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In order to reduce the brittle fracture in the boride layers, the effects of the annealing on the electroboronized samples have been studied. In the annealing of the boride layers at 800℃, the distribution of the microhardness does not change, and the Fe₂B layer does not change, too. But the compressive residual stress is reduced greatly. In the annealing of the boride layers above 850℃, the distribution of the microhardness becomes more smooth, in the boride layers the Fe₂B layer increase, the compressive residual stress is reduced greatly, too.

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The relationship between the microstructures and some their related material properties was investigated in order to design the best suitable microstructure of the Ag-Cu electrical contact alloy. The Ag-Cu eutectic alloy was unidirectionally solidified in order to obtain an anisotropic microstructure. Some part of such unidirectionally solidified eutectic alloy has undergone also the rolling deformation to get the more elongated microstructure, characterizing the more anisotropic microstructural features. The specimen of a unidirectionally solidified eutectic structure has shown the better properties in regard to its application on electrical contact than the others. Furthermore its properties relevant to the contact performance was able to be improved by an appropriate rolling deformation. The specimen of the narrower lamellar spacing obtained by rolling deformation in direction to unidirectional solidification has shonw the best properties among the various types of the specimens investigated in this study. Possible explanation on the experimental result was also carried out.

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Primary creep tests were performed on commercially pure aluminum in the temperature range of 0.32 - 0.38 T_m. The activation energies were obtained by usual method using different specimens (Q_c) and the temperature cycling method (Q_(T.C.)). The relation of activation energy with effective stress, σ_e, has been analysed. The activation length, ℓ_c^*, obtained from Q_c is linearly proportional to the inverse of affective stress. But no such relationship is observed in ℓ_(T.C).^* obtained from Q_(T.C.). The Q_c seems to have better physical meaning compared to Q_(T.C).

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The samples of used doloma-containing basic refractories of POSCO`s 300 ton capacity BOF have been taken and made into thin-sections for optical and electronic microscopic investigation to characterize the failure mechanism of the lining in the steelmaking conditions. A striking contrast has been found in the thickness of decarburized zone between those two refractories of POSCO and a Japanese steelmaker in the almost similar steelmaking and refractories practices. The decarburized zone thickness of POSCO`s lining is extremely thin. The opposite is true of that of the Japanese steelmaker. The difference in the thickness of decarburized zone in relation to the protective nature of the carbon-containing MgO-based brick has been studied mainly based on a mathematical model pertaining to the formation of the dense MgO layer close to the hot face of the brick. This study shows that maintenance of a thicker decarburized zone is one of the critical parameters involved in the extension of lining life of the BOF refractories.

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The precipitation of metastable carbide and the decomposition of retained austenite in martensitic Fe-4Cr-O. 4C steel has been studied by micro-Vickers hardness test, transmission electron microscopy and calorimetry. The results obtained are as follows. 1) Under the argon atmosphere of 1.01×10^5 Pa, the relation between apparatus constant k of DSC used in this study and absolute temperature T gives the equation as k＝1.419-9.198×10^(-4) T, where 323˚K≤T≤773˚K. 2) There are three exothermic peaks in DSC curve of martensitic Fe-4Cr-0.4C steel. The first peak corresponds to the precipitation of ξ-carbide in the first stage of tempering, the second to the decomposition of retained austenite in the second stage of tempering, and the third to the precipitation of cementite in the third stage of tempering. 3) Activation energies for the first stage and the second stage of tempering in martensitic Fe-4Cr-0.4C steel are 134.3KJ/㏖ and 153.6KJ/㏖, respectively. 4) The time indices for the first stage of tempering are determined to be 0.86 at 373˚K and 1.00 at 423˚K from the Johnson-Mehl`s equation. 5) It is found that Differential Scanning Calorimetry is convenient to study the kinetics of carbide precipitation from the martensite.

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The relationship between microstructure characteristics and strain hardening was studied for pure aluminum, Al-0.039% Zr and Al-0.09% Zr alloys subjected to wire drawing deformations to the strains of 3.69 at room temperature. Pure aluminum and the Al-Zr alloys show continued linear hardening to the range of plastic deformation of ε=3.69 after initial rapid strengthening. The accompanying microstructures evolved, in all cases in the following sequence: formation of dislocation cell structure, cell size refinement, subgrain formation and increase of misorientation angle between subgrains. The cell and subgrain structures are characterized by low angle boundaries but the subgrain structures become to be characterized by high angle boundaries with increasing plastic deformation. The subgrains are less effective as strengthening barriers, hence a single flow stress vs. substructure size relationship should not be rigorously applied. The small additions of zirconium affect the rate of substructure formation and refinement but not the relationship between substructure and strength.

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Aluminum oxide was deposited with a CVD-technique onto TiC-coated cemented carbide substrate. The effects of reaction parameters; deposition temperature, total pressure, CO₂/H₂mole ratio, AlCl₃, partial pressure, on the CVD of Al₂O₃were investigated. The experimental results showed that deposition rate was increased with an increase in deposition temperature and total pressure, and maximum deposition rate was obtained when CO₂/H₂mole ratio is unity. It was also found that up to the critical value of AlCl₃partial pressure, deposition rate was increased with an increase in AlCl₃partial pressure, but above the critical value deposition rate was decreased with an increase in AlCl₃partial pressure. The structure of Al₂O₃was changed from amorphous one to crystalline with an increase in deposition temperature. The reaction of Al₂O₃formation was controlled by chemical kinetics at lower temperature (< 1000℃), but the control mechanism of the reaction changed to mass transport at higher temperature (> 1000℃).

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