Effect of Nitrogen Content on the Microstructure and Mechanical Properties of Ti-Mo-N Coating Films

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate ( f_\textN2 ) \left( {f_{{{\text{N}}_{2} }} } \right) and showed a maximum hardness of about 30 GPa at a f_\textN2 = 0.3 \textccm f_{{{\text{N}}_{2} }} = 0.3\,{\text{ccm}} . On the one hand, the films deposited at f_\textN2 3 1.0  \textccm f_{{{\text{N}}_{2} }} \ge 1.0\;{\text{ccm}} showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at f_\textN2 = 2.0  \textccm. f_{{{\text{N}}_{2} }} = 2.0\;{\text{ccm}}.     

Density Measurements of Low Silica CaO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Slags

Density measurements of a low-silica CaO-SiO₂-Al₂O₃ system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO₂ and the CaO-Al₂O₃ binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO₂ was below the 33 pct required for the orthosilicate composition, discrete \textSiO₄^{4 -} {\text{SiO}}_{4}^{4 - } tetrahedral units in the silicate melt would exist along with O^2– ions. The change in melt expansivity may be attributed to the ionic expansions in the order of

Microstructure Refinement After the Addition of Titanium Particles in AZ31 Magnesium Alloy Resistance Spot Welds

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 ]<sub>\textMg</sub> //  [ 1[`2] 1[`3] ]<sub>\textTi</sub>  \textand ( 000 2 )<sub>\textMg</sub> //  ( 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.     

Isothermal Decomposition of Ferrite in a High-Nitrogen,Nickel-Free Duplex Stainless Steel

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]]<sub>g</sub> ||[110]<sub>s</sub> . [10\bar{1}]_{\gamma } \parallel [110]_{\sigma } . The intergranular and intragranular precipitation of Cr<sub>2</sub>N with trigonal structure were identified, and the orientation relationships (ORs) with α and γ matrix could be expressed as ( 110 )<sub>a</sub> ||( 0001 )<sub>\textCr2 \textN</sub> \left( {110} \right)_{\alpha } \parallel \left( {0001} \right)_{{{\text{Cr}}_{2} {\text{N}}}} , [ [`1]11 ]_a ||[[`1]100]<sub>\textCr2 \textN</sub>  ; (111)<sub>g</sub> ||(0001)<sub>\textCr2 \textN</sub> \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.     

Modification and Minimization of Spinel(Al<Subscript>2</Subscript>O<Subscript>3</Subscript>·<Emphasis Type="Italic">x</Emphasis>MgO) Inclusions Formed in Ti-Added Steel Melts

High-melting-point inclusions such as spinel(Al₂O₃·xMgO) are known to promote clogging of the submerged entry nozzle (SEN) in a continuous caster mold. In particular, Ti-alloyed steels can have severe nozzle clogging problems, which are detrimental to the slab surface quality. In this work, the thermodynamic role of Ti in steels and the effect of Ca and Ti addition to the molten austenitic stainless steel deoxidized with Al on the formation of Al₂O₃·xMgO spinel inclusions were investigated. The sequence of Ca and Ti additions after Al deoxidation was also investigated. The inclusion chemistry and morphology according to the order of Ca and Ti are discussed from the standpoint of spinel formation. The thermodynamic interaction parameter of Mg with respect to the Ti alloying element was determined. The element of Ti in steels could contribute to enhancing the spinel formation, because Ti accelerates Mg dissolution from the MgO containing refractory walls or slags because of its high thermodynamic affinity for Mg ( e_\textMg^\textTi = - 0. 9 3 3). ( {e_{\text{Mg}}^{\text{Ti}} = - 0. 9 3 3}). Even though Ti also induces Ca dissolution from the CaO-containing refractory walls or slags because of its thermodynamic affinity for Ca ( e_\textCa^\textTi = - 0.119 ), \left( {e_{\text{Ca}}^{\text{Ti}} = - 0.119} \right), dissolved Ca plays a role in favoring the formation of calcium aluminate inclusions, which are more stable thermodynamically in an Al-deoxidized steel. The inclusion content of steel samples was analyzed to improve the understanding of fundamentals of Al₂O₃·xMgO spinel inclusion formation. The optimum processing conditions for Ca treatment and Ti addition in austenitic stainless steel melts to achieve the minimized spinel formation and the maximized Ti-alloying yield is discussed.     

Effect of Slag Composition on the Concentration of Al2O3 in the Inclusions in Si-Mn-killed Steel

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.     

