Showing papers on "Annealing (metallurgy) published in 1976"

Vacancy defect mobilities and binding energies obtained from annealing studies. [Review, migration energies, formation heat]

Abstract: A review is given of our current knowledge of the mobilities and binding energies of vacancy defects in a number of FCC and BCC metals (i.e., Cu, Ag, Au, Pt, W and Mo) as derived from annealing experiments after quenching and/or irradiation. It is concluded that vacancy defects are retained by quenching in all of these metals, and that Stage III annealing after irradiation occurs by the migration of vacancy type defects. The annealing process after quenching is potentially complex and in Au and Al may involve at least mono-, di-, and tri-vacancies. Annealing in Stage III after irradiation can also be complex and involve at least mono- and divacancies. Great difficulties are therefore involved in extracting reliable defect properties from such experiments. The monovacancy migration energies derived from annealing experiments after both quenching and irradiation are in reasonably good agreement for most of the metals. Also, the sum of the monovacancy migration energy and the formation energy is in reasonable agreement with the activation energy for self-diffusion due to monovacancies. The temperature of Stage III annealing after irradiation is generally lower than the temperature of the annealing after quenching because of a smaller number of defect jumps to annihilationmore » in the former case. The limited available information about divacancies in the FCC metals indicates that they possess binding energies in the range 0.1 to 0.3 eV and migrate more easily than monovacancies. The even more limited information about trivacancies in Au and Al indicates that they are at least as mobile as divacancies and are rather loosely bound. No comparable information about divacancies and trivacancies in the BCC metals is yet available.« less

Electron‐irradiation‐induced divacancy in lightly doped silicon

Abstract: Two electron traps—A2 and A3—produced in n‐type silicon by 1.5‐MeV‐electron irradiation are characterized by deep level transient spectroscopy. Activation energies of trapped majority carriers and capture cross sections for majority carriers at these levels are reported. From their production rates and annealing behaviors, they have been identified as different charge states of the same defect. Detailed annealing studies show that their annealing kinetics is first order with an activation energy of 1.47 eV. It is suggested that the defect is the divacancy and that dissociation is the likely process for its removal in these devices.

Interdiffusion between GaAs and AlAs

Abstract: Epitaxial structures composed of thin layers of GaAs and AlAs were grown by the technique of molecular beam epitaxy. The interdiffusion coefficient was measured by Auger‐electron profiling after annealing the structures under As‐rich conditions over the temperature range 850–1100 °C. This coefficient was found to be extremely small, in the 10−18 cm2/sec region at the lower temperatures. It also depends on the alloy composition, decreasing with an increase in Al. Such dependence becomes stronger at higher temperatures, giving rise to activation energies of 4.3 and 3.6 eV in the limits of GaAs and AlAs, respectively.

Crack Healing and Strengthening of Thermally Shocked Alumina

Abstract: Crack healing and strengthening of thermally shocked alumina are related to pore evolution in the microstructure during annealing Grain growth is not necessary for either an increase or a decrease in strength following heat treatment

Precipitation and trapping of hydrogen in copper

Abstract: Copper samples containing dissolved hydrogen up to a few hundred atomic p.p.m. have been prepared by quenching from equilibrium at higher temperatures. Measurements of the annealing of the residual resistivity up to 150°C show that the hydrogen precipitates around room temperature and the precipitation is controlled by diffusion of the hydrogen. Microscope investigations confirm this result and show that the hydrogen precipitates as bubbles which form preferentially at grain boundaries and dislocations. The number of bubbles formed was typically 109 cm−3. Consideration of bubble growth leads to the conclusion that the increase in bubble volume during growth is due to plastic deformation of the lattice near the bubble and that the precipitation is a diffusion limited process, conclusions which are confirmed by the experimental evidence. A model for the trapping of the dissolved hydrogen at impurities is also discussed. It is shown that by quenching quickly to low enough temperatures the hydrogen i...

Formation, structure, and orientation of gold silicide on gold surfaces

Abstract: The formation of gold silicide on Au films evaporated onto Si(111) surfaces is studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). Surface condition, film thickness, deposition temperature, annealing temperature, and heating rate during annealing are varied. Several oriented crystalline silicide layers are observed.

