Residual Electrical Resistivity Research Articles

Theory of the residual electrical resistivity of binary actinide alloys

A system of self-consistent equations has been proposed for the coherent potential approximation of the multiband conductivity model for the case of conduction electron scattering from chaotic electric fields of ions of disordered binary alloy components at zero temperature. It has been qualitatively demonstrated that the deviation of the concentration dependence of the residual electrical resistivity of actinide alloys with multiband conductivity from the Nordheim rule is caused by the explicit dependence of the electrical resistivity of the alloy on the magnitude and sign of the real part of the Green’s function at the Fermi level. The derived system of equations for the multiband coherent potential approximation has been used to calculate the concentration dependence of the density of states and the residual electrical resistivity of the alloys of neptunium and plutonium. The results of the calculations have been compared with the available experimental data.

Effect of severe plastic deformation on the electronic properties of the Cu72Au24Ag4 alloy

The electrical, magnetic, and optical properties of the Cu72Au24Ag4 ternary alloy in the ordered and disordered states have been studied by the method of severe torsional plastic deformation under pressure in Bridgman anvils. It has been shown that, as a result of this deformation, the residual electrical resistivity of the alloy increases by approximately 11% and the magnitude of the negative thermopower decreases. The high diamagnetic susceptibility of the alloy has been explained by a significant role of charge carriers with the effective mass considerably smaller than the free-electron mass. The behavior of the optical conductivity has been discussed with due regard for the results of energy-band calculations. The experimental data obtained for the Cu72Au24Ag4 alloy have been compared with the results of similar studies of the Cu3Au binary alloy.

Theoretical investigation of the residual electrical resistivity concentration dependence of transuranium metal alloys

A many-band conductivity model has been derived and applied to analyze the concentration dependence of the electrical residual resistivity (RR) of several actinides based disordered alloys. It was qualitatively shown that equal probabilities of $s\ensuremath{\rightarrow}d$ and $s\ensuremath{\rightarrow}f$ transitions of scattered conductivity electrons lead to the deviations from Nordgeim's rule observed in these alloys. Numerical evaluation of RR of neptunium, plutonium, americium, and curium based alloys was made within the coherent potential approximation (CPA) derived for the many-band conductivity model. Numerical calculations were made using ab initio obtained bcc-Np and fcc-Pu, Am, and Cm densities of states, as the starting point for the iterative CPA procedure. The results of the RR modeling were compared with available experimental data and allow us to conclude that the proposed model offers promising opportunities to investigate RR of similar classes of alloys.

Effects of Room Temperature Heavy-Ion Irradiation on Magnetic and Electrical Properties of a Single Crystalline Iron Thin Film

We investigated the magnetic and electrical properties of a heavy-ion irradiated single crystalline iron film. A high quality Fe (001) film on MgO (001) was fabricated using the molecular beam epitaxy technique. The iron film was treated by 3.2 MeV Ni ion irradiation at room temperature using a tandem accelerator. Although the residual electrical resistivity increased by 0:9 � 10 � 8 � m after ion irradiation, the M-H curves did not change significantly. These results indicate that the formation of small irradiation defects such as sub-nanometer size vacancy clusters has little influence on magnetocrystalline anisotropy and the magnetization process of iron. [doi:10.2320/matertrans.MAW200907]

Probing thickness-dependent dislocation storage in freestanding Cu films using residual electrical resistivity

Residual electrical resistivity measurement is employed to study dislocation storage under tensile loading of freestanding electroplated Cu films (1–5μm grain size and 2–50μm thickness). The results indicate that the nature of thickness effects (strengthening or weakening) depends on the underlying deformation mechanisms via the average grain size. A threshold grain size of about dg=5μm is identified to distinguish grain size effects in thicker films from those in thinner films. For dg>5μm, diminishing microstructural constraint with reduced thickness weakens the films due to dislocation annihilation near the free surface. For dg<5μm, reduction of film thickness leads to strengthening via grain boundary-source starvation.

