Showing papers in "Journal of The Japan Institute of Metals in 2008"
TL;DR: In this paper, a new surface treatment system (IH-FPPsystem) combined with an induction heating and a fine particle peening machine was developed for structural steel discs using Cr shot particle at room temperature, 400°C, 600°C and 900°C.
Abstract: A new surface treatment system (IH-FPPsystem) combined with an induction heating and a fine particle peening machine were developed. FPP treatments were carried out on structural steel discs by using Cr shot particle at room temperature, 400°C, 600°C and 900°C. After characterizing the surfaces by SEM, EDX and XRD, corrosion tests were performed by a three electrode method using a computer driven potentiostat. No noticeable differences were observed on the specimen treated at RT, 400°C and 600°C. In the case of the specimen treated at 900°C, however, higher corrosion resistance which is almost the same as FPP treated stainless steel (SUS316L) was observed. This was because Cr diffused layer covered with relatively smooth oxidized surface prevented a corrosion reaction in 3%NaCl environment.
25 citations
TL;DR: In this paper, thermal desorption analysis (TDA) was used to compare the hydrogen ex-isting trapping sites using Inconel 625 and SUS 316L charged by electrolysis and high-pressure gas at 90°C.
Abstract: ) and in gaseous hydrogen at the pressure of 0.3, 10, 20 and 45 MPa at 90° C. The states of hydrogen ex- isting trapping sites were compared using thermal desorption analysis(TDA). The diffusion activation energy is 46.5(kJ/mol) and the trap activation energy is 46.3(kJ/mol) for Inconel 625. These close values indicate that the hydrogen released from FCC metals is determined not by desorption from trapping sites but by diffusion in lattice. The hydrogen content of Inconel 625 in- creased upon the quenching and coldworking. This increase in hydrogen content corresponds to the increase in the densities of vacancies and dislocations. The hydrogen peak consists of solution hydrogen and trapped hydrogen at vacancies and dislocations. The peak temperatures in the hydrogen evolution curves of Inconel 625 and SUS 316L charged by electrolysis and highpressure gas at 90° C are the same after hydrogen saturation. In addition, hydrogen contents obtained upon charging by electrolysis exceed those obtained by highpressure gas of 45 MPa. This means that higherpressure gas environments of at least 45 MPa can be substituted by electrolysis charging. The hydrogensaturated contents of the metals increase with current density and catalyst content. Sievert's law describes the relationship among hydrogen content, hydrogen gas pressure, and temperature. Therefore, the gas pressures corresponding to electrolysis charging conditions can be obtained. When hydrogen is charged by electrolysis us- ing 0.1 mass NH4SCN at 50(A/m2), the hydrogen gas pressure of 1200 MPa is actualized by electrolysis charging.
21 citations
TL;DR: In this paper, the effects of electron beam irradiation on the joining strength of different polymers without adhesive materials were investigated, and it was shown that EB-irradiation more than 300 kJ kg-1(kGy) apparently decreased the join strength.
Abstract: Joining between Nylon-film and Silicone-rubber was successfully developed by using homogeneous EB irradiation. Effects of electron beam (EB) irradiation on joining strength of different polymers without adhesive materials were investigated. Although excess EB-irradiation more than 300 kJ kg-1(kGy) apparently decreased the joining strength, the EB irradiation increased the joining strength of the joining sample between Nylon-film and Silicone-rubber. To discuss the influences of EB irradiation on the joining strength, electron spin resonance (ESR) signals related to dangling bonds were observed. Since EB irradiation generated dangling bonds on Nylon-film, dangling bonds probably supported the each other polymer at interface.
20 citations
TL;DR: In this article, the influence of sheet electron beam irradiation (SEBI) with low potential on water absorption in nylon6 has been evaluated, and the mass of water absorption was measured.
Abstract: In order to evaluate the influence of sheet electron beam irradiation (SEBI) with low potential on water absorption in nylon6, the mass of water absorption in nylon6 has been measured. The SEBI decreases the saturated mass of water absorption in nylon6 and also decreases the initial absorption rate of water, as well as the mass of absorbed water in nylon6 for each treatment time. Based on the results of ESR and XPS, the SEBI forms dangling bonds and then decreases the electrical polarization of nylon6 molecules, resulting in decreasing the mass of absorbed water in nylon6.
