Electrical Resistivity due to Short-range Order in Ni_2Cr

Residual electrical resistivity of Ni2Cr alloy due to short-range order (SRO) has been calculated at a temperature which is above the transition temperature, Tc, from long-range order to shortrange order. The atomic form factors for Ni and Cr are calculated in the pseudopotential formalism. We discuss the result of our calculations indicating a decrease in the value of residual electrical resistivity due to SRO in the light of experimental resistivity studies done on Ni72.5Cr27.5 and Ni65Cr35.     

Thermophysical Properties of Undercooled Liquid Cu–Ni Alloys

Experimental data for the surface tension, density, and electrical resistivity of undercooled liquid Cu–Ni alloys of different compositions and at different temperatures are presented. The experiments were performed in facilities that combine the containerless positioning method of electromagnetic levitation with contactless measurement techniques. Although Cu–Ni alloys are rather simple from a chemical point of view, the data for density, surface tension, and electrical resistivity unveil the occurrence of short-range atomic order processes in the melt. For the density this manifests in a composition-dependent excess volume, for the surface tension in smaller values due to an increased surface segregation, and for the electrical resistivity in a deviation from the linear temperature dependence at low temperatures.     

A study of spinodal decomposition in Ni-30 at% Cu and Cu-46 at% Ni-4 at% Fe alloys using electrical resistivity measurements

The spinodal decomposition in Ni 30 at% Cu and Cu-46 at% Ni-4 at% Fe alloys has been investigated using electrical resistivity measurements. The electrical resistivity results, for ageing temperatures between 423 and 823 K, were analysed from the equation of change of electrical resistivity for spinodal decomposition in binary alloys proposed by Kolometz and Smirnov, together with the classical spinodal decomposition theory of Cahn. This analysis enabled us to obtain a plot of the amplification factor, R(), as a function of temperature. From this plot, the coherent spinodal temperatures for Ni-30 at% Cu and Cu-46 at% Ni-4 at% Fe alloys were found at 590 and 790 K, respectively, and are in good agreement with experimental and theoretical values reported by other authors.     

Ordering and recovery processes in the Ni/Fe system near Ni3Fe

The ordering and recovery processes in 72/28 and 80/20 at.% Ni/Fe alloys have been investigated. A parameter related to the thermal scattering contribution of the electrical resistivity was used to follow the establishment of atomic order. It was found that the initial condition of the alloys — quenched or cold-worked — has little influence on the ordering kinetics at high temperatures. However, it greatly influences the recovery behaviour, as indicated by the residual resistivity measurements. Strain-ageing effects reported earlier are interpreted in the light of the present findings. Results are also discussed on the basis of existing theories for atomic ordering.     

Calculations of electrical resistivity for Al–Cu and Al–Mg–Si alloys

Abstract

A system for thermodynamical calculations (Thermo-Calc) was used to derive the solid solubility of the alloying elements in commercial Al–Cu and Al–Mg–Si alloys. The electrical resistivity was then calculated using a model developed by the authors based on the Matthiessen's rule. The calculated resistivity agreed with the observed resistivity within ±2.5 nΩ m for the Al–Mg–Si alloys and ±2 nΩ m for the Al–Cu alloys, except for Al–Mg–Si alloys containing boron or chromium and Al–Cu alloys with special compositions.     

Thermo-electrical characterization of Sn–Zn alloys

The thermo-electrical properties of Sn–Zn alloys have been investigated for four different compositions. The SEM micrographs and EDX analysis of the samples have been obtained. The electrical resistivity measurements were performed by using four-point probe technique in the temperature range 300 K–575 K. The resistivity of samples increases linearly with temperature and the electrical conductivity is inversely proportional to temperature. The electrical current preferentially flows through the pure Sn phase having lower resistivity in the matrix. Also, thermal conductivity of samples has been measured by using the radial heat flow method. It has been found that the thermal conductivity decreases with the increasing temperature and composition of Sn. The results were consistent with available experimental results of other studies. Finally, the temperature coefficient of electrical resistivity and the temperature coefficient of thermal conductivity have been determined, which were independent from the composition of Sn and Zn.     

Temperature-Induced Reversible Change of Electrical Resistivity in Sn–Bi Melts

Using a dc four-probe method, the temperature dependence of the electrical resistivity of liquid Sn–Bi alloys has been investigated. The results show that there are clear turning points both on heating and cooling for several experimental cycles. Since the electrical resistivity is one of the physical properties sensitive to structure, the unusual change of the resistivity indicates that liquid–liquid transitions (LLT) probably take place in Sn–Bi melts. Moreover, the transitions are reversible. Compared with the experimental results for pure Sn and Bi, it is assumed that Sn plays an important role in the reversible liquid–liquid transitions.     