Recombination‐enhanced annealing of the E1 and E2 defect levels in 1‐MeV‐electron–irradiated n‐GaAs

Abstract: Recombination‐enhanced annealing of the E1 (Ec−0.08 eV) and E2 (Ec−0.18 eV) defect levels in n‐GaAs has been studied by deep‐level transient spectroscopy (DLTS). The defects are controllably introduced at room temperature by irradiation with 1‐MeV electrons. Thermal annealing at reverse and zero bias yields an activation energy of ΔE=1.75±0.17 eV and shows that charge‐state effects are not operative. Recombination annealing produces an enhancement of several orders of magnitude in the annealing rate and an activation energy of 0.98±0.10 eV. The annealing reaction obeys first‐order kinetics and does not saturate with injection currents up to 350 A/cm2. The relationship of this data to earlier observations of recombination‐enhanced annealing (motion) in GaAs and GaP is discussed as well as the possible implications for injection‐mode device degradation.

Observation of athermal defect annealing in GaP

Abstract: Capacitance spectroscopy studies of lattice defects intentionally introduced into GaP diodes by 1‐MeV electron irradiation have shown a very large enhancement in the defect annealing rate under conditions of e‐h recombination. Six deep levels are observed and all exhibit recombination enhanced annealing. Four of the levels anneal athermally during recombination having the same rate at 100 K as at 300 K. Comparisons of the thermal annealing activation energy and the energy released during hole capture indicate that the observed athermal enhancement is a natural consequence of the wide GaP band gap.

Formation kinetics of CrSi2 films on Si substrates with and without interposed Pd2Si layer

Abstract: We have measured the kinetic rate of formation of CrSi2 using 2.0-MeV 4He + backscattering spectrometry. CrSi2 was formed on single-crystal 100- and 111-oriented Si and on Pd2Si grown on 100 Si. For both Si-Cr and Si-Pd2Si-Cr samples the rate of growth of CrSi2 is linear in time with an activation energy of 1.7±0.1 eV and a value of 0.7 A/sec at 450°C. For all annealing temperatures, the growth becomes nonlinear at long annealing times. The nonlinearity is attributed to a contaminant, probably oxygen. On Pd2Si, CrSi2 starts to form at about 400°C, while on Si, CrSi2 formation is observed at 450°C and above. The difference in formation temperatures is due to contamination at the Si-Cr interface, quite probably a thin oxide layer. The growth rate of CrSi2 in the Si-Pd2Si-Cr samples is independent of the thickness of Pd2Si.

Effects of deformation and annealing on magnetic amorphous alloys

Abstract: Effects of deformation and annealing on the magnetic anisotropy, stress relief rate, and fracture strain of amorphous alloys Fe 80 B 20 and Fe 40 Ni 40 P 14 B 6 were studied. It was found that deformation increases the anisotropy and the stress relief rate, while annealing reduces them. The results are shown to be consistent with the existence of structural defects in the amorphous alloys.

Structural and low-temperature magnetic studies on compounds Sm2Fe17 with aluminium substitution for iron☆

Abstract: Aluminium substitution for iron in Sm2Fe17 results in stabilization of the Th2Zn17 structure. Compounds are homogeneous from x = 0.20 to x = 0.50 in Sm0.105Fe0.895−xAlx when annealed at 800 °C. In this structure, Fe and Al are statistically distributed on 6(c), 9(d), 18(f) and 18(h) sites. Materials with x = 0–0.15 are composed of the Th2Zn17 type and Fe. The magnetic hardness at cryogenic temperatures increases rapidly around a composition with x = 0.30. A value of coercive force, Hc = 15 kOe, is obtained both on bulk and powder material with x = 0.50 at 4.2 K. This low-temperature magnetic hardness appears to be connected with the presence of highly energetic domain walls. The mechanism of demagnetization involves domain nucleation, in contrast with Sm0.167Co0.833−xAlx where demagnetization is predominantly governed by domain wall pinning.