18 citations
TL;DR: In this paper, the effect of porosity and pore shape on thermal conductivity was calculated by micromechanical analysis and it was revealed that oblate spheroidal pores are effective to decrease the thermal conductivities.
Abstract: Metal foams are attractive materials for thermal insulators because of their low thermal conductivity. Coefficient of thermal expansion (CTE) of metal foams is the same as that of cell wall materials. Therefore, the effect of thermal stress induced by a change in CTE, which is severe in the thermal barrier coating by ceramics, becomes negligible. In this study, we focus on designing metal foams as thermal insulators. The effect of porosity and pore shape on the thermal conductivity was calculated by micromechanical analysis. It was revealed that oblate spheroidal pores are effective to decrease the thermal conductivity. Micromechanical analysis also revealed that the thermal conductivity can be controlled by pore distribution of the metal foam. That is, metal foam with graded porosity has low thermal conductivity compared to uniform porosity. A diffusionbonding process enabled to manufacture 5083 aluminum alloy preforms containing TiH2 particles as a foaming agent. Foaming test by directional heating enabled to manufacture closedcell 5083 aluminum alloy foams having both oblate spheroidal pores and graded pore distribution.
17 citations
TL;DR: In this article, the gas atomized Co-29Cr-6Mo alloy powder was hot-pressed at various temperatures from 1223 K to 1357 K with applied pressures of 50 or 80 MPa for 7.2 ks.
Abstract: The gas atomized Co-29Cr-6Mo alloy powder was hot-pressed at various temperatures from 1223 K to 1357 K with applied pressures of 50 or 80 MPa for 7.2 ks. Mean grain size of the compacts hot-pressed at 1257 K is 2.7 μm and the relative density is 97%. The grain size of the compacts tends to increase with increasing sintering temperature. The σ phase is observed in the compacts hot-pressed at 1223 K to 1307 K. The ultimate tensile strength of the compacts hot-pressed at 1257 K and 80 MPa shows the highest value (1240 MPa) in the compacts due to the fine grain size (2.7 μm). Meanwhile, the compact hot-pressed at 1357 K and 50 MPa shows the highest plastic elongation (50%). This is attributed to the facts that the σ phase is dissolved in the fcc matrix during hot-pressing at 1357 K and strain-induced martensite transformation (SIMT) proceeds during plastic deformation. These values are much higher than those of as-cast Co-29Cr-6Mo alloy and comparable to those of the forged Co-29Cr-6Mo alloy.
16 citations
TL;DR: In this article, the effects of alloying elements on the stress relaxation property of Cu-Ni-Sn-P alloys have been investigated using Cu, Cu-1.5 at% (2.8 mass%) Sn alloys with and without 0.14 at%(0.07 mass%) P. Adding Sn to Cu enhances the resistance to stress relaxation by dragging atmospheres of Sn atoms behind dislocations.
Abstract: The effects of alloying elements on the stress relaxation property of Cu-Ni-Sn-P alloys have been investigated using Cu, Cu-1.5 at% (1.4 mass%) Ni alloys, Cu-0.75 at% (0.7 mass%) Ni-0.75 at% (1.4 mass%) Sn alloys and Cu-1.5 at% (2.8 mass%) Sn alloys with and without 0.14 at% (0.07 mass%) P. Adding Sn to Cu enhances the resistance to stress relaxation by dragging atmospheres of Sn atoms behind dislocations. The Cu-Ni-P alloy exhibits better stress relaxation property than the Cu-Ni and Cu-P alloys, probably because atoms caused by pairs of P and Ni chemical binding are dragged by moving dislocations. Annealing of the Cu alloys with P at a low temperature of 300°C for a short time brings about higher stress-relaxation resistance. This is ascribed to the decrease in mobile dislocation density by segregation of P atoms on dislocations during the annealing. Adding 0.1 at% (0.04 mass%) Mg to the Cu-Ni-Sn-P alloy decreases the amounts of Ni and P dissolved in the Cu matrix, resulting in lower stress-relaxation resistance. The addition of 0.1 at% (0.09 mass%) Fe to the Cu-Ni-Sn-P alloy is effective for the improvement of stress relaxation property.
15 citations
TL;DR: The microscopic mechanism of the grain boundary embrittlement in metals by solute segregation has been not well understood for many years as mentioned in this paper, and the calculated cohesive energy (2γint) of bcc iron Σ3(111) symmetrical tilt grain boundary is reduced by the segregation of sulfur (S) or phosphorous (P), while it is increased by thegregation of boron (B) or carbon (C).
