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The effect of misch metal, Ti, Ni and Mn on damping capacity of Cu-Zn-Al shape memory alloys and the optimum heat treatment condition for high damping of the alloy have been studied. Specific damping capacity(SDC) of both Cu-Zn-Al alloys and the elements added Cu-Zn-Al alloys show amplitude dependence and increase with increasing maximum strain amplitude. Maximum SDC of the Cu-Zn-Al alloys are not dependent of composition, but nearly constant about 42% in the range of transformation temperature. Maximum SDC of the elements added alloys is, however, decreased a little but the step quenching and low temperature aging process is suitable heat treatment condition to increase in SDC of the elements added alloys.

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The influence of solidification rates on the morphology and distribution of δ-ferrite and eutectic niobium carbides was studied using Bridgman-type unidirectional solidification apparatus in order to simulate the solidification pattern of a large-scale ingot of 12% chromium rotor steel. The volume fractions of the δ ferrite contained in the specimens solidified with the withdrawal speeds of 225 ㎜/hr, 45 ㎜/hr, and 4.5 ㎜/hr were measured to be 7%, 5%, and 30% respectively. δ-ferrite was finely distributed in the case of the withdrawal speeds of 225 ㎜/hr and 45 ㎜/hr, but the distribution was coarse network type in the case of the withdrawal speed of 4.5 ㎜/hr. When hot compressive working was applied in temperatures from 950℃ to 1250℃, 3-ferrite was transformed into carbides and austenite at the interface of δ-ferrite with the matrix. Subsequent heat treat melts result in a complete annihilation of δ-ferrite in the case of fast withdrawal speeds, but result in only a partial annihilation in the ca -e of the slow withdrawal speed, 4.5 ㎜/hr.

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Pellets made of blast furnace sludge were reduced utilizing mixed carbon in CO 30%-N₂70 % gas mixture, and effects of carbon content and temperature on reduction rate were studied. Swelling was observed when the pellets were reduced at 900-1,000℃, while sintering occurred at temperatures above 1,100℃. Reduction rate of iron oxide increased rapidly when the carbon content and/or temperature were increased. Formation of low-melting slag retarded the reduction rate. In order to accomplish dezincing process effectively, reaction temperature should be kept above 1,000℃.

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Effects of tensile hold time on low cycle fatigue behaviors of AISI 304L stainless steel base metal and weldment were investigated at 823 K in Ar atmosphere. The weldment was prepared by the SMAW process with the welding direction parallel to the rolling direction. The microstructure of the barre metal and the weldment consisted of γ phase and duplex γ/δ-ferrite, respectively. The experimental results indicated that, with decreasing plastic strain amplitude, the fatigue life of weldment is significantly decreased, when it is compared with that of the base metal. This is considered to be caused by the microstructural differences between the base metal and the weldment. The results of tensile peak strain hold of 10 min show the decreased fatigue life compared with that of continuous cycling. This is considered to be caused by crack growth during tensile hold time.

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The kinetics of crystallization process of amorphous Fe_(80-x)Co_xSiP_(14)(10≤X≤50) alloys has been investigated by measuring electrical resistivity in order to understand the crystallization mechanism in this system. The amorphous ribbons were prepared by rapid quenching method using a single roll. The crystallization processes with respective composition are as follows, amorphous→amorphous+ (Co -Fe)₂P→α-Fe(Co, Si)+Fe₃P+(Co-Fe)₂P for X= 10, amorphous→α-Fe(Co, Si)+Fe₃P+(Co -Fe)₂P for X=20, and amorphous-α-Fe(Co, Si)+(Co-Fe)₂P for (30≤X≤50). The first and the second activation energies for the composition of X=10 are 26 ㎉/mole and 89 ㎉/mole, respectively, The activation energy for the composition of (20≤X≤50), whose crystallization occurs in a single step, is in the range of 80-63 ㎉/mole and decreases with Co content. The first and the second crystallization temperatures of the amorphous of X= 10 are 717k and 730k, respectively. For the composition of (20≤X≤50), the crystallization temperature is in the range of 725-670K and decreases with Co content.

