen's Rule on the Surface Scattering in Aluminum

The electrical resistivity of aluminum strips has been measured for various thickness (0.02-1.48 mm) and over a temperature (1.5-60 K). The results show the deviation from Matthiessens rule (DMR) Δ s ( T ) on the surface scattering. The surface reflection parameter p is determined to be nearly zero from the temperature at which the maximum of Δ s ( T ) appears. The DMR Δ s ( T ) shows different profiles from DMR on the impurity scattering. The comparison of the present data with Husstad-Lothe theory shows that the effect of small angle electron-phonon scattering is small on the surface scattering. The present experiments can be explained by a term of the surface resistivity ρ s ( T ) (=ρ s (0)+ Δ s ( T )) deduced from Fuchs-Sondheimer theory. It is thus concluded that DMR Δ s ( T ) mainly arises from the spatial variation of the electron distribution function.

A New Method for the Determination of the Bulk Electrical Resistivity and the Bulk Mean Free Path in Metals

A new method to obtain the surface resistivity ρ s in one platelike sample is developed. The resistivity ρ s is given as the difference between the high-field magnetoresistivity in the Sondheimer geometry and that in the MacDonald-Sarginson geometry. The bulk resistivity ρ b is obtained from the apparent zero-field resistivity ρ 0 subtracted by ρ s . Using these values of ρ 0 and ρ b , the bulk mean free path l b is calculated according to the Fuchs-Sondheimer theory of the size effect for a thin film. This method has been applied to samples of zone-refined aluminium. For these samples a value of 0.18±0.01 fΩm 2 has been obtained at 4.2 K for the specific surface resistivity. The product of ρ b and l b is estimated to be 0.80±0.04 and 0.84±0.03 fΩm 2 for the single-crystal and the polycrystalline samples, respectively.

Dislocation-Solute Interaction Studied by Amplitude-Dependent Internal Friction in Al-0.01 at%Si Alloy

Amplitude-dependent internal friction was measured at the temperature range of 2–15 K on Al-0.01 at%Si single crystal and 99.999%Al. From the temperature dependence of applied strain under a constant internal friction, the binding energy U 0 between a dislocation and a pinning obstacle was determined as 0.5–0.8 eV in Al-0.01 at%Si and 0.05–0.06 eV in 99.999%Al. The value of U 0 for Al-0.01 at%Si is very large and cannot be explained as a dislocation–a single solute atom interaction. Silicon atoms in Al probably precipitated into clusters because of the very low solubility, and dislocations were thought to be pinned strongly by Si clusters.