The microstructure of the stucco surface containing Pb of the Takamatsuzuka tumulus, constructed in the 7th–8th century, has been investigated. The purpose of this research is to clarify the existing condition of Pb near the stucco surface. A spectroreflectometer, a scanning electron microscope, and a transmission electron microscope are used to analyze the microstructure. The surface of the specimen consists of three colored areas; white, dull-ocher, and ocher. Although the absorption edges of the white stucco CaCO₃ and ocher area on the surface are approximately 2.8 and 2.0 eV respectively, the dull ocher area does not show the absorption edge. The latter absorption edge is caused by Fe ion contained in the surface layer. The dull ocher area is rich in Pb. The surface layer consists of fine lead carbonate grains with a size of 100–200 nm. On the layer under the surface layer, CaCO₃ grains containing lead oxide precipitates, that is, Pb₃O₄ and Pb₂O₃, and CaCO₃ grains containing Pb atoms are observed. The size of the lead oxide in CaCO₃ is 10–500 nm. These grains are formed by the reaction between the lead carbonate and the CaCO₃ matrix. It is thought that the lead carbonate is coated on the stucco.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 326–333.

Nanocrystalline ribbons of Fe-Cu-Si-B ([Fe] = 76.5–80.7 at%) were produced by rapid quenching and subsequent annealing to obtain higher saturation magnetization. To control the thickness of the ribbons, different quenching rates were applied. The magnetic properties, even after annealing, show clear differences depending on the thickness. To understand the origin of these differences, small angle X-ray scattering (SAXS) measurements were acquired to investigate and quantify changes in the microstructures of samples of different thicknesses, with and without annealing. Since crystallization kinetics were strongly affected by sample thickness (e.g., quenching rate), the volume fraction in samples with different thickness but the same composition were varied in addition to the average size of the bcc crystals. Balancing the average size and the volume fraction gives the optimum sample thickness for obtaining the best soft magnetic properties in the Fe-Cu-Si-B ribbons.

Effects of α phase nucleating at a transition phase and dislocation on mechanical properties in a metastable β titanium alloy, Ti-6.8Mo-4.5Fe-1.5Al(mass%), were investigated. Tensile test and optical, scanning, and transmission electron microscopy were used. Two-step aging promoted the precipitation of a fine α phase in grain interiors because the α phase nucleated at a transition phase of β′. A precipitation-free zone appeared at first, but finally disappeared during aging. A specimen that included the precipitation-free zone showed lower yield strength and larger elongation than it did without the precipitation-free zone. This was because dislocation could easily glide in the precipitation-free zone, which was verified from examination of the intergranular ductile fracture surface. The transition phase of β′ promoted the disappearance of a precipitation-free zone, due to the promotion of α phase precipitation, resulting in enhancement of yield strength and deterioration of elongation. It is likely that the width of PFZ and the crystallographic orientation of β grains determine fracture mode to be intergranular ductile, intergranular brittle or intragranular fractures. Aging after tensile deformation produced α phase precipitation at dislocation. A specific variant of α phase was selected due to a stress field around the dislocation that included a planar slip band. This resulted in the formation of a large colony of the specific α variant, while elongation deteriorated because the large colony probably facilitated crack propagation.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 79 (2015) 651–656.

The rotating bending fatigue strength of gas nitrided JIS-SCM435 steel was evaluated to find the thickness that gives the highest bending fatigue strength. Four specimens were used that had different compound layer thicknesses composed of γ' (-Fe₄N) phase: 0, 2, 10, and 20 μm. The composition of γ' phase was more than 70% of the volume of the compound layer in the specimens. The increment of the fatigue strength at 10⁵–10⁷ cycles was remarkably high when the compound layer thickness was from 0 to 10 μm and gradually increased from 10 to 20 μm. The increment of the fatigue strength was caused by the increment of the γ' phase thickness and the compressive residual stress depth as the compound layer thickness increased. The gradually increasing fatigue strength of more than 10 μm thickness was responsible for the porous layer thickness increasing and the compressive residual stress reducing on the surface as the compound layer thickness increased. These findings show that the fatigue strength of gas-nitrided JIS-SCM435 steel composed of γ' phase depends on not only the compound layer thickness but also the porous layer thickness and the compressive residual stress of the compound layer.

