We suppose an idea to estimate wettability of solder. It assumes that solder-melt form some clusters in solidification process. Wettability of solder was estimated by calculating an interfacial energy of the cluster, and viscosity was reported on the experimental results for verifying this idea. Viscosity of Sn-Bi solder was measured at temperature range from 150℃ to 210℃. The results that the characteristics of Sn-Bi solder as dilant fluid decreases with temperature increased at temperature range from 150℃ to 155℃ were obtained. Above 155℃, the characteristics of the solder melt became as Newton fluid. These results indicates that the clusters are recognized in the Sn-Bi solder-melt at temperatures between 150 and 155℃.

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Characteristics of hot extruded aluminum alloy in using rapidly solidified powder via SWAP process are investigated. Spinning Water Atomization Process (SWAP) is one of advanced powder processing technologies to prepare high-performance powder particles with fine microstructures. In this study, 7000 series aluminum alloy powder via SWAP are produced, and their characteristics such as the dependence of microstructures and micro-hardness on annealing temperature have been examined. The mechanical properties of wrought aluminum alloys consolidated by hot extrusion, in employing rapidly solidified powder via SWAP, are superior to those of extruded alloys in using ingot billets. The effects of T5 heat treatment conditions on microstructures and mechanical properties of wrought aluminum alloys are investigated, and the optimization on the pre-heating temperature of billets is discussed.

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Ti-Ni-Cu Shape Memory Alloys were fabricated by mechanically alloyed powder using a pulse-current pressure sintering equipment. The effect of Cu content on the phase transformation behavior of the sintered alloys was investigated. An increase in Cu content changed the crystal structure of the alloy. The alloys in Cu content of 15at%Cu and 20at%Cu consists of B2, B19' and B19 phases. In the case of the Cu content of 20at%Cu, the alloy clearly shows the two-step transformation. The transformation hysteresis of the alloy was approximately 10K as narrow as that of the wrought alloy. The phase transformation behavior of the P/M alloy differs from that of the wrought alloy. This may be caused by a reduction of Cu content of the alloys due to composition segregation.

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The final objective of this study is to establish the optimized manufacturing method of herringbone microgrooves for fluid dynamic spindles. In this article, two kinds of fundamental coining experiments of a simple indentation are carried out to create microgrooves of 5〜10μm depth. In order to compare the coining performance, two kinds of materials are used. One is an austenitic stainless steel (SUS303) of the wrought material and the other is also an austenitic stainless steel (SUS304L) of metal injection molded (MIM) material which has 5% porosity. In experiment-1, a flat head punch with three micro projections of 10μm height is pushed into a hexahedral specimen with or without the ultrasonic vibration. The groove depth of the MIM material increases in proportion to the punch load in the static indentation and its maximum value is about 80% larger than that of the wrought material. The imparting of the ultrasonic vibration is effective to increase the amount of groove depth especially for the MIM material under the lower punch load. In experiment-2, a circular punch and a circular anvil are statically pushed into a cylindrical specimen to produce 18 parallel grooves with an equal pitch in the circumferential direction. The groove profiles become almost uniform and the burr formation at tips of groove shoulder is effectively suppressed under the excessive amount of die indentation.

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In the production of cosmetics or the medical supplies, it seems to be needed that controlling of the distribution of green density than the green strength in sintered products. Moreover, it can not be used of lubricant in the powder compaction for the avoidance of contamination. We developed an automatic powder compacting machine, it can possible to control the powder charging and the compacting conditions as punch stroke, pressure, holding time and run out.

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Magnesium alloys has low density and high dumping capacity and hence the alloys have been applied as a high strength light weight material. Magnesium alloy powders with compositions of 2 to 20 mass% MgB_2 and AlB_2 were made from pure Mg, Al and B by mechanical alloying. These powders were consolidated by hot pressing. Mechanical properties and microstructure of the alloys were investigated. Formation of MgB_2 and AlB_2 identified by X-ray diffraction improved the mechanical properties especially hardness of the alloys.

