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In this paper, the effects of Ni-P coating on SiC particle in SiC_P/2024 Al composites have been studied in relation with mechanical properties. Elastic modulus of SiC_P/2024 Al composites tends to linearly increase as volume fraction of SiC particle increases. After Ni-P coating, elastic modulus of the composites with Ni-P coated SiC particle is shown to be much higher than that of the composites with uncoated SiC particle in the range of 10 to 30 vol% SiC particle. It is observed that the hardness of Ni-P coated SiC particle reinforced composites is superior to that of uncoated SiC particulate reinforced composites. This is due to the brittle and hard Ni₃P formed at consolidation temperature of 520℃ from Ni-P coating layer. Both the tensile strength and elongation in Ni-P coated SiC particle reinforced composites was found to be decreased in comparison with uncoated SiC particle reinforced composites, because the brittle Ni₃P phase were formed at the interface between SiC particle and 2024 Al matrix.

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Synthetic chromite was used in studing the reaction mechanism and investigating the effect of variables on reduction behavior of chromite ore. The molar ratios of FeO to Cr₂O₃ and Fe to Cr₂O₃ were varied to investigate the role of FeO and Fe in the synthetic chromite, respectively. The reduction rates of CF3(2Cr₂O₃·FeO) and Cr₂O₃ with various amounts of Fe increased with increasing temperature. The reduction rates of CF3 as well as CF1(Cr₂O₃·FeO) and CF2(Cr₂O₃·2FeO) which were reported in the previous paper, increased with increasing the amounts of FeO and Fe addition in synthetic chromite. Teh presence of Fe in the synthetic chromite would increase the reduction rate due to decreasing the Cr activity.

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Microstructure and fracture behavior of pressurelessly-sintered SiAlON-SiC composite containing different SiC contents was investigated using high-resolution electron microscopy(HREM) and micro-indentation fracture(MIF) technique. The SiAlON-6%SiC composite showed the highest Vickers hardness and fracture toughness. The composite contained nanometer-size SiC particles dispersed homogeneously both in SiAlON grains and at grain boundaries. The grain boundary were formed with a 1-2㎚ thick amorphous layer regardness of the SiC content. The interface between SiAlON and SiC embedded in the grain, however, were formed without any amorphous layer. The typical fracture mode of the monolithic SiAlON was intergranular. That is, cracks propagate along The SiAlON grain boundaries with amorphous layers. In SiAlON-6wt%SiC, mixed mode of intergranular and transgranular fracture was observed, which seems to be caused by the nanometer-size SiC distributed in the SiAlON grains. In SiAlON-12wt%SiC, cracks propagated more straight through the SiAlON grains with submicron-size SiC particles, and the typical fracture mode was transgranular.

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Amorphous Al_(88)Ni_(10-x)Co_xY₂(x=1, 3) alloys were examined for their devitrification characteristics at temperatures above precipitation onset temperature(T_(xl)) of Al phase. The particle size of Al phase increases in the range of 5 to 15㎚ with increasing aging temperatures. With an increase of precipitation amount(V_f) of fcc-Al phase, the thermal stability of remained amorphous phase was significantly enhanced. These devitrified amorphous alloys at V_f=14% exhibit tensile fracture strength(σ_f) and hardness(H_v) which are about 30% higher than those of amorphous single phase alloys with the same composition, without detriment to good bending ductility (e.g., 1360MPa at 14%V_f for Al_(88)Y₂Ni_9Co₁alloy). The σ_f and fracture elongation (ε_f) in the devitrified amorphous alloys decreases with increasing Co content. This compositional effect is presumably due to an increase in embrittlement tendency caused by stronger tendency of structural relaxation in the amorphous phase with increasing Co content.