The high temperature deformation behavior of a modified AZ61 magnesium alloy was investigated by means of an isothermal compression test on a Gleeble-2000D elevated temperature simulation tester at strain rates of 0.1 s⁻¹ and 1 s⁻¹ and deformation temperatures of 523 K, 623 K and 723 K. The microstructure evolutions and second phases of the experimental alloys were analyzed. Compared to the conventional alloy, the modified specimen shows a higher degree of dynamic softening and a lower deformation resistance. The improved deformability becomes more apparent when temperature decreases or strain rate increases, and it is attributed to a great reduction in Mg₁₇Al₁₂ phase and to the formation of Al₄RE and Al₁₀RE₂Mn₇ phases caused by the simultaneous addition of Mn and mischmetal.

The phosphating of Mg alloy was performed in unagitated solutions containing 1 g·dm⁻³ of Mg, Ca, Sr, and Ba as alkaline earth metals (M) and 50 g·dm⁻³ of H₃PO₄ of pH 3 at 40℃ for 3 min. The structure and formation behavior of the phosphate films were investigated. The X-ray diffraction patterns of phosphate films broadened irrespective of the type of alkaline earth metal, which was a characteristic of an amorphous structure. XPS analysis revealed that the valence of P in the phosphate films was pentavalent. The pH in the vicinity of the Mg alloy during the phosphating, as measured using an Sb microelectrode, was approximately 10.4, 11.4, 10.7, and 12.0 in the solutions containing Mg, Ca, Sr, and Ba, respectively. This shows that phosphoric acid dissociates to the third stage during the phosphating, and the phosphate films comprising M₃(PO₄)₂ containing an alkaline earth metal are formed. The phosphating was successively performed in two types of solutions containing different alkaline earth metals, and the cross section was analyzed. As a result, it was determined that the new phosphate films were formed at the interface between the Mg alloy substrate and phosphate films, and the previously formed phosphate films were boosted in the films.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 684–690.

Cobalt oxide (Co₃O₄) nanocubes with high crystallinity and a narrow size distribution have been synthesized in one pot process under highly condensed hydrothermal reactions using cobalt(II) nitrate (Co(NO₃)₂) and sodium hydroxide or tetramethylammonium hydroxide. The particle morphology was controlled to a cubic shape by change in the initial pH. The particle mean diameter was also gradually controlled by the change in the initial pH in the range from 18 nm to 66 nm. Co(OH)₂ hexagonal thin platelet particles were obtained as the predominant product when CoSO₄, CoCl₂, and Co(CH₃COO)₂ were used as the Co-source. The result indicated that oxidation ability of nitrate anions played an important role to obtain the Co₃O₄ nanocubes in the one pot process.

A 5052-H34 aluminum alloy rod having a diameter of 5 mm was friction-welded using a conventional automatic friction welder. The effect of welding conditions on the microstructure and mechanical properties of the welded joints were investigated. The total loss of mechanical strength of welded joints increases when increasing both the rotational speed and friction time. In addition,the total loss was negligibly low when the welding condition was submitted to N = 6000 rpm and t1 = 1 s. The welded joints showed a symmetrical macrostructure with respect to the weld interface and rotational axis. A layer with fine-grained microstructure was formed at the weld interface. The layer grew thicker by increasing both the rotational speed and friction time. The heat-affected zone was formed around the fine-grained layer. It tends to be larger with an increase in both the rotational speed and friction time. The softened area of the joints reached approximately 8 mm from the weld interface. In addition, the weld interface was cured under conditions of N = 6000 rpm and t1 = 1 s. The highest tensile strength of thin diameter joints was 209 MPa, which was obtained under conditions of N = 6000 rpm and t1 = 3 s. Its joint efficiency reached 80% of that of the base metal.

This Paper was Originally Published in Japanese in J. JILM 65 (2015) 485–491.

In this study, we investigated the influence of addition of tin on JIS CAC804 properties. When tin is added, solidus and liquidus temperature of the alloy lower, and the solidification temperature range widens. Generally, if an alloy's solidification temperature range is wide, its castability is low, but not much castability difference was observed between CAC804 containing tin and that without.

