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Effects of the heating rate of primary recrystallization annealing on the textures and secondary recrystallization of 3% Si-Fe grain oriented silicon steels were studied. The heating rate was varied from 2.5℃/sec to 40℃ /sec. The higher the heating rate was, the finer microstructures was obtained in the primary recrystallized sheets. [110] pole intensity at the surface of primary recrystallized sheets became stronger as the heating rate increased whereas [222] intensity became weaker. As to the secondary recrystallization, the increased heating rates resulted in lower formation temperature and smaller grain size and, consequetly, larger scattering in the magnetic properties. In addition, 180˚domain wall spacing was widened due to the grain size as the heating rate decreased. Therefore, the effect of the tension was found to be more pronounced in the specimen treated with lower heating rate.

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Phosphorus as a strenthening element has been added in extra low carbon steels and proved to be quite effective. The investigation of its role in recrystatllization in the titanium stabilized extra low carbon steel is the main purpose in the present work. The addition of phosphorus in the titanium stabilized steel exhibited the serious retardation of recrystallization and the development of the strong {111} recrystallization texture even after annealing at 900℃ while the phosphorus free titanium steel revealed the distantlement of the {111} texture after 800℃. Phosphorus was then found to be a fairly effective element to inhibit originally the movement of dislocations during recovery and thus retard the formation of the subgrains leading to the development of the recrystallized grains.

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To ensure a uniform composite of aligned copper dendrites in a protective lead matrix for possible application as grids in lead-acid batteries, Pb-20wt%Cu alloy has been directionally solidified in a constant temperature gradient, G₁=4.5K/㎜, with constant growth velocities, 10 and 20㎛/sec. The solidification parameters of growth orientation with respect to gravity vector and sample diameter have been correlated with the resulting microstructure. At this slow growth velocity, the rejection of lead-rich liquid by the copper dendrites increases the density of the liquid, leading to convection and consequently, to severe macrosegregation and a non-uniforem structure. A novel technique in which the sample tube is rotated while being solidified in a horizontal position, has been tried and found to promote a uniorem and continuous Cu dendrite morphology.

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The properties of the metal hydride electrode prepared with PTFE as a binder have been investigated. The LMNi_(4.5)Co_(0.1)Mn_(0.2)Al_(0.2) hydrogen storage alloy powders were coated by 25wt.% electroless copper plating in an acid bath, mixed with 3 to 10wt% PTFE, and then compacted at 6 ton/㎠ at room temperature. The electrode characteristics were examined through electrochemical measurements in a half cell. The electrochemical measurement showed that the addition of PTFE decreased slightly activation time at a low current. At a high current, however, the activation rate decreased with increasing the amount of PTFE. The electrode property at low temperatures was improved by adding PTFE, whereas it became worse at hgh temperatures. When the charged electrode was stored in the electrolyte for more than 1 day, the discharge capacity decreased dramatically due to a self deactivation of the alloy surfaces, but not due to a self discharge. The charge retention was scarcely changed by the addition of PTFE. The cycle life was not influenced by either one of the addition of PTFE and graphite, and sintering. On the other hand, the sintering under argon gas of low purity has oxidied the alloy powder resulting in reduction of discharge capacity. The degadration of the electrode was strongly dependent on the exposure time to electrolyte and the number of cycles.

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Creep properties of Ni-base Mar-M247LC superalloy were investigated in the temperature range 760-980℃ as a function of the γ′ particle size. The particle size is shown to have a spectacular effect both on the creep behavior and stress rupture life in relation to the micro mechanism of plastic deformation. At the creep condition of 760℃-650MPa, the large γ′ size of 1.0㎛ results in optimum creep strength and rupture life of 150hrs. At higher temperatures, 870℃ and 980℃, the γ′ sizes which can improve on creep strength and life decrease to 0.5㎛ at 870-380MPa and 0.3㎛ at 980㎛-180MPa. The dislocation behavior of plastic deformation is related to the γ′ size and rupture life. In the large precipitates, the deformation occurred by homogeneous multiple slip in matrix leads rapidly to the formation of dense dislocation networks at the γ/γ′ interfaces and decreases the creep rate. Reducing the γ′ size promotes the heterogeneous deformation by shearing γ′ and leads to short rupture life.

