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The formation of the ears on the drawn cups of the annealed low carbon steel was interpreted by the development of the recrystallization textures. The annealing textures depended on the degree of cold rolling reductions. The inhomogeneous textures were developed through the layers of steel sheet. The 4-fold and the 6-fold ears at the drawn cups were related to the {111}//ND fiber orientations, respectively. The assumption that the amount of slip of an active slip system is propotional to the Schmid factor of the slip system was applied to calculate the R value of an orientation. A large strain at 0˚, 90˚, 180˚, 270˚ to the RD on the 4-fold ear was explained by (0˚, 10˚, 0˚) preferred orientation in the texture. A large strain on the 6-fold ear was explained by the development of the orientations near {111}〈110〉.

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Hot dip galvannealed coatings on steel sheet were evaluated with respect to minor additions of aluminum, lead or antimony in the zinc bath. The decrease of aluminum content in the bath increased alloying rate of the coating and promoted the growth of Gamma phase(Fe₃Zn_(10)) to deteriorate powdering resistance of the galvannealed coating. The variation of lead content in the bath did not noticeably change galvannealing behavior of the coating, but powdering resistance was deteriorated with lead addition. On the other hand, alloying rate of the coating increased with antimony addition, which inversely affected powdering resistance of the coating. The use of antimony tended to change a distribution of aluminum in the coating which influenced the zinc-iron allaying reaction at the interface of the coating and steel sheet.

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To identify bubble formation substance in molybdenum doped with K₂O and SiO₂ two kinds of specimens were prepared; first, solid potassium disilicate was intentionally implanted in molybdenum powder followed by compacting at 300MPa. Then the compact was sintered at 2200℃. Secondly, molybdenum powder doped with potassium disilicate was produced from the hydrogen reduction of molybdenum trioxide, MoO₃, doped with potassium disilicate in acqueous solution. The doped powder was compacted and sintered at the same conditions as the former specimen. The sintered ingot was swaged and drawn to 1mm diameter wire. To analyze the bubble formation substance during sintering, hot isostatic pressing (HIPing) at 1900℃ under 190MPa was applied to transform bubbles into solid particles and to collapse pores induced by sintering. And to analyze the entrapped substance in the bubble of molybdenum wire, HIPing was performed at 2000℃ under 190MPa after annealing at 2000℃ for 30minutes. Scanning electron micrographs were taken and bubble formation substance was analyzed by using EDX (energy dispersive X-ray spectroscopy) and WDX(wave dispersive X-ray spectroscopy). It was analyzed that the evolution of bubble was due to the vaporization of K-Si oxide during sintering and Al-K-Si complex oxide during annealing of wire. Al-oxide participated in bubble formation for wire was exidsted as separate one from K-Si oxide in sintered ingot. The substructure of as-drawn state was observed by using TEM(transmission electron microscopy) to understand the reaction of Al-oxide with K-Si oxide during wire making process. It was cautiously concluded that the participation of Al in bubble formation should be assisted by the deformation processes such as swaging and drawing inducing the distribution of bubble formation substance along the tangled dislocation cell boundaries.

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To understand the dependency of microstructures on non-sag property and ductility in molybdenum wire, five different specimens were prepared through sintering, swaging and drawing processes. Each specimen was doped with K₂O and SiO₂ in various amounts, i.e., 0, 0.028, 0.14, 0.28 and 0.49(K+Si) by weight percents, and isochronally annealed at various temperatures for 30 minutes. The microvickers hardness was measured as a function of annealing temperature and then optical micrographs were taken with each specimen annealed at 1400℃ and 2000℃. Each specimen annealed at 1000℃ and 2000℃ underwent. 90˚ repetition bending until crack occurred to evaluate its ductility. Non-Sag values were measured in temperature range from 1000℃ to 2340℃(0.9Tm) under load of 250g, and then some fractured surfaces were observed by scanning electron microscopy. The specimen doped with 0.28(K+Si) weight percent was completely recrystallized at a temperature between 1800℃ and 2000℃ and its grain structure consisted of elongated and interwoven shape grains, including many small bubbles at grain boundary, of which aspect ratio(length/width) was about 30. This grain structure showed a good ductility after recrystallization and an excellent non-sag property over 0.5T_m. When the microstructures were not fully recrystallized, however, the sagging-resistance was increased with the doping amount of K₂O and SiO₃, and the ductility was inversely decreased. Especially, when the bubbles grew, the fracture occurred easily due to a sagging phenomenon assisted by the reduction of effective area supporting the load.