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This study reveals the specific mechanical properties (especially elastic stiffness E) of APSed YSZ coating through applying the indentation method. The spray coating has intrinsic porous-microstructure, so-called splat, and this structure may lead to be one of contributing factors in the Indentation Size Effect (ISE) that E measured by Berkovich nanoindentation shows significantly decrease with increasing of the penetration depth. In this work, Berkovich nanoindentation were performed for APSed coatings and the Pop-in event, which underestimates E values, was shown in the P-h curves. Additionally, the P-h curve for polystyrene foam by Flat-punch macro-indentation showed the "plateau" region which means the beginning of the densification of foam. The Pop-in event in some APSed coating's P-h curves may indicate that the densification of splat structure occurred. Thus, it is possible that the densification would be one of influencing factors in the ISE.

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An electrochemical deposition of calcium phosphate film on commercial pure titanium by supersaturated calcium phosphate solution (SCPS) was carried out on the cathodic polarization. The calcium phosphate coating layer was successfully deposited on cp-Ti of 3mA/cm^2 current density for 45min. The major phase appeared in the film were brushite co-existed with octa-calcium phosphate (OCP) with the thickness of 50-55μm in average. After soaking in revised-simulated body fluid (r-SBF), the amorphous bone-like apatite became a single phase within a week. From the. scratch test, the highest critical loading of 87.23N was obtained. The critical loading was decreasing almost 50% after apatite precipitation in r-SBF. The decrease of critical loading might from the loosening of the film structure during the immersion of the specimens in r-SBF.

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Nozzle geometry, which influences gas dynamics and, therefore, sprayed particle behavior, is one of the most important parameters in cold spray process. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are subsonic; thus; this region is most suitable for heating spray particles. In this study, numerical simulation and experiments investigated the effect of the nozzle contour (convergent-divergent and convergent-divergent-barrel) and entrance geometry of convergent-divergent nozzle on the cold spray process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the coating properties. A copper powder was used for the experimental studies. Working gas (is nitrogen) pressure and temperature at nozzle-intake were 3MPa and 573K. The change in the nozzle contour and entrance convergent section length of the gun nozzle had a significant effect on the particle deposition.

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Cold spray is a new coating process. So the optimization of the gun nozzle and mechanisms of coating process aren't adequately revealed. This report examines the influence of the ratio of sectional areas at throat and exit of the gun nozzle and gas pressure on properties of cold sprayed copper coatings. And we got the result that there is a suitable ratio of the sectional area appropriate for nozzle intake gas pressure.

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Cold forging process is used for making many products that high strength is required. In the process, cracks sometimes appear on the surface of products because of having low plasticity limit. In this paper, the fracture process of product is investigated using FEM Computer Simulation and observation by SEM. The main results are as follow; (1) The place that cracks on the surface of the product is equal to the place that high maximum principal shear stress or maximum principal stress appear on the result of FEM. (2) It is possible to predict the place where cracks appear by investigating resulet of FEM.

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Friction stir welding (FSW) is a relatively new solid-state joining process primarily for aluminum alloys. FSW process can also be applied to the welding of a variety of other materials, including magnesium alloys, titanium alloys, stainless steels and metal matrix composites. In addition, FSW has been generating interest because of its association with friction stir processing (FSP), a new technique that essentially employs FSW tooling. FSP is being explored as a thermo-mechanical processing technique to transform a heterogeneous microstructure into a more homogenous microstructure. In this study, trials with FSP of superplastic alloys were carried out on a modified milling machine. The results of FSP on superplastic Zn-22Al alloy are discussed in terms of residual microstructure and the damping capacity.

