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1.
Gernot Kirchner Taiji Nishizawa Björn Uhrenius 《Metallurgical and Materials Transactions B》1973,4(1):167-174
New measurements of the α/γ equilibrium in the Fe-Cr system are presented and all the relevant experimental information now
available, including thermodynamic data, is evaluated using a regular solution model. The two-phase field is calculated in
good agreement with most of the experimental measurements. The point of minimum is obtained at 1119 K and 7.0 at. pct Cr (6.6
wt pct Cr) and the maximum solubility in austenite is 11.9 at. pct Cr (11.2 wt pct Cr). The thermodynamic quantities describing
the effect of chromium on the relative stability of ferrite and austenite are similar to those for manganese. The comparison
is based upon a new evaluation of the Fe-Mn system. In particular, low chromium contents are found to have a stabilizing effect
on austenite up to a temperature of 1675 K. 相似文献
2.
The α + γ two-phase fields of the Fe-Ni and Fe-Ni (P saturated) phase diagrams have been determined in the composition range
0 to 60 wt pet Ni and in the temperature range 700 to 300 °C. The solubility of Ni in (FeNi)3P was measured in the same temperature range. Homogeneous alloys were austenitized and quenched to form α2, martensite, then heat treated to formα (ferrite) + γ (austenite). The compositions of the α and γ phases were determined
with electron microprobe and scanning transmission electron microscope techniques. Retrograde solubility for the α/(α + γ)
solvus line was demonstrated exper-imentally. P was shown to significantly decrease the size of the α + γ two-phase field.
The maximum solubility of Ni in α is 6.1 ± 0.5 wt pct at 475 °C and 7.8± 0.5 wt pct at 450 °C in the Fe-Ni and Fe-Ni (P saturated)
phase diagrams, respectively. The solubility of Ni in α is 4.2 ± 0.5 wt pct Ni and 4.9 ± 0.5 wt pct Ni at 300 °C in the Fe-Ni
and Fe-Ni (P saturated) phase diagrams. Ternary Fe-Ni-P isothermal sections were constructed between 700 and 300 °C.
Formerly Research Assistant in Department of Metallurgy & Materials Engineering, Lehigh University, Bethlehem, PA. 相似文献
3.
A Cahn Electrobalance has been used to determine directly and very accurately the carbon content of α-Fe, Fe-0.48 wt pct Mo
and Fe-1.16 wt pct Mo specimens which were equilibrated with a series of methane-hydrogen gas mixtures. The equilibria investigated
involved the ferrite phases of the alloys between 682 and 848‡C. The experimental results permitted direct calculation of
the activities of carbon in the samples, relative to graphite as unity, and of other thermodynamic functions, without the
necessity for any correction factors. The results have been compared with the experimental measurements of a number of other
investigators. In ferrite, the partial molar enthalpy and entropy of solution of carbon are found to be 26,800 cal/mole, (112,
130 J/mole), and 30.59 cal/K-mole, (127.99 J/K-mole) respectively at temperatures below about 727‡C. Above this temperature,
the values are 25,200 cal/mole and 29.13 cal/K-mole, respectively. The addition of molybdenum results in an increase in these
properties below 727‡C and a decrease in the values above 753‡C, and the changes are found to be proportional to the molybdenum
content. The solubility of carbon in α-Fe is found to be 0.0176 wt pct at the eutectoid temperature. Molybdenum increases
the solubility relative to the Fe-C system at temperatures above the eutectoid and decreases it below the eutectoid. 相似文献
4.
Influence of magnetic field on the kinetics of proeutectoid ferrite transformation in iron alloys 总被引:1,自引:0,他引:1
M. Enomoto H. Guo Y. Tazuke Y. R. Abe M. Shimotomai 《Metallurgical and Materials Transactions A》2001,32(3):445-453
The kinetics of proeutectoid ferrite transformation in Fe-C base alloys in a strong magnetic field (7.5 T) were studied. The
transformation kinetics were accelerated at temperatures not only below but also significantly above the Curie temperature.
