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Spheroidal Graphite Cast Iron which was discovered a quarter century ago becomes more important as industrial materials owing to many studies and research. But there are still many problems. Authors investigated the some variables in manufaturing of pearlitic matrix-spheroidal graphite cast iron which is the strongest spheroidal graphite cast iron. The important results obtained are as follows; 1. It is important to choose good elements in manufacturing the pearlitic matrix-spheroidal graphite cast iron. Especially it is a good way to make this cast iron by addition of proper amount of the third elements like Cu, Mn in addition to C, Si. 2. To make a good pearlitic matrix spheroidal graphite cast iron (especially small size cast iron) which has no cavity, metal mold is better to be used. But in this case it is very important to choose proper temperature for the first step annealing to decompose cementite. 3. The thickness of the metal mold (cooling velocity) affects formation of cementite greatly and this cementite has influence on the effect of heat treatment.

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A series of samples from a mixture of 90 w/o W, 5w/o Ni and 5w/o Fe was compacted at 6 tons/㎠ and sintered at 1450℃ in the presence of a liquid phase at sintering times from 10 minutes to 15hours. The densities, tensile strength, elongation and Rockwell C hardness were obtained. The samples were sectioned and polished and the average size and the linear intercept distribution of the spherical tungsten grains in the matrix were determined. The densities of the samples were between 98.6 and 99.8% of theoretical density regardless of sintering time, but there appears to be a slight tendency towards lower densities, i.e. development of porosity, at sintering times longer than 4 hours. The size of the tungsten particles increases with sintering time. The tensile strenght of the samples is between 75 and 95 ㎏/㎟ and the elongation between 7 and 23 percent. It appears probable that the variation in tensile strength and elongation is related to the amount, size and distribution of porosity in the samples. The hardness decreases with increasing sintering time. When hardness is plotted vs average diameter of the tungsten particles it is found that with an average diameter of 14 microns the hardness is R_c27 but, that the hardness gradually decreases until with an average diameter of 30 microns or larger it is about R_c23. An attempt was made to interpret the data on tungsten particle size and particle size distribution as a function of sintering time on the basis of the existing theories of "Ostwald ripening". A plot of average particle size Vs sintering time shows that the relation d³=㏏ is quite well fulfilled. This according to Wagner points toward particle growth by a diffusion controlled mechanism of solution and precipitation. However, in order to make valid conclusions on the mechanism of particle growth, not only the change of average particle size with time, but also the particle size distribution must be taken into account. Therefore the linear interlept distribution was determined on more than 1000 intercepts for the samples sinterd for 1 hour and 15 hours. This intercept distribution was compared with the intercept distributions which Exner and Lakas derived from Wagner`s curves for particle size distribution for the cases of diffusion controlled and of interface controlled Ostwald ripening. It was found that it corresponded more closely to the stationary distribution postulated by Wagner for interface controlled repening than that for diffusion controlled ripening. Wagner`s distribution for diffusion controlled ripening was derived for the case where the mean free path between particles is much larger than the average particle size. Ardell modified the Wagner theory of diffusion controlled ripening for the case where the mean free path between particles is small, which is the case in the alloy of 90 w/o W-5 w/o Fe-5 w/o Ni. He showed that the dependence of average particle size upon sintering time would still follow the d³=㏏ relation, but that the stationary particle size distribution would be different from Wagner`s distribution. The smaller the distance between particles, the more would the particle size distribution approach that postulated by Wagner for interface controlled ripening. When Ardell`s theory is applied to the results for particle size and particle size distribution obtained in this thesis, it would indicate that in the W-Fe-Ni alloy the growth of the particles is due to diffusion controlled Ostwald ripening.

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Pure nickel and gold thin film were vacuum-deposited on (111) silicon single crystals. When Au/Ni/Si or Ni/Au/Si samples were heated to about 550℃ in situ, hexagonal or deformed hexagonal shaped crystallites were formed on silicon substrates. The formation mechanism and composition of these crystallites were determined by using X-ray diffraction, scanning electron microscopy and scanning Auger micro-probe methods. The crystallites were identified as NiSi₂. The crystallites on the (111) silicon plane parallel to the surface appeared as regular hexagons while the inclined crystallites resembled trapezia. The results of Auger spectra and in-depth composition profiles for Ni. Au and Si showed that the NiSi₂crystallites are islands in a matrix of Au-Si eutectic.

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Among the several known processes of semiconductor-grade silicon production, the hydrogen reduction of trichlosilane (TCS) is found to be the most convenient and economical method. In this study of high purity silicon production, the open tube flow process is used to reduce TCS with hydrogen. 99.9% pure TCS, manufactured by Ventron, is distilled for the starting material in the reduction. The distilled TCS is vaporized by bubbling at 0℃ with small quantity of hydrogen in a quartz tube. The resultant yield is compared with the theoretical one calculated thermodynamically. The yield of silicon is 60-70% at the optimum condition of 1100℃ reaction temperature and 60-100 mole ratio of hydrogen to TCS. Surface of the deposited silicon, a polycrystalline dense mass of lustrous appearance, is treated with hydrofluoric acid. By the emission spectroscopy the purity of silicon product is determined to be higher than 99.999%.

