In recent years, it has become obvious that about 70％ of clerks in the distribution industry have suffered some kind of harassment from customers, such as violence and abusive language. So, pernicious complaints, also called “customer harassment,” is now receiving attention. Who expresses ego–centric and unreasonable complaints like these？ Why do they complain？ How should companies respond to such complaints？ What psychological and social factors are involved in the growing number of pernicious complaints？ In this paper, we overviewed the various topics surrounding complaints based on psychological findings and previous studies in related fields. And finally, I gave my personal opinions on what measures companies, consumers and governments should take to respond to complaints.

Thermodynamic and kinetic databases are indispensable in providing multicomponent phase diagram and phase transformation data for materials design and process optimization. The recent progress in developing TCCU3 and MOBCU3, the thermodynamic and kinetic databases consisting of 30 elements for copper alloys, is presented in this work. The databases have been validated by ensuring their predictive capability in many multicomponent and industrial alloys following the verification of the assessed binary and ternary systems. It is shown that TCCU3 also contains molar volume data, which can be used to calculate density, coefficient of thermal expansion, and lattice parameter, etc. Applications of these databases in simulating solidification, homogenization, and aging processes are demonstrated and discussed. A case study on high/medium entropy brasses is given in the end to highlight the power of the databases in combination with adequate models.

Stacking fault energies of copper alloys were evaluated by using the first principles calculation and the cluster expansion method. The addition of Zn, Si, and Be, which are HCP stabilizing elements, showed a significant decrease in stacking fault energy, and the addition of Ni, which is FCC stabilizing element, showed an effect of increasing stacking fault energy. Furthermore, the stacking fault energy of Cu–Si, Cu–Zn and Cu–Ni binary alloys reproduced well the experimental values. In the Cu–Si–Zn ternary system, it was confirmed that the stacking fault energy was significantly reduced by the simultaneous addition of Si and Zn. On the other hand, for Cu–Si–Ni and Cu–Be–Co, the effects of the simultaneous addition of solute elements were small, and the results showed that Si and Be dominantly affected stacking fault energy.

We investigated structural and elastic properties of Cu–Ni and Cu–Zn solid solution alloys using first–principles calculations based on the special quasi–random structure （SQS） approach. The supercell modes composed of 108 atoms were employed. The atomic configurations of the supercell models was determined to set the Warren–Cowley parameter such that up to the seventh nearest–neighbor shell is close to zero. The formation energies in Cu–Ni and Cu–Zn alloys smoothly change with alloy composition, which indicates that the supercell models constructed based on the SQS method well reproduce the atomic arrangement of solid solution alloys. In Cu–Ni alloy, an overall increasing trend was observed with increasing Ni content for the Young’s and shear moduli. In the low concentration regions, local minima appeared due to the lattice strain around the solute atoms. In Cu–Zn alloy, the Young’s and shear moduli show sudden decreases at around 14 and 32 at％ Zn. In the composition at the local minima, the Fermi level lies at the sharp DOS peak, which leads to a suppression of energy loss by lattice strains. As a result, the Young’s and shear moduli are decreased. In Cu–Ni alloy, the fermi level lies near the 3d band and the change in the DOS around the fermi level is not significant in comparison with Cu–Zn alloy.

The ingots of Cu_xZnMnNi （x＝1, 2） medium–entropy （ME） brasses were fabricated by metallic mold casting process without using a vacuum chamber. The molten metal was obtained by the high–frequently melting of the mixture of pure Cu, pure Ni, pre–alloy ingots of Mn–Cu and Zn–Ni using silica–based crucible under Ar flow, then the metallic mold casting ingots were obtained by the centrifugal casting under air atmosphere. The composite of body–centered–cubic （BCC） and face–centered–cubic （FCC） phases were obtained in the ingots of equiatomic CuZnMnNi ME brass, while a single FCC phase was obtained in the ingots of non–equiatomic Cu₂ZnMnNi ME brass, where the identification of the constituent phases was mainly performed by XRD analysis. The ingots showed superior deformability and high 0.2％ proof stress during compression test at room temperature.

Compositions of the grain boundary （GB） segregation of solute elements in Cu–based alloys were calculated by CALPHAD （Calculation of Phase Diagrams） method considering the grain radius and volume fraction of grain boundary as well as the stagnant diffusivity of solute elements at low temperatures. The calculations were performed based on the parallel tangent law proposed by Hillert, in which the GB phase and its Gibbs energy were assumed to exist in polycrystalline microstructures. The Gibbs energies of the fcc–Cu and the GB phase, which was supposed as a supercooled liquid phase, were calculated by Thermo–Calc using a thermodynamic database of Cu–based alloys （TCCU2） and incorporated into the calculation program of the GB segregation via TQ–Interface. Under the equilibrium condition in the Cu–X （X＝Ag, Al, As, Be, Co, Cr, Fe, Mg, Mn, Mo, Ni, Pb, Si, Sn, Ti, Zn, Zr） binary systems, segregated compositions of X except for Ni increase monotonously with decreasing temperature. The negative segregation of Ni was changed to the positive one by addition of Si, which indicates the co–segregation of Ni and Si might be precursors for the nucleation of the Ni₂Si phase in Cu–Ni–Si alloys. It was suggested that considerable amount of B as well as Ti segregates on GB in Cu–4Ti–0.03B （at.％） alloy, which could enhance the precipitation of TiB₂ on GB and suppress the discontinuous precipitation of Cu₄Ti. The calculated GB segregation of P and Zr in Cu–Ni–Si alloys is suggested to suppress the discontinuous precipitation of Ni₂Si.

The Co was added to Cu–Ni–Si alloy containing 4〜6 wt％ Ni and 0.9〜1.5 wt％ Si, and the aging behavior was investigated. The hardness change of Cu–（6–x）Ni–xCo–1.5Si alloy aged at 500℃ showed that the time to peak aging was shifted toward to the fastest, and the maximum hardness was increased with increasing Co addition. However, the Co replacement was over the 1.9 wt％ in Cu–（6–x）Ni–xCo–1.5Si alloy, the hardness has overall low value. The discontinuously precipitated region was decreased with increasing Co substitution in Cu–4Ni–0.95Si and Cu–4.75Ni–1.13Si alloy after aging. The hardness and conductivity changes of Cu–（4–x）Ni–xCo–0.95Si and Cu–（4.75–x）Ni–xCo–1.13Si alloys revealed that the Co substituted Cu–4.75Ni–1.13Si alloy showed no sudden hardness drop during aging. The drawn Cu–3.99Ni–0.76Co–1.13Si alloy with 93.75％ area reduction has conductivity about 25％ IACS, but high tensile strength over 1100MPa. The Co substitution to Cu–Ni–Si alloy could suppress mechanically detrimental discontinuous precipitation and stabilize normal precipitation, and increase strength after drawing.