The free energy and equilibrium ferrite/austenite phase boundaries in applied magnetic fields were calculated using the reported
experimental magnetic susceptibility and Weiss molecular field theory. The persistence of magnetic field effects above the
Curie temperature can be attributed to the rapidly diminishing difference in relative stability between ferrite and austenite
toward the Ae
3 temperature of iron. 相似文献
5.
Stanko Nikolic Peter C. Hayes Evgueni Jak 《Metallurgical and Materials Transactions B》2009,40(6):900-909
Calcium ferrite slags, which are represented by the “Cu2O”-FeO-Fe2O3-CaO system at copper saturation, have been applied successfully to existing copper-converting processes. Because of the industrial
importance of this system, the characterization of the effects of oxygen partial pressure and silica on the phase equilibria
is necessary to improve the control of process parameters, which include fluxing and operating temperatures. In the current
study, experimental methods, which use the equilibration/quenching/electron probe X-ray microanalysis (EPMA) techniques with
primary phase substrate support, were subsequently developed to incorporate fixed oxygen partial pressure experiments. Experiments
were carried out at 1200 °C and 1250 °C both with and without silica additions; both liquidus and solidus data were reported
for the primary phase field of spinel and dicalcium ferrite between the oxygen partial pressures of 10−5.0 and 10−6.5 atm. The analyzed compositions of the liquid and solid phases are used to construct the phase diagram of the pseudoternary
“Cu2O”-“Fe2O3”-CaO system in equilibrium with metallic copper at fixed oxygen partial pressures and with additions of silica. The maximum
solubility of silica within the liquid slag phase, prior to dicalcium silicate precipitation, was measured at specific conditions.
Two empirical equations used for the calculation of the copper oxide concentration in calcium ferrite slag are evaluated with
the new experimental data defined in the current study. 相似文献
6.
Hitoshi Ishii Tadashi Kawarazaki Yoshinori Fujimura 《Metallurgical and Materials Transactions A》1984,15(4):679-691
The effects of twelve alloying elements on the fatigue properties of α-iron were determined. Stress-life properties, fatigue
crack propagation (FCP) rates, and stress intensity thresholds of 38 kinds of binary ferrite containing an alloying element
varying from 1 to 5 wt pct or up to its solubility limit in α-iron were experimentally determined together with those of the
base iron. It was shown that the influence of a given element on high cycle fatigue life differed from that of its effects
on FCP resistance or on stress intensity thresholds. 相似文献
7.
M. P. Papaelias M. Strangwood A. J. Peyton C. L. Davis 《Metallurgical and Materials Transactions A》2004,35(13):965-972
An electromagnetic (EM) sensor, capable of detecting the formation of ferromagnetic ferrite from paramagnetic austenite below
the Curie temperature, has been developed and assessed. In this article, results obtained using an a.c. EM sensor for a medium
(0.45 wt pct)—carbon steel slow cooled through its transformation-temperature range are presented. It was found that the EM
sensor can successfully detect the formation of ferrite below the Curie temperature, but that the transimpedance values can
be significantly affected by the formation of a decarburized ferrite ring around the samples. It was also found that the transimpedance
value is monotonically (nonlinearly) related to the ferrite volume fraction and depends on the morphology/distribution of
the ferromagnetic phase and, hence, is influenced by the prior-austenite grain size. Results from finite-element (FE) simulations
designed to enable prediction of the transimpedance from the microstructure are also presented, showing that two-dimensional
(2-D) FE simulations can be successfully used to model the experimental trends observed. The combination of modeling and measurement
has shown that EM sensors can be used to indirectly monitor the ferrite transformation (below the Curie temperature), thus
providing a measure of ferrite volume fraction and also a means of identifying the ferrite distribution in the microstructure. 相似文献
8.
9.
N. P. Fahey D. R. Swinbourne S. Yan J. M. Osborne 《Metallurgical and Materials Transactions B》2004,35(2):197-202
Continuous converting of copper matte based on calcium ferrite slag has many attractions for the copper smelting industry.
