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1.
V. V. Skorokhod V. P. Titov M. M. Churakov 《Powder Metallurgy and Metal Ceramics》2005,44(11-12):523-526
Growth kinetics for a layer of W6Co7 at the interfaces tungsten-cobalt and tungsten-melts based on copper and tin containing cobalt at 1200 °C are studied. It is established that rate constant for growth of this layer in the system with participation of tin (kSn) is much greater than in the system with copper (kCu). Dependences are determined for these constants on cobalt activity in the melt (aCo): kCu(m2/sec) = = 1.72 · 10?15(aCo ? 0.221) + 2.99 · 10?14 (aCo ? 0.221)2; kSn(m2/sec) = 1.8 · 10?14 (aCo ? 0.221) + + 9.077 · 10?12 (aCo ? 0.221)3. 相似文献
2.
Annealing of Ni’MZn reaction couples at 400°C for 1–25 h results in the formation of intermetallic layers of the γ- and δ-phases at the interface between nickel and zinc. The width of the homogeneity region for the γ-phase is 73.0–86.0 at. % Zn, while that for the δ-phase is 87.5–89.0 at. % Zn. The chemical formula for the γ-phase is thus NiZn3–6, while that for the δ-phase is NiZn7–8. The γ-phase growth kinetics is described by a parabolic equation x i 2 ’Mx 0 2 =2k1ti (xi and x0 are the thicknesses of the layer at times ti and t0=0, k1 is the growth rate constant): k1=(4.4±0.2)·10’M14 m2/sec. The δ-phase shows a deviation from the parabolic law since its growth rate constant decreases from 9.6·10’M14 m2/sec at t=1 h to 6.9·10’M14 m2/sec at t=25 h. The thickness ratio for the layers in this time interval chages by about 13%. 相似文献
3.
The solubility of copper in lime-saturated and calcium ferrite-saturated liquid iron oxide has been measured at 1300 °C by equilibrating copper-gold alloys with the melts in CO-CO2 atmospheres of oxygen potentials 10?7, 10?8, 10?9, and 10?10 atm. It was found that copper exhibits Henrian behavior in the oxide melts and that the solubility is given by $$wt pct Cu = 17.6a_{CuO_{0.5} } $$ The copper capacity of the melts, 17.6, is approximately one-half of that of silica-saturated iron silicate melts at the same temperature. The results are compared with those of previous studies, and the difference between the solubilities of copper in silica-saturated and lime-saturated melts are discussed in terms of ionic interactions in the melts. 相似文献
4.
V. V. Bogdanov V. I. Kibets L. N. Paritskaya A. A. Puzanova E. P. Sorokina M. I. Chekanov 《Powder Metallurgy and Metal Ceramics》1994,32(11-12):882-886
The effect of low hydrostatic pressures on the growth kinetics of phases in two-layer and multilayer Ni-Al diffusion specimen was studied by x-ray diffractometric, microprobe, optical and electron microscopic methods at temperatures T=0.4–0.6 Tm (Tm=melting temperature of the principal Ni2Al3 phase). Two types of specimens were investigated: massive two-layer, consisting of ∽3·10?3 m thick sheets of nickel and aluminum presintered together, and finely dispersed multilayered, consisting of alternating layers of 10?7-5·10?7 m thick nickel and aluminum sheets. It was found that theapplication of pressure accelerated the formation of the Ni2Al3 and NiAl phases in both types of diffusion specimens. This effect is attributed to the action of pressure in preventing the formation of diffusional porosity at phase interfaces, and improving diffusional contact between adjoining layers. 相似文献
5.
A new procedure for measuring the thermal diffusivity of non-metallic melts at high temperatures has been developed, and a measuring set up based on thermography and the use of a CO2 laser has been constructed. The working efficiency of the measuring procedure, together with the accuracy and reproducibility of the measured values have been checked by measurements on synthetic slags. The thermal diffusivities of synthetic slag (38% CaO – 38% SiO2 – 19% Al2O3 – 5% Fe2CO3) at temperatures from 1648 to 1740 K lie between 2.6×10?7 and 3.0×10?7 m2s?1. The mean deviation of measured values is about ±6%. The advantages of this new procedure are compared with usual laser flash methods and possible error sources are discussed. 相似文献
6.