Cu–Ti alloy is one of precipitation hardening alloys with two types of the precipitates such as β’– and β–Cu₄Ti. These precipitates dissolve in Cu matrix during cold working, lowering the conductivity considerably. To prevent the re–dissolution of them, the stability of them should be improved so that they can be stably present even after severe deformation. We have studied the effect of additional 3d transition metals （TMs） on the stability of the precipitates in Cu–Ti alloy, using the simulations based on density functional theory （DFT）. According to the DFT calculations, each Cr, Mn, Fe, Co and Ni atoms prefers to bind with a Ti atom in Cu matrix. When these 5 elements are doped in β’– and β– Cu₄Ti, respectively, the cohesive energies of two phases decrease, indicating that the precipitates can be stabilized in Cu matrix by the TM doping. Especially, Co atoms can decrease the interfacial energy and increase the most unstable stacking fault energy （USFE） for β–Cu₄Ti. It means that the Co addition can stabilize the precipitates effectively, and the slip activation barrier can increase in Co doped precipitates. Therefore, the addition of Co to the Cu–Ti alloy has a very high possibility of suppressing the re–dissolution of the precipitated phase during cold working if Co atoms are well positioned in the precipitates without making another phase.

The microstructural evolution and strengthening of Cu–20 at.％ Ni–6.7 at.％ Al alloy during isothermally aging at 450 to 650℃ were investigated to understand age–induced precipitation and hardening behavior for Cu–Ni–Al system. In an initial stage of aging, fine ordered Ni₃Al particles with a size of several tens nm was coherently formed in parent grains of Cu solid solution in a continuous precipitation manner, together with cellular components composed of Cu solid solution and fine fibrous Ni₃Al phases by grain boundary reaction. During furthermore aging, fine Ni₃Al particles in grains were continuously nucleated and grown, while cellular components at grain boundaries seemed not to be developed. The alloy exhibited a maximum hardness more than 320 Hv by aging at 550 to 650℃, which was greatest among conventional copper alloys. The hardening in the alloy was principally contributed to a high–density dispersion of fine ordered Ni₃Al particles in grains. According to the time–temperature transformation （TTT） diagram for the alloy, aging at 600 to 650℃ should be effective to obtain a microstructure with fine dispersion of ordered Ni₃Al particles and without cellular components, resulting in an excellent strength with the alloy.

The microstructure, hardness and electrical conductivity of solution–treated and aged Cu–In（indium）alloys were investigated, and the effect of the microstructure on their properties were discussed. For solution–treated Cu–（0 to 7.5）at. ％ In alloys, the Vickers hardness and electrical resistivity increased linearly with increasing the indium content. It was found that indium addition in copper imparted a relatively high solid solution hardening and a low decrease rate of electrical conductivity, compared with other solute elements such as Sn and Ni. When aging was conducted, cellular components composed of a Cu solid solution and Cu₇In₃ intermetallic phases were nucleated and grown at grain boundaries, and eventually occupied overall the alloy. The hardness and electrical conductivity of the Cu–In alloys increased by aging. Hardening for the aged Cu–In alloy was explained by an increasing of volume fraction of Cu₇In₃ phase. The increase of electrical conductivity was principally due to developing the cellular components containing high conductive Cu solid solution phase.

Solid–solute zinc in copper alloys has size effect for matrix copper element and decrease stacking fault energy. These characteristics affect strongly on the work hardening, which is proportional to square root of dislocation density. To elucidate the effect of solid–solute zinc in copper alloys on work hardening, we characterized dislocation evolution with an increase in zinc composition in copper alloys. Cu–Zn alloys with compositions of 0, 10, and 30 mass％ were tensile–deformed, and their dislocation density were evaluated by using X–ray diffraction line–profile analysis. The increase in dislocation density with tensile deformation, accompanying work hardening, was enhanced with the zinc composition. Solid–solute zinc, which has larger atomic radius than copper, retards the dislocation motion, so that dislocation generation complemented lower mobility of dislocations in higher zinc composition alloys. While dislocation multiplication became more distinct in higher zinc composition, the dislocation strengthening for unit length of dislocations became smaller with the zinc composition. Decrease in the stacking fault energy with zinc composition suppressed the dislocation cross–slip, and the frequency of dislocation intersection would be reduced. As a result, the effective dislocation density, which can act as the dislocation forest cutting, decreased.

Cu–Ni–Si alloys, so–called the Corson alloys, have been used for electronic devices such as semiconductor lead frames which have excellent electrical conductivity and strength. It is well known that Cu–Ni–Si alloys are strengthened by fine precipitates of δ–Ni₂Si（orthorhombic crystal lattice）during aging treatment. There are many reports about mechanical properties of this alloy system, however, a few papers are dealt with crystal structure evolution of both matrix and precipitates using high resolution transmission electron microscope （HRTEM）.

In this work, we prepared 3 types of Cu–Ni–Si alloys, the base（Cu–5.3 mol％ Ni–2.7 mol％ Si）, excess Ni and excess Si alloys, and the aging behavior and microstructure of those 3 alloys were investigated to understand the effect of ratio of Ni and Si（Ni/Si）added above the solvus of Ni₂Si in the Cu–Ni–Si phase diagram on the types of intermetallic compounds formed during solidification and precipitates formed by aging, and on the hardness. In as quenched samples, 2 types of intermetallic compounds were remained in the 3 alloys, namely, large ones more than 5 μm, and finer ones less than 5 μm. They are mostly identified as δ–Ni₂Si by scanning electron microscope–wave length dispersive X–ray spectroscopy（SEM–WDS）technique. In aged samples, many fine precipitates were confirmed by TEM and HRTEM observation, and they are mostly identified as δ–Ni₂Si in the base and excess Si alloys. The existence of β–Ni₃Si was also pointed out in the excess Ni alloy because of the higher ratio of Ni/Si＝4. It was suggested that the difference in hardening behavior of 3 alloys were caused by these precipitates.

