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The first-order approximated quasi-chemical model of Fe-base ternary system containing interstitial and substitutional solutes suggested by R. B. McLellan have been modified for dilute solid solutions with assumption that the interaction energy (εii) between interstitial solutes is zero. The interaction energy (Δε) between substitutional and interstitial atom and the diffusivities of interstitial elements in various substitutional compositions of Fe base system are calculated using published solubility of the system and diffusivity of Fe-interstitial binary data with above model. The nitrogen diffusivities in liquid Fe base binary alloys predicted by the above model with the assumption of ε_(NN)=0 agree with experimental results with some accommodation factor.

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This work investigates the hardening mechanism of the low carbon steel by adding NiAl inter-metallic compound. The specimens was carted to have 0.15C-Ni-Al component in which the amount of NiAl was varied. These specimens were air cooled after solution treatment at 1100℃ for 1.5 hours and aged for various holding periods at 550℃. Mechanical testings have been performed to find out the proper heat treatment condition for the best mechanical properties. X-ray diffraction and electron diffraction techniques, and transmission electron microscopic observation show that NiAl particles have been precipitated and the particles maintained coherency with the matrix. It has been concluded that the maximum strength was obtained when the specimens were aged at 550℃ for 8 hours. The strength and hardness values are increasing with the amount of NiAl component in the steel but the maximum impact strength was obtained in the sample in which 3% of NiAl component was contained.

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In the case of liquid phase sintering, the role of liquid is of great significance, since the liquid flow enhances the mass transport. And as many sintering mechanisms are involved, it is difficult to observe only one mechanism in the liquid phase sintering. In the experiment, W-Cu system with mutually insoluble component had been chosen in which the solution and recipitation does not occur, and the rearrangement of W particles had been observed in W-Cu system. The main results are summarized as follows. Liquid phase sintering occurs by the liquid coagulation and outward expansion of the dense region with the increase of sintering time. Raising the temperature increases the shrinkage of specimens. With the increase in liquid contents and the decrease in the particle size, relative density and shrinkage are increased. The disintegration of polycrystalline and agglomerated powders had been observed.

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A mathematical model for the precipitation of spherical particles has been developed for the growth stage of particles where no further nucleation is accounted for. The applicability of the model has been tested by measuring the rate of precipitation of potassium, Jarosite from ferric sulfate solution at elevated temperatures, and the agreement was found to be satisfactory. The analysis of results revealed that the precipitation of potassium jarosite is controlled by the interface process of an activation energy 6.2 ㎉/㏖. It is also interesting to note that the lower the initial concentration of ferric sulfate and the ratio of iron to potassium, and also the higher the basicity of solutions, the higher the yield was obtained.

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1. The simultaneous dephosphorization and desulphurization of carbon saturated iron were possible with the use of fluxes which contained CaF₂, Na₂CO₃, Fe₂O₃or Na₂B₄O_7 in CaO base. 2, The high desulphurization degree over 80% was obtained within 20-25 minutes, but dephosphorization degree was comparatively low as showing 40-50% and rephosphorization was occured because of reduction loss of effective components such as iron oxide and Na₂O. 3. The distribution equilibrium of phosphorus between slag and metal was formulated quantitatively by estimating the effect of slag composition on P₂O_5 activity. 4. The rate of dephosphosization and desulphurization satisfied a first order reaction equation when driving forces were expressed by differences from equilibrium concentration. Apparent rate constants were variable with slag composition and it was considered that chemical reaction is a rate determining step.

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Effects of Al content and the degree of cold working on the anneal hardening of αAl bronze were investigated by using hardness measurement and transmission electron microscopy. A maximum anneal hardening was obtained at annealing over the temperature range from 250℃ to 350℃ for about 10 mins. The hardening increased with increasing stacking fault density. The anneal hardening was influenced more by the degree of cold working than by the solute content. Rearrangement of stacking fault during heating was directly observed in an electron microscope, which might give rise to decreasing internal energy of the material. The anneal hardening of the material could be attributed to segregation of solute atoms at stacking faults.

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