However, a serious drawback is that this slag leads to shorter furnace campaigns because it is aggressive toward the magnesia-chromia
refractories that form the furnace lining. As part of an investigation into the causes of this aggressiveness with a view
to devising strategies to mitigate it, the solubility of Cr2O3 in calcium ferrite slag has been determined. The standard drop-quench experimental technique was employed at a temperature
of 1573 K and a relatively high oxygen partial pressure of 3.7×10−4 atm, conditions similar to those used in continuous converting. It was found that approximately 2 wt pct of Cr2O3 can dissolve in calcium ferrite slag under these conditions. The Cr2O3 solubility was found to be unaffected by the Cu2O content of the slag, but may decrease as CaO content decreases. The implications of these findings on the mechanism of attack
of magnesia-chromia refractories by calcium ferrite slag are discussed. 相似文献
10.
M. G. Mecozzi J. Sietsma S. van der Zwaag M. Apel P. Schaffnit I. Steinbach 《Metallurgical and Materials Transactions A》2005,36(9):2327-2340
This article deals with the austenite (γ) decomposition to ferrite (α) during cooling of a 0.10 wt pct C-0.49 wt pct Mn steel. A phase-field model is used to simulate this transformation. The
model provides qualitative information on the microstructure that develops on cooling and quantitative data on both the ferrite
fraction formed and the carbon concentration profile in the remaining austenite. The initial austenitic microstructure and
the ferrite nucleation data, derived by metallographic examination and dilatometry, are set as input data of the model. The
interface mobility is used as a fitting parameter to optimize the agreement between the simulated and experimental ferrite-fraction
curve derived by dilatometry. A good agreement between the simulated α-γ microstructure and the actual α-pearlite microstructure observed after cooling is obtained. The derived carbon distribution in austenite during transformation
provides comprehension of the nature of the transformation with respect to the interface-controlled or diffusion-controlled
mode. It is found that, at the initial stage, the transformation is predominantly interface-controlled, but, gradually, a
shift toward diffusion control takes place to a degree that depends on cooling rate. 相似文献
11.
E. Cotrina A. Iza-Mendia B. López I. Gutiérrez 《Metallurgical and Materials Transactions A》2004,35(1):93-102
The degree of ferrite grain refinement that can be reached in low-carbon microalloyed steels by thermomechanical processing
is limited, to a certain extent, by the grain coarsening which can take place behind the transformation front. The coarsening
of ferrite grains is the result of two different mechanisms: elimination of ferrite grains produced by normal grain growth
after full impingement on the austenite grain boundary plane and/or coalescence between different ferrite grains with close
orientation formed from the same crystallographic variant. The lack of experimental data to support either process is due
to the experimental difficulties encountered when analyzing the phenomenon. Some transmission electron microscope (TEM) observations
reveal that the ferrite grains formed along a prior grain boundary in deformed austenite are separated by a mixture of low
and high angle grain boundaries upon impingement. In the present work, the electron backscattered diffraction (EBSD) technique
has been applied to investigate the microstructural evolution during transformation, with special emphasis placed on the α-α grain boundary character as a means of investigating the contribution of coalescence/grain growth to coarsening. 相似文献
12.
13.
L. N. Less 《Metallurgical and Materials Transactions B》1977,8(1):219-225
Aluminas having a wide range of physical characteristics were added in the laboratory to cryolite melts under different, controlled
conditions of temperature and melt composition. Crusts were usually obtained, and their strengths, durability and solubility
noted. It was shown that well-formed crusts are produced only by aluminas that are both sandy and relatively under-calcined.
Such aluminas flow readily, and have a high surface area and a low α-alumina content. The mechanism of crusting is postulated
as an initial cooling and freezing of the melt following penetration into alumina on the surface; a strong crust is a consequence
of the subsequent growth of a network of α-alumina platelets. Aluminas initially of high α content do not form such a network.
The difference between crusts formed by alumina additions and by simple freezing of a melt is considered. The effect of different
aluminas on cell operation, as a consequence of their different crusting and solubility characteristics, is discussed. 相似文献
14.
