In this study, Zr (0.1, 0.2, 0.3 mol%) was added to a Cu–3 mol% Ag alloy, and prepared by mold casting. Homogenization treatment was conducted at 900°C for 18 ks. Hot and cold rolling were subsequently conducted. The alloys were solution treated at 850°C for 3.6 ks, quenched into water and subsequently aged at 450°C for up to 345.6 ks. Micro–Vickers hardness and electrical conductivity were measured. Tensile tests were conducted on as–solution treated alloys and peak aged alloys. X–ray diffraction (XRD) analysis, optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM) observations were carried out for the solution treated and aged alloys.

Zr addition resulted in the increase of peak hardness with less than decrease of 10%IACS in electrical conductivity. Primary particles of Cu₄AgZr was observed after casting, which resulted in grain refinement. After the solid solution treatment, mainly Ag and small amounts of Zr were dissolved into the matrix. TEM observation and XRD analysis were conducted both on the alloys and extracted precipitates. Ag precipitated during aging. In the aged samples, Zr oxide was also observed besides Ag precipitates.

In our previous study, a thin wire of a Cu–0.29wt％Zr alloy produced by repetitive intermediate annealing during rolling and wire–drawing (IA wire) exhibited values of 0.2％ proof stress σ0.2 of 600 MPa, ultimate tensile strength σ_u of 630 MPa, and electrical conductivity E of 91.7％IACS. A thin wire of the alloy produced by ECAP–Conform process and subsequent rolling and wire–drawing (ECAP wire) showed larger values of σ_0.2=730 MPa and σ_u=790 MPa but a smaller value of E=73.0％IACS than the IA wire. This study investigates the causes of the smaller value of E and larger value of σ_0.2 of the ECAP wire, and the larger value of E of the IA wire. The larger value of σ_0.2 of the ECAP wire is attributed to its smaller grain size and higher dislocation density. The smaller value of E of the ECAP wire is primarily attributable to the fact that new-found, ordered fcc precipitates having a cube–on–cube orientation relationship to the Cu matrix in the alloy produced by the ECAP–Conform process are cut by dislocations during rolling and wire drawing, resulting in dissolution in the Cu matrix. The IA wire shows the larger value of E because recrystallization by repetitive intermediate annealing changes all the fcc precipitates into incoherent fcc precipitates that are not cut by dislocations. Further, based on the obtained results, an attempt is made to fabricate thin wires of the alloy having good strength, ductility and electrical conductivity. All the fcc precipitates in the alloy are allowed to be incoherent by utilizing recrystallization after sufficient precipitation. Then the alloy is processed by ECAP and subsequently wire–drawn. The fabricated thin wire exhibits large values of σ_u=820 MPa, ε_t=4.0 ％ and E=86.9 %IACS.

The precipitation behavior in Cu alloy is been changed by the nucleation sites like a homogeneous or heterogeneous site during aging. Especially, the aspect of heterogeneous site in Cu alloy were changed with degree of deformation strain before aging. It is necessary to understand how the dislocation or shear bands would influence the precipitation behavior as a heterogeneous nucleation. In this study, Cu–3.5 wt.% (4.6 at.%) Ti alloy was fabricated by vacuum induction melting in Ar atmosphere. The alloys with 0, 15, 22, 26 and 75% area reduction after solution treatment at 885 °C for 1 hour was aged at 450 °C for various time. The plastically deformed Cu–Ti alloy under the plastic instability limit (necking point, true strain η=0.245) after solution treatment, showed slip bands as a major defects, and it acted as heterogeneous nucleation sites during aging. The alloy slightly over the necking point had a few shear bands in addition to slip bands, and these defects acted as heterogeneous nucleation sites, and the hardness and electrical conductivity was simultaneously increased during aging. The alloy far over the uniform deformation limit, η=1.38 had many shear bands more encourage heterogeneous precipitation, and it generated large particles over the 1 μm. The hardness of solution–treated alloy increased from 156 to 252 Hv with increasing degree of deformation before aging. The peak hardness value of alloy after aging at 450 °C was 274, 294, 302, 305 and 341 Hv, respectively, in order of 0 to 75% area reduction

The Cu-4Ni-1.38Si alloy was cast by vacuum induction melting with high purity Ni, Si (purity： 99.99%) and Cu (purity：99.9%). The normally precipitated (continuous precipitate, CP), bimodal and discontinuously precipitated (discontinuous precipitate, DP) structures were observed after 1, 6 and 24 hours of aging after solution heat treatment, respectively. The tensile strength of CPed alloy shows the highest value compared with other specimens, and bimodal alloy shows a smaller value than CPed alloy. Fully DPed alloy show lowest value. After 97.5% cold rolling, however, contrary to the aged state, the bimodal alloy has the highest strength value. The electrical conductivity of all specimens decreased after cold working. The degree of decreasing value of the conductivity in DPed and bimodal alloys after groove rolling was much smaller than that of CP specimens. Microstructure analysis by FESEM and TEM of cellular precipitates (DPs) in the bimodal alloy revealed that the stiff Ni₂Si precipitates were aligned along the groove rolling direction and plastically deformed without any cracking, and it leads simultaneous increasing strength and conductivity of Cu-Ni-Si alloy. A combined value of tensile strength and conductivity, 1140 MPa and 38% IACS was achieved in the bimodal Cu-4Ni-1.38Si alloy after groove rolling with a 97.5% area reduction.

Cu–Ti alloy has two types of the precipitates such as meta–stable β’–Cu₄Ti and thermodynamically stable β–Cu₄Ti. In general, the precipitation hardening alloys can be strengthened more by additional cold working after aging. However, these precipitates dissolve in Cu matrix during cold working, lowering the conductivity considerably. To find a way to increase the stability of the precipitates during cold working, we have studied the stability of the second phase using the density functional theory (DFT) calculations. First, DFT simulation showed that the cohesive energy of β–Cu₄Ti is lower than that of β’–Cu₄Ti by –5kJ/mol, while β’–Cu₄Ti has lower interfacial energy due to the small lattice mismatch between Cu and β’–Cu4Ti. Second, we evaluated the change of cohesive and interfacial energies for two precipitates with Ni to confirm the effect of Ni on the stability of them in Cu–Ti alloy. As a result, Ni can lower the cohesive energies of these precipitates although there is no effect on the interfacial energies of them. Finally, Cu–4 at.％ Ti alloys with 0, 0.5 and 1 at.% Ni were cast by vacuum induction melting in Ar atmosphere. Experiments showed that the Ni addition to alloy encourages the discontinuous precipitation. After severe deformation, the precipitates in the alloy with Ni has more retained in matrix than alloy without Ni.

