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1.
The dynamics of dislocations in both steady state and transient creep in alpha iron of about 99.5 pct purity was investigated
in the temperature interval 773 to 923 K, and the applied stress range 24.5 to 220.5 MN m−2. The applied stress sensitivity parameter of the steady state creep rate m∲ = (∂ In ε/∂ In σ)
T
increased linearly with increasing applied stress σ from about 5 at σ = 24.5 MN m−2 to about 12 at σ = 196 MN m−2. The apparent activation energy of steady state creep rate
was found to decrease linearly with stress from 89 K cal mol−1 at σ = 98 MN m−2 to 81 K cal mol−1 at a = 147 MN m−2. Measurements of the mean effective stress σ* by the strain transient dip test technique led to a nonlinear relation between σ* and σ, indicating a dependence of the ratio σ*/σ on the applied stress. The effective stress sensitivity parameter
was lower than m′.However, the apparent activation energy
was equal toQ. Using the stress sensitivity technique, the relation between transient creep rate and effective stress at various constant
internal stresses and temperatures was obtained. The effective stress sensitivity of transient creep rate
was found to be lessthan that of steady creep rate. 相似文献
2.
Joo Hyun Park Sang-Beom Lee Henri R. Gaye 《Metallurgical and Materials Transactions B》2008,39(6):853-861
3.
Silicon-oxygen equilibria in an Fe-0.003 ~ 27 mass pct Si alloy in equilibrium with the CaO-SiO2 slags were studied in the temperature range of 1823 to 1923 K using a lime crucible. At the same time, nitrogen distribution
ratios, LN, between slag and metal were measured, and from these results and the reported values for activities of SiO2, nitride capacities,
, defined by (mass pct N).
were evaluated. It was found that the values for LN decreased, whereas those for
increased with an increase in temperature. Activities of SiO2 were determined using the values for LN and
obtained in previous gas-slag experiments. These values were compared with the previous results. 相似文献
4.
Data in the literature on the Magneli oxides of titanium have been critically evaluated and equations have been developed
from these data for the standard-state Gibbs energy of formation of the following oxides: Ti4O7, Ti5O9, Ti6O11, Ti8O15, and Ti9O17. Examination of those data yielded the following:
Similar equations for Ti16O31 and Ti50O99 have been estimated from their respective data at 1304 K. The result of that analysis has lead to the following equations:
These equations, along with data in the literature, have been used to construct the Ti-O stability diagram. 相似文献
5.
K. T. Jacob Shashank Priya Yoshio Waseda 《Metallurgical and Materials Transactions A》1998,29(6):1545-1550
The activity of rhodium in solid Pt-Rh alloys is measured in the temperature range from 900 to 1300 K using the solid-state
cell
The activity of platinum and the free energy, enthalpy, and entropy of mixing are derived. Activities exhibit moderate negative
deviation from Raoult’s law. The mixing properties can be represented by a pseudosubregular solution model in which excess
entropy has the same type of functional dependence on composition as the enthalpy of mixing,
The negative enthalpy of mixing obtained in this study is in qualitative agreement with predictions of semiempirical models
of Miedema and co-workers and Colinet et al. The results of this study do not support the solid-state miscibility gap suggested in the literature, but are consistent
with liquidus data within experimental uncertainty limits. 相似文献
6.