Abstract: The microscopic mechanism of the grain boundary embrittlement in metals by solute segregation has been not well understood for many years. From first-principles calculations, we show here that the calculated cohesive energy (2γint) of bcc iron Σ3(111) symmetrical tilt grain boundary is reduced by the segregation of sulfur (S) or phosphorous (P), while it is increased by the segregation of boron (B) or carbon (C). The rate of the decrease/increase in the 2γint was excellently proportional to the experimental ductile-to-brittle transition temparature (DBTT) shift with increasing segregation; this demonstrates that the grain boundary embrittlement is governed by the change in the 2γint.
15 citations
TL;DR: In this article, the temperature dependence of the electrical resistivity and the Seebeck coefficient for the p-type Fe2(V1-x-yTixTay) alloys with compositions 0≤x≤0.03 and y=0.10 was investigated.
Abstract: We report on the temperature dependence of the electrical resistivity and the Seebeck coefficient for the p-type Fe2(V1-x-yTixTay)Al alloys with compositions 0≤x≤0.10 and 0≤y≤0.10, in addition to the composition dependence of the thermal conductivity at room temperature. While Fe2VAl (x=0, y=0) exhibits a semiconductor-like behavior in the electrical resistivity, a slight doping of Ti and Ta causes a significant decrease in the resistivity at low temperature and a large enhancement in the Seebeck coefficient, reaching 90 μV/K for x=0.03 and y=0.10. The power factor is found to be substantially larger than that for the p-type Fe2(V1-xTix)Al alloys so far reported. Although the thermal conductivity for Fe2(V1-xTix)Al remains in the range of 24∼28 W/mK for 0≤x≤0.10, it decreases significantly with the Ta substitution, reaching 11∼12 W/mK for 0≤x≤0.10 and y=0.10. We conclude that doping of heavier atoms such as Ta reduces more effectively the lattice thermal conductivity.
12 citations
TL;DR: In this paper, the effects of the second refining process, Electro-Slag Remelting (ESR), were investigated on Ta rich inclusion formation in the VIM Reduced Activation Ferritic/Martensitic steel (RAFM), F82H (Fe-8Cr-2W-V-Ta).
Abstract: The effects of the second refining process, Electro-Slag Remelting (ESR), were investigated on Ta rich inclusion formation in the Vacuum Induction Melted (VIM) Reduced Activation Ferritic/Martensitic steel (RAFM), F82H (Fe-8Cr-2W-V-Ta). The Ta rich oxides such as TaOx and TaOx-Al2O3 are major inclusion in VIMed F82H, and those were correlated with the reduction of the Charpy impact property, as those were found at the crack initiation points. It was revealed that the ESR process was effective on removing those Ta rich oxides. On the other hand, ESR process increased MnS and Al2O3 instead, and these inclusions were found at the crack initiation points. These could explain the little difference on Ductile-Brittle Transition Temperature (DBTT) of as-VIMed and ESRed F82H.
12 citations
TL;DR: In this paper, a simple testing method for mechanical properties of materials in high-pressure hydrogen environments has been developed, which does not require any high pressure vessel but the high pressure hydrogen environment is produced inside the hole in the specimen.
Abstract: A simple testing method for mechanical properties of materials in high-pressure hydrogen environments has been developed. This method does not require any high-pressure vessel but the high-pressure hydrogen environment is produced inside the hole in the specimen. The specimen temperature is easily controlled by outside environment. The effects of hydrogen environment embrittlement (HEE) for SUS304 and 304L at 298, 190, and 77 K were evaluated by the ratio of reduction of area obtained in tensile tests in hydrogen to that obtained in helium. The results of the evaluation by this testing method agreed fairly well with the results by the usual method using a high pressure vessel. The hole in the specimen was machined by electric discharge, wire-cut, and honing. The influence of surface roughness on HEE was compared among these processes and the wire-cut machining was found to be enough for this new method. Changes of HEE with temperature and fracture surface by hydrogen proved the usefulness of this new simple method.
TL;DR: In this article, the as-solutionized TNTZ rod consists of a single β phase and isothermal ω phase and α phase precipitate in the β phase of the TNTZ rods aged at 673 K for 259.2 ks.