Kinetics Parameters of Atomic Migration and Diffuse Scattering of Radiations within the F.C.C.-Ni–Al Alloys

Relaxation of diffuse-scattering intensities of various kinds of waves is a phenomenon of an especial interest since its study enables one to obtain the most detailed information on both the equilibrium short-range order (SRO) and the non-equilibrium SRO, and therefore, it is the most convenient instrument for investigating SRO kinetics. The SRO kinetics is studied by the use of available data of measurements of residual electrical resistivity for substitutional f.c.c.-Ni–Al solid solutions during their isothermal annealing. Within the framework of the first-order and (more realistic) second-order kinetics models, the maximum characteristic relaxation times and equilibrium magnitudes of the residual electrical resistivity for these solid solutions at different annealing (1273–1626 K) and quenching temperatures (≥ 1723 K) are evaluated, and the hypothetical values of similar quantities appropriate for the diffuse scattering of radiations are estimated too.

Non-microscopical methods for characterization of microstructures and properties of UFG metals

Abstract The paper reports on non-microscopical methods which allow for close investigation of ultrafine-grained metals especially of those processed by different techniques of Severe Plastic Deformation. These are as follows: (i) X-ray Bragg profile analysis, (ii) electrical residual resistivity, (iii) annealing calorimetry, and (iv) positron annihilation spectroscopy. The advantage of these methods lies in their integration/averaging over a certain sample volume so that they are often much closer to macroscopic physical properties than methods of microscopy; furthermore, the values of quantities obtained are more reliable because of strictly objective rules of determination. Typical quantities being relevant for ultra-fine grained materials are (a) grain size and grain size distribution, (b) long range internal stresses, (c) dislocation densities, and (d) concentration of vacancies and/or vacancy agglomerates. While quantities (a) and (b) are important for all classes of ultra-fine grained materials, those of (c) and (d) particularly occur with nanomaterials processed by severe plastic deformation also being responsible for their specific features such as ductility and the presence of non-equilibrium phases.

Correlation between mechanical damage behavior and electrical resistance change in CFRP composites as a health monitoring sensor

Correlation between mechanical damage behavior and the change of electrical resistance for CFRP (carbon fiber reinforced plastic) composites was experimentally investigated and simulated using neural network approach. Electrical resistance was measured under simple tension and repeated loading–unloading, and observed to remain after removing load. The value of residual electrical resistance was dependent on the maximum strain applied in the past. The failure processes of two types of CFRP were characterized under loading. Consequently, it was revealed that the behaviors of electrical resistance change of two specimens had a close relation with their failure mechanisms. Moreover, the relationship between the applied strain corresponding to the damage, and the electrical resistance change until the ultimate failure of composite was simulated using neural network. There was a fairly good agreement between the simulation and experimental results. It is suggested that this detecting technique is applicable to the health-monitoring of composite structures.

Matrix Crack Detection of CFRP Laminates in Cryogenic Temperature Using Electrical Resistance Change Method

For a cryogenic fuel tank of a next generation rocket, a Carbon Fiber Reinforced Plastic (CFRP) laminated composite tank is one of the key technologies. For the fuel tank made from the laminated composites, matrix cracks are significant problems that cause leak of the fuel. In the present paper, electrical resistance change method is adopted to monitor the matrix cracking of the CFRP laminate. Previous studies show that tension load in fiber direction causes electrical resistance increase due to the piezoresistivity of the carbon fibers, and fiber breakages also cause the electrical resistance increase of the CFRP laminates. In order to distinguish the electrical resistance changes due to matrix cracking from those due to the piezoresistivity and the fiber breakages, residual electrical resistance change under the complete unloading condition is employed in the present study. Experimental investigations were performed using cross-ply laminates in cryogenic temperature. As a result, it can be revealed that the residual electrical resistance change is a useful indicator for matrix crack monitoring of the cross-ply CFRP laminates.

Vacancy production during plastic deformation in copper determined by in situ X-ray diffraction

The discrepancy between stored energies measured by calorimetry and residual electrical resistivity, and calculated from dislocation densities measured either by transmission electron microscopy or X-ray line broadening in copper, is interpreted in terms of vacancies produced during plastic deformation. The presence of excess vacancies is further substantiated by concomitant measurements of residual electrical resistivity. Diffuse X-ray scattering is correlated with excess vacancy concentrations in the grain interior and grain boundary regions in polycrystalline copper. Grain boundaries are suggested to be the main sites for vacancy storage probably in the form of voids or free volume. This would support the concept that grain boundaries are distorted regions with considerable fractions of free volume. The vacancy storage rate is shown to depend on the mode of deformation.