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Feasibility of friction stir processing (FSP) has been examined on microstructure control of A7075-T6 Al alloy and ZK-60A Mg alloy plates. It becomes evident that FSP is quite effective for grain refinement of both A7075-T6 and ZK-60A alloys. It appears that probable mechanism for the grain refinement is dynamic continuous recrystallization. A grain-refined A7075-T6 alloy has shown superplasticity at high temperatures. Concerning FSP'ed ZK-60A Mg alloy, formation of basal plane texture around the circumferential direction of the FSP tool was observed. Although, under a few FSP conditions, formation of defects were found for the ZK-60A alloy, we have concluded that FSP is a very effective technique for producing very fine and equiaxed microstructures in the both alloy plates.

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The objective of the present study is to investigate the effect of environmental relative humidity (RH) on the friction and wear characteristics of engineering metallic materials, especially. steels with different carbon content, under fretting conditions. Flat-against-ball type fretting wear tests for the steel disk in point contact with a bearing steel ball were conducted in moist air at an amplitude of relative slip (about 50μm). From the results, the mean coefficient of kinetic friction during the tests decreases with increasing RH for the steels except cast iron. The relative humidity (RH_<max>) at which maximum wear appears tends to move to higher RH levels with increasing carbon content of the steels. It is known that adhesive wear is predominant at RH_<max>. However, RH_<max> seems to decrease with increasing carbon content above 1%.

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This research work describes the effect of fabricated surface on fretting fatigue strength of hot-rolled steel for automobile structural uses. The dog-bone shape specimens sectioned from the fabricated components after cold spinning process were used in this study. Fretting fatigue tests were carried out at frequency of 15Hz and a stress ratio of 0.1 with contact pressure of 100MPa. The results reveal that the different surface conditions impact the fretting fatigue strength. Influence of small size of fabricated surface defect induced by cold spinning on fretting fatigue strength can be ignored.

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The effects of tensile overload on fatigue crack propagation behavior of an epoxy resin filed with crushed silica particles (68.5% in weight) were investigated by measuring the crack length of CT specimen using unloading compliance method. Crack propagation after the overloading was observed to be delayed under constant ΔK, however the crack propagation behavior of the material used was much different from that on usual metal materials; the delay cycles was strongly dependant on the number of cycles of the overload, the period and hold time, because of the restraint of plastic region by large silica particles.

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In this study, self-loosening and fatigue characteristics of bolt/nut joints and bolted joints have been investigated. The results show that the amplitude threshold of transverse vibration force of the bolt/nut joint corresponding to the fatigue limit is larger than it of the bolted joint. The results also show that fretting fatigue crack causes fatigue failure if the bolt breaks in the long life region.

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The fatigue crack growth tests were performed on low carbon structural steel with five different microstructures, i.e. steel with pearlite particle (15 and 50μm grain size), with bainite particle (15 and 5μm grain size) and with martensite particle. The results showed that microstructure influence fatigue crack growth behavior in both threshold region and Paris region and the presence of hard phase enhances fatigue crack growth resistance. The results were discussed based on the crack path observation and crack closure behavior

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This paper suggested a more precise life prediction method of bellows type expansion joint made from SUS304. For this purpose, elasto-plastic analysis by finite element method (FEM) was used and Manson-Coffin law was adopted as a low-cycle fatigue life formula. Coefficients of Manson-Coffin law were calculated from date of tensile experiments, and 3 type formulas with different heat treatment were obtained. Fatigue life was predicted by substituting equivalent plastic strain amplitude and equivalent elastic strain amplitude calculated by FEM to these formulas, and compared with the result of fatigue experiments under displacement control.

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Dissimilar metals welding between SUS304 and A5052 has been carried out by using a pulse YAG laser. Weldable conditions were obtained at spot diameter of 0.2mm. According to the shear-tensile test of the joints, welding area increased with increase in heat input. However, the strength decreased with increase in heat input and the maximum failure load was obtained at a reasonable welding condition. Formation of intermetallic phase (IMP) at the interface could affect on the strength of the joint. High heat input may induce formation of IMP significantly. Temperature distribution at the interface was calculated by FEM analysis. According to the result, welding area increase with increase in heat input as shown in the experiment.