The effects ofca. 3 at. pct of Al, Si, or Co upon the kinetics of grain boundary ferrite allotriomorph formation (and thus upon hardenability)
relative to those in Fe-C alloys of comparable carbon content were evaluated. All three alloying elements displace the TTT
curve for the initiation of transformation to shorter times at the higher reaction temperatures. Both aluminum and silicon
increase the parabolic rate constant for allotriomorph thickening,α, relative to that in their counterpart Fe-C alloys; the influence of cobalt uponα, if any, is appreciably less. In the Fe-C-Al and Fe-C-Si alloys, thickening proceeds noticeably less rapidly than volume
diffusion control (as assessed by Atkinson’s analysis of the growth of an oblate ellipsoid) allows. In the Fe-C-Co and Fe-C
alloys, the average calculated and experimental α’s are in better agreement but, evidently as a result of the presence of
dislocation facets at a broad face of allotriomorphs, some allotriomorphs actually thickened more rapidly than calculated.
The substantial scatter inα in all alloys was also attributed to these facets. Indirect determinations indicated that all three elements increased the
rate of nucleation of ferrite allotriomorphs.
Formerly with Ford Motor Co., Dearborn Mich. 相似文献
15.
Ion implantation and ion backscattering analysis have been used to measure the solubility of copper in beryllium over the
temperature range 593 to 1023 K, and to determine the effect on the copper solubility of aluminum and silicon impurities.
The binary data extend 280 K lower in temperature than previous results, while the ternary measurements are unique. This information
is pertinent to the use of copper for solution strengthening of beryllium. Diffusion couples were formed by ion implantation
of copper into singlecrystal beryllium at room temperature, followed where appropriate by implantation of aluminum or silicon.
The samples were then annealed isothermally, and the time-evolution of the composition-vs-depth profile, determined by ion backscattering analysis, yielded the solubility of copper. Measurements at exceptionally
low temperatures were facilitated by the short diffusion distances, ≅0.1 μm, and the use of neon irriadiation to accelerate
diffusion. The resulting binary data for the solubilityC
0 of copper in beryllium merge smoothly into previous results at higher temperatures. The combined data, covering the temperature
range 593 to 1373 K, are well described byC
0=(12.6 at. pct)·exp(−842 K/T). In the ternary regime, the effects of aluminum and silicon on the solubility of copper were found to be small. 相似文献
16.
Stanko Nikolic Peter C. Hayes Evgueni Jak 《Metallurgical and Materials Transactions B》2008,39(2):210-217
17.
G. J. Shiflet J. R. Bradley H. I. Aaronson 《Metallurgical and Materials Transactions A》1978,9(7):999-1008
Three models of the statistical thermodynamics of interstitial solid solutions have been used to reevaluate the thermodynamics
of the proeutectoid ferrite reaction. The models of Kaufman, Radcliffe and Cohen and of Lacher, Fowler and Guggenheim, which
were em-ployed in a previous study of this type, together with the model recently developed by McLellan and Dunn are used
in conjunction with the extensive experimental data of Ban-ya, Elliott and Chipman, of Lobo and Geiger and of Dunn and McLellan
on the activities of carbon in austenite and ferrite. Application of the McLellan and Dunn model and that of Lacher, Fowler
and Guggenheim to carbon in austenite yields activities of carbon which are numerically indistinguishable and activities of
iron which are mathematically identi-cal. However, the new activity data have revealed important differences between the pres-ent
calculations and those of Aaronson, Domian and Pound. An average carbon-carbon repulsion energy in austenite of 1925 cal/mole
(8054 J/mole) was determined from the CO/CO2 data of Ban-yaet al. However, the C-C interaction energy in ferrite was found to be opposite in sign but exhibited erratic variations with temperature
despite the large amount of activity data available. The γ/(α + γ) phase boundary calculated from the new data differs significantly, at lower temperatures, from the best curves reported by
Aaron-sonet al. The calculateda/(α +γ) phase boundary also differs appreciably from the pre-vious results and exhibits only limited agreement with the experimentally
determined phase boundary. Calculation of the free energy change associated with the proeutectoid ferrite reaction andT
0- composition curves differs little from previous results; internal agreement among the new sets of curves, however, is much
improved. 相似文献
18.