Abstract: Installing a spinal fixture using implant rods is one of the effective operations for spinal diseases. Most of the implant rods are made of Ti-6Al-4V ELI alloy (Ti64). However, some problems regarding the Ti64 rod have been pointed out; it contains vanadium, which is considerably toxic to the human body, and exhibits a much higher Young's modulus than that of the cortical bone. Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) developed by the authors exhibits good biocompatibility due to its nontoxic- and allergy-free elements, and has a lower Young's modulus than that of Ti64. In addition, the mechanical properties of TNTZ can be changed drastically according to various heat treatments. The mechanical properties of TNTZ rods subjected to various heat treatments have been investigated in this study. The as-solutionized TNTZ rod consists of a single β phase. Isothermal ω phase and α phase precipitate in the β phase of the TNTZ rod aged at 673 K for 259.2 ks. Only α phase precipitates in the β phase of the TNTZ rod aged at 723 K for 259.2 ks. Tensile strength and 0.2% proof stress become larger in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks, while elongation is smaller in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks. Young's modulus become larger in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks.
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TL;DR: In this article, first-principles calculation revealed that Na atoms were expected to be primarily located Mg sites in Mg2Si and X-ray diffraction experiments showed that the prepared samples were composed of a single Mg 2Si phase.
Abstract: First-principles calculation revealed that Na atoms were expected to be primarily located Mg sites in Mg2Si. Densities of electronic states of the Na-doped Mg2Si showed p-type. To obtain a good p-type thermoelectric material, Na-doped Mg2Si (Mg66.7-xSi33.3Nax) were fabricated by solid-liquid reaction using spark plasma sintering. The X-ray diffraction experiments showed that the prepared samples were composed of a single Mg2Si phase. Electrical resistivity, ρ, and Seebeck coefficient, α, were measured in the temperature range from room temperature to around 600 K for samples with various Na contents. The α of samples in the Na composition range of x≥0.5 were positive values (p-type). The results of first-principles calculation and experiment showed that Na was employed as acceptor in Mg2Si system. The maximum power factor of 0.44×10-3 W•m-1•K-2 was obtained at 313 K for the Mg65.7Si33.3Na1.0 sample.
TL;DR: In this paper, the formation process of conical protrusions on the surface was investigated by changing the sputter etching time, and the tensile and bending tests of the specimens were carried out to examine whether the delamination between the protrusion and matrix occurs or not.
Abstract: Austenitic stainless steel (SUS304) specimens were sputter-etched by using argon ions, and the formation process of protrusions on the surface was investigated by changing the sputter etching time. In addition, tensile and bending tests of the specimens were carried out to examine whether the delamination between the protrusion and matrix occurs or not. When the sputter etching time is 0.9 ks, fine conical protrusions with diameter smaller than 2 μm are formed relatively homogeneously on the surface. When the sputter etching time is 1.8 ks, they grow to more than 5 μm. In some cases, the holes and cracks are formed on the wall of protrusions. When the sputter etching time is 3.6 ks, the protrusions grow further and occupy whole surface, and finally they collapse to form ring-shaped protrusions. The tensile test of the specimens with conical protrusions shows that, even at a fracture strain of 0.53, the shape of the cones is almost maintained and the plastic deformation occurs mainly in the region around them without delamination of the cones. Also in the bending test, the similar behavior to the tensile test is observed. The tensile test of the specimen with ring-shaped protrusions also shows that the deformation does not largely occur in the protrusion but occurs in the region outside of them. The reasons for the above characteristics seem to be that the outer shell of the protrusion with higher Cr content is strong and the protrusion grows from interior of specimen keeping high coherency to matrix.
TL;DR: In this paper, the evolution of the solidified structure of Sn-Ag-Cu alloys has been studied and it was found that a small undercooling was necessary for nucleation of eutectic.