V. V. Skorokhod V. P. Titov Z. V. Sichkar' M. M. Churakov 《Powder Metallurgy and Metal Ceramics》2005,44(5-6):271-275
We have studied the solubility at 1200°C of tungsten in Cu - Co melts and the growth kinetics of a W6Co7 layer at the tungsten — melt interface. We have established the composition of the melt in the three-phase equilibrium tungsten
— W6Co7 — melt: 0.0195 Co, 4.8 · 10−5 W, the rest is Cu (in atomic fractions). In the studied composition range for the melt, the solubility of tungsten is described
well by the expression: lgXW = −7.117 + 25.7 · XCo
1/2 − 41.06 · XCo, where XW and XCo are the atomic fractions of the corresponding elements in the melt. We have determined the correlation between the growth
rate for a layer of tungsten-containing phase at the tungsten — melt interface and the thermodynamic characteristics of the
melt.
__________
Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 81–86, May–June, 2005. 相似文献
7.
N. P. Gorbachuk V. R. Sidorko S. N. Kirienko I. M. Obushenko 《Powder Metallurgy and Metal Ceramics》2008,47(7-8):451-456
The heat capacity and enthalpy of HoGe is investigated for the first time over a temperature range between 51.62 and 2096 K. The values of heat capacity, entropy, reduced Gibbs energy (J · mole?1 × × K?1), and enthalpy (J · mole?1) are determined at 298.15 K: C °P(T) = 49.63 ± 0.20; S °(T) = 89.1 ± 0.7; Φ′(T) = 50.9 ± 0.8; H °(T) ? H °(0 K) = 11391 ± 57. Temperature dependences of enthalpy (J · mole?1) for holmium monogermanide are determined as follows: H °(T) ? H °(298.15 K) = 8.474 × × 10?3 · T2 + 47.13 · T + 226747 · T?1 ? 15565 and H °(T) ? H °(298.15 K) = 88.91 · T ? 26507, for 298.15–1765 K and 1951–2096 K, respectively. The enthalpy and entropy of HoGe melting are calculated: Tm = 1765 ± 35 K, ΔHm = 36.3 ± 2.9 kJ · mole?1, ΔSm = 20.5 ± 1.6 J · mole?1 · K?1. 相似文献
8.
《粉末冶金学》2013,56(29):55-66
AbstractA study of the sintering behaviour of iron compacts containing additions of tin up to 1 wt.-% has been made. A tensile strength of 234 MN/m2 (34 x 103 lbf/in2) has been achieved with an optimum tin addition of 0·5 wt.-%, sintering being carried out for 10 min at 1100°C (1373 K) in a reactive halide atmosphere. Combination of the two ‘activating’ techniques (addition of tin and sintering in a reactive atmosphere) permits current properties to be attained at considerably lower sintering temperatures or sintered densities, and is much more effective than when they are applied individually. A tensile strength of 165·3 MN/m2 (24 x 103lbf/in2), achieved by sintering at 1200°C (1473 K) for 10 min with an addition of 0·5 wt.-% tin can be obtained by reactive-sintering the same composition at 900°C (1173 K) for 10 min. Alternatively, the density of the part can be reduced from 6·7 to 6·2 g/cm3 with no loss of strength or elongation. Tin in excess of 0·5 wt.-% causes deterioration in properties under the sintering conditions studied and a reason for this is cited. The improvements in properties are lost also if admixed lubricant is used in the compactionprocess. 相似文献
9.
The diffusivity and solubility of oxygen in liquid tin and solid silver in the temperature range of about 750° to 950°C (1023
to 1223 K) and the diffusivity of oxygen in solid nickel at 1393°C (1666 K) were determined using the electrochemical cell
arrangement of cylindrical geometry: Liquid or Solid Metal + O (dissolved) | ZrO2 + (3 to 4%)CaO | Pt, air The diffusivity and solubility of oxygen in liquid tin are given by:D
O(Sn) = 9.9 × 10−4 exp(−6300/RT) cm2/s (9.9 × 10−8 exp − 6300/RT m2/s) andN
O
S
(Sn) = 1.3 × 105 exp(−30,000/RT) at. pct The diffusivity and solubility of oxygen in solid silver follow the relations:D
O(Ag) = 4.9 × 10−3 exp (−11,600/RT) cm2/s ( 4.9 × 10−7 exp − 11,600/RT m2/s) andN
O
S
(Ag) = 7.2 exp (−11,500/RT) at. pct The experimental value for the preexponential in the expression forD
O(Ag) is lower than the value calculated according to Zener’s theory of interstitial diffusion by a factor of 11. The diffusivity
of oxygen in solid nickel at 1393°C (1666 K) was found to be 1.3 × 10−6 cm2/s (1.3 × 10−10 m2/s).
Formerly Graduate Student, Department
Formerly Graduate Student, Department
Formerly Graduate Student, Department
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10.