The concentration metamagnetic transition in Tm1−x TbxCo2 compounds

The Tm1−x TbxCo2 (0 ≤ x ≤ 1) system was studied by measuring the magnetic susceptibility, electrical resistance, and neutron diffraction. In the compounds with 0 < x ≤ 0.15, an inhomogeneous magnetic state characterized by the existence of large regions (up to 100 A in size) with short-range ferrimagnetic order was found to occur. The maximum of the residual electrical resistance observed in the compound with x = 0.1 at the magnetic ordering temperature was established to be due to the scattering of conduction electrons by localized spin fluctuations associated with f-d exchange fluctuations caused by the substitution of terbium for thulium. The increase in the terbium concentration to x ≥ 0.15 leads to a sharp increase in the Co sublattice magnetization and the establishment of a long-range ferromagnetic order, which indicates a concentration metamagnetic transition in the band subsystem.

Matrix crack detection of CFRP using electrical resistance change with integrated surface probes

For the cryogenic tanks of next generation reusable launching vehicles, the laminated composite tank is one of the key technologies. For composite fuel tanks made from laminated carbon fibre reinforced polymers (CFRP), matrix cracking is a significant problem that may cause fuel leakage. In the present paper, an electrical resistance change method with integrated probes on a single side of the surface of a CFRP composite structure is adopted to detect the matrix cracking of the laminated composites. For a fuel tank structure made of a CFRP laminate, we cannot mount electrical probes on the end of structure or on the inside of the tank structure. We have to mount all probes only on the outside surface. The present method used finite element analyses (FEA) to search for the best placement of probes for matrix crack detection using a rectangular plate. To simulate the tank structure, all probes are placed on a single surface of the CFRP plate specimen. The present study adopted a four-probe method for measuring the electrical resistance change. The FEA revealed that the electrical resistance increases linearly with increase in the number of matrix cracks inside of the probes. By means of thin CFRP cross-ply laminate, the method was experimentally confirmed to be useful for detecting matrix crack density between the probes. Residual electrical resistance at the completely unloaded condition increased with increase in matrix crack density. Measurements of the residual electrical resistance enabled us to detect the matrix crack density without loading.

Kinetics of L10 Long-Range Ordering in FePd Thin Film

AbstractDue to their high magnetic anisotropy, L10-ordered intermetallics when ferromagnetic bear a potential as high density magnetic recording materials. In their case the c-axis of the tetragonally distorted structure is the easy axis of magnetization. We present preliminary results on the details of ordering kinetics on FePd films (thickness 100 nm) epitaxially co-deposited on MgO substrates. From the observation of so called ‘order-order relaxations’ during isothermal small-step anneals monitored by residual electrical resistivity (REST) measurement we determine an ordering activation energy of about 2.4 eV, which is somewhat below the value of 2.7 eV obtained in a previous investigation on bulk material.

Anomalous concentration dependence of residual electrical resistivity in Fe-Cr alloys

Experimental data on the residual electrical resistivity in concentrated Fe-Cr alloys point to strong deviation from Nordheim-like behavior: resistivity stays nearly constant over $10--60\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Cr concentration range. These data are compared to the results of calculations conducted in a two-band coherent potential approach for a ferromagnetic phase. The anomalous behavior of residual resistivity turns out to be a result of two opposite tendencies: increasing with chromium concentration scattering probability is compensated by concurrent reduction in density of states at the Fermi level.

Detection of Matrix Cracking of CFRP Using Electrical Resistance Changes

stract. Effect of thickness of 90o-plies on a method for detection of matrix cracking of CFRP inates is investigated here. Three types of cross-ply CFRP laminates are adopted here: [0/90/0]T, 90]S and [0/902]T. Tensile cyclical loading tests are performed with increasing the maximum load plied cyclic loading. Electrical resistance changes are measured using silver paste electrodes by ans of a four-probe method. As a result, it was revealed that residual electrical resistance under mplete unloaded condition was not applicable for an indicator of creation of matrix cracking in the ck cross-ply laminates. For the thick cross-ply laminates, tensile residual stress in the middle o-plies is smaller than that of the thin laminates. This small tensile residual stress causes crack sure when the specimen is completely unloaded. When the cross-ply laminates are reloaded, the ctrical resistance increased rapidly with the small increase of load due to the opening of matrix cks. From this result, we proposed a new method for detections of matrix cracking using the rapid rease of electrical resistance in small reloading.