A large portion of added tin is distributed in γ phases in the form of solid solution, causing ductility to decline. Although results of erosion-corrosion resistance test differ depending on the test conditions, it is clear from the results of the tests we performed using two different solutions that tin has a function of alleviating weight loss in JIS CAC804.

This Paper was Originally Published in Japanese in J. JFS 87 (2015) 844–848.

Erosive wear (or erosion) is a phenomenon where the material surface is damaged and removed by the continuously impacting of particles. According to researches on erosion, three types of parameters affect erosion, namely, particle properties, impacting condition, and target material properties.

This study investigated the impact angle dependence of erosion by 3D Finite-Element-Method (FEM).

In the FEM analysis, the velocity of impact particles was set as 20 m/s and the analysis duration was 0.01 ms. The size of the target material was 10 × 10 × 10 mm. The parameters of the target materials were set same as spheroidal carbide cast iron (SCI) and spheroidal graphite cast iron (FCD). The impact particle was spherical shaped steel grits with a diameter of 700 μm. The impact angle was changed from 10 degree with a 10 degree interval, up to 90 degree. To verify the analytical results, single particle impact tests was conducted at the same time.

The results showed no difference in the equivalent plastic strain and Von Mises stress for spheroidal carbide cast iron with increasing impact angle, respectively. Both the equivalent plastic strain and Von Mises stress of FCD were largest around 60～80 degree. In addition, both the experimental and analytical results of the materials showed the same tendency. Therefore, by focusing on the plastic deformation of the material surface, it is possible to verify impact angle of dependence by 3D FEM analysis. The results of analysis indicate that spherical carbides can restrain the plastic deformation of the eroded surface.

This Paper was Originally Published in Japanese in J. JFS 88 (2016) 252–257.

In this study, we fabricated bulk nanocrystalline Ni–W–B alloys by electrodeposition, using trimethylamine-borane (TMAB) as a boron source, showing how B doping affects tensile properties. In electrodeposition, the TMAB concentration was varied from 0 to 5.0 g/L. Adding TMAB to the deposition bath increased the B content of the electrodeposited alloys up to 0.36 at%, but did not significantly change the W content or grain size. Adding more TMAB than 0.1 g/L drastically decreased the material's tensile elongation. Cross-sectional hardness tests on alloys with poor ductility revealed non-uniform hardness and that the initial layer had a high hardness of 6.3–8.7 GPa. This result indicated that the TMAB had immediately decomposed and that the boron decomposition product was mixed into the initial electrodeposited layer. In contrast, the alloys electrodeposited with 0.01–0.05 g/L TMAB showed good tensile elongation of 11%. Our results reveal the appropriate amount of added TMAB in order to produce electrodeposited bulk samples with good ductility.

The effects of particle surface contamination and of the prior particle boundary on the microstructure and mechanical properties of hot-isostatic-pressed IN718 alloy were investigated in this study. A thermal-plasma-droplet-refining technique was conducted to reduce the surface contamination; i.e., oxygen and carbon contents in the gas-atomized IN718 powder. The tensile ductility of hot-isostatic-pressed materials was comparable to those of conventionally wrought materials at room temperature and at 650℃. At 650℃, the hot-isostatic-pressed and heat-treated specimens exhibited worse ductility than the conventionally wrought specimen because of the increased number of brittle precipitates, such as oxides, oxy-carbides and δ phases in the heat-treated specimens. The process of crack nucleation and propagation along the prior particle boundary will take place more easily at high temperatures.

Catheter intervention is used for the treatment of various diseases inside the body. This non-surgical technique is widely used because of its clinical and economic benefits. Although the mechanical properties of a catheter shaft are important to conduct operations using catheters safely, there is no standard testing method for the mechanical properties of the catheter shaft. In this study an evaluation method for the mechanical properties of the catheter shaft under cyclic bending was proposed. Cyclic bending tests were conducted to compare mechanical properties (radial strength and resistance of buckling) of three kinds of specimens. One is the outer layer of the catheter shaft, and the other two are a steel-ribbon catheter shaft and a W-ribbon catheter shaft. Load difference defined by the maximum load of each cycle was used to decide the buckling displacement. Additionally, finite element analysis (FEA) was performed to analyze the deformation behavior of the catheter shaft during a three-point bending test. The load-displacement curves obtained from the FEA showed a good agreement with the envelope of the load-displacement curves in the experiment. It was also revealed from FEA that the deformation behavior of the catheter shaft at the loading point was different from the material of the wire mesh in the catheter shaft. These results suggest the radial strength of the wire mesh increases the buckling displacement of the outer tube and enhances the buckling strength of the catheter shaft. These results also showed that the W-ribbon catheter shaft demonstrated the highest load resistance and the highest buckling displacement. Thus, it was shown that the proposed experimental procedure based on the cyclic bending tests was effective to compare the mechanical properties of various catheter shafts.