Work hardening of solid–solution copper alloys is enhanced by dislocation multiplication during plastic deformation, and work hardening coefficients depend on alloying elements. To understand the effects of alloying elements of solid–solution copper alloys on work hardening, we investigated the dislocation evolution of Cu–2 at％ MS （MS＝Mg, Sn, Si） during tensile deformation by using electron backscatter diffraction （EBSD） and X–ray diffraction （XRD）. While the Cu–Mg and Cu–Sn alloys exhibited higher work hardening than the Cu–Si alloy, geometrically necessary dislocation （GND） density, which was evaluated from kernel average misorientation observed in the EBSD measurements, increased similarly with tensile deformation, irrespective of the alloying elements. Thus, the multiplication of GNDs depends not on the alloying elements but on the amount of the plastic deformation. XRD line–profile analysis can analyze total dislocation density including not only GNDs but also statistically stored dislocations （SSDs）. The increase in the total dislocation density of the Cu–Mg and Cu–Sn alloys with the tensile deformation was higher than that of the Cu–Si alloy. This was consistent with their work hardening behaviors. The SSD density was estimated by subtracting the GND density from the total dislocation density, and it was confirmed that the multiplication of SSDs depends on the alloying elements and caused the different work hardening behaviors among the copper alloys. Furthermore, the dislocation mobility in the copper alloys was discussed from the dislocation arrangement parameter, which was obtained from XRD line–profile analysis, to understand why the dislocation multiplications were different with alloying elements. The dislocation mobility of Cu–Mg and Cu–Sn alloys was lower than that of Cu–Si alloy. To compensate the lower dislocation mobility of the Cu–Mg and Cu– Sn alloys, the dislocation multiplication was enhanced.

In our previous study, a thin wire of a Cu–0.29wt％Zr alloy was produced by annealing after rolling and then by two intermediate annealings during wire drawing（IA wire）. The IA wire had a value of ultimate tensile strength σ_u of 610 MPa, and had a small value of total elongation εt of 1.2％ despite a small value of grain size D of 240 nm. In this study, a thin wire of the alloy was produced by annealing after rolling and by subsequent wire drawing（S wire）. Even though the S wire had almost the same values of σ_u＝620 MPa and D＝230 nm as the IA wire, the S wire exhibited a larger value of ε_t＝2.9％. This study investigates the cause of the smaller value of ε_t for the IA wire. In both the IA and S wires, voids are formed by decohesion of the interface between the Cu matrix and particles consisting of eutectic phase（Cu＋Cu₅Zr） during wire drawing； however, the fraction of the eutectic particles with voids is larger in the IA wire than in the S wire. The IA wire exhibits the lower ductility as a result of easier linking of the voids during tensile testing. In addition, the larger fraction of the eutectic particles with voids in the IA wire is attributed to the fact that the size of recrystallized grains generated by the intermediate annealing during wire drawing become larger than that of grains before the intermediate annealing, and during subsequent wire drawing, dislocations accumulate significantly around the eutectic particles, resulting in large stress concentration.

Microstructures and mechanical properties of Cu–Zr and Cu–Zr–B alloys were systematically investigated and the origin of their differences was precisely discussed. Addition of 100 ppm B to Cu–Zr alloy could drastically improve the mechanical properties, even while the microstructure and electrical conductivity were unchanged. Especially the tensile strength and ductility were evidently raised by the slight addition of B. From the above experimental results, a hypothesis that extremely low mixing enthalpy can probably cause formation dipoles and/or clusters of the impurity elements which contribute to strengthening without spoiling electrical conductivity has been proposed.

Changes in electrical conductivity and mechanical characteristics, after cold rolling up to a maximum cold working ratio of 80％, were investigated for a CuCrTi alloy, Corson copper alloy and C2600. Electrical conductivity of all alloys decreased with increasing cold rolling working ratio. The drop in electrical conductivity was different among the alloys. In the case of C2600, it was about 3％ IACS, while in the case of CuCrTi alloy, the drop was about 8％ IACS. Changes in volume resistivity were investigated while maintaining a temperature of 300℃, and in the results, C2600 exhibited a trend thought to be recovery of processing strain. With CuCrTi alloy, on the other hand, there was no change in volume resistivity. The results of TEM observation of internal structure showed a trend of reduction due to rolling of Cr–based precipitate, suggesting that resolution of Cr–based precipitate is one cause of the drop in electrical conductivity.

Although pure copper has good electrical and thermal conductivity, it is often used in combination with other metals due to its poor strength. An inexpensive austenitic stainless steel that has excellent corrosion resistance is a good joining material for pure copper, and the joining of these dissimilar metals enables the fabrication of parts for a wide range of applications. However, it is difficult to weld pure copper and stainless steel due to the large differences between their thermal properties. Therefore, in this study, the pulsed–electric–current bonding was applied to achieve solid state bonding of oxygen–free copper （OFC） and SUS304 austenitic stainless steel, and the bonding characteristics were investigated. The results show that the joint tensile strength improves with the increase in the bonding temperature and the applied pressure, and the sample bonded at 973 K with an applied pressure of 20 MPa exhibited a high strength of greater than 200 MPa, which caused a fracture in the OFC base material.

Heat–exchanger tubes mainly consist of phosphorous–deoxidized copper, which has excellent ductility, thermal conductivity, and corrosion resistance. However, in recent years, there has been an increased demand for high strengths and additional corrosion resistance, such as ant–nest corrosion. C1260 containing 0.20–0.40 mass% phosphorus in copper is a promising alternative material for heat–exchanger tube, where previous studies have reported restricting for ant–nest corrosion in the thickness direction. In this study, the plastic deformation behavior of C1260 was investigated at temperatures ranging from room temperature to 200°C by performing tensile and creep tests. With decreasing deformation rate, improved ductility was observed via advances in the recovery process. Furthermore, the time to fracture of C1260 in the creep test was significantly increased compared with a test specimen that does not contain phosphorus. TEM observations of fractured C1260 during the creep test show the presence of dynamic recrystallized grains, suggesting a decrease in the stacking fault energy upon increasing the amount of additive phosphorus to the C1260 sample.

