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The effect of second phase on the plastic strain ratio in multiphase steel was studied in 1.5% Si steel which has high strength and good elongation. When the second phase was elongated to the width direction, the internal stress created by the inhomogenious deformation between matrix and second phase was larger in the width direction than in the thickness direction. So deformation in the width direction would be more restricted than in the thickness direction and the degree of decrease in plastic strain ratio of multiphase steel would be increased. And when the second phase was elongated to the thickness direction, the plastic strain ratio of multiphase steel would be increased. In case that the second phase was sphere, the plastic strain ratio of multiphase steel would not be effected by second phase. As the volume fraction of second phase increased, texture was not changed greatly but plastic strain ratio decreased.

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In order to verify the accuracy of a one-dimensional computer program of finite difference heat transfer model for heat flow analysis in continuous casting process, computed surface temperature and solidified shell thickness were compared with measured values. The computed results showed a good agreement with measured values. This implies that the computer program is effective means for predicting temperature profile and solidified shell thickness of slab. The computed solidification constant(k) with S3 cooling pattern(Specific water flow : 0.57㎏-water/㎏-steel) was 23.8㎜/min^(0.5) and k with FK cooling pattern(Specific water flow : 0.94㎏-water/㎏-steel) was 26.3㎜/min^(0.5) in No.2 Continuous Slab Caster of POSCO. Relationship between heat transfer coefficient(h : J/㎡ see·℃) and water flux on the surface of hot slab was obtained as following equation by the laboratory scale experiment. h=14.02 W^(0.7◎)

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Mechanical alloying of rapidly solidified 2024 Al alloy and commercial SiC₁ powders has been studied by using a high energy ball mill. The 3 wt.% methanol as a milling agent, has been added to maintain a balance between cold welding and fracturing. Mechanical alloying proceeds by the continual cold welding and fracturing of the constituent powder particles when subjected to the large compressive forces between steel balls. The steady-state processing condition, i. e., an equiaxed particles, an uniform powder size distribution and a saturation hardness signifying the completion of MA, has been reached at the attrition velocity 150rpm and MA time more than 300min. The MA powders were produced by cold pressing, degassing and hot extrustion, and their microstructures and hardness were investigated. Isochronal annealing experiment revealed that thermal stability was high at temperature up to 350℃ On the other hand, the aging hardenability of these alloys was lower than rapidly solidified 2024 Al alloy.

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This paper presents the effect of vanadium on the high temperature strength of interstitial-free molybdenum. Interstitial free Mo-V alloys were prepared by arc-melting with addition of 0.2wt% Sc, and annealed at 1373K for stress relief and 1873K for recrystallization. With those materials the tensile test was conducted at temperature up to 1473K. The tensile properties of interstitial-free molybdenum were significantly improved by addition of small amounts of vanadium. The strengthening ratio, (σ_(MO·V)-σ_(MO))/σ_(MO), increased with temperature up to 673K, but above that temperature the ratio remained nearly constant. Except for Mo-2.0wt%V alloy the ductility of molybdenum was not much affected by addition of vanadium

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The microstructural change and penetraion phenomenon of the 0.25% C-Mn-Mo-B steel plate were studied by impacting the blunt. type cylindrical steel rod with high velocity. The projectiles were accelerated to the range of 500m/sec-700m/sec, and the impact velocity was measured by means of light screen. The perforated hole diameter was increased as the hardness of the steel plate was decreased. This corelation of hole diameter and hardness was not related to the penetration resistance : the penetration resistance showed maximum value around HRC33, and then decreased due to the adiabatic shear band farmed in accordance with increased hardness. The average width of adiabatic shear bands was 5-25㎛, and the microhardness of the band, 780-890HV, was much higher than that of matrix, 320-435HV. The microstructure of adiabatic shear band was found to be untempered martensite with high dislocation density and very fine grains.

