Diffusion Coefficient Of Copper Research Articles

Ni-Cu合金中のNi<SUP>63</SUP>およびCu<SUP>64</SUP>の拡散

The self-diffusion coefficients of nickel and copper in nickel-copper alloys containing 0 to 100%Cu have been measured with a usual lathe sectioning technique. Polycrystalline specimens having 1 to 4 mm grain size were used. Measurements were carried out at the high temperature range near the melting point of each alloy. In this alloy system, copper atom diffuses more rapidly than nickel atom, and for each composition the ratio of diffusion coefficient of copper to that of nickel is from 2.5 to 6 over the temperature range examined. Diffusion rates of both elements increase with increasing copper contents. The frequency factors for nickel self-diffusion are determined to be 1.9, 35, 17, 0.063 and 1.7 cm2/sec, and the activation energies are 68.0, 74.9, 66.8, 49.7 and 55.3 kcal/mol in alloys containing 0,13.0, 45.4, 78.5 and 100 at% copper, respectively. For copper self-diffusion in respective alloys, the frequency factors are 0.57, 1.5, 2.3, 1.9 and 0.33 cm2/sec, and the activation energies are 61.7, 63.0, 60.3, 55.3 and 48.2 kcal/mol.

Diffusion of Copper in Polycrystalline Silver Selenide

The diffusion of copper in polycrystalline Ag2Se was determined from measurement of the rate of change of the resistivity profile of a partially copper-plated ingot of the semiconductor material. The copper concentration profile that was determined from the resistivity profile, was found to agree very satisfactorily with a theoretical concentration curve computed from a normalized complementary error function. The room temperature diffusion coefficient of copper in Ag2Se was computed from these data and was found to be 4.7×10−8 cm2 sec−1.

Observations of precipitation in thin foils of aluminium +4% copper alloy

Abstract A high temperature specimen stage has been used to study precipitation in thin foils of Al +4% Cu alloy directly in the electron microscope. Precipitates a few hundred Angstroms in size am observed to form in a few minutes at temperatures ∼250° to 300°c. This initial precipitation has been identified by electron diffraction as the θ′ phase, and is found to occur in e well-defined single orientation with respect to the matrix. The orientation observed is consistent with one of those of θ′ formed in bulk material. The growth at higher temperatures of larger θ precipitates at the expense of the θ′ precipitates has also been studied. The results show that precipitation in thin foils Mars from that in bulk material due to the fact thee the surfaces act as preferential nucleation sites. Most of the precipitates in the thin foils appear to be at the surfaces. In aged bulk material preferential precipitation occurs on helical dislocations formed from screw dislocations by vacancy climb. The precipitates are observed to go into solution at ∼500°c. Measurement of the rate of dissolution by ciné techniques has enabled an estimate of the diffusion coefficient of copper in aluminium to be made. Other observations include the formation of regions denuded of small precipitates near grain boundaries and large precipitates, and the growth and dissolution of precipitates under a fluctuating temperature.

A study of solute diffusion in liquid tin

The diffusion of aluminum, zinc, silver, copper and nickel in liquid tin has been investigated by the capillary-reservoir technique in a temperature range from about 240°C to 480°C. All of the solutes investigated were present in dilute solutions ranging from 0.2 to 0.7 wt.%. The solutes were chosen so as to cover a range of relative partial molal enthalpies from large positive values to large negative values. On the basis of the self-diffusion of tin, it is found that the ratios of D solute to D self are 4.70, 1.90, 1.57, 1.15 and 1.10, respectively for aluminum, zinc, silver, copper and nickel within ± 15 or 20 per cent error. Diffusion coefficients of copper and nickel can be considered to be identical with that of tin within experimental error. The Stokes-Einstein and Eyring equations which consider only the factor of atom size, do not predict accurately the relative order of diffusion coefficients amongst the solutes. They do, however, predict the order of magnitude of the diffusion constant. On the basis of fluctuation theory, it is expected that those solutes which have a large positive relative partial molal enthalpy diffuse considerably faster than those solutes which have a large negative relative partial molal enthalpy since there is a much higher probability of significant density fluctuations occurring in the vicinity of the solute atoms in the former case. The data appear to be in agreement with this conclusion. Unfortunately no quantitative comparison is feasible at the present time because of the lack of potential energy versus distance data for solute-solvent neighbors in solution. It is further proposed that in dilute solutions, the diffusion coefficient of a solute approaches that of the solvent if the solute has a zero or large negative relative partial molal enthalpy in the solvent.

The effect of pressure upon void formation in diffusion couples

Sandwiches of copper and nickel have been diffused under various hydrostatic pressures. This reduces the number of voids and above a critical pressure there are no voids. Similarly, voids previously formed by an anneal in vacuo are eliminated by applying pressure during a subsequent heat treatment, but the critical pressure is greater than that necessary to prevent them forming. It is concluded that the vacancy supersaturation is about 1 per cent and that the voids nucleate heterogeneously upon nuclei (about 10 −5 cm in size) which are included in the weld between the two metals. There is no evidence of an alteration in the diffusion coefficient of copper into nickel with the pressures used.