High strength copper dilute alloys are expected to apply alternative heat-exchanger tube material. However, strength of materials is reduced by brazing during process of a heat exchanger. So, it was thought to be important that the decrease in strength can be suppressed by controlling the microstructure with the cooling rate. In this study, we investigated the effect of the cooling rate on the aging characteristics after brazing simulated heat-treatment of Cu-Ni-P alloy. Hardness of the specimens as simulated brazing heat-treatment after cooling decreased with increasing cooling rate. From these results, there is a correlation between the cooling rate and the initial hardness after simulated heat-treatment of brazing. Therefore, it is considered that the increase in hardness immediately after cooling is caused by precipitates formed in the cooling process after the simulated heat-treatment by brazing. The peak hardness of specimens with furnace cooling, which was the lowest cooling rate in this study, aged at 498K was achieved the maximum hardness, which was approximately 130 HV. These results suggested that the strength of the Cu-Ni-P alloy can be further increased by controlling the cooling rate after simulated heat treatment of brazing.

Young’s modulus of a copper single crystal depends heavily on its crystallographic orientation. It is known that the <111> direction with the maximum value shows nearly three times higher Young’s modulus than the <100> direction with the minimum value. In polycrystalline metals of copper and its alloys, the Young’s modulus is closely related to crystallographic texture. Texture control is necessary to increase in a specified direction the properties such as an elastic modulus which does not change greatly by adding alloying elements. In the present study, Cu–30％Zn alloy (brass) was cold rolled to an 85％ reduction in thickness, warm rolled to a 40％ reduction at various temperatures of 573 to 723 K, and finally annealed at 723 K for 1.8 ks to obtain recrystallized microstructure. Adding warm rolling led to a great increase in the Young’s modulus at a direction of 90° to the rolling direction (at the transverse direction, TD) compared to a conventionally cold rolled sheet. The highest value of 122 GPa was achieved for the cold–rolled, warm–rolled at 623 K and annealed sheets. High Young’s moduli at the 90° direction in the annealed sheets are attributed to the recrystallization texture consisting mainly of {011} <322> orientations close to the Brass orientations {011} <211>. It is possible to predict a change in the Young’s modulus at TD with warm rolling temperature from the orientation distribution functions of the annealed sheets. In addition, the mechanism of the {011} <322> recrystallization texture evolution was investigated in the early stages of recrystallization by electron back–scatter diffraction (EBSD) measurements.

The copper tubes of heat exchangers for various types of equipment used in air conditioning and sanitary equipment have been reported to show type I pitting corrosion due to the synergistic effects of carbon film and water quality. To quantify the carbon film, the inner surfaces of the tubes after degreasing with acetone are dissolved with a mixture of nitric acid and hydrochloric acid to allow collection and analysis of the attached carbon. However, there are concerns about the difficulty and danger of this procedure. Therefore, a simple and versatile method for quantifying carbon film is required. We prepared a potential difference calibration curve for corrosion potential measurement as a simple means of quantifying carbon film. The results of the present study showed that the carbon film can be measured by preparation of a potential difference calibration curve for the potential difference ΔE 30 s after immersion in 0.5 M KCl test solution at pH 6. It was also confirmed that the calibration curve was useful for actual tubes.

We have been investigated the effects of residual carbon on the corrosion of copper tubes. It has been revealed that type I” pitting corrosion is significantly suppressed by reducing the residual carbon to less than 2 mg/m² or by removing fine particles in water. In order to evaluate the corrosion inhibition effect of the developed water treatment chemical, a 3–month field test was conducted using copper tubes with different adhesion quantity of residual carbon. The pitting was not observed in copper tubes with residual carbon below 0.5 mg/m² under current chemical water treatment, however, the potential and pitting increased in copper tubes with its value of 6.1 mg/m². The potential of all copper tubes remained low and the pitting corrosion was not observed under the developed chemical treatment. Therefore, it was found that the developed chemical had an effect of suppressing pitting corrosion. In addition, we had been evaluated the “initial treatment” for forming the inhibition film on the copper surface by chemical treatment. It was suggested that the initial treatment was effective in controlling pitting corrosion.

We have been investigated the effects of residual carbon on the corrosion of copper tubes. In the previous study, the developed water treatment chemical could suppress pitting corrosion of copper tube even with 6.1 mg/m² of residual carbon amount in the field test. The effects of the residual carbon and the water treatment chemical were investigated by the electrochemical characteristics using the actual open circulation cooling water. In the anodic polarization measurement under the deaerated condition, the tube with the residual carbon showed a lower natural potential and a higher current density than those of the tube without the residual carbon. In the cathodic polarization measurement under the open–air condition, the tube with residual carbon showed a higher natural potential and a lower current density than those of the tube without residual carbon. Regarding the difference between the water treatment chemicals, there was no significant difference in cathodic polarization behavior, however, a difference in anodic polarization behavior was observed. In the treatment with the developed chemical, the current density at near 0 mV vs. SSE tended to be slightly higher with residual carbon of 6.6 mg/m² or more than it of 0.5 mg/m² or less.

Corrosion has been reported to occur in copper tubes of heat exchangers in multiple circulation hot water supply systems. We have been investigating the applicability of high–strength Cu – 0.65 mass% Sn – 0.014 mass% Zr – 0.020 mass% P alloy as a countermeasure material. Field tests were performed and each part of the heat exchanger was examined. Film formation on the heat–affected part was slower than that on the non heat–affected part, but the heat–affected part showed such excellent corrosion resistance as the non heat–affected part by long–term use. In addition, the alloy also suppressed the progress of galvanic corrosion at the brazing part. The alloy is expected to be better than copper as a corrosion–resistant material for heat exchanger tubes.

An electrochemical approach to reproduce the corrosion morphology of copper in formic and acetic acid environment was examined. Anodic polarization measurement and potentiostatic polarized test for a phosphorous deoxidized copper（PDC）tube in 1000 ppm copper formate and copper acetate aqueous solutions were conducted to investigate the electrochemical behavior of the PDC tube in the solution containing both copper and carboxylate ions. The anodic polarization curve of the PDC tube in copper acetate solution has an inflection point of the current density at about 700 mV vs. Ag/AgCl. Many hemispherical pits occurred on the PDC tubes after the anodic polarization test in copper acetate solution. The hemispherical pits were also observed on the PDC tubes after the potentiostatic polarized test in copper acetate solution, whereas the branched pits occurred on the PDC tubes after the potentiostatic polarized test in copper formate solution. Hemispherical pits occurred in copper acetate solution and branched pits occurred in copper formate solution by these electrochemical methods have characteristics similar to the form of corrosion in acetic acid and formic acid environment respectively.

