A study of the thermotransport behavior of cobalt in thorium

The heat of transport,Q*, for cobalt in α-thorium was determined by a combination of single-phase, steady-state and two-phase, nonsteady-state techniques. The heat of transport,Q*, is temperature-dependent, decreasing from +20 kj/mol at 1125 K to s-60 kJ/mol at 1460 K. This is best described by a linear relation,Q* = 214 s-0.24T kJ/mol. The observed temperature dependence ofQ* can perhaps be attributed to the electronic contribution to the heat of transport, as postulated in Hehenkamp’s model. Formerly Associate Professor, Metallurgical Engineering Department, South Dakota School of Mines and Technology.     

Mn-C interaction in Fe-C-Mn steels: Study by thermoelectric power and internal friction

A new methodology based on the coupling of thermoelectric power (TEP) and internal-friction (IF) measurements was developed to evaluate quantitatively the two populations of carbon atoms present in the solid solution of Fe-C-Mn steels: one is constituted of single carbon atoms and the other of carbon atoms in interaction with manganese atoms. From the evaluation of the concentration of these two populations at different temperatures and assuming that the distribution of the carbon atoms in the iron matrix can be described by the Maxwell-Boltzmann statistical theory, the binding energy of the Mn-C dipoles could be assessed. Finally, this methodology was used to follow the precipitation kinetics of the two populations of carbon atoms during an isothermal treatment.     

Anomalously fast diffusion in the Fe-Zn System

The rate of diffusion of Zn into Fe in solid Fe/Zn diffusion couples is found to be two to four orders of magnitude greater than would be predicted by lattice diffusion. The penetration depth varies markedly from sample to sample. It is achieved primarily in an initial transient, and then stops even though a steep concentration gradient persists in the ferrite. The maximum concentration of Zn in the ferrite surface layer often exceeds the published solubility of the first intermetallic phase, gamma, in ferrite. The initial Zn penetration seems to occur by DIGM. The mechanism for continued penetration is less clear. The variability in percent Zn in the ferrite, and possibly the variation in penetration depth, must stem from the delay in the nucleation of the most iron rich intermetallic phase, gamma. He was a Visiting Scholar at OSU at the time this work was done.     

Superplasticity and internal friction of nickel-base superalloy

Temperature spectrums of internal friction, in other words, specific points have been investigated and discussed in the wide temperature range from room temperature to melting point for nickel-base superalloy in order to measure a grain boundary peak which is associated with superplasticity. Large boundary peaks of Pα and Pβ have been observed at the temperature range from 1173 to 1423 K. The activation energy of former Pα peak has been calculated to be 428–434 kJ·mol⁻¹ at the temperatures of 1213–1283 K, and this peak seems due to the grain boundary sliding which can be accomodated by the motion of lattice or local dislocations. The activation energy of later Pβ peak has been calculated to be 341–379 kJ·mol⁻¹ at the temperatures of 1333–1373 K, and this peak seems due to the grain boundary sliding which can be accommodated by the diffusive flux of nickel or the other elements. Furthermore, it has been examined whether non-destructive tests would be possible by using internal friction experiments instead of tension tests for superplasticity.     

Determination of total nitrogen in solution in Fe-Mn-N alloys by internal friction

The internal friction of 22 Fe-Mn-N alloys with 0 to 2 pct Mh and 23 to 170 ppm N was measured at 1 Hz and temperatures between 220 and 525 K. The Snoek spectra were resolved into sets of Debye peaks of heightp _i. This resolution was accomplished with five independent sets of Debye parameters (number of peaks, activation energies, and peak temperatures), which were obtained from the literature. The five resulting sets ofp _i were correlated with the chemically determined nitrogen (Nch) by multiple regression analyses. A high degree of correlation was obtained with all five sets of parameters. For ease of calculation, we recommend resolving the spectra into the three Debye peaks determined by Couper and Kennedy. The regression equation obtained by applying these parameters was N_ch (ppm) = 11.9 + 2.33p ₁ + 0.83p ₂ + 0.75p ₃ with a standard error of estimate of 6.8 ppm. The first term on the right-hand side was interpreted as nitrogen precipitated by traces of refractory metals. The sum of the last three terms on the right was interpreted as the total nitrogen in solution. A procedure for determining total nitrogen in solution in Fe-Mn-N alloys is recommended and described in detail.     

Characterization of medium- and low-temperature carbides in a low-carbon steel by internal friction

The formation of carbides during the aging of a quenched steel with mass contents of 0.04% carbon was investigated by means of internal friction by measuring the carbon Snoek peak height. The aging was carried out at different temperatures ranging from 40 to 350°C so that different types of carbides were formed. Low-temperature carbides develop after aging below 100°C. The Johnson-Mehl equation is applied to evaluate the kinetics of precipitation and re-dissolution of the different carbides. The solubility of carbon in ferrite is influenced by the pre-existing carbides, which is, in part, the reason for the variation of thermodynamic data in previous work.     