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Microstructural and mechanical characteristics of Mg-4Li-1Al, Mg-9Li-1Al and Mg-16Li-1Al have been investigated in the present study. Alloy microstructures have been observed by optical microscopy and mechanical properties have been investigated by tensile test and hardness measurement. The matrix phases of Mg-4Li-1Al, Mg-8Li-1Al and Mg-16Li-1Al are the α,α+β,β phases respectively, depending upon the alloy compositions. As expected From the crystal structure of the α and βphases, Mg-16Li-1Al shows the best workability and Mg-4Li-1Al shows the worst. Generally, the as-rolled alloys show bet: ter mechanical properties than the solution treated-aged alloys, which indicates that alloy weakening due to the recrystallization of deformed structure is more significant than alloy strengthening due to age hardening. Mg-9Li-1Al and Mg-16Li-1Al show slight age hardening behaviour at room temperature. The mechanical properties of the alloys are relatively stable with annealing at 60℃, but deteriorate rapidly with annealing at higher temperatures above 100℃.

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The thermal expansion and the high temperature deformation behaviors have been studied in the composition range of 0-50% Ni for Fe-Ni binary alloys. With increasing Ni content, the α-γ transformation temperature decreases and the thermal expansion coefficients of α and γ phases decrease above 10% Ni. The thermal expansion coefficients of Fe-Ni alloys with Ni content lower than 30% Ni or greater than 40% Ni are about 10^(-5) but chat of 36% Ni alloy is smaller than 10^(-6). The composition showing the lowest thermal expansion coefficient was dependent on the tested temperature range, and the compositions are 36%, 45% and 27.5% Ni in the temperature range of RT-50℃, 50-200℃ and 200-500℃, respectively. With increasing Ni content the compressive true peak stress and its true peak strain at 1000℃ are increased. The yield stress and the compressive peak stress at 1000℃ reached to the high stresses at 25-30% Ni after a steep .increase at about 20% Ni, and then slightly decreased to 36% Ni. The relation between the true stress and the true strain in the compression test at 1000℃ was of the typical power expression type(σ=Kεⁿ) in the strain hardening region. The strength coefficient and the strain hardening coefficient in 20% Ni are estimated 8㎏/㎟ and 0.29 as the highest values while the coefficients in 36% Ni are 4.62 ㎏/㎟ and 0.1 as the lowest values, respectively.

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The alloys Ni-30Cr, Fe-18Cr-6Al-1Hf and Ni-20Si were studied in oxidizing(air) and carburizing(CH₄/H₂) atmospheres at 950℃ to characterize their behavior. The carburization of Fe-18Cr-6A1-1Hf and Ni-20Si at 950℃ was negligible, due to rapid formation of oxide scales because the dissociation pressures of Al₂O₃ and SiO₂ scales are very low. The carburization of Vi-30Cr at 950℃ did not produce a continuous carbide layer, but discrete, globular carbides(Cr_7C₃) on the surface along with internal carbides(Cr₂3C_6)

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The recovery of copper was studied from industrial discard copper slags. In flash smelter and electric furnace slags, it was obtained the most Cu recovery when 5% carbon added to slags by carbothermic reduction, and 7% FeS added to 5% carbon by sulfide washing. Also, Cu recovery was very increased when 5% CaO added to 7% FeS with 5% carbon but, Cu recovery was lower Na₂CO₃ added to 7% FeS with 5% carbon than CaO added. These results were investigated with A.A, ICP, XRD, SEM-EDX, SEM-WDX and chemical analysis etc.. In this study we can get the most Cu recovery after 4 hours reaction in flash smelter and electric furnace slags.

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Using a high temperature mixing calorimeter the mixing enthalpies of liquid Al-Te, In-Te and Al-Se alloys have been determined. The strongly asymmetric concentration courses and triangular shapes of the mixing enthalpies can be attributed to the existence of associate in the alloy melts. Almost complete association formations are assumed in the alloy melts, which can also explain miscibility gaps in the liquid state of the systems. According to the experimental results and to a comparative study, it is mostly like that liquid demixing occurs also in the Al-Se system.

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