Improvement of bending workability of a heavily cold–rolled Cu–Ni–Si alloy sheet by surface wire brushing was investigated. Coarse pancake–like microstructure and sharp {110} texture developed in the heavily cold–rolled sheet were changed to equiaxed fine ones and rather randomized by the brushing at the vicinity of surface. Still more, work hardening induced by brushing penetrated into the deep areas of 500 μm from the surface. Such work hardening occurred more significant and severe with increasing applied pressure stress of brushing. By the modification of surface microstructure, bendability was largely improved without spoiling other mechanical properties, i.e., strength and ductility. R/t value of 1.2 by good–way bending, where R and t are the bending radius and thickness of sheet, was almost constantly achieved after ageing, while those without brushing were over 3 at best. It is revealed that the sufficient depth of work–hardened and influenced areas by brushing is 250 μm for the improvement of bendability. Furthermore, the orientation–randomized and fine–grained areas developed at the surface is more important than the wok–hardened area to achieve superior bendability.

Stress relaxation resistance is often required in application of electrical parts for copper and its alloys. The stress relaxation behavior should be influenced by stored strain through manufacturing process. In the present study, Cu–Ni–Si alloy solution–treated sheet was subjected to continuous cyclic bending (CCB), which was proposed as a useful straining technique to produce the higher strain on the surface and the lower strain in the center layer of metal sheets. Samples were analyzed by scanning electron microscope/ electron back scatter diffraction (SEM/EBSD) technique to investigate stored strain and stress relaxation process. CCB raised up the strength of Cu–Ni–Si alloy sheets at room temperature. The stress relaxation ratios of the CCBent sheets increased with an increment of holding time. The stress relaxation process was accompanied with change in kernel average misorientation (KAM) of the samples. The change in KAM through the stress relaxation test was understood as a result of release of residual and applied stresses with consumption of stored strain.

Recently, the compatibility of the strength, the workability, and high conductivity are needed in copper alloy materials which are produced by controlling in the combined process of cold working and aging treatment, in response to downsize of electronics connector and increase of the mount density, in improving performance of electronic device. Especially, in the solution hardening alloy, microstructure change in cold working process becomes very important factor, although the microstructure change behavior is extremely complicated. In this report, the calculation model to evaluate microstructure changes which are resulted from the introduction of dislocation, the formation of dislocation cell/substructure and the deformation twin, and the effect of dynamic recovery in deformation processing, was proposed. And the microstructure change by cold working processing was analyzed with this model about a relationship between a processing condition, the microstructure, and the flow stress. By applying evaluation to various Cu–Zn–Si system alloys which have different stacking fault energy, the validity of calculation model was confirmed by comparing experimental and calculated results. And the concept of microstructure control in the deformation twin formation based on results of this model calculation was summarized.

Cryogenic high–speed rolling, where sheet specimen cooled in liquid nitrogen was supplied to a rolling mill with rolls rotating at 1500m/min at room temperature, was applied to Cu–5mass% Zn sheets. After 80% reduction of the cryogenic high–speed rolling by 2–pass operation, the rolled sheet showed tensile strength of 576MPa, total elongation of 5.3% and electrical conductivity of 54%IACS, while that by low–speed (5m/min) cold rolling showed 521MPa, 5.3% and 52%IACS, respectively. The improved balance of the cryogenic high–speed rolled sheet was attributed to fine–grained microstructure with deformation twins and brass–type rolling texture which were realized by the short contact duration of the cryogenic sheet with the rolls at room temperature.

The effects of the crystal grain size and the crystal orientation distribution before cold rolling on the formation of the deformation induced fine crystals were investigated using a Cu-30Zn alloy. The effect on the mechanical properties of the microstructure was also investigated. The TEM observation from TD and the ODF analysis based on the X-ray pole figures were used in combination to analyze the structure and to consider the development of the microstructure. As a result, the heavier the cold rolling or the smaller the grain size before rolling, the finer the matrix caused by orientation split was obtained. On the other hand, the larger the grain size before rolling or the more the Cu orientation {112}<111> in the rolled intermediate plate thickness, the more deformation twins were formed. Even with the same alloy composition, different microstructures were obtained. The effect of the fine matrix that enhances the flow stress was greater than that of the amount of the deformation twins. When the rolling ratio was 98％ (No RA sample), it showed the highest tensile strength of 903 MPa. The elongation at break was around 2% regardless of the matrix structure and the amount of deformation twin. The strain-induced fine crystals have the property which achieve both the strength and the electrical conductivity as compared with the existing alloys such as brass or phosphor bronze. It is expected that such a high performance copper alloy will improve the function of electrical contacts.

The effects of Ti or Si addition on precipitation of Cu-Cr based alloy were studied with hardness, electrical conductivity and microstructure. As a result of aging at 723K after 90％ cold rolling, Ti added Cu-Cr-Ti based alloy has higher increment of hardness than Cu-Cr based alloy and Cu-Cr-Si based alloy. Microstructures of Cu-Cr based alloy and Cu-Cr-Ti based alloy were observed by transmission electron microscope. Cr system precipitate of up to 15nm was observed in Cu-Cr based alloy. In the case of Cu-Cr-Ti based alloy, Cr-Ti based precipitate of up to 5nm was observed, too. Number density of precipitate in Cu-Cr-Ti based alloy is about 5 times bigger than Cu-Cr based alloy.

Cu-Ni-P alloys are the typical precipitation-hardening material. Thus, Cu-Ni-P alloys are expected to apply alternative materials for heat-exchanger tubes. Therefore, it was investigated that the effect of isothermal artificial aging and the heat-treatment simulated brazing on mechanical properties of Cu-Ni-P alloy in this study. From Vickers hardness test for each artificial aging time, the peak hardness after aging for 10.8 ks achieved at approximately 130 HV. Furthermore, tensile strength of the peak hardness specimen was shown approximately 250 MPa, which was approximately 60 MPa higher than the specimen as solution heat treated. The nominal strain till fracture with isothermal artificial aging was almost equal to the specimen as solution heat treated. These results suggest saving energy in production process for heat exchangers. Spherical or circular precipitates with 5-10 nm diameters were observed in a material which exhibited the peak hardness by transmission electron microscopy. Furthermore, the hardness of specimen as heat-treatment simulated brazing after solution heat treated was shown approximately 105 HV. The peak hardness and tensile strength of the specimen as performed aged at 498 K for 43.2 ks following with the heat-treatment simulated brazing achieved at approximately 140 HV and 260 MPa, respectively. From these results, it is expected the application to higher-strength tube for heat-exchanger after brazing in a furnace.

