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The work hardening behavior of lamellar-γ two-phase TiAl alloys has been investigated through compression test at ambient temperature. The yield stress and compressive ductility showed a maximum at ∼0.5 and ∼0.32 of lamellar volume fraction, respectively. The true stress-true strain curves of lamellar-γ two-phase TiAl alloys have been analyzed using four different constitutive equations proposed by Hollomon, Voce, Ludwik, and Swift. The deformation behavior of two-phase TiAl alloys was described by Ludwik and Swift equations, which are obviously delineated by three deformation stages of work hardening. In the early stage of deformation(ε=0.01), the work hardening rate as a function of lamellar volume fraction increases linearly up to f_L=∼0.5 and establishes a nearly constant value at high lamellar volume fraction. Upon increase of the true plastic strain(ε=0.03-0.08), the work hardening rate showed a maximum at f_L=∼0.7. True plastic strain range of deformation stage II and III establishes a nearly constant value up to f_L=∼0.32 and contracts largely with the increase in the lamellar volume fraction. The compressive ductility showed the linear dependence with the work hardening exponents n_L and n_L in Crussard-Jaoul plots. The work hardening exponent n_H of Hollomon equation has a higher value of 0.3-0.5 in the deformation stage II and III. This result suggests that the deformation of lamellar-γ two-phase TiAl alloys operates through deformation twinning in addition to slip.

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In order to produce the high clean steel, control of dissolved oxygen in the melt is extremely important. Deoxidizing behaviors in the Al killed SUS430 melt were studied with the variation of synthetic CaO-SiO₂-Al₂O₃(CaF₂) slags. A new deoxidation limit considering the interfacial energy barriers for the nucleation of the oxides has been suggested and used to rationalize the experimental results. To improve a real deoxidization limit, a nucleation rate should be accelerated by decreasing interfacial energy. The basicity of the slags also affected the reoxidation of the melt and in turn the achievable deoxidation limit. The more SiO₂ content in the slag, the less deoxidation ability was expected.

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The sulfur reaction between the CaO-MgO-Fe₁O-SiO₂-MnO-∑M_xO_y, slags saturated with MgO and molten iron was investigated by changing the MnO content from 2 to 30mass% in the temperature range of 1823K to 1973K. The sulfur distribution was analyzed in terms of the slag composition and temperature. The results obtained are as follows; 1) The sulfur distribution ratio increases with the increase in B≡(CaO+MgO+MnO)/(SiO₂+P₂O_5+Al₂O₃,+TiO₂) as well as the decrease in temperature. Although iron oxide decreases the sulfur distribution ratio when B is 3.5 and above, it behaves reversely below 3.5. Following equations are obtained by analyzing the effect of slag compositions and temperature influencing the sulfur distribution ratio. 2) Upon many trials for analysing various sulfide capacities, the capacity has no relation with the temperature, and has following relations with the slag composition.

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The behaviors of physico-chemical and metallurgical properties of CaO-MgO-Fe₁O-SiO₂-MnO-∑M_xO_y(M_xO_y=P₂O_5, Al₂O₃, TiO₂, CaF₂, S) stags were discussed in terms of the concept of the optical basicity. The stags were saturated with MgO and in equilibrium with molten iron, and its MnO contents was varied from 2 to 30wt% in the temperature range of 1823 to 1973K. The phosphate capacity and the activity of P₂O_5 were well correlated with the theoretically driven optical basicity, the sulfide capacity was related with the optical basicity after Wrampelmeyer et al. Also, the activity coefficient of MnO and the manganese capacity had good agreements with the optical basicity proposed in the previous work". Following equations were obtained as the results.

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This study investigated the behaviors of zinc, lead and chlorine in EAF dust for recovery of iron and zinc in the oxidation and reduction atmosphere respectively between 800 and 1300℃. The removal of chlorine was easy under oxidation atmosphere rather than reduction atmosphere, and proper temperature was 1100℃. The volatilization rate of Pb was decreased over 1000℃ under oxidation atmosphere because of formation of PbO-SiO₂ melt. The volatilization of zinc was rapidly increased between 900℃ and 1000℃ under reduction atmosphere. The residual content of zinc could be presented over 1100℃ as following equation. log(%Zn)=logM_(Zn)+logn_r+log(P_(CO₂),/P_(CO))+logP_(Zn)- log_γ_(ZnO)+96456.42/T-4.5683