Abstract: Recently, lead-free solders have been used in electronic equipments. Sn-Ag-Cu system is an important alloy for lead-free solders. There have been so many reports for mechanical properties of bonding. It is important to understand the evolution of solidified structure of these alloys, though, such reports are few. In order to understand the solidification process of Sn-Ag-Cu alloys, Sn-Ag alloys have been used in this study. Three alloys, hypo-eutectic, eutectic, and hyper-eutectic alloys have been prepared. The specimen was quenched during solidification and the solidified structure was interrupted and compared with thermal history. In the case of hypo-eutectic alloy, the specimen was composed by primary Sn and eutectic. It was found that a small undercooling was necessary for nucleation of eutectic. Such undercooling was not observed in eutectic and hyper-eutectic alloys. This may be interpreted by the difference in the liquid composition when the eutectic solidification starts. In the case of eutectic and hyper-eutectic alloys, the eutectic as well as β-Sn may form at almost the same time of recalescence. In the case of hyper-eutectic alloy, it was found that a large undercooling was not necessary for nucleation of Ag3Sn, even though it was facetted phase. Since the primary Ag3Sn was surrounded by the halo of β-Sn and eutectic, the Ag3Sn phase may be a site for nucleation of β-Sn and eutectic.
TL;DR: In this paper, the giant magnetostriction and its susceptibility of Fe3.2Tb alloy thin film on polyurethane rubber substrate with low deformation resistance by using direct current magnetron sputtering process were investigated.
Abstract: Magnetostriction and its susceptibility of Fe3.2Tb alloy thin film deposited on polyurethane rubber substrate with low deformation resistance by using direct current magnetron sputtering process were investigated. When both residual gas pressure before argon sputtering and sputtering pressure of argon gas (5 N) were less than 5.0×10-4 Pa and 2.0×10-1 Pa, respectively, the thickness of the Fe3.2Tb films deposited was about 2.96 μm. The giant magnetostriction was found in the Fe3.2Tb alloy film on polyurethane rubber sheet, rather than on other polymer sheets. Giant motion strain of Fe3.2Tb alloy film largely depended on deformation resistance of substrate.
TL;DR: In this paper, the formation and growth processes of conical protrusions were investigated and the polarization behavior of SUS304 stainless steel specimens in 3.5% NaCl aqueous solution and the surface morphology after the polarization test were examined.
Abstract: The sputter etching of SUS304 stainless steel specimens was carried out, and the formation and growth processes of conical protrusions was investigated. In addition, the polarization behavior of the specimens in 3.5%NaCl aqueous solution and the surface morphology after the polarization test were examined. At an early stage of the sputter etching, the conical protrusions form mainly along grain boundaries. However, with increase in the sputter etching time the protrusions form also within the grains. With further increase in the sputter etching time, some protrusions grow largely and the entire surface is covered by the huge conical protrusions and the irregular small ones around them. The outer layer of the huge protrusion contains larger chromium but smaller nickel amount than matrix, and the interior has almost the same composition as the matrix. This means that the protrusion has a shell structure. For the specimen with short time sputter etching, the corrosion potential becomes nobler and the pitting corrosion potential becomes smaller, while the passive current density is smaller than those of non-sputter-etched specimen. In these specimens, the corrosion occurs preferentially along grain boundaries and around protrusions in grains. For the specimen with long time sputter etching, where the entire surface is covered by protrusions, the pitting corrosion potential increases and the corrosion progresses mainly from the interior of the specimen leaving the surface layer with many protrusions. In some cases, only the outer layer of the shell remains separately as a result of the corrosion of the interior and root of the huge protrusion.
TL;DR: In this article, the wettability between Nd2Fe14B and Nd-rich phases has been investigated through the sessile drop method, where the contact angles between the two phases were measured under controlled temperature.
Abstract: The wettability between Nd2Fe14B and Nd-rich phases has been investigated through the sessile drop method. The compositions of prepared Nd-rich ingots were Nd72.0Fe26.1B1.9 (ternary) and Nd72Fe22.4Cu3.7B1.9(Cu-added). Nd-rich ingots were cut and put on a polished Nd2Fe14B plate and heated in a furnace. Contact angles between Nd2Fe14B plate and Nd-rich ingots were measured as a parameter of wettability under controlled temperature. For the Cu added sample, both contact angles in all temperature range and temperatures when contact angle starts to change were lower than those for ternary sample. These results indicate Cu substitution yields improvement of wettability. DTA measurements for two Nd-rich ingots reveal that their contact angles starts to change at lower temperature than their melting points It is considered that those phenomena are derived from the existence of Nd2Fe14B/Nd-rich interface.
TL;DR: In this paper, the bending motion of a moverboard with a platinum-coated La-Ni alloy on a polyimide sheet has been successfully developed and the influence of the operating temperature on the motion strain has been evaluated, and the maximum value of bending strain (Δe) is 408 ppm, which is 1.4 times larger than that of an unheated film operated at 323 K.