The shape memory effect (SME) is a unique property that the plastic deformation preliminarily given in alloys recovers with reverse transformation of martensite. Although Ni–Ti based shape memory alloys (SMA) show the best shape memory effect and are widely put in practical use, their high fabrication cost and low deformability hinder in the prevalence of Ni–Ti alloys. Thereby, intensive research and developments have been expected to provide alternative Cu based SMA materials. In this work, we have investigated the SME in copper–base Cu–Sn–X alloys. The present study has revealed the following results in Cu–Sn and Cu–Sn–X alloys. A binary Cu–Sn alloy with the β–phase forms precipitates in aging at room temperature and this phenomenon caused the degradation of SME properties . However, the addition of Mn to Cu–Sn and Cu–Sn–Si stabilized the β phase, and suppressed the precipitation in Cu–Sn–Mn and Cu–Sn–Mn–Si alloys. Those new alloys accordingly exhibited good super–elasticity. The addition of Si was also expected to make the β–phase region stable, and the water–quenched sample of the Cu–Sn–Si alloy exhibits large super-elasticity. However, Cu–Sn–Si alloy formed precipitates in room temperature aging. First principles density–functional theory (DFT) calculations using Akai KKR have revealed that Mn–Sn bonds are more stable than Sn–Sn bonds. The present DFT calculations suggest that suppression of Sn–Sn bonds with Mn addition led to the restraint of the precipitation in the Cu–Sn–Mn and Cu–Sn–Mn–Si alloys.

Titanium (Ti) has been added for improvement of the critical current density (Jc) to Nb₃Sn superconductor. In this work, the effect of Ti on microstructure of Nb₃Sn filaments in Nb/Cu–12 mass% Sn–6 mass% Zn wires has been investigated by transmission electron microscopy (TEM) and Field Emission Scanning electron microscopy (FE–SEM). From the results of SEM observation and FE–SEM observation, it was confirmed that Nb–Sn intermetallic has been formed at the interface between Nb filament and Cu alloy for the cross–sections of Ti–free and Ti–bearing wires after heat treatment. Selected Area Electron Diffraction (SAED) patterns and TEM–EDS profile obtained from Nb–Sn layers in Ti–free and Ti–bearing wires which were prepared by focused ion beam (FIB) method could be indexed and analyzed as Nb₃Sn of A15 structure.

The area fraction of Nb₃Sn layer in Ti–bearing wire per unit filament was higher than that in Ti–free wire. It has been in good agreement with that remained Sn content of the Cu matrix in Ti–bearing was lower than that in Ti–free wires, and the hardness value by nano–indentor of the Cu matrix in Ti –bearing wire was also lower than that in Ti–free wire.

To improve the mechanical properties and to optimize the manufacturing process of Cu–Ti alloy, we investigated the effect on the homogenization heat treatment and the effect on the cooling rate in solidification of Cu–3 mass%Ti alloy. In the as–cast sample, the lattice parameter increased and electrical conductivity decreased with increasing cooling rate, because of the increase in the Ti solubility. In addition, the secondary dendrite arm spacing and size of particle precipitated in inter–dendritic decreased with the increasing cooling rate in solidification. The deviation in the mechanical properties change with the cooling rate shown in the as–cast sample decreased after the homogenization heat treatment. In addition, even in the process without homogenization heat treatment, the deviation in the properties change with the cooling rate decreased after the solid solution heat treatment. The process of which cold working was applied prior to the solution heat treatment showed the improvement of mechanical properties compared to other processes. Microstructures of the alloy revealed that there was no difference in the precipitates shape according to the type of the process. However, the volume fraction of grain boundaries increased due to the grain refinement in the mechanical properties improved process. Therefore, the volume fraction of precipitates highest at the improved process and the precipitates were finely distributed.

In this study, we prepared Cu–(2. 7 to 4. 3) at. % Ti alloy wires according to a procedure of over–aging and intense drawing, and evaluated their strength and electrical conductivity, as well as their microstructure, in order to clarify the effect of alloy composition on wire properties. The microstructure of all over–aged Cu–Ti alloys before drawing is dominated by coarse cellular components laminating the plates of a terminal Cu solid solution and a β–Cu₄Ti intermetallic compound precipitated discontinuously by grain boundary reaction. The volume fraction of β–Cu₄Ti plates increases with increasing Ti content of the alloy, although the composition of both constituent phases remains constant, as expected by the Cu–Ti phase diagram. The wires intensely drawn from the over–aged alloys show monotonically increasing strength with increasing Ti content because higher Ti content wires have a higher number density of hard β–Cu₄Ti fine–fibers, which are transformed from laminating plates by extreme drawing. Conversely, the electrical conductivity of the wire decreases gradually, which is caused by increasing the volume fraction of β–Cu₄Ti with a lower conductivity than that of the Cu solid solution phase. We also demonstrate that the combined strength and electrical conductivity of Cu–Ti alloy wires with a high Ti content is superior to that of conventional Cu–Ti alloy wires fabricated by peak–aging and drawing, and competitive with the strongest and most conductive commercial Cu–Be alloy wires.

In the present study, I investigate tension–compression asymmetry (i.e., strength differential effect, SDE) in an industrial pure copper sheet using universal testing machine and a newly developed in–plane reverse loading test method. First, we carried out monotonic tension and compression tests on a 6000 series aluminum alloy sheet (JIS A6061–T6) to verify the efficiency of the developed test method. In the case of the A6061–T6 sheet, no significant difference between monotonic tension and compression tests results was observed. This observation is consistent with corresponding results found in the literature. Next, monotonic tension and compression tests on industrial pure copper sheet (JIS C1020–1/2h annealed at 650°C, 1.5 h) in the rolling direction (RD), a direction of 45° relative to RD (45°), and the transverse direction (TD) were carried out. The samples in 45° and TD showed significant difference between flow stresses in tension and compression tests. Thus, it was experimentally confirmed that the C1020–1/2H sheet in 45° and TD persistently has the tension–compression asymmetry even after full annealing.