The thermodynamic equilibria between CaO-Al2O3-SiO2-CaF2-MgO(-MnO) slag and Fe-1.5 mass pct Mn-0.5 mass pct Si-0.5 mass pct Cr melt was investigated at 1873 K (1600 °C) in order to understand the effect of slag composition on the concentration of Al2O3 in the inclusions in Si-Mn-killed steels. The composition of the inclusions were mainly equal to (mol pct MnO)/(mol pct SiO2) = 0.8(±0.06) with Al2O3 content that was increased from about 10 to 40 mol pct by increasing the basicity of slag (CaO/SiO2 ratio) from about 0.7 to 2.1. The concentration ratio of the inclusion components, \( {{X_{{{\text{Al}}_{2} {\text{O}}_{3} }} \cdot X_{\text{MnO}} } \mathord{\left/ {\vphantom {{X_{{{\text{Al}}_{2} {\text{O}}_{3} }} \cdot X_{\text{MnO}} } {X_{{{\text{SiO}}_{2} }} }}} \right. \kern-0pt} {X_{{{\text{SiO}}_{2} }} }} \) , and the activity ratio of the steel components, \( {{a_{\text{Al}}^{2} \cdot a_{\text{Mn}} \cdot a_{\text{O}}^{2} } \mathord{\left/ {\vphantom {{a_{\text{Al}}^{2} \cdot a_{\text{Mn}} \cdot a_{\text{O}}^{2} } {a_{\text{Si}} }}} \right. \kern-0pt} {a_{\text{Si}} }} \) , showed a good linear relationship on a logarithmic scale, indicating that the activity coefficient ratio of the inclusion components, \( {{\gamma_{{{\text{SiO}}_{2} }}^{i} } \mathord{\left/ {\vphantom {{\gamma_{{{\text{SiO}}_{2} }}^{i} } {\left( {\gamma_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{i} \cdot \gamma_{\text{MnO}}^{i} } \right)}}} \right. \kern-0pt} {\left( {\gamma_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{i} \cdot \gamma_{\text{MnO}}^{i} } \right)}} \) , was not significantly changed. From the slag-steel-inclusion multiphase equilibria, the concentration of Al2O3 in the inclusions was expressed as a linear function of the activity ratio of the slag components, \( {{a_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{s} \cdot a_{\text{MnO}}^{s} } \mathord{\left/ {\vphantom {{a_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{s} \cdot a_{\text{MnO}}^{s} } {a_{{{\text{SiO}}_{2} }}^{s} }}} \right. \kern-0pt} {a_{{{\text{SiO}}_{2} }}^{s} }} \) on a logarithmic scale. Consequently, a compositional window of the slag for obtaining inclusions with a low liquidus temperature in the Si-Mn-killed steel treated in an alumina ladle is recommended. 相似文献
7.
Various theoretical dendrite and cell spacing formulas have been tested against experimental data obtained in unsteady- and
steady-state heat flow conditions. An iterative assessment strategy satisfactorily overcomes the circumstances that certain
constitutive parameters are inadequately established and/or highly variable and that many of the data sets, in terms of gradients,
velocities, and/or cooling rates, are unreliable. The accessed unsteady- and steady-state observations on near-terminal binary
alloys for primary and secondary spacings were first examined within conventional power law representations, the deduced exponents
and confidence limits for each alloy being tabularly recorded. Through this analysis, it became clear that to achieve predictive
generality the many constitutive parameters must be included in a rational way, this being achievable only through extant
or new theoretical formulations. However, in the case of primary spacings, all formulas, including our own, failed within
the unsteady heat flow algorithm while performing adequately within their steady-state context. An earlier untested, heuristically
derived steady-state formula after modification,
ultimately proved its utility in the unsteady regime, and so it is recommended for purposes of predictions for general terminal
alloys. For secondary spacings, a Mullins and Sekerka type formula proved from the start to be adequate in both unsteady-
and steady-state heat flows, and so it recommends itself in calibrated form,
for future predictions.
Control parameters in Eqs. [1] through [8]: X
o, G, and R Constitutive parameters in Eqs. [1] through [8]: k, m, D, T
M, ΔH, σ, ɛ, and G
o 相似文献
8.
The solubility and diffusivity of fluorine in solid copper were determined electrochemically using the double solid-state cell $$Ni + NiF_2 \left| {CaF_2 } \right|Cu\left| {CaF_2 } \right|Ni + NiF_2 .$$ In the temperature range 757 to 920°C, the diffusivity of fluorine in solid copper was found to be $$D_F \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 9.32 \times 10^{ - 2} \exp \left( {\frac{{ - 98,910 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$ . The results obtained for the dissolution of fluorine as atoms in solid copper showed large scatter. However, the equilibrium dissolution of fluorine follows Sieverts’ law. Above the melting point (770°C) of CuF2, the mean solubility of fluorine in solid copper, for the equilibrium Cu(s)+ CuF 2(l), follows the relationship $$N_F^s (atom fraction) = 0.98 \exp \left( {\frac{{ - 79,500 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$ 相似文献
9.
Grain-growth inhibition in an Fe-10 mass pct Ni alloy, which was continuously cooled from a melt, was studied at 1673 K in
the presence of primary deoxidation products of ZrO2 or MgO particles. The mean grain size and grain-size distribution in a cross section were measured as a function of holding
time for up to 240 minutes. The grain growth was strongly inhibited by the inclusion particles and was influenced by the dissolved
Zr. In the Zr deoxidation, the number of particles per unit area (N
A) ranged from 80 to 650 mm−2, the ZrO2 particle size (
) varied from 1.1 to 1.6 μm, and the dissolved Zr level was below 1800 mass ppm. In the Mg deoxidation, the particle-number density was 90 to 270 mm−2, the MgO particle size was 1.1 to 1.7 μm, and the dissolved Mg level was below 20 mass ppm. In a logarithmic plot of the ratio of limiting mean grain diameter (
) to the mean particle diameter (
) against the volume fraction of particles (f
V), both the
value for a given f
V value, which ranged from 0.014 to 0.074 pct, and the slope were significantly lower than that predicted from the two-dimensional
relation
=(4/π) · f
V
/−1
, i.e., Zener’s limit. This discrepancy is discussed in light of the fraction of particles at the grain boundaries measured experimentally.
