共查询到20条相似文献,搜索用时 31 毫秒
1.
The Au diffusion in the Ti3Al compound was investigated at six compositions from 25 to 35 at. pct Al by using the diffusion couples (Ti-X at. pct Al/Ti-X at. pct Al-2 at. pct Au; X = 25, 27, 29, 31, 32, and 35) at 1273 to 1423 K. The diffusion coefficients of Au in Ti3Al
( D\textAu\textTi3 \textAl ) \left( {D_{\text{Au}}^{{{\text{Ti}}_{3} {\text{Al}}}} } \right) are relatively close to those of Ti. The
D\textAu\textTi3 \textAl \texts {D}_{\text{Au}}^{{{\text{Ti}}_{3} {\text{Al}}}} {\text{s}} slightly increase with Al concentration within the same order of magnitude. The activation energies of Au diffusion,
Q\textAu\textTi3 \textAl \texts, Q_{\text{Au}}^{{{\text{Ti}}_{3} {\text{Al}}}} {\text{s}}, evaluated from the Arrhenius plots were relatively close to those of Ti diffusion,
Q\textTi\textTi3 \textAl \texts, Q_{\text{Ti}}^{{{\text{Ti}}_{3} {\text{Al}}}} {\text{s}}, rather than those of Al diffusion,
Q\textAl\textTi3 \textAl \texts; {Q}_{\text{Al}}^{{{\text{Ti}}_{3} {\text{Al}}}} {\text{s}}; therefore, it was suggested that Au atoms diffuse by the sublattice diffusion mechanism in which Au atoms substitute for
Ti sites preferentially in Ti3Al and diffuse by vacancy mechanism on Ti sublattice. The influence of the D019 ordered structure (hcp base) of Ti3Al on diffusion of Au and other elements is discussed by comparing the diffusivities in Ti3Al and α-Ti. 相似文献
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3.
Tae-Ho Lee Heon-Young Ha Byoungchul Hwang Sung-Joon Kim 《Metallurgical and Materials Transactions A》2012,43(3):822-832
The formation and crystallography of second phases during isothermal decomposition of ferrite (α) in a high-nitrogen, nickel-free
duplex stainless steel was examined by means of transmission electron microscopy (TEM). At an early stage of aging, the decomposition
of α started along the α/γ phase boundaries where sigma (σ) phase and secondary austenite (γ
2) precipitated in the form of an alternating lamellar structure. The combined analyses based on the simulation of diffraction
patterns and stereographic projection have shown that most of the σ phase was related to the γ
2 by the following relation: (111)g ||(001)s (111)_{\gamma } \parallel (001)_{\sigma } and [10[`1]]g ||[110]s . [10\bar{1}]_{\gamma } \parallel [110]_{\sigma } . The intergranular and intragranular precipitation of Cr2N with trigonal structure were identified, and the orientation relationships (ORs) with α and γ matrix could be expressed as
( 110 )a ||( 0001 )\textCr2 \textN \left( {110} \right)_{\alpha } \parallel \left( {0001} \right)_{{{\text{Cr}}_{2} {\text{N}}}} ,
[ [`1]11 ]a ||[[`1]100]\textCr2 \textN ; (111)g ||(0001)\textCr2 \textN \left[ {\bar{1}11} \right]_{\alpha } \parallel [\bar{1}100]_{{{\text{Cr}}_{2} {\text{N}}}} \,;\,(111)_{\gamma } \parallel (0001)_{{{\text{Cr}}_{2} {\text{N}}}} , and
[ [`1]10 ]g ||[ [`1]100 ]\textCr2 \textN , \left[ {\bar{1}10} \right]_{\gamma } \parallel \left[ {\bar{1}100} \right]_{{{\text{Cr}}_{2} {\text{N}}}} , respectively. The precipitation of intermetallic χ phase was also observed inside the α matrix, and they obeyed the cube-on-cube OR with the α matrix. Prolonged aging changed both the structure of matrix and the distribution of second phases. The γ
2, formed by decomposition of α, became unstable because of the depletion of mainly N accompanied by the formation of Cr2N, and it transformed into martensite after subsequent cooling. As a result, the microstructure of the decomposed α region was composed of three kinds of precipitates (intermetallic σ,χ, and Cr2N) embedded in lath martensite. 相似文献
4.
Microstructural evolution of AZ31 magnesium alloy welds without and with the addition of titanium powders during resistance
spot welding was studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM).
The fusion zone of AZ31 magnesium alloy welds could be divided into columnar dendritic zone (CDZ) and equiaxed dendritic zone
(EDZ). The well-developed CDZ in the vicinity of the fusion boundary was clearly restricted and the coarse EDZ in the central
region was efficiently refined by adding titanium powders into the molten pool, compared with the as-received alloy welds.
A microstructural analysis showed that these titanium particles of approximately 8 μm diameter acted as inoculants and promoted
the nucleation of α-Mg grains and the formation of equiaxed dendritic grains during resistance spot welding. Tensile-shear testing was applied
to evaluate the effect of titanium addition on the mechanical properties of welds. It was found that both strength and ductility
of magnesium alloy welds were increased after the titanium addition. A TEM examination showed the existence of an orientation
matching relationship between the added Ti particles and Mg matrix, i.e.,
[ 0 1[`1]0 ]\textMg // [ 1[`2] 1[`3] ]\textTi \textand ( 000 2 )\textMg // ( 10[`1]0)\textTi \left[ {0 1\bar{1}0} \right]_{\text{Mg}} // \, \left[ { 1\bar{2} 1\bar{3}} \right]_{\text{Ti}} \,{\text{and}}\,\left( {000 2} \right)_{\text{Mg}} // \, ( 10\bar{1}0)_{\text{Ti}} in some grains of Ti polycrystal particles. This local crystallographic matching could promote heterogeneous nucleation of
the Mg matrix during welding. The diameter of the added Ti inoculant should be larger than 1.8 μm to make it a potent inoculant. 相似文献
5.