Copper alloy is one of metals that possess high X–ray absorption. Therefore, application of tomography to copper alloy is limited. In this study, ability of visualization by synchrotron radiation microtomography was examined about ductile voids of copper alloys formed by tensile test. Inspections of ductile voids formation and failure process were available in copper alloys if certain conditions about sample size and void size were satisfied. However, not only synchrotron radiation microtomography but also other conventional inspection method, like fracture surface observation by scanning electron microscope, should be utilized to understand certain fracture mechanism, because spatial resolution of the tomography was limited.

Recently, due to the increase of experiments using synchrotron X–rays, the studies of precipitates by SAXS（Small angle X–ray scattering） measurement with high energy X–ray are also increasing. Although a scattering profile measured from metallic materials contains information about the size, shape and number density of precipitates, only precipitate size was evaluated with a spherical shape approximation in a number of studies using the SAXS method. There is little investigation of precipitation morphology from SAXS profiles. In this study, the SAXS measurements with synchrotron high energy X–ray of three kinds of Cu alloys, which are including various sizes and shapes of precipitates, were carried out. The fitting analysis using the local monodisperse approximation with the most appropriate form factor was adopted to estimate the size and shape of precipitates. These results were compared to the values analyzed by previous TEM observations. The sizes of Fe precipitates with a spherical shape and Co–Fe precipitates which changes from sphere to rectangular plate–like form via cuboid were accurately calculated by the local monodisperse approximation with the form factor of a sphere. On the other hand, Ni₂Si precipitates were analyzed with the form factor of a tri–axial ellipsoid. The size and long axis/short axis ratio of ellipsoidal precipitates could be evaluated from the scattering profiles.

In this paper, a heat transfer model between the mold and the ingot with convex and concave surfaces for continuous casting (CC) process of copper and copper alloys is proposed and discussed. Conventionally, during CC process, vibration of the mold leads to ingot with convex and concave surfaces known as oscillation marks. These marks may cause heat resistance between the mold and the ingot. In the model, three areas where heat resistances occurs were considered： (ΔR₁) non–contacting area, (ΔR₂) concave area derived from decrease of thermal conductivity, and (ΔR₃) area where non–effective heat flow exists in solid phase. The heat resistance values were obtained either analytically or by numerical methods for conditions typically observed in the CC process. Quantitative analyses and comparison of heat resistance values indicated that ΔR₃ was the most significant factor and that ΔR₁ and ΔR₂ was negligible. Furthermore, it was found that slight changes in contact condition results in a large change in heat resistance.

In fabrication and in operation，the copper–stabilized RE (Y, Sm, Dy, Gd, …. ) Ba₂Cu₃O₇–δ superconducting tapes are subjected to thermal, mechanical and electromagnetic stresses/strains. When the superconducting layer is cracked by such stresses, the critical current of the tape is reduced. It has been reported that, in the case where a specifically large crack is formed in addition to many small cracks in the superconducting layer, the critical current value is low when the voltage probe distance in four probe sensing for measurement of voltage–current curve is small, but it becomes higher when the voltage probe distance is larger. In the present work, a simulation study was conducted to describe the variation of critical current value with voltage probe distance under the co–existence of a specifically large crack and many small cracks, by using a model specimen of copper–stabilized superconducting tape, a current shunting model at cracks, and a Monte Carlo method. With the present approach, the experimentally observed increase in critical current value with increasing voltage probe distance was reproduced well. Also, it was shown that the variation of critical current value with position along the longitudinal direction of specimen becomes smaller with increasing voltage probe distance under heterogeneous cracking of the superconducting layer. This result was also in good agreement with the experimentally known feature that the critical current–information is diluted when the voltage probe distance is large.

The present work investigated the cooling effect of roll equipment on high–strength Cu–Be–Co alloy (C17200) solution–treated strips in the Dynamic–Thermo Mechanical Treatments (D–TMT). An FEM–based computer simulation (Fluent v6.1) was also implemented to consider the experimental results, with a model including contact thermal resistance from a strip material to a roll, as well as convection and radiation. The combination of the experiments and the simulation has revealed that the D–TMT method attained cooling rate higher than the water cooling method, and the present analysis also proved that the D–TMT method is suitable for continuous processing. On the other hand, the present examination exhibited that the experimental results were in good accordance with the simulation, taking (i) contact heat transfer between strip and roll in addition to heat transfer of the air layer in the vicinity of its contact point, (ii) thermal conduction of roll, (iii) heat transfer from roll to cooling water and the calculation results of the temperatures of the strip and the roll after cooling. The combination of simulation and experimental analysis shown in this work is useful for understanding and optimizing the cooling effect of the D–TMT roll equipment.

This paper presents the experimental results of image processing for liquid film thickness at square frustum projection side wall on falling film evaporation tube. Image processing area was aimed at the upper part of the enhanced test tube has square frustum projections. The image files is the photographed at 500 frames per second using a high speed video camera. Heat transfer test tubes of falling film evaporation have 1024 projections per meter. The refrigerant in the present tests used water. The heat transfer test conditions of take a photograph were water vapor pressure 0.8 kPa and refrigerant mass flow rate per unit length on both side of the tube 0.75 kg/m–min.

As a result of the image processing, the center of the groove between the projections was easily flow liquid refrigerant at all times. However, the liquid film at the root of the groove the projections showed residual. On the other hand, the liquid film of the projections side wall showed easily flow liquid refrigerant when leaving distance from the grooves root. From these image processing results, it was concluded that the liquid film thickness at the halfway point of the projections side wall was approximately 0.054 mm.

In this study, the condensation flow patterns of R32 in horizontal small–diameter microfin tubes with outer diameter of 4 mm were experimentally visualized. Two kinds of copper microfin tubes were used： HF40 had 40 fins, with fin height of 0.18 mm and helix angle of 17°； and LF50S had 50 fins, with fin height of 0.12 mm and helix angle of 25°. The experiments were carried out at mass velocities from 50 to 400 kgm^–2s^–1 at a saturation temperature of 35°C. The flow pattern of small–diameter microfin tube was classified as annular, wavy, and slug flows. It is also confirmed that the annular liquid film in the microfin tube swirled along the direction of the inner grooves. Comparing the results of the HF40 and LF50S, the transition from annular flow to wavy flow is similar to each other. The condensation flow pattern of the microfin tubes were compared with that of the smooth tube. The transition of smooth tube from annular to wavy flows occurred at higher mass velocity and lower wetness than the microfin tubes.