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The Structure and magnetic properties of amorphous Fe_(80-x)Co_xSi_6P_(14) (10≤X≤50 mole %) alloys have been investigated. The amorphous films were manufactured by a single roll rapid quenching method. The coordination number and the average distance of nearest neighbor were determined from X-ray diffraction experiment, using the dense random packing model, and are 12.2±0.2 and 2.50 ± 0.03A, respectively. The saturation magnetization and the average magnetic moment of a transition metallic atom at OK are 163emu/gr and 1.87 for X=10, and 130 emu/gr and 1.53 for X=50, respectively, The Curie temperature are 630 K for X=10 and 727 K for X=50. The saturation magnetostriction, coercive force and maximum permeability of the amorphous are 9×10＾(-6)∼16×10＾(-6), 0.2∼0.3 Oe and 4.0×10⁴∼5.0×10⁴, respectively. The Curie temperature increases with Co content While the saturation magnetization, the average magnetic moment, coercive force and the saturation magnetostriction decrease with Co content.

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The microstructures of pure Co and Co-transition metal binary alloys made by sputtering have been studied. The film structure of pure Co is the randomly oriented hcp structure. The interplanar spacing of Co-Nb, Co-Ti and Co-Mo alloys continuously increases with increasing the solute concentration, but that of Co-Zr initially increases and does not change from 4 at.% Zr. This trend was interpreted as the difference of solute limit. In Co-Mo alloys, the phenomena which grain size is remarkably increased with decreasing the cooling rate is revealed, and this is discussed as the preferred growth effect of [001] direction perpendicular to the film plane.

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The effect of TAHA treatments involving pre-aging, plastic deformation and final-aging on the fatigue crack propagation near ΔK_(th) in 7050 Al alloy was investigated. The TAHA treatments could improve the ΔK_(th) value nearly 10% without sacrifice of the tensile properties when compared to the conventional T6 treatment. The fatigue crack propagation rate near threshold was studied using the ΔK decreasing method. The crack growth rate near ΔK_(th) in T6 and TMT treatments markedly decreased as ΔK decreased compared to that in T74 treatment. This is thought to be resulted from the roughness-induced crack closure due to the planarity of slip caused by shearability of precipitates and the crack deflection. The ΔK_T transition values and the degree of roughness-induced crack closure were thought to be the controlling parameters to determine the ΔK_(th) values in this alloy.

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The effect of deformation on the transformation behavior in Ti-Ni alloy was studied. Coil spring of Ti-Ni alloy used as element of tilt plate type heat engine, was cyclically expanded and contracted by temperature difference. The Results obtained in this study are as follows. 1. By the cyclic deformation, M_s and A_f decreased with increasing the number of cycles, however, M_s remained constant. The cycling effect was caused by the generation of dislocation during cyclic deformation 2. The cycling effect (decrease of M_s and A_f) increased with the increase of the heat treatment temperature and deformation strain. When the cyclic deformation was conducted in the temperature range of B2↔R-phase, transformation temperature changed little. 3. That unrecovered strain appeared to be proportional to the amount of decrease of M_s and A_f confirmed that cycling effect was caused by introduction of dislocation during deformation.

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SGCI(spheroidal graphite cast iron), CVGCI(CV graphite cast iron) and FGCI (flake graphite cast iron) were made as cast, SGCI was rolled and the resonant frequency, damping coefficient, hardness and tensile strength were investigated. As the reduction rate of as rolled SGCI increases, the resonant frequency decreases and damping coefficient increases. As the graphite nocularity increases in as cast iron, the resonant frequency increases and damping coefficient decreases. Above 30% reduction rate, as roiled SGCI shows the better damping capacity than that of as east CVGCI and above 60% reduction rate, as rolled SGCI shows the better damping capacity than thats of as cast FGCI As the reduction rate of as rolled SGCI increases, the hardness and tensile strength increase.

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