Normal grain growth was confirmed from the grain-size distribution observed as a function of holding time, which was best
described by the log-normal distribution. 相似文献
10.
Hideki Ono-Nakazato Kenji Taguchi Tateo Usui Keishi Tamura Yuuji Tomatsu 《Metallurgical and Materials Transactions B》2001,32(6):1113-1118
The standard Gibbs energies of formation of Cr2N and CrN have been measured by an equilibration technique and by using thermogravimetry and differential thermal analysis
(TG-DTA) at temperatures ranging from 1232 to 1523 K. The results are expressed as follows:
The standard Gibbs energies of formation of Cr2N and CrN determined by the present work are more negative than the values in the JANAF Tables by about 14 and 5 kJ/mol, respectively,
in the measured temperature range. 相似文献
11.
Z.H. Nie Y.D. Wang G.Y. Wang J.W. Richardson G. Wang Y.D. Liu P.K. Liaw L. Zuo 《Metallurgical and Materials Transactions A》2008,39(13):3113-3119
The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory
alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed
on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the
neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected
to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the
as-cast specimen was composed of
, , , and , which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants
(and ) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical
axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent
Bain-distortion energy.
This article is based on a presentation given in the symposium entitled “Neutron and X-Ray Studies for Probing Materials Behavior,”
which occurred during the TMS Spring Meeting in New Orleans, LA, March 9–13, 2008, under the auspices of the National Science
Foundation, TMS, the TMS Structural Materials Division, and the TMS Advanced Characterization, Testing, and Simulation Committee. 相似文献
12.
Hongsheng Xu Chang Wei Cunxiong Li Zhigan Deng Minting Li Xingbin Li 《Metallurgical and Materials Transactions B》2014,45(5):1622-1633
The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with “ash” layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established: $$ 1.21\ln \left( {1 - 0.83x} \right) - \left[ {1.02\ln \frac{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} - 0.59\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }}{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} + 1.18\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }} + 3.52\arctan \left( {1.96\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} - 0.58} \right)} \right] + 2.06 = 42,192.59{\text{e}}^{{ - \frac{44,900}{{{\text{R}}T}}}} t. $$ 相似文献
13.
14.
Nikhil Dhawan M. Sadegh Safarzadeh Mustafa Birinci 《Russian Journal of Non-Ferrous Metals》2011,52(3):209-216
The dissolution kinetics of smithsonite ore in hydrochloric acid solution has been investigated. As such, the effects of particle
size (−180 + 150, −250 + 180, −320 + 250, −450 + 320 μm), reaction temperature (25, 30, 35, 40, and 45°C), solid to liquid
ratio (25, 50, 100, and 150 g/L) and hydrochloric acid concentration (0.25, 0.5, 1, and 1.5 M) on the dissolution rate of
zinc were determined. The experimental data conformed well to the shrinking core model, and the dissolution rate was found
to be controlled by surface chemical reaction. From the leaching kinetics analysis it can be demonstrated that hydrochloric
acid can easily and readily dissolve zinc present in the smithsonite ore, without any filtration problems. The activation
energy of the process was calculated as 59.58 kJ/mol. The order of the reaction with respect to HCl concentration, solid to
liquid ratio, and particle size were found to be 0.70, −0.76 and −0.95, respectively. The optimum leaching conditions determined
for the smithsonite concentrate in this work were found to be 1.5 M HCl, 45°C, −180 + 150 μm, and 25 g/L solid to liquid (S/L)
ratio at 500 rpm, which correspond to more than 95% zinc extraction. The rate of the reaction based on shrinking core model
can be expressed by a semi-empirical equation as:
$1 - \left( {1 - X} \right)^{{1 \mathord{\left/
{\vphantom {1 3}} \right.
\kern-\nulldelimiterspace} 3}} = k_0 \left[ {HCl} \right]^{0.70} \left( {\frac{S}
{L}} \right)^{ - 0.76} r_0^{ - 0.95} \exp \left( {\frac{{ - 59.58}}
{{RT}}} \right)t.$1 - \left( {1 - X} \right)^{{1 \mathord{\left/
{\vphantom {1 3}} \right.
\kern-\nulldelimiterspace} 3}} = k_0 \left[ {HCl} \right]^{0.70} \left( {\frac{S}
{L}} \right)^{ - 0.76} r_0^{ - 0.95} \exp \left( {\frac{{ - 59.58}}
{{RT}}} \right)t. 相似文献
15.