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The reduction behavior of iron ore fines of multi-sized distribution in a fluidized bed has been extensively investigated in the aspects of degradation and elutriation. The present study has endeavored to obtain fundamental data for effective plant operations and improvements of devices in fluidized-bed systems through fully understanding the effects of operating parameters and dimension or design of reactor on the degradation and elutriation of ore fines during the fluidized-bed reduction. In the fluidizedbed reduction of iron ore fines of multi-sized distribution, the minimum fluidization velocity for fine ore particles smaller than 1500㎛, of which fluidization behavior is governed by the viscosity of gas, decreases with a increase in temperature while that for coarse ore particles larger than 1500㎛, of which fluidization behavior is governed by the force of inertia, increases with temperature. The minimum fluidization velocity equation proposed by Wen and Yu shows most reliable prediction in this study. The abrasion and degradation during fluidized-bed reduction are more severe when the ore particles are coarse, and in this study, the weight pct of ore particles smaller than 250㎛ increased from 27wt% to 45wt% and that of ore particles smaller than 500㎛ increased from 42wt% to 57wt% after the fluidized-bed reduction. It has been confirmed with a mathematical model of elutriation loss that as the superficial gas velocity increases, the fluidization of coarse ore becomes more vigorous but the elutriation rate and the concentration of iron ore fines entrained in gas also increase and it finally results in a high elutriation loss.

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Currently more than 80 % of raw iron ore is produced in a state of fines under 8 ㎜ in diameter in the world. In order to produce metallic products such as DRI (Direct Reduced Iron) and/or hot metal directly from fine iron ore without pretreatment, a fluidized bed technology should be adopted. In the present study, characteristics of a fluidized bed with iron ore fines in the size range of 1 to 5 ㎜ have been investigated at high temperature (700-850℃) in terms of the minimum fluidization velocity, fluidization patterns, the pressure drop, the solid hold-up in the reactor, etc. using a laboratory scale fluidized bed reactor. It was observed that the minimum fluidization velocity of particles in wide size range is equivalent to that of the particle of harmonic mean size. The optimum gas velocity for fluidization is about 1.2 to 1.3 times of the minimum fluidization velocity and this is similar to the result observed in the experiments in cold (room temperature) state. During heat-up and reduction in the reactor, iron ore particles are degraded due to the thermal and reduction reaction shocks. It was also found that the degradation of ore particles was completed in the early stage of reduction reactions, within 10 minutes.

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316L stainless steel plates, which are usually used for metallic components of molten carbonate fuel cells, were coated with nickel and aluminum successively for the enhancement of their corrosion resistance. Electroplating and pack cementation were employed respectively for nickel and aluminum coating. The corrosion property of the coated specimen was checked by dipping test and anodic polarization test, and compared with those of the bare stainless steel and the one coated only with aluminum. In the case of dipping test the specimen was characterized, before and after the test, using optical microscopy to study the morphology of its cross-section, and X-ray diffraction to identify the phases of the coated layer. Intermetallic compound of Al₃Ni₂ was formed on the surface of the coated specimen and this specimen turned out to be highly resistant to corrosion, even more than the one coated only with aluminum.

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In order to investigate the effect of the solid lubricants on the wear properties of tin-bronze alloys, Cu-l0wt%Sn tin bronze alloys containing WS₂ and MoS₂were produced by the powder metallurgical method and tested by a reciprocal type wear testing machine. The wear surfaces of the specimens and the counter steels were observed and analyzed by SEM, EDS, AES and XPS. Application of the solid lubricants in the alloy composites reduced the friction acting on the contact surface. Addition of WS₂ was effective to improve the wear resistance at the higher applied load since a uniform lubricating layer formed on the worn surface. MoS₂ in the samples was transformed to copper sulfides during the sintering process. This led to an increase in wear loss because the strength of the alloy matrix was lowered by the formation of copper sulfides.

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The effect of extrusion on tensile properties of the Ni-P coated SiC particle reinforced Al composites has been studied. The X-ray diffraction and DTA analysis revealed that the amorphous Ni deposits is crystallized into brittle Ni₃P intermetallic compound and Ni crystallite. After hot presssing, the tensile strength and elongation of composites reinforced with Ni-P coated SiC particle were decreased comparing with the uncoated SiC particle reinforced composites. It was suggested that the Ni₃P compound layer in Ni-P deposits acts as a crack initiation site during tensile loading. After hot extrusion, the tensile strength of the Ni-P coated composites was higher than that of uncoated composites, because Ni₃P intermetallic compound layers in Ni-P deposits were pulverized and then dispersed to the matrix by plastic deformation of Al matrix during hot extrusion. It is obviously shown that the micro-vickers hardness of the Ni-P coated composites is higher than that of uncoated composites. This is due to the disperssion of Ni₃P compound in AI matrix during extrusion process.

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