P. Vizcaíno A. D. Banchik J. P. Abriata 《Metallurgical and Materials Transactions A》2004,35(8):2343-2349
In this work, the dissolution enthalpy, ΔH
δ→α, of the δ hydride phase in the αZr matrix in ZIRCALOY-4 has been determined with a differential scanning calorimeter (DSC)
in two different ways: by means of a van’t Hoff equation, measuring the terminal solubility temperature in dissolution, TSSd,
and by direct measurement of the dissolution heat, Q
δ→α, as the area between the base line and the calorimetric curve. The application of the DSC technique to the hydride dissolution
heat measurements, a transformation which covers an extended temperature range, is completely original and requires a special
treatment of the calorimetric curve. These measurements were done on samples that practically cover the entire solubility
range of hydrogen in αZr phase (80 to 640 ppm). The values obtained, 36.9 and 39.3 kJ/mol H, respectively, are self-consistent
and in good agreement with the values of the more recent revisions, but reduces considerably the scatter of the literature
data. 相似文献
19.
C. F. Willis R. Gronsky T. M. Devine 《Metallurgical and Materials Transactions A》1991,22(12):2889-2902
Transmission electron microscopy (TEM) and microanalytical chemistry were performed on sensitized samples of duplex welds
that exhibited both skeletal ferrite microstructures and lath ferrite microstructures. The objective was to understand why
welds with lath ferrite, contrary to a theoretical prediction, are not immune to sensitization. Most of the ferrite-austenite
(α-γ) interphase boundaries in the welds with skeletal ferrite were curved and incoherent, while those in welds with lath
ferrite were predominantly planar and semicoherent. The density of carbide precipitation on incoherent boundaries was much
greater than that on semicoherent boundaries. Carbide precipitates on incoherent boundaries were typically equiaxed, while
those on semicoherent boundaries had very high aspect ratios and appeared to form along ledges in the interphase boundary.
During sensitizing heat treatments, the chromium-depleted zone on the ferrite side of the interphase region transformed to
austenite, causing the α-γ interphase boundary to move into the ferrite region. This markedly increased the width of the chromium-depleted
zone in the austenite phase and extended the time of heat treatment required to replenish the zone with chromium. It is proposed
that migration of the α-γ interphase boundary, which occurs to a much greater extent in the welds with lath ferrite, is responsible
for their unexpected susceptibility to sensitization at 550°C. 相似文献
20.
John W. Elmer Joe Wong Thorsten Ressler 《Metallurgical and Materials Transactions A》2001,32(5):1175-1187
Phase transformations that occur in the heat-affected zone (HAZ) of gas tungsten arc welds in AISI 1005 carbon-manganese steel
were investigated using spatially resolved X-ray diffraction (SRXRD) at the Stanford Synchrotron Radiation Laboratory. In situ SRXRD experiments were performed to probe the phases present in the HAZ during welding of cylindrical steel bars. These real-time
observations of the phases present in the HAZ were used to construct a phase transformation map that identifies five principal
phase regions between the liquid weld pool and the unaffected base metal: (1) α-ferrite that is undergoing annealing, recrystallization, and/or grain growth at subcritical temperatures, (2) partially transformed
α-ferrite co-existing with γ-austenite at intercritical temperatures, (3) single-phase γ-austenite at austenitizing temperatures, (4) δ-ferrite at temperatures near the liquidus temperature, and (5) back transformed α-ferrite co-existing with residual austenite at subcritical temperatures behind the weld. The SRXRD experimental results were
combined with a heat flow model of the weld to investigate transformation kinetics under both positive and negative temperature
gradients in the HAZ. Results show that the transformation from ferrite to austenite on heating requires 3 seconds and 158°C
of superheat to attain completion under a heating rate of 102°C/s. The reverse transformation from austenite to ferrite on
cooling was shown to require 3.3 seconds at a cooling rate of 45 °C/s to transform the majority of the austenite back to ferrite;
however, some residual austenite was observed in the microstructure as far as 17 mm behind the weld. 相似文献