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For the analysis of the fiber-and sheet-type texture of materials with hexagonal crystal system, two computer programs, TXFIBH and TXSHTH, were developed based on Bunge`s series expansion method. The pole figures measured on Zircaloy-4 rod and sheet samples by neutron diffraction were analyzed to obtain the crystal orientation distribution functions and theoretical direct and inverse pole figures. Analytical errors were studied in terms of numbers of input pole figure and degrees of series expansion. Based on ODF, some discussions were made to understand the distinctive features of observed textures.

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In order to provide further evidence to support the mechanism of the reverse shape memory effect(RSME) in a Cu-Zn-Al alloy, more detailed investigations have been carried out in DO₃ type CuZnAl alloys which are Cu-24.0Zn-6.1Al and Cu-24.4Zn-5.3Al in composition. The Cu-24.0Zn-6.1Al alloy shows both SME(301∼503K) and RSME(563∼673K) with increasing temperature after bending deformation. The shape change of the sheet occurs spontaneously and the amount of shape change by RSME is much larger than that of SME. The other specimen of the Cu-24.4Zn-5.3Al alloy not. occured the tw-step transformed martensite(α₁`) and the reversible shape memory. Comparing the scanning electron micrographs of the bainite morphology of the two alloys, RSME observed when the directional bainite exits. It should be noted that directional bainite is produced when the two-step transformed martensite(α₁`) exits. It is concluded that the RSME is attributed to the directional bainites produced due to two-step transformed martensite(α₁`).

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Ultrafine BaTiO₃ powder was prepared by hydrothermal synthesis with the treatment of Ba and Ti hydroxide at temperatures ranged from 120℃ to 180℃ The effects of synthesizing conditions on the properties and the crystal structure of powder were investigated using x-ray, SEM, TEM and chemical analysis. BaTiO₃ powder obtained from the optimum condition exhibited spherical shape, high purity, submicron size with a narrow size distribution but some agglomeration. The rate of BaTiO₃ formation was very fast and about 99% yield of BaTiO₃ was obtained at 120℃

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High power carbon dioxide LASER weldability of a structual steel has been studied. The effect of welding parameters i.e. travel speed, power level applied, postion of focus and assist gas flow rate, on the weld penetration is discussed in this paper. Test results showed that penetration depth of the weld was increased with increasing applied LASER power. The ratio of the penetration depth to the bead width has a tendency of steady increase with increasing the travel speed up to 1.4m/min. Optimum range of the position of focus was proved to be 1.5±0.5㎜ beneath the surface.

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Joining of 304 stainless steel to Si3N₄, ceramic using Cu-34.8%Ag-6.2%Ti brazing alloy was made in vacuum furnace. Effect of In addition in Cu-Ag-Ti alloy, brazing temperature, and brazing time on interfacial rections and bonding strength of Si₃N₄-STS304 joints were investigated. Bonding strenght was determined by fracture shear loading and high shear strength value of more than 195 MPa were obtained for joints brazed with Cu-Ag-Ti-1.4% In alloy at 1123 K for 1.2ks. The strong bonding is attributable to the formation of continuous Ti_5Si₄(/TiSi) layer with 0.2㎛ thick by redox reaction between Si₃N₄ and Ti at Si₃N₄ ceramic interface. The Ti_5Si₃(/Ti_5Si₄) was formed on the continuous Ti_5Si₄(/TiSi) layer and the FeTiSi on those layers was uniformly formed by solid-state reaction of Ti_5Si₃(/Ti_5Si₄) with Fe segregated/diffused from stainless steel. Thickness of interfacial reaction layer was increased and bonding strength was decreased as brazing temperature and brazing time were increased. Types of fracture observed at the strength test of Si₃N₄/STS304 joints was classified and schematic diagram of fracture mode with joint strength was proposed.