This paper describes the initial behavior of formicary corrosion for copper tubes in a vapor containing formic acid. Phosphorous–deoxidized copper (C1220) and oxygen–free copper (C1020) tubes were exposed to the vapor in touch with 0.1 mass％ formic acid solution at 40°C and up to 48 h. The corrosion behavior of the tubes was investigated by mass gain measurement, X–ray diffraction (XRD) analysis, optical microscope observation and cross–sectional examination. Potential–pH diagrams were constructed using thermochemical data for Cu in water containing formic acid. Formation of the corrosion product initiated within two hours from the start of the exposure and the surface coverage of the corrosion product increased with time. Careful scrutiny through dye penetrant test, microscopic observation and cross–sectional examination confirmed that no corrosion pit occurred until six to eight hours of exposure, indicating the existence of the incubation stage for precursor of formicary corrosion. Penetration depth increased linearly with time after the onset of the pit and reached approximately 100 µm with branched morphology at 48 hours. XRD analysis revealed that the corrosion product are mainly composed of Cu(OH)₂・H₂O during the initial stage, followed by the formation of Cu₂O after six to eight hours of exposure. There was no significant difference in the corrosion behavior between C1220 and C1020 tubes. The initiation mechanism of formicary corrosion attack was discussed based on the potential–pH diagrams. Uniform corrosion dominates during the initial stage of the exposure, forming Cu(OH)₂・H₂O film. Corrosion attack (anodic reaction) is confined to the film defect such as discontinuity, resulting in localized corrosion. Formation of Cu₂O probably relates to the onset of formicary corrosion pit.

Ant’s–nest corrosion forms a three–dimensional complicated pit in copper tube. This corrosion becomes fatal problems in air conditioner. As a countermeasure for this corrosion, it is required to clarify the mechanism of progress. However, current process is cut out the observational parts, it becomes to be unavailable to observe the progress of corrosion continuously.

In this study, by combining the small test container and the semi–immersion method for observation using CT scanner, it was continuously observed the progress of corrosion pits while maintaining the corrosion test environment.

It clarifies the transition of corrosion rate in progress by continuous observations. All corrosion pits progress are seems to become slower in 4days since it occurred, It is estimated due to the outflow of phosphoric acid.

The galvanic corrosion rate of galvanically coupled Cu–Al and Sn–Al was measured in a 3 wt.% sodium chloride aqueous solution in the previous study. A fundamental mass transfer/reaction model was constructed to analyze a rate controlling step and the effect of dissolved oxygen concentration for galvanic corrosion. It is well known that galvanic corrosion of Al–Cu is diffusion–limited for dissolved oxygen. This behavior can be well explained by the present model. On the other hand, in the case of Sn–Al, it was suggested that the galvanic corrosion rate is a mixed rate controlling of oxygen diffusion and a cathode reaction. The galvanic current depends on the dissolved oxygen concentration in the low oxygen concentration region. And the effect of the reaction rate constant on the galvanic current is large in the high oxygen concentration.

A transmission line model involving constant phase element（CPE）was applied to the impedance analysis of brass in order to evaluate dezincification corrosion depth of brass. The brass after susceptibility test of dezincification corrosion（Brass–sdc）for arbitrary time was used for the impedance measurement. The impedance spectrum of Brass–sdc showed a locus in the high frequency range and a part of loop in the low frequency range. As the distributed constant region and lumped constant region were observed in the impedance spectrum, the impedance at transition frequency could be determined. Because the angle composed of locus in the high frequency range and real axis on the Nyquist plane became small due to the current distribution related to the growth of porous copper rich layer on the brass surface, it is difficult to determine the impedance at transition frequency in the impedance spectrum. In the present study, we employed the transmission line model involving CPE to the impedance analysis of Brass–sdc in order to determine the impedance at transition frequency in the impedance spectrum. The evaluation method for dezincification corrosion depth from impedance at transition frequency in the impedance spectrum of brass was discussed.

Our research group investigated influence of LiOH, CuBr and CuBr₂ concentration and temperature on corrosion behavior of copper which is used as heat exchanger tubes in the concentrated LiBr solution. Test solutions were fully deaerated 65 % LiBr + X % LiOH（X=0〜0.2）+ Y % CuBr（Y=0〜0.04）+ Z %CuBr₂（Z=0〜0.054）. Here, % represents mass %. After a temperature of the solution reached a specific value between 353 and 413 K, a cathodic polarization curve was firstly measured from the corrosion potential to –1.4 V_Ag/AgCl. Thereafter, an anodic polarization curve was measured from the corrosion potential to 0 V_Ag/AgCl. As the result, the anodic current density was independent of LiOH concentration and temperature. The cathodic current density decreased with an increase in LiOH concentration, but increased with a rise in temperature. There were two reactions in the cathodic polarization curve. In one reaction, the cathodic current density increased with a constant Tafel slope as a potential shifted lower. In the other reaction, the cathodic current density was almost independent of potential by diffusion control reaction. Concentrations of CuBr and CuBr₂ did not affect the shape of anodic polarization curve. The cathodic current density below –1.0 V_Ag/AgCl was independent of CuBr and CuBr₂ concentrations. In the potential region of diffusion control reaction, the cathodic current density increased with an increase in CuBr and CuBr₂ concentrations．

The research aimed to investigate the corrosion behavior of Cu–Sn–Zn–S alloy（as one of lead–free Cu alloys）in CuCl₂ aqueous solutions. JIS CAC411（Cu–Sn–Zn–S alloy）, Cu and Sn were used as specimens. Test solutions were CuCl₂ ＋ NaCl solutions whose Cu^2＋ and Cl⁻ concentrations were controlled. A polarization curve of each specimen in each solution was measured. The results were described as follows：Increase in Cu^2＋ concentration accelerated cathodic reaction and made corrosion potential of Cu and CAC411 specimens higher, however hardly changed shapes of the anodic polarization curves. On the other hands, increase in Cl⁻ concentration accelerated anodic reaction and decrease corrosion potential of Cu and CAC411 specimens. 1.0 mass％ CuCl₂ solution which generally employed in the jet–in–slit test facilitated to form corrosion product layer consisting of CuCl. Sn was concentrated in the corrosion product layer formed on CAC411 specimen. The particles of the corrosion product formed on CAC411 was finer and the corrosion product layer was denser than that on Cu.