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Dissimilar metals joints are very important for various industrial arenas. The strength of dissimilar metals joints is greatly affected by the Interface morphology. This paper has proposed a method to control interface morphology of laser welded dissimilar metals joints by geometry of faying surface.

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A mismatch of different material properties in joints may cause stress singularities, which lead to the failure of the bonding part. It is very important to reveal a stress singularity field for evaluating the strength of interface in three-dimensional joints. Furthermore, thermal residual stresses occur in a cooling process after bonding the joints, and the stress singularity for thermal stresses also occur. In the present study, the intensity of singular field at the edge in the interface Si-resin joint with different thickness in silicon and resin is investigated using boundary elemant method.

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The 3DFEM of piezoelectric joints is presented. The influence of the angle of comer on the order of stress singularity in the case of Three-dimensional corner shape of having various angles, various piezoelectric joints angle and various piezoelectricity poled directions, is analyzed in this paper. The eigen equation determining the stress singular order and, the stress, displacement and electric displacement fields near the interface are deduced in details.

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The direct processing of the high-hardness die materials by a pulse laser is considered to have a great potential in rapid machining with little thermal effect. In this study, a femtosecond laser has been used to fabricate microstructures on cemented tungsten carbide. Development of a hole depth and its shape with irradiated number of pulses in percussion drilling are examined in detail by making its replica. Results for machining a square dent by beam scanning are also presented.

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Magnesium alloys are very attractive in such applications as automotive, railway and aerospace. Demand for improvement of mechanical properties in magnesium alloys, therefore, becomes greater. However, their mechanical properties are still inferior to aluminum alloys. Their range of application has been limited. Recently we have found that Mg-Zn-RE (RE is rare-earth metals) cast ingot formed a long period stacking ordered (LPSO) structure as well as rapidly solidified alloys, and exhibited excellent mechanical properties which completely overturn common knowledge regarding such materials. The LPSO magnesium alloys are expected to yield a new concept of strengthening in magnesium alloys such as the discovery of GP zone precipitation strengthening in aluminum alloys, bringing out a revolution in magnesium alloys.

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BMGs have been successfully welded together and to some crystalline metals by supercooled liquid phase welding using friction method. The successful friction welding was due to the thermal stability and superplasticity of the supercooled liquid of the BMGs. The supercooled liquid was discharged from the interface and formed a protrusion by the superplastic deformation. The supercooled liquid easily achieved full contact of the interface on the atomic scale, resulting from the superplastic viscous flow through atomic movements. The discharge of the oxide film in the interface accompanied the formation of the protrusion, resulting in metallurgical bonding through the freshened surfaces. Given the possibility of welding BMGs, one can expect that the BMGs will make further progress in diverse applications.

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Sapphire is commonly used as substrate for white light emitting diodes. Smooth surface after a grinding process is required to reduce a processing period for fabrication of flat surface. In this paper, surface roughness was controlled by a number of abrasive grains which pass through sample surfaces. This number is obtained by a quantity of abrasive grains on grinding wheel surface, a wheel rotation speed and a table feeding speed. Newly developed diamond grinding wheels are assembled by hexagonal grinding stones, which have layers with abrasive grains at sides of hexagons and filled up porous material without abrasive grains inside of the hexagons. The quantity of diamond grains on a grinding wheel surface is controlled by a size of hexagonal grinding stone and a layer thickness at edge of grinding stone. When the number of abrasive grains that pass through sample surface increases, surface of sapphire becomes smooth. Surface roughness decreases at a larger quantity of diamond grains on a grinding wheel surface, a higher wheel rotation speed and a higher table feeding speed. Surface roughness ground by a conventional wheel which has abrasive grains on all grinding wheel surface is rougher than that by developed diamond grinding wheels. The results indicate that almost abrasive grains on developed diamond grinding wheels are used for grinding of sapphire, and 1/5 of abrasive grains on a conventional wheel are contributed for grinding of sapphire.

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