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Effects of WF_6 gas flow rate on the propeerties of selective CVD-W by SiH₄ reduction have been investigated. SEM microstructure for W film changes from a leaf-shaped large grain, via a starshaped small grain and a small oval grain to a fine grain with decreasing WF_6 flow rate. The thickness of WSi_x transition layer increases with increasing for SiH₄/WF_6=R$lt;0.9, but it decreases rapidly for with increases 0.9 $lt; R $lt; 1.1 These changes seem to be related to the phase transition from α-W to β-W. In addition deposition rate tends to decrease, and resistivity also tends to decrease with increasing WF_6 flow rate. The largest decrease in deposition rate and resistivity occurs for the WF_6 flow rate in the range of 9-11 sccm.

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A study has been made of the crystallography and thermal stability of Cu-Zn-Al Shape Memory Alloys. The structure and the phase transformation of the alloys were studied by X-ray diffractometer, electron microscopy and resistivity measurement. The damping characteristics of them were also measured. The Ms temperatures varied from -61℃ to 77℃ with concentration of Zn and Al. The cystallographic structure of the parent phase and martensite was found to be DO₃(or L2₁) and modified 18R(β=88°) respectively. When aged at temperatures ranged from 250 to 350℃, the transformation temperatures were lowered and a maximum hardness was obtained. The aged Cu-26Zn-4.75Al and Cu-21Zn-6Al alloys had the structure of mixture of αand βwhereas the Cu-14.9Zn-8Al alloy had a and r structures. The Cu-14.9Zn-8Al alloy had a considerably higher thermal stability than others.

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A study has been made of the crystallography and thermal stability of Cu-Zn-Al Shape Memory Alloys. The structure and the phase transformation of the alloys were studied by X-ray diffractometer, electron microscopy and resistivity measurement. The damping characteristics of them were also measured. The Ms temperatures varied from -61℃ to 77℃ with concentration of Zn and Al. The cystallographic structure of the parent phase and martensite was found to be DO₃(or L2₁) and modified 18R(β=88°) respectively. When aged at temperatures ranged from 250 to 350℃, the transformation temperatures were lowered and a maximum hardness was obtained. The aged Cu-26Zn-4.75Al and Cu-21Zn-6Al alloys had the structure of mixture of αand βwhereas the Cu-14.9Zn-8Al alloy had a and r structures. The Cu-14.9Zn-8Al alloy had a considerably higher thermal stability than others.

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Effects of the cobalt content on the recrystallization temperature were studied in Ni-Co binary alloys. As the cobalt content was decreased from 65wt% Co, the number of dislocation cell in unit area of the Ni-Co alloy cold-rolled 90% at room temperature was increased, and the dislocation cell wall thickness and dislocation density in it became smaller. The specific peak area in the DTA curves of the cold-rolled Ni-Co alloys was almost constant regardless of the cobalt content below about 30wt%, but was increased rapidly with increasing the cobalt content above 30wt%. The recrystallization temperature of the Ni-Co binary alloy was increased with increasing the cobalt content below about 30wt%, but was decreased with increasing the cobalt content above 30wt%. From this result, it was concluded that the recrystallization nucleation occurred by the cell coalescence in the composition range below about 30wt% Co, but in the composition range above the 30wt% Co the nucleation occurred under the stored energy acting as driving force for the nucleation like the classical homogeneous nucleation theory in phase transformation.

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The effects of sulphur and phosphorus segregated at grain boundaries on the hydrogen trapping in S-steel and Ni-Cr-steel as compared to pure iron have been studied using gas phase hydrogen charging and electrochemical detection techniques. The segregation of sulphur and phosphorus was performed by tempering the Fe-S and the Fe-Ni-Cr-P specimens, respectively. This was ensured form AES spectroscopy and SEM micrography, respectively. The hydrogen trap densities and trap binding energies were determined from plots of time lag against inverse square of input hydrogen pressures. The trap densities for the annealed Fe-S specimen and the tempered Fe-S specimen were found to be about 1.1×10^(-7) and 3.0×10^(-7)㏖/㎤, respectively, and the trap binding energy for the both specimens was determined to be about -57kJ/㏖. In the case of pure iron specimen, the trap density and trap binding energy were 1.2×10^(-7)㏖/㎤ and -56kJ/㏖, respectively. The annealed Fe-Ni-Cr specimen and the tempered Fe-Ni-Cr-P specimen showed the trap binding energies of -53 and -55kJ/㏖, respectively, and the both specimens had approximately the same trap density of 1×10^(-6)㏖/㎤. From the experimental results, it is suggested that sulphur and phosphorus segregated at grain boundaries act as saturable deep trap sites for hydrogen in S-steel and Ni-Cr-steel, respectively.