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Microstructure and magnetic properties of CoCrPt/Cr thin films were investigated as a function of sputtering condition during the deposition of CoCrPt thin films. Strong separation of Co grains was observed with increasing argon sputtering pressure due to the enhanced scattering of argon ions with sputtering particles, thereby resulting in the reduced exchange coupling and also the increased coercivity by a factor of four. Plane and cross sectional TEM indicated that most Co grains sputtered at high pressure were separated by 10-20Å thick boundary and share their growth on bigger Cr grains. The Co grain separation decreased with the application of substrate bias and disappeared by -200V bias. The bias sputtered CoCrPt thin films decreased their grain size and increased epitaxial growth on Cr layer and also (101￣0) texture. The slight decrease in squareness of bias sputtered films resulted from the residual stress in the films. The required magnetic field to saturate the film significantly increased with increasing substrate bias.

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Diamondlike carbon films were fabricated by PECVD with a low discharging frequency and effects of heat treatment on the C-H bonding states as well as the microhardness were investigated. It turned out that the discharging frequency has a considerable effect on the thermal stability of DLC thin films. DLC films fabricatd with 450 kHz discharging frequency did not show any delamination from the silicon substrate even after annealing at 900℃ and the microhardness of the films showed less sensitivity to temperature than the DLC films with 13.56MHz discharging frequency. Improvements on the thermal stability were attributed to the C-H bonding states of such films, which is related to the energy of depositing species in PECVD.

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Using high frequency induction furnace, the reaction of pig iron and Ti-ore was carried out at temperatures between 1450 and 1600℃. After 40 minuters reaction, samples of molten pig iron and slag were taken and their chemical compositions were analyzed. The ratio of TiO₂(in slag)/TiO₂(in ore) and desiliconization of pig iron were investigated in relation to the amount of Ti-ore, temperature and type of crucible. The concentration of TiO₂ in slag and the desiliconization of pig iron were increased with increasing Ti-ore content and decreasing temperature. The ratio of TiO₂(in slag)/TiO₂(in ore) was 2.6∼2.8 in magnesia crucible and 3.5∼5.6 in graphite crucible. The desiliconization of pig iron became better in magnesia crucible than in graphite crucible. The desulfurization and dephosphorization effects were not observed.

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Directional solidification experiment has been carried out on Fe-3.4wt.%C-2.0wt.%Si alloys with and without the addition of 0.02wt.%S. The effect of O on the transitions in graphite morphology was investigated by controlling the O₂ partial pressure of solidification atmosphere. The use of pure Ar, or 10 volume %O₂ or H₂ plus balance Ar atmosphere has produced a definite effect on the graphite morphology solidified from high purity alloys. Contrary to the results of other works oxygen was found to promote coral growth by suppressing flake graphite, while hydrogen was counteracting the O effect. The addition of S to the high purity alloys greatly promoted the formation of flake graphite regardless of the solidification atmosphere, indicating that the effect of O on graphite morphology was neutralized in the presence of S.

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A new powder-making process named centrifugal emulsification process(CEP) has been developed and tested for the Pb-Sn eutectic alloy system. The underlying principle of CEP was to fabricate the powders in inorganic oil(or salt) using centrifugal force. Since the alloy powders did not contact directly with oxygen throughout the process, the powders could be produced without oxidizing contamination. The mean particle size and size distribution could be controlled by various processing parameters such as filter rotating speed, the size of meshes and oil temperature. The morphology of the particles could also be customized using spherodization vs. solidification time ratio. The amount of undercooling of the CEP powders was also detactable and might be used further to understand the solidification behaviors. The microstructures of the Pb-Sn eutectic CEP powders were very close to those of the RSP powders.

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Aluminum 6063 and Al-8wt%Si powders were produced by centrifugal atomization and mixing. They were sintered under pressure in N₂ atmosphere to make porous sound absorbing plate. The micromorphology of powder and sintered plate was observed by SEM and optical microscope. It is found that Si is thoroughly dispersed in the matrix (Al 6063 powders) of the plate. For the sound absorbing coefficient measurement, impedance tube method was applied. The relation between sound absorbing coefficient, density of sintered plate, volume and distribution of porosity was investigated. Sound absorbing effect through the influence of binder which leads to the constructive variation of porosity was also investigated.

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