Abstract: Hydrogenation operates the bending motion of mover device, which is a platinum coated La-Ni alloy film deposited on a polyimide sheet, has been successfully developed. Influence of the operating temperature on the motion strain has been evaluated. When the operating temperature is 373 K, the maximum value of bending strain (Δe) is 408 ppm, which is 1.4 times larger than that (300 ppm) of an unheated film operated at 323 K.
TL;DR: In this paper, a gas atomized Co-29Cr-6Mo alloy powder was hot-pressed in Ar, Ar and N2 (Ar+N2) atmosphere at 1273 K and 80 MPa for 7.2 ks.
Abstract: The gas atomized Co-29Cr-6Mo alloy powder was hot-pressed in Ar, Ar and N2 (Ar+N2), and N2 atmosphere at 1273 K and 80 MPa for 7.2 ks. Nitrogen content in the compacts can be controlled by the mixture ratio of Ar and N2 gases and the compacts contains nitrogen as high as 0.81 mass%. Microstructure and constituent phase of the compacts depends on the nitrogen content. In the compacts containing nitrogen less than 0.2%, the γ(fcc) e (hcp) and σ phases coexist in the compacts. The volume fraction of σ phase decreases with increasing nitrogen content up to 0.2%. The γ phase is dominantly confirmed in the compacts with nitrogen content of approximately 0.2%. In the compacts containing nitrogen over 0.2%, Cr2N phases in addition to the γ and e phases are detected in the compacts. This result suggests nitrogen suppress the σ phases formation and stabilize γ phase in the Co-29Cr-6Mo alloy. When the Co-29Cr-6Mo alloy compacts are hot-pressed with Cr2N powder as a nitrogen source, the σ and nitrides coexist and the microstructure is inhomogeneous. Therefore, it is found that controlling the mixture ratio of Ar and N2 gases during hot-pressing is effective methods to distribute nitrogen uniformly in the Co-Cr-Mo alloy compacts.
TL;DR: In this paper, a Cu-30 mass%Zn alloy was multi-directionally forged (MDFed) at 300 K and 77 K. When MDFed to a cumulative strain of ΣΔe=6, the grain size obtained was 18 nm at 77 K and 22 nm at 300 k.
Abstract: A Cu-30 mass%Zn alloy was multi directionally forged (MDFed) at 300 K and 77 K. Dislocation walls, subboundaries and grain boundaries were gradually developed with increasing strain to form ultra fine grains (UFGs). Furthermore, the evolution of UFGs was drastically stimulated by mechanical twinning. Therefore, it was revealed that the grain refinement in a Cu-Zn alloy during MDF was induced by both mechanisms of mechanical twinning and continuous dynamic recrystallizatrion. When MDFed to a cumulative strain of ΣΔe=6, the grain size obtained was 18 nm at 77 K and 22 nm at 300 K. The MDFed alloy exhibited almost constant ductility irrespective of cumulative strain and MDF temperature, while the tensile strength increased monotonically with increasing cumulative strain. Thermal stability of the UFGed Cu-Zn alloy decreased with increasing cumulative strain and decreasing MDF temperature.
TL;DR: In this paper, the solidification structure of the coating layer in hot-dip Zn-11%Al-3%Mg-0.2%Si coated steel sheet was studied via metallographic examinations together with the calculation of a phase diagram based on Thermo-Calc.
Abstract: The solidification structure of the coating layer in hot-dip Zn-11%Al-3%Mg-0.2%Si coated steel sheet was studied via metallographic examinations together with the calculation of a phase diagram based on Thermo-Calc. The solidification structure observed, which exhibited a combination of the Zn/Al/MgZn2 ternary eutectic structure, the primary Al phase and the MgZn2 phase, turned out to be different from the predicted one under an equilibrium state in the sense that MgZn2 instead of Mg2Zn11 was observed under the present condition. Excluding the Mg2Zn11 phase from the equilibrium phase diagram, the metastable phase diagram was calculated and excellent agreement obtained between the calculation and the experiment in terms of the solidification structure of the coating layer. Consequently MgZn2 is considered to form easily as the metastable structure known as the Laves phase, because the high cooling rate associated with the present experiment does not provide any potential for peritectic-eutectic reactions, which usually occur in the equilibrium state. Furthermore, MgZn2, which has a C14 type Laves structure and a high rate of nucleation in the liquid phase, is considered to cause the preferential Zn/Al/MgZn2 ternary eutectic reactions.