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Thin Al₂O₃ films were prepared by dipping substrates into coating solutions, pulling them up, drying and then hearing processes. A sol-gel process, which comprises precipitation of aluminum monohydroxide, formation of sol and gel, was used to produce coating solutions. Effect of preparation conditions on the properties of films was examined. The viscosity of coating solutions was controlled by gelling time, and two kinds of substrates, slide glass and stainless steel were used. The contact angle between the substrate and coating solution was measured by the captive bubble method. An air bubble in the solution was not adhered to both slide glass and stainless steel. These phenomena mean the wettabilities of solution to the substrates are good. The thickness of coating films was increased with increasing the viscosity of solution, and with increasing the number of coating cycle. Defects such as, crack, opaqueness or peeling off were observed when the viscosity was higher than 10 cps. Scanning electron microscopy and wavelength dispersive X-ray analysis have been used to determine the interaction occuring at the interface. The diffusion of aluminum from the film into the substrate is confirmed by these analyses. Therefore possible bonding mechanism of Al₂O₃ films at the interface may be explained in terms of mixture of chemical reactions and diffusion of multi-component oxides.

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The impact energy of 93W-4. 9Ni-2. 1Fe(wt %) alloy decreases sharply with the concentration of sulfur added up to 200 ppm even after heat-treatment at 1150℃ in N₂ atmosphere and waterquenching. The result shows definitively that the S present at the level of a few tens ppm causes an embrittlemext of this alloy. The structure and the composition of the fracture surface are consistent with the previous suggestion that the embrittlement arises from S segregation at the grain-matrix interface. With the addition of Ca or La to the S doped alloy the impact energy increases to that of the alloy without S. The fracture structure and the S concentration measured at the interfaces also show that Ca or La addition suppresses effectively the S segregation at the grain-matrix interface by forming S containing Ca or La compounds. When Ca is added to the alloy to which no S was deliberately added (with about 19 ppm P and 1 ppm S), the impact energy does not vary with the cooling rate after the heat-treatment at 1150℃, and is unaffected by additional heat-treatment at 600℃. It appears that P segregation and its embrittling effect are also reduced by forming P containing Ca compounds. The variation of the impact energy of this alloy with the amount of S or P in the raw material powder or with the heat-treatment condition can therefore be substantially reduced by adding Ca or La.

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This study aims to investigate the effects of vanadium(V) and titanium(Ti) alloying elements additions and cooling rate on the morphologies of eutectic carbide, secondary carbide, the austenite retention in the matrix, and heat treatment characteristics for hypoeutectic chromium cast iron with 2.5% C, 14% Cr, 0% to 2.2% V, or 0% to 0.6% Ti alloying elements. The specimens for unidirectional solidification were melted at 1500℃ and casted into an exothermic furan mold(30㎜×70㎜) placed on the water cooled copper chill, and were solidified unidirectionally. Also, the specimens for study of heat treatment characteristics were casted into the furan mold and were treated by different heat treatments (cyclic heat treatment, destabilization heat treatment). The eutectic and eutectoid transformation temperature rise both with the increase of Ti and V contents in the specimen. With the increase in Ti and V contents, the eutectic carbide is decreased, the second carbide is increased. The morpholigies shape of second carbide is changed from the bar to the finer granular type as increase in both(Ti,V) contents. For cyclic heat treatment, the hardness is improved with the increase of number of cycles, because hardness depend on the fine matrix as well as the amount of carbide and martensite.

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Mechanical alloying of Al-8wt % Fe mixed powder has been studied. The effects of process control agent(stearic acid), the ratio of grinding media/powder and mechanical alloying times on the microstructure were investigated. Differential Scanning Calorimetry(DSC) measurements indicated that most of process control agent was dispersed through the body of each mechanically alloyed powder particle during milling. After 1000 minutes milling, mechanically alloyed particles were shown the character of steady state. At steady state the particles have a uniform size distribution, a saturation hardness, an equiaxed shape, a composite structure and a chemical homogeneity. The intermetallic compound phase of Al₃Fe was identified by Xray diffraction analysis.

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Since the reverse shape memory effect(RSME) has been reported in a Cu-Zn-Al alloy, further studies have been done to ascertain the mechanism of this phenomenon and are reported to be caused by the bainitic transformation(β₂→α₁→α) on heating. But in the previous work, we suggested that the RSME in a Cu-Zn-Al alloy is not caused by the shear process involved in the bainitic transformation but by transformation from two-step transformed martensite(β₂→ β`₂→α`₂) t a phase by means of the XRD, TEM and micrographic observations. On heating after bending deformation in a parent phase state, the specimen shows both shape memory effect(303-473 K) and RSME(493-693 K) with increasing temperature, thus the shape change of sheet changed spontaneously. During aging at below and above of the bainitic transformation temperature, the sheet showed a small shape change but, heating to 693 K after aging, it showed a large shape change. Therefore the RSME occurs when the remaining two -step transformed α₂ phase introduced by bending deformation or heating is transformed into α phase and the bainitic transformation is not a principal mechanism although it contributes to the RSME.

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