Influence of Rare-Earth Elements on ElectricalProperties of Pd

The influence of RE (RE = La, Ce. Pr. Nd, Sm, Eu, Gd. Tb. Dy, Er, Yb) additives with dilute concentrations on the electrical properties of Pd has been studied. All RE elements increase the specific resistivity (ρ) and decrease the resistance temperature coefficient (α) of Pd. and (ρ.α) Pd-RE ls equal to (ρ· α)Pd.The RE elements before Gd reduce the thermo-emf of Pd on Cu. other heavy RE enhance the thermo-emf.The experimental data of normalized Pd-0.1 at.-%RE alloys indicate that the effect of light RE additives on the specific resistivity of Pd is larger than that of heavy RE and Ce. Eu and Yb show anomalous strong effect. The valence and atomic size are main factors influencing the electrical properties.     

Comparison of experimental, calculated and observed values for electrical and thermal conductivity of aluminium alloys

A model has been developed for calculating the electrical resistivity of commercial aluminium alloys from composition and heat treatments using the Matthiessen rule. The model is based on the approximation that the solubility of the alloying elements in heat treated alloys is equivalent to the equilibrium solubility at a higher temperature. These temperatures were determined from heat treatment data. The resistivity of a wide range of commercial alloys was calculated using the model, showing an agreement with most observed resistivity values of within 3 nΩm, except for alloys with special composition characteristics. According to the model, magnesium and manganese are important contributors to the resistivity for all main groups of alloys. In heat treated alloys the contribution of precipitates is 6–17% of the total resistivity. Thermal conductivity was calculated for alloys given in the literature using the Wiedeman–Franz law and the calculated resistivity. The calculated thermal conductivity agreed with the experimental values for the AlMg-alloys, but it was lower than the experimental values for pure aluminium and the AlCu-alloys in the annealed condition. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of Rapid Solidification on Structure and Properties of Some Lead-Free Solder Alloys

Four of the binary lead-free solder alloys of compositions Sn-0.5Cu, Sn-3.5Ag, Sn-5Sb and Sn-9Zn, were rapidly solidified by melt-spinning technique as a technique for producing new alloy compositions. The results show that rapid solidification causes formation of some intermetallic compounds such as Ag₃Sn and Cu₆Sn₅ in the two alloys Sn-3.5Ag and Sn-0.5Cu, which cannot be formed at the equilibrium phase diagram at these compositions; contraction in the volume of the unit cell of the tetragonal Sn; reduction of the melting points due to the decrease in the crystalline size of Sn matrix; and formation of some vacancies in the resulting alloys, which cause reduction of the measured density than that calculated by mixture rule and increase the electrical resistivity.     

Characteristics of ultrahigh electrical conductivity for Cu–Sn alloys

Abstract

The resistivity and mechanical properties of Cu–Sn alloys with different compositions were explored by casting, normalising, cold work and subsequent annealing treatment. Results indicated that the Cu–Sn alloy had the characteristics of ultrahigh electrical conductivity, when the Sn content was ～0·5 wt-%. Note that the resistivity of the as cast and annealed Cu–0·5 wt-%Sn alloys is 1·55 and 1·26 μΩ cm respectively.     

Electrical resistivity measurements on binary Al-15 wt-%In alloy

Abstract

A rotational contactless inductive measurement technique has been used to determine the electrical resistivity of an Al-15In (wt-%) binary alloy over a wide range of temperatures. It is shown that the electrical resistivity depends on the distribution of the indium within the aluminium matrix. The results can be considered as a first attempt to detect the onset of the sedimentation process, which occurs in alloys of this type, by measuring the electrical conductivity of immiscible alloys.     

Electrical resistivity of thin bismuth films

The thickness dependence of electrical resistivity of thin bismuth films deposited on to glass substrates has been studied in the temperature range 77 to 350 K. The structural studies show that films are polycrystalline with grain size increasing with thickness. The electrical resistivity decreases with increasing temperature. This type of temperature dependence of electrical resistivity arises due to the competition between the temperature dependences of carrier density and carrier mobility, the temperature coefficients of which are opposite in sign. The electrical properties of bismuth films are greatly affected by the presence of surface states. The size effect theory of Pichard and colleagues (PTT) has been modified to investigate the variation of charge carrier concentration with thickness. The experimental results on electrical resistivity are found to be consistent with the predictions of this modified three-dimensional model (PTT). The value of specularity parameter,p, is about 0.43 and it exhibits no temperature dependence. The experimental results on grain-boundary resistivity agree fairly well with the theoretical variations. The values of transmission coefficient,t, are determined from the experimental data.     

Thermal conductivity and electrical resistivity of Nb---Ti alloys at low temperatures

Results are presented of an experimental study of the thermal conductivity, electrical resistivity, critical temperature and upper critical field of solid solutions of Nb---Ti with 22–80 at % Nb in cold-worked and recrystallized states. The temperature range of the measurements is 4.2 to 30 K. The correlation between the critical parameters and the behaviour of the thermal conductivity and electrical resistivity has been found. The residual resistivity increases and the thermal conductivity decreases with increasing the Ti concentration.     