Joo Hyun Park Sang-Beom Lee Henri R. Gaye 《Metallurgical and Materials Transactions B》2008,39(6):853-861
6.
Takashi Nagai Yusuke Tanaka Masafumi Maeda 《Metallurgical and Materials Transactions B》2011,42(4):685-691
The thermodynamic properties of the CaO-P2O5 system are important to develop an effective refining process in the iron and steel industry. In this study, the thermodynamic
properties of (CaO)2P2O5 were investigated because the properties are necessary to develop a new dephosphorization process. The vapor of gaseous phosphorus
and phosphorus oxide in equilibrium with a mixture of (CaO)2P2O5 and (CaO)3P2O5 at 1373 K to 1498 K (1100 °C to 1225 °C) were detected directly as an ion current by double Knudsen cell mass spectrometry.
Comparing the ion currents with those from a mixture of Al2O3P2O5 and Al2O3, which is used as a reference mixture in this study, the Gibbs energy change of the following reaction was calculated:
2\textCaO( \texts ) + \text P2 ( \textg ) + \frac52\textO2 ( \textg ) = ( \textCaO )2 \textP2 \textO5 ( \texts ) 2{\text{CaO}}\left( {\text{s}} \right) \, + {\text{ P}}_{2} \left( {\text{g}} \right) \, + \frac{5}{2}{\text{O}}_{2} \, \left( {\text{g}} \right) = \left( {\text{CaO}} \right)_{2} {\text{P}}_{2} {\text{O}}_{5} \left( {\text{s}} \right) 相似文献
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Jian-Guang Yang Chao-Bo Tang Yong-Ming Chen Mo-Tang Tang 《Metallurgical and Materials Transactions B》2011,42(1):30-36
The main purpose of this study is to characterize and separate antimony from a stibnite concentrate through a low-temperature
sulfur-fixing smelting process. This article reports on a study conducted on the optimization of process parameters, such
as flux and zinc oxide weight percentage, in charging, smelting temperature, smelting duration on the antimony yield, resultant
crude antimony grade, and sulfur-fixing rate. A maximum antimony recovery of 97.07 pct, crude antimony grade of 96.45 pct,
and 98.61 pct sulfur-fixing rate are obtained when a charge (containing 63.20 wt pct of flux and 21.30 wt pct of stibnite,
a flux composition of
W\textNaOH /W\textNa 2 \textCO3 W_{\text{NaOH}} /W_{{{\text{Na}}_{ 2} {\text{CO}}_{3} }} = 10/147, where W represents weight, and more than 10 pct of the stoichiometric requirement of zinc oxide dosage) is smelted at 1153 K (880 °C)
for 120 minutes. This smelting operation is free from atmospheric pollution because zinc oxide is used as the sulfur-fixing
agent. The solid residue is subjected to mineral dressing operation to obtain suspension, which is filtered ultimately to
produce a cake, representing the solid particles of zinc sulfide. Based on the results of the chemical content analysis of
as-resultant zinc sulfide, more than 90 pct zinc sulfide can be recovered, and the recovered zinc sulfide grade can reach
66.70 pct. This material can be sold as zinc sulfide concentrate or roasted to regenerate into zinc oxide. 相似文献
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Sound velocity values for 32 liquid metals at their melting point temperatures have been predicted using two models that we
presented; most of these metals are transition and rare earth metals. The sound velocities for most of these liquid metals
have yet to be measured experimentally. Dimensionless common parameters, denoted by
x\textT1/2 \xi_{\text{T}}^{1/2} and
x\textE1/2 , \xi_{\text{E}}^{1/2} , were determined on the basis of the predicted sound velocities. These common parameters, which characterize the liquid state
(i.e., an atom’s hardness or softness and its anharmonic motions), allow for better predictions of several thermophysical properties
(e.g., surface tension, viscosity, self-diffusivity, volume expansivity) of liquid metallic elements. The values of both the common
parameters
x\textT1/2 \xi_{\text{T}}^{1/2} and
x\textE1/2 \xi_{\text{E}}^{1/2} vary periodically with atomic number. Using our viscosity model in terms of the parameter
x\textT1/2 , \xi_{\text{T}}^{1/2} , values of melting point viscosity were calculated for liquid molybdenum and platinum. The agreement obtained between calculated
and experimental values is good when using predicted values of
x\textT1/2 \xi_{\text{T}}^{1/2} to calculate their viscosities. 相似文献
11.
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
12.
The solubility of indium in a molten CaO-SiO2-Al2O3 system was measured at 1773 K (1500 °C) to establish the dissolution mechanism of indium under a highly reducing atmosphere.
The solubility of indium increases with increasing oxygen potential, whereas it decreases with increased activity of basic
oxide. Therefore, a dissolution mechanism of indium can be constructed according to the following equation:
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