Hydrogen-solute interaction in nickel-based dilute alloys studied by internal friction technique

The internal friction has been measured for dilute NiM alloys (M = Ti, Si, Co, Cr, Cu, Fe, Mn, Pd, V) containing hydrogen over a temperature range from 60 to 400 K. An internal friction peak due to the interaction between substitutional solute atoms and interstitial hydrogen atoms (SI peak, SIP) is observed around 160K except for the NiCo alloy. Detailed measurements have been performed on the NiTi alloy; the binding energy for the TiH pair; evaluated from the solute and hydrogen concentration dependence of the peak height, is smaller than 2 kJ/mol. The relaxation strength of the SIP is comparable to the Snoek peaks in b.c.c. metals, and is closely related to the dilatation of the host Ni lattice by alloying. Below 120 K, a background internal friction is observed in specimens which show the SIP. The background is explained in terms of the magnetomechanical damping accompanied by the hydrogen reorientation around solute atoms under a static stress due to magnetostriction.     

Reaction mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust

Abstract

The experiments in this paper were performed to research the mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust. The reduction potential of zinc during cementation was determined to investigate the morphology of products. Residues after the cementation process from zinc sulphate solution were analyzed by SEM and EPMA to investigate the morphology of products. Different temperature will cause different structure of particles. The reaction mechanism of cobalt removal by zinc dust is thought to be as follows: first, the Co2+ forms Co–Zn alloy with zinc particles, and the reaction reaches equilibrium quickly; second, the Co–Zn alloy continues reacting to Co with Co2+, which is the control process of the whole reaction.     

The fast diffusion of Au in Pb

A treatment of the phenomenon of fast diffusion in lead is presented. The model used is based upon the fast diffusion of free solute interstitials. The very large negative enhancement coefficients found in the Pb-(Au, Ag) systems is explained by the formation of first and second order clusters of vacancies and substitutional solute atoms.     

Determination of diffusion coefficients by measurements of electrical resistivity

The evolution of the electrical resistivity of ribbons and wires in which a transient diffusion process occurs is calculated. From these results the optimal experimental procedure is inferred for determining the diffusion coefficient without the use of correction procedures.     

Solute interaction and internal friction spectra in solid solutions

On purpose to verify the applicability of models of solute atoms interaction in b.c.c. metals internal friction due to “diffusion under stress” of interstitials was calculated. For interstitial-interstitial (i-i) and interstitial-substitutional (i-s) interaction a strain-induced interaction model with additional Coulomb repulsion in (i-i) case and additional “chemical” interaction in (i-s) case was used. Calculations were made with concrete values of interaction energies. It was shown that the Snoek peak's shape in Ta-O was very sensitive to the (i-i) potential details. Computer simulation showed that the broadening of the maximum in experiments is caused by appearance of short-range order due to long-range (i-i) interaction and the Coulomb repulsion is important up to the third coordination shell. The used (i-i) interaction model is applicable to Ta-O solid solution. In the (i-s) case the influence of s-atoms on the Snoek relaxation due to O and N in V, Nb and Ta and N and C in α-Fe was calculated by using Koiwa's theory. On the whole there is a good agreement between experimental and calculated spectra for Nb, V, Ta and no agreement for α-Fe. Thus the used (i-s) interaction model is only applicable to V, Nb and Ta solutions.     

Amplitude dependence of the internal friction of plasma-sprayed coatings

Conclusions An internal friction study of plasma-sprayed coatings has shown that the application of such coatings substantially changes the ADIF parameters (decreases _cr and increases tan ) of a clad specimen. The effects of the dislocation structure of a basis on the physicomechanical properties of a plasma-sprayed coating applied to it have been established.Translated from Poroshkovaya Metallurgiya, No. 2(206), pp. 30–32, February, 1980.     

Annealing and aging of interstitial C in α-Fe,As measured by internal friction

The diffusion of interstitial C in α-Fe has been studied by the dynamic mechanical relaxation method, and the isothermal aging kinetics of the removal of interstitial C by precipitation from its saturated state has been measured at several temperatures. The height of the Snoek peak is found to decrease according to the relation Q_max ^-1(T,t) = Q_max ^-1(T,t → ∞) + δQ_max ^-1(T) exp {- t/[k₀ exp (E/RT)}], where t is the aging time, k₀ a time constant, and E the activation energy for the precipitation of C atoms. The anelastic relaxation time is independent of the amount of C in α-Fe and varies according to Τ = 3.45 × 10^-15 exp [80.0 (kJ/mol)/RT]. The diffusion coefficient varies according to D = 6.61 × 10^-3 exp [-(80.0/RT) cm² s^-1 over the temperature range 303 to 357 K. The effect of chemical composition on k₀ has been determined and a procedure for determining the constant of proportionality between Q_max ^-1 and the amount of dissolved carbon in steel is described. A concept of accumulated equivalent aging time is introduced and theoretically justified on the bases of time-temperature superposition of aging effects. Calculations and experiments show that a substantial decrease occurs in the C content of steel when it is heated to high temperatures and that this effect alters the shape of the Snoek peak.