2.22 The deposition by evaporation of CuAl alloy films

3hin films of CuAl alloys from pure Cu to pure Al were deposited by vacuum evaporation from single alloyed sources heated by electron bombardment. Information about the composition of the films obtained by electron microprobe was completed by lattice parameter measurements and structure information obtained by X-ray diffraction, as well as electrical resistivity measurements. The anticipated compositions of the films were calculated from the vapor pressures of the pure elements and thermodynamic data for liquid CuAl alloys at 1373 K. The agreement between the calculated values and the experimentally observed compositions is good only for alloys with low Al concentrations: less than 20 at.% Al in the source material. For the remainder of the CuAl system with more than 20 at.% Al in the source, the films were found to contain less Al than was calculated. This discrepancy might be due to too high values for the reported vapor pressures of Al.     

Short-range order in some alloys of the Ge-As-Te semiconducting glassy system by X-ray diffraction

A study of short-range order in amorphous semiconducting alloys of the Ge-As-Te system has been carried out by X-ray diffraction. The different hypotheses on germanium coordination have been taken into account, following the different criteria cited in the literature for binary Ge-Te alloys. The result of this study shows the possibility of structural units based on tetra-or tricoordinated germanium atoms, which bonded together give way to short-range order in these alloys. !t has also been found that, for these alloys, germanium dicoordination is not compatible with the data obtained experimentally.     

Magnetotransport in Pd-Rich PdFe Alloys

The transport properties of Pd-rich PdFe alloys are investigated as a function of the atomic and magnetic orders on the L2₁ (Cu₃Au) lattice. The residual resistivity, anisotropic magnetoresistance (AMR), and anomalous Hall effect are calculated from first-principles as a function of the atomic order. The calculations are based on the relativistic generalization of the transport Kubo–Greenwood approach as formulated in the framework of the first principles TB-LMTO method and Coherent Potential Approximation (CPA). The effect of the thermal magnetic disorder on the resistivity and AMR has been also studied using the disordered local moment approach based on the CPA. Our results are in an overall good agreement with available experimental data.     

Effect of different copper fillers on the electrical resistivity of conductive adhesives

The effects of different copper fillers with different morphology and particle size have been studied in terms of electrical resistivity and thermal stability on the electrically conductive adhesives. The copper fillers used in this study were prepared by wet chemical reduction, electrolytic and gas atomization method, respectively. The as cured ECAs filled with different type of Cu fillers showed significant difference in electrical resistivity. Cu filler with smaller particle size showed higher packing density and larger surface area, which would enhance formation of conductive channels and increased conductive network in the ECAs, leading to a lower electrical resistivity. In addition, thermal stability of the ECAs were investigated under high temperature exposure at 125 °C and high humidity aging at 85 °C/85% RH for 1,000 h. Results showed that ECAs with Cu fillers of relatively small particle size and rough particle surface have excellent thermal stability due to enhanced adhesion and contact area between Cu fillers and the polymer matrix. A very low resistivity at an order of magnitude of 10^?4 ?? cm could be maintained for these ECAs after 1,000 h at 125 and 85 °C/85% RH.     

Effect of prior cold work on mechanical properties, electrical conductivity and microstructure of aged Cu-Ti alloys

The mechanical properties, electrical conductivity and microstructure of Cu-2.7wt%Ti and Cu-5.4wt%Ti alloys have been studied in different conditions employing hardness and resistivity measurements, tensile tests and optical, scanning and transmission electron microscopy. Ageing of undeformed as well as cold worked alloys raises their hardness, strength and electrical conductivity. The hardness increased from 120 VHN for solution treated Cu-2.7Ti to 455 VHN for ST + cold worked + peak aged Cu-5.4Ti alloy. While tensile stength increased from 430 to 1450 MPa, the ductility (elongation) decreased from 36 to 1.5%. A maximum conductivity of 25% International Annealed Copper Standard (IACS) for Cu-2.7Ti and 14.5% IACS for Cu-5.4Ti is obtained with the present treatments. Peak strength was obtained when the solution treated alloys are aged at 450°C for 16 hours due to precipitation of ordered, metastable and coherent , Cu₄Ti phase having body centred tetragonal (bct) structure. While mechanical properties of Cu-Ti alloys are comparable, electrical conductivity is less than that of commercial Cu-Be-Co alloys.     

Experimental investigation of the electrical resistivity of some molten bismuth-tin binary alloys and of the thermal conductivity of bismuth,tin, and a eutectic bismuth-tin alloy

The paper gives the results of an experimental determination of the electrical resistivity of some binary alloys of bismuth and tin, as well as the thermal conductivity and electrical resistivity of bismuth, tin, and a eutectic bismuth-tin alloy. It describes the design of the apparatus used for measuring the electrical resistivity by the contact method. The error of the measurements was ±1.5% for the electrical resistivity and ±10% for the thermal conductivity.Translated from Inzhenerno-Fizieheskii Zhurnal, Vol. 26, No. 1, pp. 46–50, January, 1974.