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The wear mechanism of hypereutectic Al-Si alloys was almost independent of the initial shape and size of Si particles. However, the wear of this alloy depended on the hardness of counterbody and the sliding velocityIn experiments conducted on the counterbody having a hardness of 36HRC at sliding velocities from 0.074 to 0.277m/sec, a complex wear of the abrasive, the delamination and the adhesive wear took place. In case of the counterbody having a hardness of 51HRC at sliding velocities from 0.074 to 0.277m/sec, the wear resistance of T6 heat treated alloys increased with decreasing size and aspect ration of Si particles. The wear volume decreased with increasing counterbody hardness. The elasto-plastic finite element analyses have been made of the rotation of Si particles, the stress distribution in surface layer and the effects of morphology of Si particles on the stress distributions at the Si particle-Al matrix interface during slow sliding.

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The Effect of substrate materials on diamond deposition behavior was investigated by hot filament CVD method. The growth rates of diamond particles on Cu, W, Mo, Ti, Si, SiC, Si₃N₄ and Al₂O₃ substrates are identical under a given deposition condition. On the other hand, for Cr, Fe, Co and Ni substrates, the shape and growth rate of diamond were observed to be dependent on the substrate materials. Furthermore, the deposition behavior is different from those of above-mentioned series of substrate. The substrate atom is detected on the surface of diamond particles in the case of Cr, Fe, Co, Ni. This result is inconsistent with the previous reports that the growth rate is dependent on the substrate materials as Cu, W, Mo, Ti, Si, SiC, Si₃N₄ and Al₂O₃ substrates. The possibility of this inconsistence is discussed in terms of a possible error in surface temperature measurement.

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Functionally gradient materials(FGM) are hybrids of two dimensional materials in which effective properties change gradually over a macroscopic distance. On the basis of this construction of materials the optimum composition profile was proposed to reduce thermal stress for two kinds of ceramic-metal assemblages. The effective properties and thermal stresses were calculated by numerical method assuming spherical ceramic particles were embeded in the metal matrix. Tensile thermal stresses were greatly reduced in the ceramic-to-metal transition zone and the stress distribution was changed with the composition profile and the dimension of transition zone.

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A systematic study of crystallization characteristics in the Fe-Ni-B amorphous alloys has been carried out by annealing at temperatures ranging samples from room temperature to 970K in vacuum. The analysis of the Mo ssbauer spectrum along with supporting X-ray diffraction and DSC measurements is presented. By the Mo¨ssbauer spectroscopy, the crystallized phase in the Fe_(80-x)Ni_xB_20 amorphous alloys consisted of γ-(FeNi), t-Fe₃B or γ-(FeNi), o-(FeNi)₃B, t-Fe₃B for x≤30, γ-(FeNi) and o-(FeNi)₃B for x=40. Two-step crystallization was observed in the alloy system of (Fe_(0.5)Ni_(0.5))_(100-x)B_x for x＜18(amorphous→amorphous+γ-(FeNi)→γ-(FeNi)+o-(FeNi)₃B) and o-(FeNi)₃B was observed for x>20. The t-Fe₃B phase is unstable and changes to t-Fe₃B at higher temperature. The phase transition for t-Fe₃B to t-Fe₂B sensitively depends on the Ni content in the Fe_(80-x)Ni_xB_20 amorphous alloys with x≤30. Increasing the amount of either Ni or B in the alloys, it is easier for the o-(FeNi)₃B phase to be found. The results indicate that a chemical ordering occurs between the metal(Ni) and metalloid(B) atoms that decreases the crystallization temperature and activation energy.

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The aim of this paper was to optimize the fabrication of SiC_P/Mg alloy composite using AZ91D Mg alloy machined chips which have the difficulty of the recycling. The mixtures of Mg alloy machined chips and SiC particles were consolidated by vacuum hot pressing(pressing pressure : 100MPa, pressing temperature : 410℃). Extrusion was conducted at 300℃ with ram speed of 13㎝/min under hot extrusion ratios 25 : 1 and 40 : 1. Tε treatment was performed up to 150h at 170℃ after extrusion. Mg alloy chips was also extruded and heat-treated at the same condition as a reference material. Microstructural observation and tensile test were carried out to investigate the effects of extrusion on the microstructure and mechanical property of the composite. Microstructural observation showed that both extruded composite and extruded Mg alloy chips have fine grain sizes due to dynamic recrystallization during hot extrusion. It has been observed that tensile strength of extruded composite is superior than that of extruded Mg alloy machined chips. This may be attributable to the effect of SiC particles and the fine grain size along the periphery of SiC particle. In the T_6 condition, extruded Mg machined chips showed a small decrease of tensffe strength, whereas extruded composite showed an increase of tensile strength. This may be because SiC particles restricted the grain growth of the Mg matrix during solution treatment.

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