Defect based micromechanical modelling and simulation of nanoSPD CP-Ti in post-deformation

The paper concerns the dislocation based modelling and simulation of room temperature post-compression hardening after warm equal channel angular processing (ECAP) of grade 2 CP-Ti. The post-deformation behaviour is well simulated by the Zehetbauer model which already succeeded in describing the evolution of strength and structural parameters during conventional and severe plastic deformation. The model yields excellent fits to the experimental post-compression hardening characteristics (stages II, III and IV) as well as to the evolution of dislocation density. The physical quantities involved in the resulting fit parameters take reasonable values. In particular, the calculations yield a satisfactory agreement with the experimentally gained data of the cell size and the concentration of lattice vacancies, as it is shown by comparisons with X-ray profile investigations and measurements of residual electrical resistivity. As a difference to previous modelling of large strain hardening, edge dislocation density saturates at smaller strains than screw density which seems to be a consequence of the much finer initial grain structure and of the elevated ECAP deformation temperature.

Lattice defect investigation of ECAP-Cu by means of X-ray line profile analysis, calorimetry and electrical resistometry

Cu rods have been deformed by equal channel angular pressing (ECAP) up to shear strains γ ≈ 5 while applying various deformation paths A, B C and C. X-ray Bragg profile analyses (XPA), differential scanning calorimetry (DSC) as well as residual electrical resistivity (RER) measurements have been performed, in order to detect the densities of various deformation induced lattice defects and/or their arrangements. The results have been analysed in terms of annealing of deformation induced dislocations and vacancies (vacancy agglomerates). Compared to conventional cold work procedures, deformation by ECAP achieves a strongly enhanced concentration of vacancy type defects.

Residual electrical resistivity in dilute nonmagnetic alloys of transition metals

The residual electrical resistivity in dilute alloys of nonmagnetic transition metals is calculated within Mott's two-band model without using the electron-impurity interaction as a small parameter. The linear dependence between reduced residual electrical resistivity and square of modulus of the nondiagonal element of the scattering T matrix is found for row transition metals dilute alloys. Experimental and calculation results are compared.

Effects of deposition parameters on residual stresses, hardness and electrical resistivity of nanoscale twinned 330 stainless steel thin films

We have explored the influence of sputtering parameters on the structural, mechanical, and electrical properties of nanoscale twinned 330 stainless steel thin films. As the residual stress in the film is changed from tensile to compressive by varying the growth conditions, the nanoscale twinned structure, the average columnar grain size and texture of the film show little or no change. Hardness of the film in compression reaches 7GPa, compared to about 5.5GPa in films with high residual tension, and an order of magnitude higher than that of bulk 330 stainless steel. Molecular dynamics simulations indicate that twin boundaries pose a strong barrier to glide dislocation transmission under applied in-plane biaxial loading, consistent with the GPa level strengths measured in these films. The increase in the room temperature electrical resistivity of these films, compared to bulk 330 stainless steel, is found to be small, indicating that nanoscale twinned structures may provide the best combination of high mechanical strengths and high electrical conductivity.

Kinetics of short-range order formation in the ternary Au–Ag–Pd alloys

The kinetics of formation and destruction of short-range order (SRO) were investigated in the ternary Au 40Ag 40Pd 20 alloy using the residual resistometry. The changes in residual electrical resistivity were measured during down-quenching (DQ) and up-quenching (UQ) 1 1 In up-quenching (UQ) experiments T q < T a and in down-quenching (DQ) experiments T q > T a. T q and T a are the quenching and annealing temperatures. cross-over annealing experiments. The quantitative analysis of the resistivity data showed that three kinetic processes are involved in the short-range ordering and disordering process. The results agree qualitatively with the Yu–Lucke model for the kinetics of SRO in the fcc ternary alloys. However, the kinetic parameters derived from the cross-over experiments during ordering and disordering was found to be complicated and different from the unidirectional isothermal kinetics. These differences suggest that the reaction paths during ordering and disordering are different.