Cold-rolling and annealing of amorphous ribbons

Abstract: Cold-rolling of Fe 40 Ni 40 P 14 B 6 amorphous alloy ribbon results in a large increase in coercive force and a large decrease in magnetization in low fields. It is suggested that these changes are the result of both the sliplike structures developed by the rolling and the strain-magnetostriction induced anisotropy. On annealing the rolled ribbon to temperatures below the crystallization temperature, the magnetic properties recover to the values obtained on annealing as-cast ribbon, but higher temperatures are required. The rolled ribbon showed no evidence for structural changes in high resolution electron micrographs; x-ray and electron diffraction patterns showed no change in the width or position of the diffuse rings; and the glass and crystallization temperatures remained unchanged. However, small angle x-ray scattering showed a decrease in intensity at small angles, and stress relief measurements showed a small increase in the stress-relief rate. Both as-cast and rolled ribbons when annealed even to within a few degrees of the start of crystallization showed no change in the width or position of the diffraction peaks, and no change in the heat of crystallization, glass transition, or crystallization temperature. However, on annealing, the small angle x-ray scattering increased, and stress-relief rate decreased. The change in small angle scattering is qualitatively interpreted as being due to the removal of scattering nuclei on rolling and their development during annealing. The stress relief results are discussed in terms of changes in short-range atomic order.

Growth of polymer crystals during annealing

Abstract: Observations by transmission electron microscopy are reported on the processes involved in polymer crystal growth during annealing. The observations suggest that crystal growth occurs by two processes. One process involves the melting of those regions of the crystals in which the melting point is lower than the annealing temperature. The polymer melt due to the melting process gradually becomes incorporated into the unmolten crystals, resulting in crystal growth. The alternative process is solid-state crystal growth by the migration of the amorphous region between crystallites.

Ti and V layers retard interaction between Al films and polycrystalline Si

Abstract: Fine-grained polycrystalline Si (poly Si) in contact with Al films recrystallizes at temperatures well below the Si-Al eutectic (577 °C). We show that this interaction can be deferred or suppressed by placing a buffer layer of Ti or V between the Al film and the poly Si. During annealing, Ti or V form TiAl3 or Val3 at the buffer-layer–Al-film interface, but do not react with the poly Si so that the integrity of the poly Si is preserved as long as some unreacted Ti or V remains. The reaction between the Ti or V layer and the Al film is transport limited ([proportional]t^1/2) and characterized by the diffusion constants 1.5×10^15 exp(–1.8eV/kT) A^2/sec or 8.4×10^12 exp(–1.7eV/kT) A^2/sec, respectively.

Capless annealing of ion‐implanted GaAs

Abstract: A method is reported for capless annealing of ion‐implanted GaAs which gives electrical activation of Se‐implanted wafers nearly identical to that obtained with sputtered silicon nitride caps. State‐of‐the‐art performance has been realized from Schottky‐gate FET’s fabricated from this material.

Transport properties of very pure copper and silver below 8.5K

Abstract: Measurements of the thermal and electrical conductivity and thermopower of very pure copper and silver have been made between 1 and 8.5K. The copper samples have been distilled in graphite crucibles to reduce the concentration of magnetic impurities to less than 1 part in 109, which is an order of magnitude improvement over the standard technique of annealing in oxygen. A maximum has been found in the thermopower of silver around 6K and is attributed to phonon drag which is dominated by the scattering of phonons by electrons in the 'neck' region of the Fermi surface. The maximum is suppressed in less pure samples and in samples containing lattice defects. The characteristic thermopower of dislocations in silver is estimated to be between 11 T and 19 T nV K-1 depending on crystal orientation. A similar phonon drag contribution to the thermopower of copper is obscured by a large, negative Kondo term arising from the residual magnetic impurities.

Superconductivity and phase stability of Nb3Ge

Abstract: The A-15 phase of chemically vapor-deposited Nb3Ge has been investigated by annealing techniques in the temperature range 700–1450°C and by irradiation with high-energy neutrons (E>1 MeV). By x-ray diffraction analysis the samples were found to contain about 55 wt % of the A-15 phase, 35 wt % of tetragonal Nb5Ge3, and minor amounts of NbO2, NbO, and hexagonal Nb5Ge3. The superconducting transition temperatureTc and lattice parametera0 of the A-15 phase have been measured as a function of annealing temperature and neutron irradiation.Tc for the unirradiated sample remained above 19 K for long-term anneals in the temperature range 700–1000°C but decreased rapidly above 1000°C, reaching a limiting value of about 6 K at 1250°C, compared to the as-deposited value of about 20 K. The decrease inTc was accompanied by an increase ina0 and an increase in the amount of tetragonal Nb5Ge3 to about 50 wt %. The observed decrease inTc was irreversible in that subsequent annealing at 1100°C did not result in any increase inTc or decrease ina0. Large depressions inTc were also observed in a sample irradiated with high-energy neutrons. The sample having aTc of about 21 K was found to exhibit no superconductivity to 1.5 K after exposure to a fluence of ∼5×1019 n/cm2. An increase ina0 was also found as a function of neutron irradiation. However, in this case the effects were reversible in thatTc anda0 of the irradiated sample could be restored to close to their original values by annealing in the 800–900°C range. The results are discussed in terms of stability of the A-15 phase and the effect of site-exchange disorder and composition on the superconducting properties and lattice parameters. It is concluded that the stoichiometric composition is metastable and upon annealing transforms to a stable, Nb-rich A-15 phase containing about 83 at % Nb with aTc of ∼6 K accompanied by precipitation of tetragonal Nb5Ge3.