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In order to obtain uniformly distributed tungsten-copper powder, the submicron tungsten powder was coated with copper by a newly developed process : fluidized bed reduction. Tungsten powder was initially coated with copper dichlorides and then reduced in fluidized beds by hydrogen gas flow. By the same method, cobalt was added to this binary alloy for the purpose of altering the chemical relations between tungsten and copper. In case of 75W-25Cu, full densification could not be attained even after the prolonged sintering of 4 hours at 1200 C because of a large wetting angle of copper on tungsten. The addition of cobalt of 0.5 weight percent, however, considerably enhanced the densification of 75W-24. 5Cu-0.5Co and high density above 95% was attainable within ramping-up to 1200℃. The enhancement of sintering by cobalt addition was revealed to result from the decrease of the wetting angle of liquid copper, which was due to the formation of an intermetallic compound between tungsten and cobalt dissolved in liquid copper.

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The constant load creep test has been conducted in order to estimate the temperature and stress dependence of the steady-state creep behaviour of the TiAl base cast alloys, Ti-47Al-2Mn and Ti-48Al(at.%), respectively. Two microstrutural conditions were evaluated as follows : FL scheme consisting of a coarse grained fully transformed lamellar structure with α₂/γ lath within a grain, and duplex scheme consisting of fine grained equiaxed γ with α₂/γ lamellar. Steady-state creep behaviour of the both microstructural conditions was studied as a functions of stresses between 70 and 300MPa, and temperatures between 700 and 900℃. Apparent creep activation energies and stress exponents were measured for both microstructural conditions in each composition. The temperature and stress dependence of the steady-state creep rate of bath microstructures can be described well by the power law creep equation. Therefore, dislocation motion is proposed as a predominant creep mechanism in the stresses and temperature regime investigated in this study. At temperatures and stress levels in which the present investigation was made, the steady-state creep rate of the FL structures exhibits an order of magnitude lower than that of the duplex ones.

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Microstructural effects on crack initiation toughness (J_(IC)) and crack growth toughness (T_R) have been examined for HP9-4-20 steel and ASTM A710 steel. Microstructural changes, which increased the fracture strain (ε_f) and decreased the yield strain (ε_o), improved both J_(IC) and T_R, and had the larger effect on T_R for ASTM A710 steel with law strength. Observation of crack profiles revealed a zig-zag fracture which propagated along the spiral slip lines emanating from the blunted crack tip for ASTM A710 steel, and along the straight slip lines characteristic of a non-blunted crack for HP9-4-20 steel.

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Cr₃C₂-25wt.%NiCr coatings on mild steel substrate by plasma spray process were produced to evaluate microstructural characterization and mechanical properties. As-deposited Cr₃C₂-NiCr coating samples were subjected to two heat treatment conditions such as annealing under H₂ gas circumstance and hot press treated condition. The two heat treated coatings were investigated in terms of microhardness, adhesion strength, wear resistance, surface roughness, porosity formation, and microstructures. The microstructure of as-coated Cr₃C₂-NiCr samples displayed layered structure with 3∼4㎛ thickness and 0.2㎛ grain size. The degree of porosity formation and surface roughness were decreased as increasing temperature range of 400℃∼1200℃, and showing better wear resistance, microhardness and adhesion strength for the annealed conditions. And wear resistance and adhesion strength also were improved as increasing the temperature range of 300℃∼ 700℃ and pressure range of 50MPa∼200MPa for the hot press treated condition. Further, microhardness values were increased as increasing temperature only. It was also indicated that mechanical behaviors and microstructural characteristics of the two heat treated conditions were superior to those of the as-deposited condition according to the comparison studies.

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The erosion behavior of mild steel, 304, 410 stainless steel and Inconel 600 superalloy was investigated. Erosion tests were conducted in the air at room temperature using angular SiC particles. Erosion rates were determined as a function of impact angles, impacting particle sizes and velocities. All tested materials showed the maximum erosion rate at impact angles between 20℃ and 30℃. Erosion rates increased with increase of the impacting particle size and velocity. The effect of particle-velocity increase on erosion rate decreased above velocities of 60m/sec. SEM observations of the eroded surfaces indicate that shearing process is a major erosion mechanism at low impact angles, while at high angles, platelet formation was a major erosion mechanism. It was found that erosion in ductile materials is a deformation-controlled process and none of the published empirical models or simple tensile parameters explain the difference of erosion rates among the tested materials.

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Erosion tests were performed on mild steel, 304, 310, 410 stainless steel and Inconel 600 superalloy in the air at room temperature using round Al₂O₃ pariticles. Erosion rates were calculated and eroded surfaces were examined using SEM. SEM observations indicated that platelet formation was a major erosion mechanism and size of the platelet was inversely proportional to the erosion rate. The erosion characteristics was investigated using the localized deformation model. It was found that the localized deformation model characterizes the erosion test results and strain hardening coefficient is the most influential parameter to the model Strain hardening coefficient at the early stage of plastic deformation during simple tensile tests of the alloys could qualitatively explain the difference of erosion rates among the tested materials.

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