Heterogeneous nucleation of pb particles embedded in a Zn matrix 总被引:1,自引:0,他引:1
R. Goswami K. Chattopadhyay W. T. Kim B. Cantor 《Metallurgical and Materials Transactions A》1992,23(12):3207-3218
Zinc-10 and 20 wt pct Pb alloys have been rapidly solidified by melt spinning to obtain a very fine scale dispersion of nanometer-sized
Pb particles embedded in Zn matrix. The microstructure and crystallography of the Pb particles have been studied using transmission
electron microscopy (TEM). Each embedded Pb particle is a single crystal, with a truncated hexagonal biprism shape with the
6/mmm Zn matrix point group symmetry surrounded by and
facets. The Pb particles solidify with a well-defined orientation relationship with the Zn matrix of
. The melting and solidification behavior of the Pb particle have been studied using differential scanning calorimetry (DSC).
The Pb particles solidify with an undercooling of approximately 30 K, by heterogeneous nucleation on the {0001} facets of
the surrounding Zn matrix, with an apparent contact angle of 23 deg. 相似文献
16.
17.
Parham Rostami Ghader Faraji Alireza Sadeghi Mostafa Baghani 《Transactions of the Indian Institute of Metals》2018,71(5):1083-1090
In this study, microstructural evolution and mechanical properties of commercial purity titanium after a combined equal channel angular pressing (ECAP) and warm caliber rolling (WCR) was investigated. The ECAP process was applied to enhance the hardness and strength of the specimen by decreasing the grain size and producing UFG microstructure. WCR was applied to reduce cross-section and increase the ductility of the ECAPed specimens. Results show that WCR reduces the work-hardening rate by increasing grain size and also increases elongation and workability while it reduces the yield and ultimate tensile strength. It has been shown that the strength ratio (\({{\sigma_{UTS} } \mathord{\left/ {\vphantom {{\sigma_{UTS} } {\sigma_{y} }}} \right. \kern-0pt} {\sigma_{y} }}\)) and strain ratio (\({{\varepsilon_{UTS} } \mathord{\left/ {\vphantom {{\varepsilon_{UTS} } {\varepsilon_{t} }}} \right. \kern-0pt} {\varepsilon_{t} }}\)) of the processed samples are comparatively larger than all previously post processed ECAPed materials at lower temperatures. 相似文献
18.
R. J. Fruehan 《Metallurgical and Materials Transactions B》1971,2(4):1213-1218
For solutions from which complex species vaporize (Bi2, Si2, Al2O, Sb4, and so forth) new methods of determining the thermodynamic properties from mass spectrometric data are demonstrated. In order to test the feasibility of these new techniques, experiments have been carried out on the liquid Bi-Pb and Bi-Tl systems for which adequate thermodynamic data are available. In evaluating the thermodynamic properties, the ion current ratiosI Pb +/IBi2/+ andI Tl +/IBi2/+ were employed,e.g. $$\log {\text{ }}\gamma _{{\text{Bi}}} {\text{ = - }}\mathop {\int {\frac{{N_{Pb} }}{{1{\text{ + }}N_{Pb} }}d} }\limits_{N_{Bi} = 1}^{N_{{\text{Bi}}} = N_{Bi} } {\text{ }}\left\{ {{\text{log}}\frac{{{\text{1}}_{{\text{Pb}}}^{\text{ + }} {\text{ }}N_{Bi}^2 }}{{I_{Bi2}^ + {\text{ }}N_{Pb} }}} \right\}$$ Measuring these particular ion current ratios eliminates errors resulting from the fragmentation of the complex vapor species in evaluating the thermodynamic properties. A dimer-monomer technique, which corrects for fragmentation, was also demonstrated. The results using these two independent approaches are in good agreement with each other as well as with previous investigations. The activity coefficients in both systems adhere to the quadratic formalism over large composition ranges,e.g. $$\begin{gathered} \log {\text{ }}\gamma _{{\text{Pb}}} {\text{ = - 0}}{\text{.255 }}N_{Bi}^2 {\text{ }}N_{{\text{Bi}}} {\text{< 0}}{\text{.8}} \hfill \\ \log {\text{ }}\gamma _{{\text{Tl}}} {\text{ = - 0}}{\text{.805 }}N_{Bi}^2 {\text{ }}N_{{\text{Bi}}} {\text{< 0}}{\text{.7}} \hfill \\ \end{gathered} $$ 相似文献
19.
This article describes kinetic modeling of titania reduction and carburization by methane-containing gas, based on experimental
data reported previously by Zhang and Ostrovski. A sequence of titania reduction to titanium oxycarbide,
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