It is known that a fiber laser has a small spot size and is suitable for fine processing. In addition, it is also characterized in that a high energy density can be obtained by the small spot size, and a welded portion with a high aspect ratio can be obtained even for a conductive material having a high thermal conductivity. However, welding defects such as sputtering and blow holes tend to occur in welding of highly conductive materials such as pure copper because of high thermal conductivity and low light absorption rate. Since these defects cause decrease in tensile strength, fatigue strength and sealing property, therefore all these problems need to be overcome. In this study, five types of representative copper and copper alloys with different thermal conductivity were used to investigate the solidification structure and mechanical properties of the fiber laser irradiated part, and the following conclusions were obtained.

The low thermal conductivity alloy has a wide laser condition for obtaining the entire melted structure and can be considered to be a suitable material for laser welding. The narrower the solidification width is, the less the decrease in tensile strength becomes. In applications requiring strength, it is considered effective to narrow the solidification width. In a precipitate strengthened alloy such as Cu – Ni – Si alloy, there is concern that the tensile strength greatly decreases due to dissolution of precipitates. Alloys containing high amounts of elements with high vapor pressure such as C2600 are prone to have welding defects, therefore the approach to prevent leaving of vaporized elements is necessary.

Voids are generally formed when spreading a molten brazing filler metal into gaps owing to such factors as the brazing conditions and flux. In previous studies, it was confirmed that the gap affects the shape of the void, but it is not known in detail how much the gap size is related to the void ratio. Therefore, the purpose of the present study is to investigate the influence of the gap on the void formation more in detail.

Using C3604 as a base metal, two specimen shapes and six gap sizes were prepared. The specimen was heated in an electric furnace, X–rays were irradiated onto the side surface of the test piece during the temperature increase, and a video was taken. In addition, a gap was made using C3604 and glass, and the flux behavior during the heating process was observed. Based on the results of the X–ray transmission test, it was found that the void ratio increased as the gap size was decreased in the range under 300µm. Observation results during the heating process showed that the bubble of boiled flux was increased in number and decreased in size as the gap size was decreased. From these facts, it is thought that the behavior of the flux is changed by changing the gap, thereby changing the void ratio.

Traditionally, Pb has been added to brass to improve machinability, and it has been used for piping parts and mechanical parts. However, due to the revision of the Drinking Water Quality Standards , there was a limitation on the Pb content of the materials used for piping parts. Therefore, Pb–free brass and solder materials have been developed and put into practical use. In the previous study, a method to evaluate soldering ability of Pb – free solder to Pb – free brass using X – ray transmission image was established. In addition, it was possible to classify the voids generated in the soldered region into four types of “voids in invasion region”, “spherical voids”, “nonspherical voids”, and “shrinkage voids”. It was suggested that the generation of bubbles from the flux was confirmed during the previous research and the cause of the spherical void was caused by the generation of this bubble. Therefore, we focused on flux and conducted experiments. In–situ observation experiments were conducted to confirm the occurrence of bubbles in the flux. It was found that when the in situ observation experiment was carried out, it was possible to suppress the generation amount of bubbles by using the dry flux in which the solvent amount of the flux was reduced. Therefore, a soldering experiment using dry flux was carried out. A parallel two–plate test piece was used as a sample shape. Used flux was dry flux and regular flux. As a result, it was confirmed that when the drying flux is used, the amount of spherical voids can be reduced.

Pure copper powder was mechanically milled (MMed) using a vibration type of ball mill, and the milled powders were consolidated into bulk materials by spark plasma sintering (SPS). Effects of the rate of heating to sintering temperatures on hardness and electrical conductivity of bulk SPS materials were investigated. The selected heating rate in the present research was 1.67 K/s, and then the properties of SPS materials using the rate of heating of 4.17 K/s previously reported⁴⁾ were compared to those of the SPS materials using the rate of heating of 1.67 K/s. When MMed 32 h powder was consolidated into bulk SPS materials at 1073 K with heating rate of 4.17 K/s⁴⁾, Vickers hardness and electrical conductivity of the bulk SPS materials exhibited 115 HV and 62.2%IACS, respectively. When the heating rate was decreased from 4.17 K/s⁴⁾ to 1.67 K/s in SPS process, Vickers hardness, relative density and electrical conductivity decreased, which was due to formation of Cu₂O on the surface of MMed powders during SPS process.

Pure copper powder and pure zinc powder of 65/35 composition were mechanically alloyed (MAed) using a vibration type of ball mill, and MAed powders were consolidated into bulk materials by spark plasma sintering (SPS). The ball to powder weight ratio was selected in 7：1 as the previously reported and in 14：2 as the present research for the process of MA. Effects of the ball to powder weight ratio 14：2 on hardness and electrical conductivity of MAed powder and bulk SPS materials were investigated by Vickers hardness and electrical conductivity measurements, respectively. The obtained results under the weight ratio of 14：2 were compared to those of the weight ratio of 7：1. Vickers microhardness of MAed powders produced by the weight ratio of 14：2 exhibited higher than that of 7：1 previously reported suggesting that producing the MAed powder may be possible to scale up. The optimal sintering temperature of SPS for fabrication from MAed powder was 873K in terms of the Vickers hardness values. The electrical conductivity of the bulk SPS materials fabricated from various MAed powders was lower than that of 27%IACS listed in Japan Industrial Standardization (JIS H 3250) for wrought Cu–35% Zn alloy.