The distribution of silver between molten metal and matte was determined at temperatures of 1150 to 1250°C. The partition coefficient (KAg-ratio of wt pct silver in matte to wt pct silver in metal) was 0.46 and was essentially independent of silver concentration, temperature, iron content and oxygen and SO2 partial pressures over the ranges studied. Only the presence of nickel significantly affected KAg, causing it to rise from 0.46 to 1.16 within the region of liquid immiscibility. Outside this region all silver was intimately associated with chalcocite, rather than the heazel woodite or metallics, formed during solidification. Studies on other precious metals showed that KAu=8×10?3, KPd=6×10?3 and KPt=4×10?4 in the Cu?S system at 1200°C. Application of these results to actual operations is discussed, as is the chemical behavior of precious metals during matte smelting. 相似文献
11.
Experiments have shown that the sorption of uranium from strong phosphoric acid solutions onto four D2EHPA/TOPO based ion exchange resins and one aminophosphonic acid resin is particle diffusion controlled in the uranium concentration range 42–780 μM. Interdiffusion coefficients of about 10?12 m2s?1 were obtained for D2EHPA/TOPO resins and 0.14 × 10?12 m2s?1 with the aminophosphonic acid exchanger at 20°C in 3 M H3PO4. Both homogeneous particle diffusion, based on Fick's Law, and the ash layer diffusion model fitted the kinetic measurements. 相似文献
12.
The diffusion of liquid copper in iron from a notched surface has been studied by metallographic, microanalysis, and sessile drop techniques. The diffusivity of copper was found to be 0.59×10?6 sq cm per sec at 1100°C and 0.97×10?6 sq cm per sec at 1130°C. The diffusion factor,D 0 was 0.78×10?3 sq cm per sec and the activation energy 19.0 kcal per mole. The predominant mode of copper penetration was along grain boundaries, but when larger volumes of copper at the iron surface were used, surface diffusion increased and grain boundary penetration remained constant. The most frequently occurring dihedral angle for liquid copper was 34 deg at 1100° and 1130°C. The liquid copper/austenite interfacial energy was found to be 444 ergs per sq cm between 1100 and 1130°C. From sessile drop measurements, the contact angle was determined as 35 deg at 1100°C and 28 deg at 1130°C, from which values the respective interfacial energies were calculated to be 387 ergs per sq cm and 301 ergs per sq cm. 相似文献
13.
Measurements of oxygen activity in molten copper, Cu-Sn, and Cu-Ag alloys at 1135°C have been made utilizing the solid-state electrolyte technique. The activity coefficient of oxygen in molten copper at low oxygen levels (<0.1 pet) was found to be 0.12. The interaction parameters of silver and tin on oxygen were found to be ε O Ag = 4.52 and ε O Sn =-10.5. Comparison of experimental data with solution models revealed that the behavior of oxygen in Cu-O-Ag alloys is in accordance with predictions of Alcock and Richardson’s quasichemical model when a coordination number between 1 and 4 is assumed, depending on the silver and oxygen content. Furthermore, agreement with Belton’s quasichemical model based on the assumption of Ag-O dipoles serves to strengthen the evidence for the existence of Ag-O species in solution. The behavior of oxygen in the Cu-O-Sn system also shows better agreement with the quasichemical model than with the random model, with low coordination numbers favored in dilute tin solutions, increasing to larger values in Cu-60 Sn solutions. 相似文献
14.
V. M. Denisov L. T. Antonova Yu. S. Talashmanova 《Russian Journal of Non-Ferrous Metals》2007,48(6):430-432
Kinetic regularities of oxidation of Sn-Ag liquid alloys at T = 1273 K in air are investigated. The so-called catastrophic oxidation of melts containing 70 and 80 at % Ag is found. X-ray powder diffraction analysis of the scale forming on all Sn-Ag alloys, including such oxidation, showed that it consists of SnO2 and silver metal. It is found that, in the range T = 1234–1303 K, the limiting wetting angle of liquid silver on tin dioxide is invariable and amounts to 72.4° ± 4.3°. 相似文献
15.
The tracer diffusivities of Ca45 and Fe59 in silica saturated FeO-CaO-SiO2 melts have been determined, at 1600 °C, using the porous frit technique. The frits were made by sintering silica powder into quartz tubing. Diffusion occurred in a semi-infinite medium from a plane source of doped material with the same chemical composition. The tortuosity of each frit was determined by calibration with a resistivity cell. The diffusivity values obtained are about 2.0 · 10?6 cm2 s?1 for Ca45 and 1.0 · 10?5 cm2 s?1 for Fe59. The higher diffusivity of iron is possibly due to the different bonding by oxygen which causes a transition state in the jumps of Fe2+ ions from one site to the next. 相似文献
16.