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In order to study the wear-resisting property of the austenitic high manganese steel, the wear rate per unit load was measured using the wear tester manufactured to simulate the abrasive condition. Hardness of the bulk and the abraded surface and the metallographic structure were also studied in relation to the abrasive wear resistance of the steel. It is shown that the wear rate per unit load (M) is related with each of the bulk hardness (H_B) and the abraded surface hardness (H_(A.S)) as follow: 1) M×10^5＝(14.008±1.758)－(0.0291±0.0046) H_(A.S) ㎎/㎝-㎏ 2) M＝24/1000(60)^(-n)×1/H_B ㎎/㎝-㎏ Expression 1) is empirical while expression 2) is semiempirical formula which has a relation with the bulk property of the steel. On the view of microstructure of the steel, it is found that the grain size (r) has no effect on the wear-resisting property of the steel, but the intercarbide spacing (d) has an marked influence on the M, and the obtained relationship is as follow: M×10^5－(5.4±0.3)－(43.0±6.07)×1/√d ㎎/㎝-㎏

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The effects of tungsten powder size, matrix phase content, copper addition, and sintering temperature on density and mechanical properties cf sintered W-Ni-Fe heavy alloy have been studied. The W particle sizes were 0.95μ, 2.91μ, 6.0μ, and (Ni＋Fe) contents were 10% and 2%. The Ni to Fe ratio were always maintained at 1 to 1. For 90W-5Ni-5Fe specimens part of Ni and Fe were replaced by 0.5, 1, and 2% Cu. The tensile test specimens were prepared by usual powder metallurgy techniques. The compacts were sintered at various temperatures between 1000℃, and 1460℃, for 30 minutes in hydrogen atmosphere. The density, ultimate tensile strength, elongation, and hardness of the sintered specimens were measured. For all 90W-5Ni-5Fe specimens with different W powder size densities around 99% of the theoretical density were obtained after sintering in the liquid phase sintering temperature. In solid state sintering, the specimens with smaller W powder size showed larger sintered density. Both the ultimate tensile strength and elongation of these specimens show rapid increase when the sintering temperature approaches the expected solidus range. Although for specimens sintered at around 1400℃ it is possible to obtain high densities, the mechanical properties were found to be poor. In solid state sintering between 1100-1350℃ the specimens with 2% (Ni＋Fe) show higher relative density than those with 10% (Ni＋Fe). This result appears to be consistent with Brophy`s observation that n activated sintering of W-Ni compacts the highest densification occurs with 0.25% Ni. The specimens with 2% (Ni＋Fe) showed low tensile strength and quite brittle at all sintering temperatures. For 90 W-5 Ni-5 Fe specimens, the size of W grains after 30 minutes of sintering at 1460℃ appears to be independent of the original W powder size. And the W grain size of 90 W-5 Ni-5 Fe specimens are smaller than that of 98 W-1 Ni-1 Fe after liquid phase sintering. For 90 W-5 Ni-5 Fe specimens small Cu addition has little effect on densification during sintering. Substituting 1 or 2% of copper for (Ni+Fe) in the matrix phase produced a typical liquid phase sintered microstructure, in the temperature range of 1350 to 1400℃, which was not found in the specimens with 0.5% copper added or without copper. The Tensile and elongation properties of the specimens with 1 or 2% of copper were at a maximum at the lowest temperature which gives typical liquid phase sintered microstructure. By increasing the temperature above the lowest liquid phase sintering temperature, the tensile strengths and elongations of the specimens were decreased. Some attempts were made to explain the observed results by the present theories of liquid phase sintering and activated sintering. The results on W grain growth are difficult to explain unambiguously by present theories.

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The equilibrium partial pressure of oxygen obtained by mixing CO₂and H₂gas was determined with (ZrO₂)_0.85 (CaO)_0.15 solid state cell by means of E.M.F. measurement and the compound of SrO-Fe₂O₃system was studied. The results obtained as follows 1) The oxygen partial pressure by E.M.F. measurement was consistent with that which was calculated from equilibrium data when the initial ratio of mixing was nearly 1 2) Sr₃Fe₂O_(7-x) was tetragonal. According to decreasing oxygen contents of this phase, lattice constant of a_o was increased and b_o was decreased. 3) The composition of SrFeO_(2.50－2.34) was rhombohedral single phase, SrFeO_(2.54－2.74) contained cubic and rhombohedral two phases, and SrFeO_2.74 was single cubic phase.

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The effect of iron on the mechanical properties and microstructures of Cu-11.2 weight % Al alloy in the isothermal transformation was investigated by tensile test and metallographic techniques. This investigation results showed that the addition of two weight % iron in Cu-11.2 weight % Al alloy with proper heat treatments produced the fine microstructures and the fine precipitate particles in the α phase and these microstructures had pronounced effects on the ultimate tensile strength. The ultimate tensile strength of 110,000 psi was obtained at room temperature.

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