Exchange reaction of D₂O and H₂ giving D₂ (D₂O+H₂→H₂O+D₂) was performed via redox reaction of Cu(O)⇄Cu(　) on Cu/SiO₂ catalyst which shows activity for water gas shift (WGS, CO+H₂O→CO₂+H₂) reaction. It was suggested by means of temperature–programmed reduction(TPR) measurement that reduction of CuO to Cu on SiO₂ support was occurred around 275°C which was agreeable with values reported in references. Therefore it was deduced that the reduction process is conducted to the catalyst precursors (prec–CuO/SiO₂) over the temperature where the active sites of Cu(　) generate on SiO₂ support to promote the following exchange reaction. However the exchange reaction proceeded sufficiently at 150 °C on the Cu/SiO₂ catalyst at which the initiation step was carried out. Therefore, experiments were carefully carried out on the process to form the active site (Cu(　)/SiO₂) from prec–CuO/SiO₂ in initiation step, regeneration of Cu(　)/SiO₂ from Cu(O)/SiO₂ in the exchange reaction, measurements of the exchange reaction rate on the Cu/SiO₂ to which the initial activation steps were made at various temperatures, and measurement of apparent activation energy regarding the reduction of prec–CuO/SiO₂. Both the initiation step to form Cu(　)/SiO₂ from CuO/SiO₂ and the regeneration step giving Cu(　)/SiO₂ from Cu(O)/SiO₂ proceeded at a temperature less than 275°C. Apparent activation energy (E_act) of the reduction of CuO/SiO₂ was measured by means of closed circulating apparatus, and as a result, E_act was estimated around 56.7 kJ・mol^–1 which was close to values (50.4, and 60.9 kJ・mol^–1) already reported on copper(II) oxide. Upon comparing the rate of CuO/SiO₂ reduction with that of the exchange reaction involving the redox of Cu(O)/SiO₂+H₂⇄Cu(　)/SiO₂+H₂O, the rate of the exchange reaction was higher than that of the reduction of CuO/SiO₂. It was deduced that oxygen of Cu(O) on the silica support behaved like oxygen on copper based catalyst used for WGS reaction, while oxygen of CuO supported on the support showed the analogous property to copper(II) oxide species. In addition, it was suggested that reduction rate of CuO on the support at low temperature range for the initiation step was hardly detected by the usual TPR method which requires high temperature raising rate.

The insolubilized alginate membrane was obtained by drying the soluble alginate solution, followed by crosslinking with calcium ion. The alginate membrane had smooth surface and applicable mechanical strength for practical use. Isothermal ion–exchange adsorption of Cu²⁺ in batch process was conducted on alginate membranes obtained. The result was consistent with the Langmuir type isotherm, and the Cu²⁺ ion–exchange capacities were estimated by fitting of the experimental data. It was found that the ion–exchange capacity of the alginate membrane was equivalent to alginate gel beads. For an improvement of water permeability, polyethylene glycol was added in the casting solution before drying process, and then, was removed from the prepared membrane. The permeation flux of the membrane was determined from the amount of pure water permeated under pressure and its value increased with the amount of polyethylene glycol added in the casting solution. An in–line removal experiment using the prepared membranes was also attempted and succeeded in removing Cu²⁺ ion under flowing condition. In addition, novel calcium alginate membrane embedded with zeolite as an ion–exchange material was successfully prepared for heavy metal ions removal from aqueous phase.

We report a novel Ag@Nano–C composite film electrodeposited on Cu alloy sheets by a hybrid electro–plating in a commercial non–cyanate silver plating bath containing nano–C powder, which formed by an electro–peeling method from a commercial graphite plate．The addition of nano–C in Ag plating bath showed little effect on deposition rate while, unexpectedly, improved the uniformity of plating films at higher current density．EDS and GD–OES measurements confirmed the inclusion of C component in 3〜9 at.％ throughout the Ag film thickness, increasingly with deposition current density．Moreover, the nano–C that included in Ag films were determined as graphene by Raman spectra and XRD patterns．More importantly, the Ag@Nano–C composite films exhibited a high electric conductivity that is equivalent to the pure Ag film, inferring a promising application for automotive connectors with high conductivity.

Impurity content in the copper films fabricated by electroplating with supercritical CO₂ emulsified electrolyte (EP–SCE) and supercritical CO₂ suspension (EP–SCS) is studied by glow discharge optical emission spectroscopy to reveal the feasibility to apply EP–SCE and EP–SCS in copper interconnect technology. Distributions of carbon from top surface to interface between the electroplated copper and the substrate in copper films fabricated by EP–SCE and EP–SCS are similar to those of films fabricated by the conventional electroplating (CONV). Distributions of oxygen in the films fabricated by EP–SCE and EP–SCS are also similar to those of films fabricated by the CONV. The results confirm the CO₂ and surfactants used in the EP–SCE and EP–SCS would not cause any impurity problems in applications.

Gel plating in liquid (Liquid-Gel Plating) was developed for the partial copper plating using gel electrolyte. The developed method can be performed by following procedure：(1) Gel-formed cathode substrate is prepared by formation of the gel electrolyte on the cathode substrate. In this case, the gel electrolyte contains the copper plating solution, (2) Galvanostatic polarization of the gel-formed cathode substrate is carried out by a two-electrode system in liquid, (3) Gel electrolyte removes from the gel-formed cathode substrate after galvanostatic polarization. The pattern area of the plating on the cathode substrate can be selected using gel electrolyte because the electrodeposition of copper occurs on the cathode substrate covered with the gel electrolyte. As the developed method can be employed in the liquid, the arbitrary size and position of the anode electrode can be chosen in the measurement, namely, the current is distributed uniformly on the gel-formed cathode substrate during electrodeposition. The suitable compositions of gel electrolyte and liquid were examined for the Liquid-Gel Plating, and the electrochemical behavior of the copper electrodeposition was investigated by the cathodic polarization curve measurement and potentiostatic polarization. The partial plating of copper was successfully performed by the Liquid-Gel Plating on the copper substrate.

A screen–printing using gel electrolyte was developed for the copper pattern plating. This method allows for the pattern fabrication and the copper electrodeposition simultaneously. The measurement device was composed of the printing squeegee and the conductive squeegee. The gel was printed on the cathode copper plate by the printing squeegee, then the constant voltage was applied to the conductive squeegee as the anode copper electrode. It was confirmed that the electrodeposit of copper was observed on the cathode copper plate clearly. The suitable conditions of gel electrolyte and voltage for copper electrodeposition were discussed.

A partial plating method using solid electrolyte deposition (SED) was developed for the partial plating of copper. An electrochemical cell was fabricated by 3D printer. Firstly, the solid electrolyte membrane is set on the cathode metal plate. The anode metal bar is then vertically contacted to the solid electrolyte membrane. Finally, the electrodeposition can be performed by applying the constant current or voltage. In the present study, the copper plate and the copper bar were used as the cathode and the anode for the copper electrodeposition, respectively. The effect of adhesion of the solid electrolyte membrane to the cathode copper plate on the electrodeposition was investigated by controlling the pressure on the anode copper bar. The suitable conditions for the copper electrodeposition using developed method were discussed.