TL;DR: In this paper, a new process was proposed to reduce V2O5 by using calcium in molten CaCl2 for vanadium production, which consists of the calcium reduction in molten CACl2 and the electrochemical reaction for the recovery of Ca from CaO in the same bath.
Abstract: A new process is proposed to reduce V2O5 by using calcium in molten CaCl2 for vanadium production. It consists of the calcium reduction in molten CaCl2 and the electrochemical reaction for the recovery of Ca from CaO in the same bath. V2O5 pellet was placed on cathode in order to react with Ca electrochemically generated near the cathode. V2O5 exists as liquid at the experimental temperature (1123 K), because of the melting point of 963 K for V2O5. At the initial stage of the reduction, liquid sample is reduced to solid CaV2O4. As the supplied quantity of electricity increased, the oxygen concentration in the vanadium samples decreased exponentially. Vanadium containing only 1800 ppm oxygen was obtained after the electrolysis for 34.4 ks.
TL;DR: In this article, mono-sized spherical particles of Fe-Co-based metallic glass were prepared by Pulsated Orifice Ejection Method (POEM) and the capabilities of their micro-forming process in the glass transition temperature were investigated.
Abstract: Metallic glasses are potentially applied for accurate micro parts because of their good formability and transferability as well as high mechanical properties and excellent magnetic properties. So the raw materials that the volume is precisely controlled are needed for a highly accurate processing. In this study, mono-sized spherical particles of Fe-Co-based metallic glass were prepared by Pulsated Orifice Ejection Method (POEM) and the capabilities of their micro-forming process in the glass transition temperature were investigated. Mono-sized spherical particles of Fe-Co-based metallic glass particles with 200-500 μm of diameter have been obtained by Pulsated Orifice Ejection Method (POEM). The XRD pattern of the particles shows only broad peaks without any crystalline peak. A bright field TEM image of the particles and the selected area diffraction patterns shows only halo patterns that indicate fully amorphous phase. DSC curve shows that supercooled liquid region was ΔT=48 K and a TTT curve can be constructed by isothermal DSC.
TL;DR: In this paper, the role of stress-induced martensitic transformations in the TRIP effect, stress-strain curves and TRIP effects in two types of metastable austenite steel (JIS-SUS304 and JIS -SUS301L) were compared.
Abstract: To investigate the role of stress-induced martensitic transformations in the TRIP effect, stress-strain curves and TRIP effects in two types of metastable austenite steel (JIS-SUS304 and JIS-SUS301L) were compared. In static tensile tests, the tensile strength (TS) of SUS301L steel was larger than that of SUS304, and the 0.2% proof stress and uniform elongation (U.El) were both similar for the two steels. The transformation rate and strength of martensite in the stress-induced martensitic transformation were compared by X-ray diffraction and Vickers hardness tests. At the same strain, SUS301L contained a larger volume fraction of martensite than did SUS304. Both steels showed similar values of the Vickers hardness. The difference between SUS301L and SUS304 is mainly due to the transformation rate of stress-induced martensite. The effects of the transformation rate and martensite strength on the TS/U.El balance in metastable austenite steels were demonstrated by means of the Weng secant method, based on a micromechanical model.
TL;DR: In this article, the effect of nitrogen on tensile properties and deformation structure of Ti-N alloys with different nitrogen content were tested, and then the effect was investigated.
Abstract: Ti-N alloys with different nitrogen content were tensile-tested, and then the effect of nitrogen on tensile properties and deformation structure were investigated. With increasing nitrogen content, the 0.2% proof stress and tensile stress were markedly increased accompanied with the lattice distortion of enlargement of c/a ratio. Since the work hardening rate was also increased, the uniform elongation was not significantly decreased by the addition of nitrogen. However, the local elongation was reduced drastically through the occurrence of intergranular brittle fracture even by a small amount of nitrogen addition. In the tensile-deformed pure Ti, many deformation twins and dislocations were observed. On the other hand, few deformation twins and a high density of planar dislocation arrays were observed in the high nitrogen alloys. The changes in deformation structure might have caused the reduction of local elongation in nitrogen added alloys because of the intergranular brittle fracture derived from the suppression of twinning deformation and the stress concentration at grain boundary due to piled-up dislocations in the planar array.