2-layer laminated sheets (PE/PET) with Polyethylene (PE) and Polyethylene Terephthalate (PET) were prepared by a new adhesion method, a double-step treatment consisting of applying low dose (≦1.30 MGy) homogeneous low energy electron beam irradiation (HLEBI) prior to hot-press under 5 MPa and 403 K. Although the weak hot-press adhesion of the PE/PET was observed without HLEBI, the new adhesion mostly raised the bonding force at interface as evidenced by the mean adhesive force of peeling resistance (^oF_p). Based on the 3-parameter Weibull equation, the lowest ^oF_p value at peeling probability (P_p) of zero (F_s) could be estimated. An increasing trend in F_s occurred by the double-step treatment applying HLEBI up to 1.08 MGy reaching a maximum at 16.0 N·m⁻¹, improving the safety level without radiation damage. When HLEBI cut the chemical bonds in PE and PET, and generated terminated atoms with dangling bonds, they probably induced the chemical bonding. Therefore, increasing adhesion energy between the laminated sheets could be explained.

We have operated a 4V-class bulk-type, all-solid-state LiCoO₂/Li battery at room temperature. The battery consisted of a Li₄(BH₄)₃I complex hydride electrolyte as the electrolyte layer, and a 80Li₂S 20P₂S₅ sulfide glass as an electrolyte in the positive electrode layer. The assembled battery exhibited a 92 mAh g⁻¹ initial discharge capacity at 298 K and 0.1 C. The discharge capacity for the 20^th cycle remained as high as 83 mAh g⁻¹, corresponding to a capacity retention ratio of nearly 90%.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 720–725.

This study investigates how changes in the surface properties of three representative sulfide minerals (galena, sphalerite and chalcopyrite) affect their floatability in the presence of an oxidizing agent (H₂O₂). Tests were conducted at four molar ratios of H₂O₂:mineral (0, 0.5, 1.0, and 2.0). To better capture the effect of surface oxidation, the tests were conducted at both acid and basic conditions (i.e., pH = 3 and 10). In all surface property and floatability evaluations, the pH and Eh were equilibrated. The surface properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential measurements and contact angle analyses. The floatability was evaluated by a microflotation method. At the acidic initial pH, galena most sensitively reacted with H₂O₂, followed by chalcopyrite and sphalerite, whereas at pH 10, the reactivity differences were insignificant. H₂O₂ addition changed the sulfide species (initially present on the mineral surface) to sulfate or hydroxyl species, and decreased the mineral floatability. To investigate the surface property that mainly reduced the mineral floatability in the presence of H₂O₂, we measured the zeta potentials and contact angles, which are closely associated with the electrostatic and hydrophobic forces, respectively. The floatability depended on the contact angle after the H₂O₂ addition, implying that the floatability was mainly reduced through oxidation reactions, which increased the hydrophilicity of the mineral surface.

A dismantling process for separating electric and electronic components (EECs) from printed circuit board (PCB) was developed by using hydrochloric acid (HCl) leaching with stannic ions (Sn⁴⁺). The use of HCl solution with Sn⁴⁺ ions dissolves tin (Sn)-alloy solder that holds EECs on bare board, which allows the EECs to be detached from PCB. The feasibility of the new dismantling process was investigated by examining the effects of temperature, initial Sn⁴⁺ concentration and agitation speed on the dismantling of PCB. The effect of agitation speed was negligible and the dismantling-completion time was reduced rapidly with increasing temperature and initial Sn⁴⁺ concentration. The dismantling of PCB was completed within 30 min under the leaching conditions; HCl concentration, 1 mol/L; initial Sn⁴⁺ concentration, 13,000 mg/L; temperature, 90℃; and agitation speed, 300 rpm. Each metal was enriched after dismantling process; e.g. the content of Ag increased from 0.016% in PCB to 3.118% in registor. It was expected that efficient PCB recycling process could be designed to recover metals from EECs with higher concentrated metals.