The initial increasing of contact resistance by the fretting corrosion phenomenon is an important problem as it may cause contact failure of tin–plated terminals in the automotive connectors. In this study, the factors that affect the initial increasing of contact resistance was investigated by focusing on the layer structure of tin–plated materials. As a result, it was found that a shape of underlayer (alloy layer under tin plating) is a dominant influencing factor in the initial increasing of contact resistance. In particular, the form of wear was different depending on the shape of the underlayer. For example, in the case of rugged underlayer, initial increasing in contact resistance occurs as the abrasion powder was crushed finely, the oxidation of the abrasion powder progressed, and the oxide accumulated at the contact part. However, in the case of fine and flat underlayer, initial increasing in contact resistance did not rise because the abrasion powder becomes pasty and the oxidation was slower than in the case of rugged underlayer. The above result suggest that the fretting corrosion characteristics can be improved if the shape of the underlayer can be controlled.

The influence that the electric current gave on a fretting corrosion phenomenon of reflowed tin plating was investigated. In this report, contact resistance behavior and wear behavior under fretting corrosion were investigated when the electric current was between 1A and 100A.

From the result of the fretting corrosion test, the peak value of contact resistance was found to decrease with the increasing electric current. In addition, the wear of the tin plating under fretting corrosion test was increased with the increasing the electric current.

When the electric current is increased, the joule heat is increased. It is considered that the joule heat causes the fritting, the sticking or the partial deformation. As a result, the true contact area is increased. The contact resistance is decreased because the concentrating contact resistance is decreased by the increasing the true contact area. In addition, it is considered that the partial destruction becomes easy to occur by the fritting, the sticking or the partial deformation. The wear of the tin plating is increased because the Cu–Sn intermetallic compound is peeled by the partial destruction.

Multiway connectors made of silver–plated copper and copper alloys are widely used in automotive electronic control systems because of their high conductivity and low contact resistance. With the development of autonomous car, these systems will be expected to require more these connectors. On the other hand, these connectors require high insertion force, which makes the assembly operation difficult. Therefore, demand of lower insertion force has grown for a silver plating. We are developing silver composite plating which is made by co–deposition of sub–micron order silica particles. It is important to evaluate the size and distribution of the silica particles in order to form a low insertion force composite plating without losing the conductivity, and then the small angle X–ray scattering measurements (SAXS) is the most suitable analysis method. The size of the silica particles in a silver plating estimated from synchrotron SAXS measurement agrees with the measured size from SEM investigation. On the other hand, it was found that the distribution of the silica particles is changed by the difference of the X–ray scattering of Ag plating.

We have investigated the precipitation process of Cu based alloys containing ferromagnetic solute atoms and the relationship between microstructure and magnetic properties. We prepared and used Cu–Ni–(Fe,Co), Cu–Ni–Fe and Cu–Ni–Co alloy samples in this work. The samples were first solution–treated at 1323 K and isothermally annealed at several temperature levels between 573K and 1073K for various times. The microstructural evolution and associated change of magnetic properties of those samples were examined, using a TEM–EDX, a SQUID magnetometer and a magneto–thermogravimetric (MTG) balance. Based on TEM–EDX and magnetic SQUID and MTG measurements, we concluded that magnetic interaction between particles is essential to interpret the microstructural evolution and magnetic properties consistently and properly. We carried out first–principles KKR calculations to implement the interpretation. From the present results, we concluded that dipolar magnetic interactions worked during the precipitation process, and realized linear alignment of nano–scale precipitates. Ni addition also affected the microstructure and magnetic properties.

In this study, we investigated the influence of nickel composition on microstructural evolution and magnetic properties in bulk–type copper–based nano–granular magnetic materials with nickel and cobalt. We prepared six Cu–Ni–Co alloys comprising copper, cobalt and nickel from 0〜25 at.%, particularly to focus on the influence of nickel compositions. TEM observations confirmed the linear arrangements of precipitates along the <100> directions of copper matrix were formed, as seen in copper–based nano–granular magnetic materials. However, we found that the microstructure of cobalt–rich magnetic precipitates changed at the later stage of annealing, depending on the nickel composition. The present study suggested that the coercivity was susceptible to the microstructural factors of the magnetic nanoparticles, while the Curie temperature strongly depended on the composition of the magnetic nanoparticles, but not on the microstructure.

The effects of addition of Mg, Sn and Ag to the Cu–0.25 mass%Cr on the tensile strength, electrical conductivity, and stress relaxation property were studied. The addition of 0.1mass% Mg satisfied both high electrical conductivity and high tensile strength in the Cu–Cr alloy. On the other hand, the addition of Sn and Ag did not influence the tensile strength and recrystallization temperature, and decreased the electrical conductivity in the Cu–Cr–Mg alloy. When the Cu–Cr–Mg alloy system was aged at 350℃, the stress relaxation rate was 20% or less which means that the addition of 0.1mass% Mg improved about 40% of the stress relaxation rate in the Cu–Cr alloy. In this study, it was found that the Cu–0.25mass%Cr–0.1mass%Mg alloy has high electrical conductivity, high tensile strength and good stress relaxation property.

This study aims to evaluate lubricant which is useful for metal forming processes restricted by thin oil film formation. Tribological characteristics of lubricants for copper products were evaluated by carrying out a series of plane strain cold extrusion experiments. An extrusion apparatus with a combination of a taper die and plane plate tool with a small extrusion ratio of 1.1 was used to measure the amount of plastic deformation that resulted from using different lubricants. The variation in degree of plastic deformation, extrusion load, and surface condition of the billet due to sliding friction, were investigated depending on lubricant type and initial mass of oil film on the test surface of the taper die. The billet was made of OFC：Oxygen–Free Copper, C1020 (JIS) and the extrusion apparatus was made of SKD11 (JIS). Two types of different mineral oils；paraffinic mineral oil and naphthenic mineral oil, were used as test lubricants in the experiments and five different viscosity grade oils were prepared from each mineral oil. The amount of plastic deformation in the deformation zone of the billet when paraffinic mineral oils were used was found to be larger than that of naphthenic mineral oils, and the difference of ratio of plastic deformation to extrusion load affects plastic deformation near the surface of the billet.