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For joints showing high shear strength value of more than 160-202 ㎫ at room temperature, fracture mode and strength distribution were investigated after the introduction of thermal shock by water-quenching at 893K. Average shear strength of thermally-shocked Si₃N₄/304 joints were 64.7, 86.6 and 75.1 ㎫ respectively for Cu-Ag-Ti, Cu-Ag-Ti-Mo and Cu-Ag-Ti-Al alloy. Factor dominated the fracture mode and the strength distribution of thermally-shocked Si₃N₄/304 joints was four types of defects introduced by water-quenching. Predominant factors of these defects were maximum tensile component of residual stress formed into the Si₃N₄ ceramic under the reaction layer interface and cracks formed at the interface between 1`st(Ti_5Si₄/Ti_5Si₃) and 2`nd reaction layer(FeTiSi).

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The effects of boron and titanium on the hot ductility of 18Cr-8Ni austenitic stainless steel which was annealed at various soaking temperatures were investigated. Boron addition up to 54ppm increases hot ductility of this steel. Ti addition with small amount increases hot ductility slightly, however, more addition beyond 680ppm reduces its ductility significantly. The fracture crack by high temperature tension test was initiated and propagated mostly at r/δ-boundary or grain boundary. The cracks are, therefore, initiated and propagated earlier at the higher b-ferrite content. As δ-ferrite dissolution rate increases at lower soaking temperature within the range of 1230-1300℃, the hot ductility increases at lower soaking temperature.

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The effect of strain rate on the low cycle fatigue (LCF) properties of CM 247LC superalloys were studied. Two different strain rates of 0.05 ㎐ and 0.003 ㎐ were used for polycrystalline of Cm247LC. The microstructural changes and dislocation structures were investigated by electron microscopy. It was found strain rate does not affect cyclic dislocation structures, but dislocation recovery was believed to be affected by strain rates. At lower strain rate, i.e. 0.003 ㎐, the plastic strain was larger at constant total strains but the applied stress was smaller at constant plastic strain range. The increase in LCF life was resulted from the lower applied stresses at constant plastic strain range due to the recovery of dislocations at the lower strain rate.

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The present work is concerned with spheroidization of sulphidic inclusions in the heavy forged carbon steels by Ca treatment. Three kinds of, reduction processes(ⓐ conventional Al-deoxidation ; ⓑ Si-deoxidation with subsequent Ca-and Zr-addition;ⓒ : Al-deoxidation with subsequent Ca-addition) were conducted to correlate the measured oxygen contents during the reduction with the morphology of non-metallic inclusions. Elongated sulphidic inclusions were observed in the forgings made from the process ⓐ. Coarse or spheroidized non-metallic inclusions were observed in the forgings from the process ⓑ, depending upon the amount of dissolved oxygen. However, finely spheroidized inclusions were uniformly distributed in the forgings from the process ⓒ, whose dissolved oxygen was controlled to below 5-l0ppm. The optimum plant conditions for the formation of the finely spheroidized inclusions were obtained as follows: 1) Dissolved oxygen and total oxygen contents in the killed steel should be below 5-l0ppm and 60-70ppm, respectively, before Ca is treated. 2) Al content in steels should be above 0.007-0.019% prior to Ca adding. 3) The effective ratio of % Ca_(eff) to % S is 0.53-0.80, which is provided by addition of 0.020-0.025% Ca.

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To improve the corrosion resistance of heat resistant stainless steels (HRSS) at high temperature, pack aluminization of these steels was performed. Two kinds of HRSS (MO-RE 1, HK40) were used for pack aluminization during which the activity of an aluminum source was varied. Various microstructures of the aluminized HRSS were studied. To evaluate and study the corrosion resistance, cyclic corrosion tests in simulated COG (coke oven gas) combustion environment were performed. After the tests, the degradation mechanisms of the pack aluminized HRSS were presented. Especially, the inward diffusion rate of aluminum in aluminized HRSS was more pronounced than that in aluminized Ni-base alloys. In addition, the pack aluminized HRSS in the medium low activity of the aluminum source showed much better corrosion resistance than the uncoated HRSS.

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