《粉末冶金学》2013,56(23):193-208
AbstractThe creep behaviour of high-density silicon carbide has been examined under four-point transverse bending in air at temperatures from 1000 to 1300°C. Stresses in the range 0·207 GN m?2 (30 000 Ib in?2) to 0·496 GN m?2 (72000 lb in?2) were applied.In tests lasting up to 3·6 Msec (1000 h) the creep strain (?p) increased with time (t) as ?p = Atk where k was between 0·2 and 0·5. The dependence of A on stress (σ) and absolute temperature (T) was found to be with n between 1 and 2 and Q~230 kJ mole?1 (55 kcal mole?1).These results are compared with estimates of creep in SiC obtained by extrapolation of steady-state creep data from higher temperatures. 相似文献
17.
《钢铁冶炼》2013,40(4):323-330
AbstractThe rate of MgAl2O4 spinel inclusion dissolution in CaO–SiO2–Al2O3 slags at 1504°C has been measured using a laser scanning confocal microscope. It was found that the mechanism of spinel inclusion dissolution was at least in part controlled by mass transfer in the slag phase for the slag compositions used. Evidence in support of this finding was that the calculated diffusion coefficient was inversely proportional to the slag viscosity and that the diffusion coefficients were in reasonable agreement with those obtained in a separate study on alumina dissolution. The diffusion coefficients obtained were in the range of 0·76–2·2 × 10?10 m2 s?1. 相似文献
18.
《Acta Metallurgica》1982,30(8):1597-1604
The influence of oxygen on surface tension of liquid silver has been studied in a pressure range from 10−20bar to 1 bar at 1100°C. For pure silver a surface tension σ = 890 [mNm−1] at its melting point and a surface entropy of −0.16 [mN m−1 K−1] have been found. Oxygen is highly surface active and segregates to the free liquid surface up to high partial pressures (−80 mbar). At this pressure a surface excess concentration Γ = 18.8·10−6 [molem−2] has been calculated, which corresponds to a surface area per oxygen atom A = 8.8·10−2 [nm2atom−1], suggesting the presence of a Ag-O surface structure with the oxygen ions protruded towards the gas phase. Measurements made on vitreous carbon, alumina and silica supports demonstrated that the lower thermodynamic stability and faster decomposition kinetics of the latter oxide prevent accurate measurements below about 10−10 mbar. At the same time, in the high pO2 range, silicates form on the surface of liquid silver resting on silica supports. 相似文献
19.
The enthalpy of the La3Se4 and La2Se3 boundary compositions of the La3?xSe4 phase (0 ≤ x ≤ 1/3) at temperatures from 370 to 2260 K is studied calorimetrically. The values obtained are used and the equilibria of the La-Se system are analyzed to establish, for the first time, the temperature-concentration relationships for the thermodynamic properties of La3?xSe4 selenides in the homogeneity region at 298 K ≤ T ≤ 2123 K. The enthalpy function (J/mole) of La3?xSe4 is given by H(T) ? (298 K) = (3837 · 103T?1 ? 85852 + 266.925 · T ? 8.7503 · 10?2 T2 + 3.437 · 10?5 T3) · e?0.2869x. The formation and melting enthalpies of La3Se4 are determined: ΔfH °(298 K) = ?1340 ± ± 28 kJ/mole), ΔmH = 147.5 ± 9.6 kJ/mole. It is shown that the high-temperature stability of different La3?xSe4 compositions is strongly dependent on pressure: as pressure decreases and temperature increases, the selenium content is reduced and the composition tends to La3Se4. 相似文献
20.
G. E. Maurer D. J. Duquette N. S. Stoloff 《Metallurgical and Materials Transactions A》1976,7(5):703-709
High-cycle fatigue tests have been conducted on specimens of an Al?Al3Ni eutectic alloy, unidirectionally solidified at selected rates from 1.39×10?4 cm/s to 0.3 cm/s. Tests were conducted in air at 298, 458 and 683 K. Room temperature fatigue lives were independent of growth rate at low solidification rates (1.39×10?4–8.33×10?3 cm/s, but were markedly improved in samples grown at 0.3 cm/s. Materials grown at 8.33 × 10?3 cm/s exhibited fatigue lives similar to those of the lower growth rates, despite gross misalignment due to cellular growth. At 0.5T m (458 K) and 0.75T m (683 K), the fatigue lives of the material grown at low solidification rates were dependent on growth rate. The dependence of fatigue life on growth rate at elevated temperatures appears to be due primarily to differences in cyclic creep rates as a result of varying interfiber spacings. Crack initiation and propagation mechanisms were established by metallographic and fractographic examination. Dislocation substructure-fiber interactions were studied by transmission electron microscopy. 相似文献