Evaluating the Diffusion Coefficient of Sulfur in Low-Silica CaO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Slag

The chemical diffusion coefficient of sulfur in the ternary slag of composition 51.5 pct CaO-9.6 pct SiO₂-38.9 pct Al₂O₃ slag was measured at 1680 K, 1700 K, and 1723 K (1403 °C, 1427 °C, and 1450 °C) using the experimental method proposed earlier by the authors. The P_\textS2 P_{{{\text{S}}_{2} }} and P_\textO2 P_{{{\text{O}}_{2} }} pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS. The density of the slag was obtained from earlier experiments. Initially, the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration curve for sulfur obtained from the program was in good fit with the experimental results. The diffusion coefficient of sulfur in 51.5 pct CaO-9.6 pct SiO₂-38.9 pct Al₂O₃ slag was estimated to be in the range 3.98 to 4.14 × 10⁻⁶ cm²/s for the temperature range 1680 K to 1723 K (1403 °C to 1450 °C), which is in good agreement with the results available in literature     

Oxidation and Condensation of Zinc Fume From Zn-CO<Subscript>2</Subscript>-CO-H<Subscript>2</Subscript>O Streams Relevant to Steelmaking Off-Gas Systems

The objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO₂-CO-H₂O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H₂O or CO₂ does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO₂/CO = 40/7). Rate expressions that correlate CO₂ and H₂O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows:

$$ {\text{Rate}}\left( {\frac{\text{mol}}{{{\text{m}}^{2} {\text{s}}}}} \right) = 406 \exp \left( {\frac{{ - 50.2 \,{\text{kJ}}/{\text{mol}}}}{RT}} \right)\left( {p_{\text{Zn}} p_{{{\text{CO}}_{2} }} - p_{\text{CO}} /K_{{{\text{eq}},{\text{CO}}_{2} }} } \right)\,\frac{\text{mol}}{{{\text{m}}^{2} \times {\text{s}}}} $$

$$ {\text{Rate}}\left( {\frac{\text{mol}}{{{\text{m}}^{2} {\text{s}}}}} \right) = 32.9 \exp \left( {\frac{{ - 13.7\, {\text{kJ}}/{\text{mol}}}}{RT}} \right)\left( {p_{\text{Zn}} p_{{{\text{H}}_{2} {\text{O}}}} - p_{{{\text{H}}_{2} }} /K_{{{\text{eq}},{\text{H}}_{2} {\text{O}}}} } \right)\,\frac{\text{mol}}{{{\text{m}}^{2} \times {\text{s}}}} $$

It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO₂ and H₂O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the measured data. For the conditions used in this study, the rate equations for the oxidation of zinc by carbon dioxide and water vapor as well as the homogeneous nucleation model of metallic zinc were applicable for various temperatures, zinc partial pressures, CO₂:CO ratios, and H₂O partial pressures.

     

The Thermodynamic Behavior of Copper in the CaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> and BaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> Slag System

The Cu solubility was measured in the CaO-B₂O₃ and BaO-B₂O₃ slag systems to understand the dissolution mechanism of Cu in the slags. The Cu solubility had a linear relationship with oxygen partial pressure in the CaO-B₂O₃ slag system, which corresponds with previous studies. Also, the Cu solubilities in slag decreased with increasing the slag basicity, which value of slope was close to –0.5 in logarithmic form. From the results of experiment, the Cu dissolution mechanism established as follows:

Fabrication and Characterization of Naturally Selected Epitaxial Fe-{111} Y2Ti2O7 Mesoscopic Interfaces: Some Potential Implications to Nano-Oxide Dispersion-Strengthened Steels

The smallest features of ≈2 to 3 nm in nanostructured ferritic alloys (NFA), a variant of oxide dispersion-strengthened steels, include the Y₂Ti₂O₇ complex oxide cubic pyrochlore phase. The interface between the bcc Fe-Cr ferrite matrix and the fcc nanometer-scale Y₂Ti₂O₇ plays a critical role in the stability, strength, and damage tolerance of NFA. To complement other characterization studies of the actual nanofeatures (NF) themselves, mesoscopic interfaces were created by electron beam deposition of a thin Fe layer on a 5 deg miscut {111} Y₂Ti₂O₇ bulk single crystal surface. While the mesoscopic interfaces may differ from those of the embedded NF, the former facilitate characterization of controlled interfaces, such as interactions with point defects and helium. The Fe-Y₂Ti₂O₇ interfaces were studied using scanning electron microscopy, including electron backscatter diffraction, atomic force microscopy, X-ray diffraction, and transmission electron microscopy (TEM). The polycrystalline Fe layer has two general orientation relationships (OR) that are close to (a) the Nishiyama–Wasserman (NW) OR $ \left\{ {110} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 110 Fe | | 111 Y 2 Ti 2 O 7 and $ \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 110 Y 2 Ti 2 O 7 and (b) $ \left\{ {100} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 111 Y 2 Ti 2 O 7 and $ \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 110 Y 2 Ti 2 O 7 . High-resolution TEM shows that the NW interface is near-atomically flat, while the {100}_Fe grains are an artifact associated with a thin oxide layer. However, the fact that there is still a Fe-Y₂Ti₂O₇ OR is significant. No OR is observed in the presence of a thicker oxide layer.     