TL;DR: In this paper, the as-solutionized TNTZ rod consists of a single β phase and isothermal ω phase and α phase precipitate in the β phase of the TNTZ rods aged at 673 K for 259.2 ks.
Abstract: Installing a spinal fixture using implant rods is one of the effective operations for spinal diseases. Most of the implant rods are made of Ti-6Al-4V ELI alloy (Ti64). However, some problems regarding the Ti64 rod have been pointed out; it contains vanadium, which is considerably toxic to the human body, and exhibits a much higher Young's modulus than that of the cortical bone. Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) developed by the authors exhibits good biocompatibility due to its nontoxic- and allergy-free elements, and has a lower Young's modulus than that of Ti64. In addition, the mechanical properties of TNTZ can be changed drastically according to various heat treatments. The mechanical properties of TNTZ rods subjected to various heat treatments have been investigated in this study. The as-solutionized TNTZ rod consists of a single β phase. Isothermal ω phase and α phase precipitate in the β phase of the TNTZ rod aged at 673 K for 259.2 ks. Only α phase precipitates in the β phase of the TNTZ rod aged at 723 K for 259.2 ks. Tensile strength and 0.2% proof stress become larger in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks, while elongation is smaller in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks. Young's modulus become larger in order of as-solutionized TNTZ rod, TNTZ rod aged at 723 K for 259.2 ks and TNTZ rod aged at 673 K for 259.2 ks.
TL;DR: In this article, the corrosion behavior of Mg alloys has been investigated by the polarization test and electrochemical impedance spectroscopy test for their practical use for automotive, aerospace and electronic industries because of their low density and excellent strength to weight ratio.
Abstract: Though Mg alloys are the outstanding candidates for the use in automotive, aerospace and electronic industries because of their low density and excellent strength to weight ratio, they have a great disadvantage in corrosion resistance. In this study, their corrosion behavior has been investigated by the polarization test and electrochemical impedance spectroscopy test for their practical use. AZ series Mg alloy samples produced by conventional ingot metallurgy showed a little slight decrease Ecorr with an increase of Al content, while they indicated a remarkable decrement of Icorr with increasing amount of Al content.
TL;DR: In this paper, a new process was developed to synthesize the precious alloy directly from the oxide mixtures, which consists of calciothermic reduction in molten CaCl2 and electrochemical reaction for the recovery of Ca from CaO in the same bath.
Abstract: A new process is developed to synthesize the precious alloy directly from the oxide mixtures. This process consists of calciothermic reduction in molten CaCl2 and electrochemical reaction for the recovery of Ca from CaO in the same bath. The molten CaCl2 can dissolve Ca and CaO for complete reaction. The oxide mixture consisting of TiO2, Al2O3, and V2O5 was prepared. Either a simple mixture of oxides or its calcined sample was reduced in the molten CaCl2+CaO. The obtained metallic powder was identified as α-Ti single phase and it contained only about 3000 mass ppm oxygen. Although its metallic composition was close to Ti-6Al-4V, this reduced powder had a broad compositional distribution. This inhomogeneous distribution was improved by the subsequent sintering in argon.
TL;DR: In this paper, a pressure vessel was designed to enable the measurement of actual tensile load on a specimen by an external load cell without the influence of axial load due to high pressure in the vessel and the friction between the O-rings and the pull rod.
Abstract: Testing equipment for materials under high-pressure hydrogen of 120 MPa at the temperature range of room temperature up to 393 K has been developed. The pressure vessel was designed to enable the measurement of actual tensile load on a specimen by an external load cell without the influence of axial load due to high pressure in the vessel and the friction between the O-rings and the pull rod. The hydrogen gas embrittlement (HGE) of austenitic stainless steels of SUS304, 316, 316L, 316LN and 310S was examined in 70 and 105 MPa hydrogen and argon by slow strain rate technique (SSRT) test at room temperature. Hydrogen showed a marked effect on the tensile properties of SUS304 and 316 stainless steel, a minimal effect on those of SUS316LN, and no effect on those of SUS316L and 310S. The HGE of sensitized SUS304, 316 and 316LN was larger than that of solution-annealed ones. It was observed that hydrogen caused brittle transgranular fracture along the strain-induced martensite in solution-annealed steels, and intergranular fracture in sensitized steels respectively.