To evaluate the corrosion mechanism of copper artifacts and to propose the effective reburial method that suppresses the corrosion of copper artifacts at the underwater archaeological site, corrosion tests were carried out at the Takashima underwater archaeological site using copper and copper with wood. The results of the corrosion test specified that corrosion proceeded by the effect of H₂S or HS^–even in dissolved oxygen （DO）–depleted conditions at the underwater archaeological site. In the case of the copper with wood, the corrosion rate dramatically increased in comparison with the copper samples due to the effects of wood as nutrient salt for sulfate–reducing bacteria. These results indicate that it is necessary to control the mass transfer of chemical species like H₂S, HS^–, and Cu⁺ for suppression of corrosion of copper artifacts at underwater in addition to DO–depleted conditions. The results of the study also suggest that covering copper artifacts using porous media like sandy soil is an effective means for the preservation of them.

Geological disposal of high–level radioactive waste in Japan is based on the concept of a multi–barrier system constituted of the engineered and natural barriers. For the disposal system, the high–level radioactive waste is enclosed in a metal container（overpack, hereafter）fixed in a bentonite buffer. The overpack is aimed at preventing contact of the waste to groundwater during the period longer than 1000 years in which relatively high heat is continuously generated. The overpack, therefore, requires holding corrosion resistivity/prevention and structural stability against mechanical loading at least for 1000 years. In this study, we overviewed bibliographic works on the copper–steel composite containers proposed by the geological disposal organizations in several foreign countries and then suggested for the waste in Japan the preliminary design of the copper coating container that is based on the new copper coating technologies developed by NWMO.

The intergranular fracture rarely takes place in the polycrystalline Cu–Al–Mn shape memory alloy. This fracture mode, however, is easily induced by stress corrosion cracking. In order to overcome this problem, the grain boundary design and control were performed with various heat treatment conditions. The frequency of coincidence site lattice （CSL） boundary increased in the specimen slowly heated from α ＋ β dual–phase to β single–phase regions. The｛211｝＜011＞ recrystallization texture also developed strongly in the slowly heated specimens. On the other hand, the frequency of CSL boundary decreased and the recrystallization texture hardly developed in the rapidly heated specimen. Consequently, the suppression of intergranular fracture and the improvement of superelastic property were achieved simultaneously with a relatively simple heat treatment procedure.

Research was conducted to prevent galvanic corrosion, which occurs between the Al wires and Cu terminals of the aluminum wire harness, by surface treatment. When zinc is added by 2 wt% or more to the tin electrodeposit, the corrosion potential becomes lower than the pitting potential of aluminum, and the aluminum wires can be protected. As a method for alloying Sn and Zn, the method of electrodeposition, the method of supplying Zn from the Zn underplate to the Sn surface, and the method of reflowing Sn and Zn were compared. As a result, in the method by electrodeposition, Zn was deposited as a concentrated phase in Sn layer. That concentrated phase of Zn was dissolved early, and the effect of keeping the low potential was not maintained for a long time. The method of reflowing Sn and Zn was inferior to the other methods in the anticorrosive effect. The method of supplying Zn from the Zn underplate to the Sn surface showed an excellent anticorrosive effect over a long period of time as compared with the electrodeposited Sn–Zn alloy in which the Sn phase and the Zn phase are separated. The surface treatment found in this study eliminates the need for anticorrosion treatment such as resin molding, which is conventionally used for aluminum wire harnesses, and is expected to contribute to the miniaturization and cost reduction of aluminum wire harnesses.

For the present study we tried to visualize the formation of aqueous Cu²⁺ ion induced reactive oxygen species （ROS） and subsequent damage to cell components in Synechococcus elongatus PCC 7942 （S. elongatus） cells, either in the presence or absence of Zn²⁺ and Ni²⁺ ions. Metal ion ratios in aqueous solutions were prepared by simulating the metal compositions of five different standard alloys including pure Cu, Brass （C2600）, Brass （C2680）, Nickel Silver （C7521） and Nickel Silver （C7701）. Live images of interactions of cyanobacteria cells with different metal ion solutions were taken by fluorescent microscope equipped with a multicolor time lapse recording system. Ultrastructural changes were observed by transmission electron microscope （TEM）. ROS, DNA and chlorophyll fluorescence of cyanobacteria cells were dynamic over time and remarkably diverse depending on the aqueous metal ion compositions. In contact with Cu²⁺ ions alone, cyanobacteria gained an extreme level of ROS while DNA fluorescence rapidly disappeared. Presence of Zn²⁺ ions prevented the DNA fluorescence disappearance caused by Cu²⁺ ions and abolished adverse effects induced by ROS synthesis. Addition of Ni²⁺ ions caused distinct chlorophyll fluorescence reduction. Ultrastructural observations showed severe damage to the cytoplasm, thylakoid membranes and carboxysomes after interaction with all tested aqueous metal ion combinations.

In Japanese traditional exterior wood constructions, such as temples, timber bridges, castles and old folk houses, copper based metal fittings are used to cover the edge of wood members. The fitting is considered to protect wood from the rain waters and decay. However, bio–deterioration of wood was inhibited also widely around the fittings in many cases. It is supposed that copper ion might be eluted from the fitting to the neighbored wood and inhibited decay. In the recent field analytical work on the traditional bridge, which has the bronze fittings, copper was detected in high concentration from the wood around fittings, and in the laboratory wood decay tests, copper plates suppressed the wood decomposition by decay fungi. These results support the possibility of copper and copper based metal as items to improve the durability of wood constructions. In this study, to understand the basic antifungal properties of the copper ion, the minimum inhibition concentrations (MIC) of water soluble copper salts, such as CuSO₄, Cu(NO₃₎₂, Cu(CH₃COOH₎₂ and CuCl₂, against wood decay fungi, Fomitopsis palustris, Trametes versicolor, were determined by a broth dilution method. The MIC of metal salts containing Zn, Ni, K and Na, were also determined. The MIC of salts were converted to MIC of metals and anions, and compared with one another. As a result, MIC of each metals were consistent and were not affected by the kind of the anions. It is confirmed that antifungal effect of the soluble metal salts, such as copper salts, is dependent on the concentration of metal ions and not affected by the anions.