The effect of direct electric current on precipitation in a bulk Al-4 wt % Cu alloy

Abstract: The effect of the stress of direct electric current on precipitation in a quenched Al-4.15 wt % Cu alloy is investigated by measurement of the change in electrical resistance of a bulk specimen as a function of current density up to about 3000 A cm−2 at a given annealing time. A similar effect of d.c. stress is observed at 50, 75 and 100‡ C. For a lower current density, a constant or slightly increasing resistance is observed, while for a current density higher than a critical value, the resistance decreases with an increase in density. On the assumption that the temperature increase of a specimen due to the Joule heating is proportional to the square of the current density, it is concluded that there exists some effect of d.c. stress per se to prevent the precipitation reaction, aside from the effect of the temperature increase due to the Joule heating, and it is suggested that this retarding effect is related to the sweeping out of quenched-in excess vacancies into grain boundaries by electromigration.

Annealing effect on the microstructure of poly(vinyl chloride)

Abstract: The effect of annealing on the microstructure of commercial grade poly(vinyl chloride) was investigated by calorimetric, X-ray and viscoelastic measurements. The degree of crystallinity increases with increasing annealing temperature from above the glass transition temperature up to 130°C, at which point the degree of crystallinity takes on a maximum value. Also, the crystal melting temperature increases with increasing annealing temperature. Thermal analysis and X-ray study suggest that the crystallite of poly (vinyl chloride) decomposes by thermal degradation when annealed, above 170°C. The isothermal crystallization process is analyzed using Avrami's equation employing the degree of crystallinity as a function of annealing time at various annealing temperatures. The crystallization rate has a maximum value at around 140°C. It is expected that the crystalline texture grows in the shape of a lineal-like habit, judging from the magnitude of Avrami's constant and from a study of the X-ray intensity distribution. The αf-transition was observed to occur at temperatures 5 to 10°C lower than the crystalline melting temperatures for annealed specimens of poly(vinyl chloride) using a dynamic spring analysis. The αf-transition may be attributed to thermal molecular motions with a long time scale, resulting from the cross-link points introduced by the small crystallites.

Kinetics of interstitialcy diffusion in electron-irradiated Cu-Ni alloys

Abstract: The residual electrical resistivity of an alloy Cu+58.7 at% Ni has been measured during 3 MeV electron irradiation at temperatures between 120K and 570K as well as during isothermal and isochronal annealing up to 570K. During isothermal irradiation the resistivity decreases due to decomposition of the alloy. For the temperature range 120-370K the observed decomposition kinetics are consistently interpreted by interstitialcy diffusion and a diffusion path of the three-dimensionally-migrating interstitials which is terminated by trapping and recombination reactions. The interstitials trapped during low-temperature irradiation are detrapped during 350K annealing. The reaction parameters obtained by a fit of the model calculations to the data amount to the same order of magnitude as the parameters found for pure Cu and dilute Cu alloys.

The mechanisms of anneal hardening in Cu-Al alloys

Abstract: The anneal hardening behavior of a Cu-16 at. pct. Al alloy was investigated by tensile testing, measurement of Young’s modulus and electrical resistivity, and electron microscopy. It was shown that three main stages of annealing processes can be distinguished. Stage 1 atT ≤ 150°C is characterized by vacancy annihilation and short-range diffusional processes giving rise to three successive, low maxima in yield and tensile strength. Substages in this temperature range are also evident from resistivity measurements. Stage 2 at 150 ≲ 275°C is essentially associated with solute segregation to dislocations giving rise to the main increase in flow stress. In Stage 3 at 725 ≤T ≤ 350°C recrystallization takes place.