Separation of Antimony from a Stibnite Concentrate Through a Low-Temperature Smelting Process to Eliminate SO<Subscript>2</Subscript> Emission

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.     

Thermodynamic Measurement of Di-calcium Phosphate

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:

Distribution Ratios of Phosphorus Between CaO-FeO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Na<Subscript>2</Subscript>O/TiO<Subscript>2</Subscript> Slags and Carbon-Saturated Iron

In order to effectively enhance the efficiency of dephosphorization, the distribution ratios of phosphorus between CaO-FeO-SiO₂-Al₂O₃/Na₂O/TiO₂ slags and carbon-saturated iron (\( L_{\text{P}}^{\text{Fe-C}} \)) were examined through laboratory experiments in this study, along with the effects of different influencing factors such as the temperature and concentrations of the various slag components. Thermodynamic simulations showed that, with the addition of Na₂O and Al₂O₃, the liquid areas of the CaO-FeO-SiO₂ slag are enlarged significantly, with Al₂O₃ and Na₂O acting as fluxes when added to the slag in the appropriate concentrations. The experimental data suggested that \( L_{\text{P}}^{\text{Fe-C}} \) increases with an increase in the binary basicity of the slag, with the basicity having a greater effect than the temperature and FeO content; \( L_{\text{P}}^{\text{Fe-C}} \) increases with an increase in the Na₂O content and decrease in the Al₂O₃ content. In contrast to the case for the dephosphorization of molten steel, for the hot-metal dephosphorization process investigated in this study, the FeO content of the slag had a smaller effect on \( L_{\text{P}}^{\text{Fe-C}} \) than did the other factors such as the temperature and slag basicity. Based on the experimental data, by using regression analysis, \( \log L_{\text{P}}^{\text{Fe-C}} \) could be expressed as a function of the temperature and the slag component concentrations as follows:

$$ \begin{aligned} \log L_{\text{P}}^{\text{Fe-C}} & = 0.059({\text{pct}}\;{\text{CaO}}) + 1.583\log ({\text{TFe}}) - 0.052\left( {{\text{pct}}\;{\text{SiO}}_{2} } \right) - 0.014\left( {{\text{pct}}\;{\text{Al}}_{2} {\text{O}}_{3} } \right) \\ \, & \quad + 0.142\left( {{\text{pct}}\;{\text{Na}}_{2} {\text{O}}} \right) - 0.003\left( {{\text{pct}}\;{\text{TiO}}_{2} } \right) + 0.049\left( {{\text{pct}}\;{\text{P}}_{2} {\text{O}}_{5} } \right) + \frac{13{,}527}{T} - 9.87. \\ \end{aligned} $$

     

Kinetic Analysis of Alumina Change in Mold Slag for High Aluminum Steel during Continuous Casting

A kinetic calculation model considering both a molten slag reaction with molten steel and an Al₂O₃ inclusion absorption in molten slag was developed to estimate the change in Al₂O₃ in molten slag during the continuous casting of high aluminum steel. Practical casting experiments of high aluminum steel were conducted to investigate the change in composition in the molten slag and to validate the proposed model. The calculated results show that the Al₂O₃ concentration in the molten slag increases quickly during the initial stage and gradually approaches a steady-state value after 900 seconds of casting, which agrees well with the experiment outcome. The change in Al₂O₃ in molten slag is mainly affected by the initial Al₂O₃ concentration w ⁰ of the mold powder, reaction equilibrium concentration of Al₂O₃ w* at the slag-steel interface, mass transfer coefficient \textk_{\textF,\textAl2 \textO3} {\text{k}}_{{{\text{F}},{\text{Al}}_{2} {\text{O}}_{3} }} in molten slag, Al₂O₃ inclusion concentration w _M , and absorption coefficient β in molten steel during continuous casting of high aluminum steel. The experiment result shows that the concentration of Al₂O₃ in molten slag increases significantly and that SiO₂ decreases strongly, while the other components in the molten slag can be negligible comparatively. Mold slag properties at 0, 5, and 45 minutes change greatly, which can deteriorate the performance of the mold slag.     