In order to produce composite powders exhibiting higher hardness and magnetic properties, pure copper powder and pure zinc powder together with ferrite（FR）powder were mechanically alloyed（MAed）using a vibration type of ball mill. The composite powders were evaluated by hardness, X–ray diffraction（XRD）and magnetic properties. The hardness of the composite powders increased as increasing of MA time and the amount of FR powder. No solid–state reaction among copper, zinc and FR for all composite powders was detected by XRD analysis suggesting that the composite powders can be exhibiting magnetic properties. No change was observed in the saturation magnetic flux after MA process. Whereas the coercive force increased as increasing MA time.

Pure copper powder and pure zinc powder together with ferrite （FR） powder were mechanically alloyed （MAed） using a vibration type of ball mill, and obtained MAed powders were consolidated into bulk materials by spark plasma sintering （SPS）. Effects of sintering temperatures on hardness and electrical conductivity of bulk SPS materials were investigated by hardness and electrical conductivity measurements, respectively. The constitute phase for the SPS materials was identified by X–ray diffraction. In addition, magnetic properties of the SPS materials were evaluated. The optimal sintering temperature was 973 K in terms of hardness value in the SPS materials. The maximum value of Vickers hardness was over 500 HV for the Cu–35 Zn with 50 mass% FR composite material at the sintering temperature of 973 K. The SPS materials exhibited to attach the permanent magnetic. The combination of MA–SPS process can be beneficial for fabricating bulk materials from composite powders produced by mechanical alloying process.

Copper matrix composites were prepared from the mixture of flake–like graphite and pure copper powder by spark plasma sintering （SPS）. As the SPS process is a two–axial compression press machine, flake–like graphite shows a special distribution form, which lay to the vertical direction of two–axial pressure, and we can define this distribution as orientation. In this study, the effect of size, volume fraction of flake–like graphite and cold–rolling rate on the orientation of flake–like graphite and thermal conductivity of the composites. As a result, the size did not have a meaningful influence on orientation. But as increasing the volume fraction, orientation to the vertical direction for pressure increased. In addition, the orientation greatly improved by the cold–rolling. Furthermore, by measuring the shape and orientation of the graphite from the photo of composite microstructure with the various volume fraction of graphite, the thermal conductivity of the composites was predicted by computer simulation. The predicted thermal conductivity showed good agreement with experimental values.

Cu–2.3%Ni–0.55%Si （mass%） sheets, which had been aged at 723K after solution treatment at 1173K or 1273K, were subsequently processed by either （a） low–speed rolling （LSR） （5 m/min at RT） or （b） cryogenic high–speed rolling （C–HSR） （1500 m/min at 77K）. The total reduction in thickness of 78% was applied in 3–pass operation. Mechanical properties, electrical conductivity, and microstructure of the as–rolled sheets were investigated. The LSRed sheet showed tensile strength of 731 MPa and electrical conductivity of 27.9%IACS, while the C–HSRed sheet showed 822 MPa and 26.2%IACS. The C–HSRed sheets contains more deformation twins and shear bands in the microstructure than the LSRed sheet. Using a modified Hall–Petch equation, it is recognized that the higher strength of the C–HSRed sheet is attributed to fine–grained microstructure and increased dislocation density.

Conventional brass rods are added a little lead to improve machinability. However, lead is a toxic heavy metal. So it is expected that lead–less brass rod will be advanced in the future. Following these trends, we need strengthen lead–free brass to obtain the same high strength and excellent machinability as conventional materials.

In this study, we strengthened lead–less brass rods by groove rolling, and examined the microstructure and mechanical properties of them. It is known that rod materials such as extruded materials differ in hardness between the central part and edge part, because of difference in processing degree. So we investigated the effect of groove rolling on hardness distribution on a cross section of lead–less brass rods. It can be expected that groove rolling can be processed until the center compared to the extrusion method.

Lead–less brass had few β’ phases and coarse grains compared with lead added brass. But the grains were refined by groove rolling. Strength increased by grain refinement and work hardening, while elongation was reduced. The difference in hardness between the edge and the center of the groove rolled rods was almost the same as that of the drawn rods.

The effect of Mn, P and Sn addition on the wear resistance of Cu–Zn alloys was studied. Ingots were prepared by adding Mn, P and Sn to Cu–45% Zn alloy one by one. A test piece was cut out from the ingot and wear testing was performed. The comparative abrasion quantity and metallic structure after the wear testing were investigated. In all the cases of the three additives, specific wear rate was increased by the addition when the additive amount was small, while it was decreased beyond that amount and reached a minimum. In the case of Mn addition, excessive addition did not cause a large change with no appearance of a second phase, but specific wear rate was again increased by the excessive P and Sn additions. This was presumed to be due to the aggregation of the second–phase compound on the friction surface, which caused the compound to fall out. For P–added materials, the minimum value of the comparative abrasion quantity was taken in this study.

The squared resonant frequency and internal friction in commercial copper and copper alloy rolled sheets was measured as a function of temperature, using resonant method. The squared resonant frequency of Oxygen free copper rolled sheet falls when the temperature increases, subsequently rises at around the recrystallization temperature. In the case of brass rolled sheet and iron particle dispersion copper alloy rolled sheet, the squared resonant frequency of these alloys rapidly falls at around the recrystallization temperature. The internal friction curves of these copper rolled sheets consist of background and high peak at around the recrystallization temperature. In the case of the iron particle dispersion copper alloy rolled sheet, the internal friction curve has the small peak at 373K to 473K. The point of inflection of the temperature dependence of squared resonant frequency of these alloys occurs at around these temperatures. An optical length measurement method reveals permanent elongation in the rolled direction and permanent shrinkage in the perpendicular direction to the rolled direction, when the particle dispersion copper alloy rolled sheet is heated at 473K, subsequently is cooled to room temperature. These permanent deformation by heating and cooling affects the temperature dependence of squared resonant frequency.

