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The hydrogen storage properties of TiFe and its alloys, partially substituted by Mn or A1 for Fe were studied. Sievert`s type apparatus and high pressure autoclave were used. When Fe is partially substituted by Mn, the hydrogen storage capacity is little changed and the stability of the hydride was slightly increased ans activation is promoted. Partial substitution by Al promotes activation markedly but reduces hydrogen storage capacity significantly. Enthalpy changes of hydride formation calculated by applying Lutz`s are in good agreement with those from experiment in TiFe_(l-x)Mn_(x-)H system. The cracking phenomena on hydride formation is closely related to activation procedure.

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Temperature dependence of the hyperfine field and the isomer shift at (119)^Sn nuclei in fcc and hexagonal Co has been measured from 83˚K to 754˚K. The hyperfine field of fcc and hexagonal Co are 18.5 and 50.8 k0e respectively at 83˚K, 3-0 and 9.5 k0e at 673˚K. The dependence of the field on temperature is quite anomalous and shows a similar fashion in both structures. This dependence might be caused by the formation of localized moment at the Sn atom.

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Dual phase steels with 0.03％ carbon and various manganese contents of 1.4％, 1.9％ and 2.3％ were made in laboratory, and their mechanical properties and ageing behaviors were studied. In the water-quenched dual phase steels, as manganese content increased, work hardening rate and strength-ductility combination increased. Due to the higher manganese content, dual phase steels of ferrite and martensite were able to be obtained by slow cooling instead of water-quenching. Mechanical properties of dual phase steels made by slow cooling were superior to those made by water-quenching, because slow cooling made the ferrite matrix cleaner by decreasing the solute carbon content. The activation energy for ageing was estimated as 27±3 ㎉/mole in 1.4％ Mn dual phase steel. This value is higher than that for carbon diffusion in ferrite, 20 ㎉/mole. This difference seems to be attributed to the attraction between carbon and manganese atoms.

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The normal AISI 52100 steel widely used as bearing steels shows very different properties with austenitizing and tempering temperatures. A study on the 1.0％C-1.4％Cr steel revealed that the contents of undissolved carbide was decreased with austenitizing temperature, and the martensite was plate martensite which has internal twins oriented {112}_T, the retained austenite was increased with the austenitizing temperature, and transformed to martensite with sub-zero treatment, with tempering temperature, the carbide was increased and over aged at 250℃ and the orientation relationship with matrix was as follows. { 011 } m // { 0001 }_ε The hardness value was increased with austenitizing temperature, but above 840℃ the hardness value was changed slightly and decreased with tempering temperature.

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Microstructure and texture of 3% silicon-iron alloys containing boron, carbon, sulfur and manganese were studied as a function of cold work using two stage cold reduction method. The amounts of cold reduction were 20∼80 percent in both the first and the final cold rolling stages. A new phenomenon was observed; it was found that, contrary to the previous reports, a final cold reduction of 80% or more is not necessary to develop strong (110) [001] texture in the boron silicon steel. It was also found that the texture inhibition plays no significant role on the secondary recrystallization in the boron silicon steel.

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Effects of austenitizing and tempering temperatures on the Charily impact toughness of AISI 4340 steel have been investigated. The ductile to brittle transition temperature of AISI 4340 steel is lowered with increasing austenitizing temperature from 790℃, showing a trough at 900℃, and then is raised with increasing austenitizing temperature beyond 900℃. The room temperature impact toughness of AISI 4340 steel is also superior when austenitizing treatment is done at 900℃, while the toughness is inferior when the austenitizing temperature is deviated from the 900℃. A trough in room temperature Charpy impact energy, indicative of temper embrittlement, is observed at 350℃ tempering. This temper embrittlement phenomenon is also observed in ductile to brittle transition temperature and -196℃ impact energy. The prior austenite grain size is gradually increased with increasing austenitizing temperature from 790˚to 900℃, however, the grain coarsening proceeds rapidly with increasing austenitizing temperature above 900℃.

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A droplet emulsion technique which allows a deep undercooling (0.3-0.4Tm) at slow cooling rate (10-30℃/min) has been applied as a model approach to study the basic solidification mechanisms associated with rapid solidification processing. When a liquid metal is undercooled substantially, the crystal growth following nucleation will be rapid regardless of the cooling rate. Often, the usual solidification reactions can be suppressed at high undercooling by the formation of metastable solid solutions, intermediate phases and in some cases amorphous solids. The kinetic phase selection mechanism has been examined by a controlled nucleation catalysis experiment in which the primary solid solution is established as one type of suitable catalytic site for the generation of metastable phases during nucleation. Phase selection promoted by undercooling and known nucleation catalysis reactions provides numerous possibilities for nucleation controlled structure modification. This indicates that rapid solidification powder processing not only has a valuable potential for grain refinement, but also has extensive possibilities for microstructural modification.

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