Interfacial Microstructure in a B4C/Al Composite Fabricated by Pressureless Infiltration

In this work, B₄C particulate-reinforced Al composite was fabricated by a pressureless infiltration technique, and its interfacial microstructure was studied in detail by X-ray diffraction as well as by scanning and transmission electron microscopy. The B₄C phase was unstable in Al melt during the infiltration process, forming AlB₁₀-type AlB₂₄C₄ or Al_2.1B₅₁C₈ as a major reactant phase. The Al matrix was large grains (over 10 μm), which had no definite orientation relationships (ORs) with the randomly orientated B₄C or its reactant particles, except for possible nucleation sites with { 011}_{\textB4 \textC} \{ 011\}_{{{\text{B}}_{4} {\text{C}}}} almost parallel to {111}_Al at a deviation angle of 1.5 deg. Both B₄C–Al and reactant–Al interfaces are semicoherent and free of other phases. A comparison was made with the SiC/Al composite fabricated similarly by the pressureless infiltration. It was suggested that the lack of ORs between the Al matrix and reinforced particles, except for possible nucleation sites, is the common feature of the composites prepared by the infiltration method.     

Effects of Interfacial Lattice Mismatching on Wetting of Ni-Plated Steel by Magnesium

In this study, wetting has been characterized by measuring the contact angles of AZ92 Mg alloy on Ni-electroplated steel as a function of temperature. Reactions between molten Mg and Ni led to a contact angle of about 86 deg in the temperature range of 891 K to 1023 K (618 °C to 750 °C) (denoted as Mode I) and a dramatic decrease to about 46 deg in the temperature range of 1097 K to 1293 K (824 °C to 1020 °C) (denoted as Mode II). Scanning and transmission electron microscopy (SEM and TEM) indicated that AlNi + Mg₂Ni reaction products were produced between Mg and steel (Mg-AlNi-Mg₂Ni-Ni-Fe) in Mode I, and just AlNi between Mg and steel (Mg-AlNi-Fe) in Mode II. From high resolution TEM analysis, the measured interplanar mismatches for different formed interfaces in Modes I and II were \( 17{\kern 1pt} \;{\text{pct}}_{{\{ 10\overline 11\}_{\text{Mg}} //\{ 110\}_{\text{AlNi}} }} \)-\( 104.3\;{\text{pct}}_{{\{ 110\}_{\text{AlNi}} //\left\{ {10\overline{1}0} \right\}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} }} \)-\( 114\,{\text{pct}}_{{\left\{ {0003} \right\}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} //\{ 111\}_{\text{Ni}} }} \) and \( 18\,{\text{pct}}_{{\{ 10\overline 11\}_{\text{Mg}} //\{ 110\}_{\text{AlNi}} }} \)-\( 5\,{\text{pct}}_{{\left\{ {110} \right\}_{\text{AlNi}} //\{ 110\}_{\text{Fe}} }} \), respectively. An edge-to-edge crystallographic model analysis confirmed that Mg₂Ni produced larger lattice mismatching between interfaces with calculated minimum interplanar mismatches of \( 16.4\,{\text{pct}}_{{{\text{\{ 10}}\overline 1 1 {\text{\} }}_{\text{Mg}} / / {\text{\{ 110\} }}_{\text{AlNi}} }} \)-\( 108.3\,{\text{pct}}_{{{\text{\{ 110\} }}_{\text{AlNi}} / / {\text{\{ 10}}\overline 1 1 {\text{\} }}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} }} \)-\( 17.2\,{\text{pct}}_{{{\text{\{ 10}}\overline 1 1 {\text{\} }}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} / / {\text{\{ 100\} }}_{\text{Ni}} }} \) for Mode I and \( 16.4\,{\text{pct}}_{{{\text{\{ 10}}\overline1 1 {\text{\} }}_{\text{Mg}} / / {\text{\{ 110\} }}_{\text{AlNi}} }} \)-\( 0.6\,{\text{pct}}_{{{\text{\{ 111\} }}_{\text{AlNi}} / / {\text{\{ 111\} }}_{\text{Fe}} }} \) for Mode II. Therefore, it is suggested that the poor wettability in Mode I was caused by the existence of Mg₂Ni since AlNi was the immediate layer contacting molten Mg in both Modes I and II, and the presence of Mg₂Ni increases the interfacial strain energy of the system. This study has clearly demonstrated that the lattice mismatching at the interfaces between reaction product(s) and substrate, which are not in direct contact with the liquid, can greatly influence the wetting of the liquid.