Fully-densified mullite nanocomposites dispersed with 5 vol% nano-Ni particles were fabricated by the pulsed electric current sintering technique to investigate their self-healing function. The investigation on thermal oxidation for healing the mullite composites was conducted at temperatures ranging from 1000 to 1200℃ for 1–24 h in air. Surface cracks with a total length of 180 µm completely disappeared by heat-treatment at 1100℃ for 6 h in air. Bending strength of the as-cracked samples which were prepared with three Vickers indentations on the tensile surface only achieves 113 MPa. Disappearance of surface cracks realizes a recovery of bending strength up to 434 MPa, which is comparable with that of as-sintered samples (405 MPa). With heat-treatment in Ar-1%H₂ at 1100℃ for 6 h, the samples show neither surface crack-disappearance nor strength recovery. It is clear that the oxidation of Ni particles at high temperatures induces the self-healing mechanism. The surface crack-disappearance in Ni/mullite is available at lower heat-treatment conditions than the other metal/oxide composites such as Ni/Al₂O₃ and Ni/(ZrO₂+Al₂O₃). Additional information on mechanical properties such as hardness and fracture toughness of the composite are also provided. Dispersion of Ni particles in mullite matrix does not give effect to their hardness and fracture toughness.

The possibility for reduction in tension-compression asymmetric behavior and the effect of alloying elements on room temperature compressive behavior were investigated using extruded pure magnesium, several Mg-0.3 at.%X (X = Al, Li, Mn, Y and Zn) binary alloys and the commercially AZ31 alloy. They had fine-grained structures of an average grain size of 3–5 μm, except for the AZ31 alloy. The compressive deformation behavior was influenced by the alloying elements. The Mg-Al, Mg-Zn and Mg-Y alloys showed sigmoidal shaped stress vs. strain curves, irrespective of the strain rates, due to the contribution of deformation twinning. On the other hand, pure magnesium and those alloys added with manganese or lithium as alloying elements did not exhibit such stress vs. strain behavior. Instead of deformation twinning, they had high strain rate dependence, i.e., the m-value of more than 0.1, which indicated that grain boundary sliding played an important role in deformation during compression testing. Under such a condition, in particular for the strain rates of 10⁻⁴–10⁻⁵ s⁻¹, it is interestingly noted that these specific materials showed isotropic tension-compression behavior. They also displayed good room temperature deformability, such as accordion-like deformation, which has never been observed in magnesium alloys.

A porous Ni film with numerous through-holes was prepared by electroplating deposition for use as a novel metal support for Pd alloy membranes. The porous Ni film with 5 μm thickness maintained its shape after calcination in air at 500℃ for 1 h, which indicated its high thermal stability despite being electrodeposited. On the other hand, the calcined normal electrodeposited Ni crumbled and thus could not retain its original shape. The calcined porous Ni film also showed high mechanical strength, as its displacement was twice that of the normal Ni film. Hydrogen flow through the calcined porous Ni film was much higher than that observed for an approximately 5 μm-thick Pd alloy membrane, thus demonstrating the potential application of the film as a novel support for Pd alloy membranes in hydrogen production.

In this study, hybrid composites reinforced with Carbon short fibers and alumina short fibers were optimized using low-pressure casting. The total fraction of fibers in the composite was 10 vol%, with equal parts of Carbon short fibers and alumina short fibers (i.e., 5 vol% each). For comparison with the hybrid composites, two composites were separately reinforced with 10 vol% each of the Carbon short fibers and alumina short fibers. All the composites were fabricated using a low-pressure casting process by infiltrating molten Al (A1070) into a preform. Both types of short fibers were randomly distributed inside the Al matrix, and the low-pressure casting method achieved dense hybrid composite materials (over 98% relative density). The Vickers hardness and thermal conductivity of the composites were investigated.