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The interfacial reaction and the fracture behavior of 2024 aluminum alloy reinforced with cobalt coated Al₂O₃ fibers with particular attention on effect of coating-fiber interface have been investigated. The cobalt coated fibers were annealed at temperature ranging from 300 to 1000℃ in a vacuum furnace to generate interfacial reaction between the cobalt coating and the Al₂O₃ fiber. Microstructural analysis revealed that the formation of Al_9Co₂ and Co₂O₃ phases resulted from coating-fiber interfacial reaction at high annealing temperature. The tensile tests revealed that both tensile strength and elongation of the composite increased significantly as the fiber annealing temperature increased. In-situ fracture study and SEM fractographic analysis showed that the major fracture behavior of the composite changed from interfacial debonding to matrix deformation.

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The effects of sulphur content and hot-band annealing temperature on the magnetic properties of non-oriented electrical steels containing 3.1 wt% of Si were investigated in the range of 12ppm∼120ppm in sulphur content and 950℃∼1100℃ in hot-band annealing temperature. It was found that the lower the sulphur content was, the less core loss was obtained due to the increased grain size. In the same manner, the increase in hot-band annealing temperature improved the core loss value as well as the magnetic induction. However, the improvement was found to become less pronounced as the sulphur content decreased.

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Deformation behavior in axisymmetric upsetting of porous specimens has been simulated using elasto-plastic finite element method in order to predict forming limit diagram of porous metals. Strain instability of porous cylindrical specimens could be predicted by calculating strain paths during their deformation. By using the load of onset of instability as ductile fracture criteria, a calculated forming limit diagram agree well with the experimental one. The relative density in crack initiation is higher than the critical relative density R_c.

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The interfacial characterization of Al alloy reinforced with Al₂O₃particulates was performed using X-ray diffraction and transmission electron microscopy. Layer of MgAl₂O₄ single crystals having octahedral shape was observed either at (Al₂O₃)_p/Al interface or near (Al₂O₃)_p. Based on the experimental observations and thermodynamic considerations, MgAl₂O₄ crystals formed at the surface of (Al₂O₃)_p are believed to grow by consuming Al₂O₃. Significant surface erosions of (Al₂O₃)_p around MgAl₂O₄ were also observed along a certain crystallographic orientation of (Al₂O₃)_p irrespective of the shape of MgAl₂O₄. Accompanying the interfacial reaction between Mg and Al₂O₃, reduction in precipates density was observed in the vicinity of Al₂O₃.

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The stoichiometric relation for the solvent extraction of gallium in sulfuric acid solution had been studied with D2EHPA(di-2-ehtylhexyl phosphoric acid) and Versatic Acid-10, respectively. The results showed that the gallium was extracted by solvated organo-metal compound with one molecule of the D2EHPA monomer like [GaR₃·RH] and by non-solvated form like [GaR₃] with Versatic Acid-10. The extraction reaction and equilibrium constant would be as follows: For D2EHPA, [Ga^(3+)]_aq + 2[R₂H₂]_(org)↔[GaR₃·RH]_(org) + 3[H^+]_(aq) K_c = 9.77 ×10³ For Versatic Acid-10, [Ga^(3+)]_(aq) + 3/2[R₂H₂]_(org)↔[GaR₃]_(org) + 3[H^+]_(aq) K_c=4.07 ×10^(-10)

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A 2-D coupled analysis of heat transfer and fluid flow was conducted in continuously cast bloom. Latent heat of fusion was considered by modifying the heat capacity/temperature relation, which is so called the effective heat capacity method. To consider the curved type geometry, boundary-fitted coordinate(BFC) system was employed. Water cooling in the mold was simulated by considering the known heat flux and the secondary cooling by considering air cooling and air-mist spray. In this study, the fluid flow and the temperature profile in the continuous casting system of bloom were simulated with the variation of casting speed, tundish superheat. Thus, the effects of casting variables on the distribution of surface temperature, shell thickness, metallurgical length were predicted.

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A series of thermochemical hydrogenation processing(THCP), in which hydrogen used as a temporary alloying element. The microstructural refinement and mechanical properties of Ti-6Al-4V alloy subjected to various THCP has been investigated. Very fine equiaxed and broken-up structures(BUS) are developed with THCP, and the finest equiaxed structure is developed with post-treatment at 750℃ after hydrogenation at 700℃. The hardness is decreased with increasing temperature with regardless of the structure, and increased with increasing the hydrogen content. Hydrogenated structure showed to the highest value in elongation among hydrogenated initial structures, but showed lower value in tensile properties than Widmansta¨tten structure. In comparing with the tensile properties of equiaxed structure before hydrogenation, hydrogenated equiaxed structure improved in the tensile properties up to 13℃ with small variation in elongation. According to the increment of hydrogen content, the yield strength and elongation of equiaxed structure increased linearly. In case of the hydrogenated structure, the fracture surface of equiaxed structure exhibits ductile fracture mode with very fine dimple pattern, and that of BUS(broken-up structure) had showed dimple mode and facets in some region. The process of thermochemical hydrogenation, post-treatment and dehydrogenation is obtained to far more fine structure than conventionally solution treatment, and in view of mechanical properties, the former processes is found to be effective for achieving a good balance of tensile strength and elongation.

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Characterization of the interface of SiC_p/Al composites was performed based on the experimental data obtained from X-ray diffraction, SEM, TEM, EDS, AES, and DSC. X-ray diffraction performed on the electrochemically extracted SiC_p showed that the interfacial reaction products consist of Al₄C₃ and pure Si having hexagonal and diamond cubic crystallographic structure, respectively. According to the experimental results obtained from the interfacial reaction products using SEM, TEM, and AES, Al₄C₃ was found to have a hexagonal plateletshape and Si is observed to exist as a dendritic pattern. Although severe interfacial reaction tends to occur at elevated temperature. Al₄C₃ and Si were found to form at the composite even at 450℃.

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The present study aims at investigating the effects of microstructure on fracture toughness of A356 aluminum matrix composites reinforced with 15 volume percent SiC particulates. These A356 Al SiC_P composites were processed by conventional permanent mold resting and squeeze casting methods, and notch fracture toughness tests were conducted on these two composites in order to identify critical fracture parameters using a critical strain criterion. The composite microstructure was composed of SiC particulates and eutectic Si particles which were mostly segregated at intercellular boundaries. Tensile properties of the squeeze cast composite were superior to those of the re-past composite because of more homogeneous distribution of SiC and eutectic Si particles and elimination of cast defects. Fracture toughness analyses revealed that the improved fracture toughness of the squeeze cast composite, compared to the re-cast composite, was due to the increase in the reference critical strain while intercellular sizes are similar.

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The interfacial characterization of Al alloy reinforced with Al₂O₃particulates was performed using X-ray diffraction and transmission electron microscopy. Layer of MgAl₂O₄ single crystals having octahedral shape was observed either at (Al₂O₃)_p/Al interface or near (Al₂O₃)_p. Based on the experimental observations and thermodynamic considerations, MgAl₂O₄ crystals formed at the surface of (Al₂O₃)_p are believed to grow by consuming Al₂O₃. Significant surface erosions of (Al₂O₃)_p around MgAl₂O₄ were also observed along a certain crystallographic orientation of (Al₂O₃)_p irrespective of the shape of MgAl₂O₄. Accompanying the interfacial reaction between Mg and Al₂O₃, reduction in precipates density was observed in the vicinity of Al₂O₃.

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