In-situ measurement method with a confocal laser microscope to observe the strain-induced free surface roughening behavior is developed for ultra-thin copper sheets. In this system, a compact Marciniak testing apparatus was installed on the laser microscope. The strain distribution was evaluated by digital image correlation (DIC) technique at the same time for observing strain-induced surface roughening behavior. Pure copper C1020R-O foil with thickness of 0.05mm was used. The strain distribution and free surface roughening behaviors under various strain states from uni-axial to equi-biaxial were evaluated and its effect on fracture behavior is investigated. As a result, it is found that the concentration of strain-induced surface roughening causes onset of necking and fracture.

In order to reduce environmental pollution, efforts are made to minimize the use of internal combustion engines as much as possible, and the development of vehicles powered by electricity such as hybrid vehicles and electric vehicles has been actively research．However, there is a problem of low cruising distance and low power compared with engine vehicles．Therefore, in this research, we focus on the magnet wire used for the hybrid motor and aim to elucidate the optimum drawing condition for manufacturing the shaped copper magnet wire by using the deformed drawing process．First, in order to investigate the optimum reduction and die half–angle using FEM analysis, the drawing process was performed under various drawing conditions, the drawing stress at that time, the, contact area, and the die pressure were calculated, and optimum drawing conditions were established．In addition, by investigating the dimensional accuracy and surface properties of the drawn wire, it was investigated whether or not high quality shaped copper magnet wire can be produced only by shaped wire drawing．

In order to investigate the influence of various copper alloys and their mechanical properties on the punch edge wear during press working, the punch wear after the press test using Phosphor bronze, Corson alloy and Titanium copper alloy as worked material area was quantitatively evaluated. The press test was performed by a turret punch press, and the punch edge wear after pressing the sample to 200,000 shots was evaluated as a wear area. Normally, press processing use lubricating oil, but in order to eliminate the influence of press oil, it was done without lubrication. In the test, punch and die were given a hardness difference so that the punch side wears preferentially. The appearance of the punch was observed using a microscope and a confocal microscope, and the amount of cutting edge wear of the punch was evaluated as the wear area. As a result of investigation, the wear area was the smallest in titanium copper, and in the order of phosphor bronze and Corson alloy, it increased. In the case of the same kind of copper alloy, the higher tensile strength reduces the punch edge wear. If the shearing surface which is the contact surface between the punch and the workpiece is shortened, the punch edge wear was reduced.

The moderate hardness and ductility of brass make microcutting relatively easy. Therefore, brass has long been used in applications such as precision machinery. When brass contains lead at 0.4% or more, lead precipitates at grain boundaries and inside grains. This precipitated lead provides solid lubrication, and thus improves machinability. However, regulations such as the EU’s Restriction of Hazardous Substances Directive have made it difficult to use leaded brass. In general, the machinability of lead–free brass is inferior to that of leaded brass. Cutting fluids are used to improve the machinability, but there are only a few studies that have examined the effect of cutting fluid on cutting behavior in microdrilling of brass.

Therefore, in this study, wet microdrilling of C2801 brass with a water–insoluble cutting fluid and a semi–solid cutting fluid was carried out using a cemented carbide microdrill with a diameter of 0.3 mm. Dry microdrilling without a cutting fluid was also performed, and the cutting behaviors were compared.

When microdrilling was performed by applying the semi–solid cutting fluid at a thickness of 0.3 mm, the drill broke early because the chips came out in clumps with poor chip flow. This was because the lubricating action of the cutting fluid was poor. Next, when microdrilling was performed by applying the semi–solid cutting fluid at a thickness of 2 mm, a longer drill life was achieved than when using the water–insoluble cutting fluid. The cutting resistance was high until the semi–solid cutting fluid liquefied, but after that, the cutting resistance was approximately the same as that of the water–insoluble cutting fluid.

Generally, lead–added brass is commonly used as a valve material for water supply, air conditioning equipment, small parts for watches, etc. because of its excellent machinability, it is called free–cutting brass. The concentration of lead in brass is regulated in several countries and regions because its lead may cause health problems in the human body. In consideration of this problem, raw material suppliers have developed several types of lead–free brass in recent years. However, since the machinability of lead–free brass is lower than that of free–cutting brass, cutting force is large and problems such as handling of long chips are pointed out. Therefore, improvement of machinability of lead–free brass is required. In this study, we investigated the effect of tool material, tool shape and coating treatment on cutting tool on cutting force in lead–free brass machining. Orthogonal cutting experiments were also conducted to evaluate the frictional force between the cutting tool and the workpiece during the machining process and the shear force on the shear surface. EPMA measurement of the tool rake face was carried out and the influence of the material of the cutting tool and the coating on adhesion to the tool rake face was investigated. From the results, it was clarified that leadless brass can be cut with cutting force as low as that of lead–added free–cutting brass by using PCD cutting tool. The reason for this was suggested that material adhering to PCD tool hardly occurred and frictional force was remarkably low. In addition, it showed that the effect of reducing the thrust force is particularly large by using a tool with a large tool rake angle, and small cutting edge roundness is effective to reduce the principle force. For coatings that are expected to have high practicality, the cutting force reduction effect of DLC coated carbide tools was found to be about 10％ lower than that of uncoated carbide tools. However, it was found that the diamond coating had no effect of lowering the cutting force. This is thought to be due to an increase in the roughness of the rake face and an increase in the cutting edge roundness due to the coating treatment. Through this study, it was shown that by using PCD tool for cutting of lead–free brass it is possible to process with the same cutting force as conventional lead–free free–cutting brass. Also, a shape of a cutting tool suitable for cutting of lead–free brass was proposed.

This paper studies the fatigue response of Cu–Al–Mn superelastic alloy bars to repeated tensile load at room temperature. The test specimens have 3 relative grain sizes d/D (d：grain size and D：specimen diameter)； poly–crystal (d/D≒0.2), bamboo crystal (d/D≒2) and single crystal bars produced by different cycle heat treatment. Strain–controlled tensile load is applied for 300 cycles with strain amplitudes of 4%. In the test, variations are monitored in the stress–strain curve, the residual strain, and the transformation critical stress. We observe the surface and microstructure before and after the test. The fatigue characteristics are strongly affected by the dislocations generated by the restraining forces at grain boundaries. Therefore, the poly crystals bar with small grains had the worst fatigue property. The bamboo crystal bar with large grains had good initial characteristics, although deterioration due to the dislocation at grain boundaries was still observed. In the single crystal bar, the degradation was caused only by the residual martensite phase, and the fatigue property was most excellent.