Cyclic softening is typical deformation behavior of ultrafine grained （UFG） metals fabricated by severe plastic deformation process such as ECAP （Equal channel angular pressing）. The softening is occurred with the formation of shear bands and the dynamic grain coarsening. In this study, the plastic strain amplitude dependence of cyclic deformation behavior of UFG Cu alloys containing Fe precipitates was investigated to understand the effect of the Zener pinning force to fatigue properties. Specimens of an UFG Cu–Fe alloy were made by the ECAP after aging treatment at 923 K for 95min. Fully–reversed tension–compression tests were carried out under constant plastic strain amplitudes of ε_pl＝2×10⁻⁴, 1×10⁻³, 2×10⁻³ at room temperature. The cyclic softening occurred in all conditions during fatigue tests. These cyclic softening curves were consisted of the rapid softening region and the steady softening region. There was a linear relationship between the softening rates calculated from the steady softening region and the plastic strain amplitudes. The softening rates of UFG Cu–Fe specimens were lower than that of the UFG Cu specimen.

Fatigue endurance of copper foils on Flexible Print Circuits （FPCs） is critical factor for the life of electrical devices. In recent years, FPCs are adopted for not only smartphones and tablets but also on–vehicle apparatuses and wearable devices. In this report, fatigue endurance of copper foils is evaluated by torsion test, vibration test and thermal cycle test for more practical evaluation methods as well as by IPC sliding bending test for a general evaluation method. It is found that highly flexible rolled annealed copper foil （RA）, which has extremely cubic recrystallization texture, shows higher fatigue endurance than electro deposited copper foil （ED） in the all fatigue tests. The longer life of RA can be explained by a relationship between a progress direction of intrusions in copper foil and grain boundaries vertical to the stress axis.

Heterogeneous–nano （HN） structures induced by heavy cold rolling of Cu–Be–Co alloys and their influence on the mechanical properties were systematically investigated to develop thermo–mechanical process applicable to the industrial mass–production. The HN–structure was successfully developed by the combination of differential speed cold rolling and simple cold rolling with the reduction up to 97％ at maximum after the solution–annealing between 850 and 867°C. The HN structure possessed characteristic eye–shaped domains consisting of alternatively stacked deformation twin bands. Aging at 285°C of the HN structured Cu–1.86mass％Be–0.23mass％Co alloy caused a marvelous tensile strength of 1.78 GPa, which was significantly higher than that of 1.3 GPa of a conventional Cu–Be–Co alloy （C17200） fabricated by conventional thermo–mechanical processes. It was also shown that the developed HN structured Cu–Be–Co alloy exhibited comparable bending formability and electrical conductivity with those of the conventional one. While, in contrast, the fatigue strength was slightly lower than that of the conventional one. It is confirmed that introduction of HN structured Cu–Be–Co alloys can be fabricated by means of a newly developed thermo–mechanical process applicable to the industrial–scale mass production.

From the background of miniaturization and high–density mounting in mobile information communication devices such as smartphones and tablet terminals, micro connectors are getting thinner and narrower. It is therefore, required to improve the strength and electrical conductivity of copper alloys used in the devices. Recently, our group successfully found that the procedure of finish–rolling and then annealing at a low temperature was available to provide a 0.2% proof stress exceeding 1000 MPa and an electrical conductivity exceeding 30% IACS for a Cu–2.4Ni–1.2Co–0.90Si alloy (mass%). In this study, we investigated the strength, electrical conductivity, and microstructural evolution of before and after annealing at a low temperature for the Cu–2.4Ni–1.2Co–0.9Si alloy, by means of XRD, EBSD, FE–SEM, TEM, and three–dimensional atom probe (3DAP). According to the 3DAP analysis, clusters of Ni, Co, and Si with a size of approximately 1 nm were formed after annealing at a low temperature. It is suggested that fine age–induced precipitates, (Ni,Co)₂Si, with a size of 5 nm, should be sheared by the finish–rolling procedure and then ultrafine clusters should be formed by annealing at a low temperature. Therefore, the strengthening by annealing at a low temperature must be contributed to ultrafine clusters.

The effect of 0–0.5wt%Ni addition on recrystallization behavior during solution treatment at 825–1000°C, strength, electrical conductivity after aging at 475–600°C of Cu–1.0wt%Co–Xwt%Si–Ywt%Ni–0.15wt%Cr alloy （X＝0.28〜0.44, Y＝0〜0.5, （Co＋Ni）/Si≒3.4） was studied. The addition of Ni enhanced recrystallization temperature of the alloy. In the case of 0wt%Ni, recrystallization temperature was 825°C. In the case of 0.5wt%Ni, that was 950°C. On the other hand, electrical conductivity saturated at 950°C regardless of the concentration of Ni. Grain size at 950℃ was about 20μm regardless of the recrystallization temperature. The highest tensile strength after solution treatment at 950℃ and subsequent aging at 525°C was enhanced from 575 to 675 MPa as the concentration of Ni and Si increased. The increase of tensile strength was the result of the increase of （Co,Ni）Si precipitates. The electrical conductivity at 525℃ was lowered from 53 to 66%IACS. The tensile strength was more enhanced by cold rolling at 75% before aging. The electrical conductivity was slightly enhanced. The tensile strength＝about 700MPa, electrical conductivity＝59%IACS and MBR/t =0 were achieved by Cu–1.0wt%Co–0.33wt%Si–0.15wt%Cr–0.1wt%Ni alloy.

Changes in microstructure and mechanical properties of Cu–Ti alloy sheets during cold rolling were studied with Cu–Ti precipitates in the initial microstructures. Second phase particles, which are presumably β–Cu₄Ti precipitates, were observed in the Cu–Ti alloy before cold–rolling along the grain boundaries, and their Ti concentration and size are near 7 wt.％ and are less than 1μm. Pre–existing Cu–Ti precipitates were plastically deformed and severely elongated along the rolling direction via cold rolling, accelerating the formation of a nano–lamellar structure. A mean lamellar boundary spacing of 20 nm was achieved at an equivalent strain of 6.7. This exceptional refinement during cold rolling can be mainly attributed to pre–existing precipitates, which can effectively subdivide the matrix microstructure. Ultimate tensile strength, 0.2％ proof stress and Vickers hardness increased with decreasing lamellar boundary spacing, following the Hall Petch relationship. Therefore, the strength of heavily deformed Cu–Ti sheets can be primarily attributed to grain boundary strengthening related to the lamellar boundaries. These results suggest that pre–existing precipitates promote microstructural refinement during heavy cold rolling, leading to excellent mechanical properties.