The interactions between edge dislocations and 〈112〉-axis symmetric tilt grain boundaries (GBs) in Al, Cu and Ni were analyzed by molecular dynamics simulations. Absorption, transmission and pile-up were all observed while absorption is the dominant phenomenon, especially in Al. The leading partial dislocation was spontaneously absorbed into the GB without any resistance, as was even the trailing partial dislocation in Al for the high-energy GBs. However, for all the GBs in Cu and Ni, further external shear loading was necessary to trigger the defect interactions. Σ11A GB requires the largest shear stress to trigger the absorption of trailing partial dislocation, and the other GBs follow a general trend that the critical shear stress would decrease as the GB energy increases since the low-energy GB shows a more stable state. For the most stable GB of Σ11A in Al, Cu, Ni, and the further addition of Au and Pd, the critical interaction shear strain to trigger the interaction is proportional to a physical parameter which is based on the difference between the unstable and stable stacking fault energies.

In recent years, ultrasonic welding technology has developed rapidly and is applied in many fields. The research and application of piezoelectric ceramic materials in ultrasonic welding have received significant attention from researchers and commercial manufacturers. In this work, we have studied, designed and fabricated piezoelectric ceramic materials described by the general formula Pb_(1−x)Sr_x(Zr_0.53Ti_0.47)O₃ or (PSZT) with x = 0.6 mol%. In addition, the experimental fabrication process of PSZT piezoelectric ceramic transducer in the form of a ring by ball milling and solid-state reaction process are also presented. Adding hard dopants Sr²⁺ to the A (of Pb²⁺) position in the perovskite structure is considered to improve the dielectric and piezoelectric properties of Pb(Zr_0.53Ti_0.47)O₃. The results show that the dielectric constant (ε_r) is 1707.4, and the dielectric loss (tan δ) is 0.0034 at room temperature and 1 kHz. The hysteresis loop of the non-polar PSZT piezoelectric ceramic sample shows the same behaviour as the hard PZT ceramic with a remnant polarization of 2.0 µC/cm² and a force field of 5.5 kV/cm. The Curie temperature (T_C) is determined to be about 342°C. The piezoelectric properties of the PSZT piezoelectric ceramic ring were also measured: the effective electromechanical coupling coefficient (k_eff) of 0.40, electromechanical coupling coefficient (k_p) of 0.48, mechanical quality factor (Q_m) of 270.92, piezoelectric coefficient (d₃₃) is 314 pC/N, respectively. This result demonstrates that the fabrication process of Pb_1−xSr_x(Zr_0.53Ti_0.47)O₃ or (PSZT) ceramic rings with x = 0.6 mol%, exhibiting superior characteristics, is entirely suitable for practical applications such as the production and substitution of piezoelectric sensors for high-power ultrasonic welding technology operating at a resonant frequency ranging from 30 to 40 kHz.

A narrow-gap semiconductor with a complex crystal structure was recently discovered in the Al–Ru–Si system. To determine the homogeneity range of the semiconductor phase and further discover new phases, phase equilibria in the Al–Ru–Si system near 1200 K were investigated through prolonged-annealing experiments. Eleven new ternary phases including two incommensurate composite-crystalline and an icosahedral quasicrystalline phases were identified using powder and single-crystal X-ray diffraction, and their compositions at two-phase and three-phase equilibria were evaluated by means of electron-probe X-ray microanalysis. On the basis of the data obtained in this study and those adopted from the literature, a tentative isothermal section of the Al–Ru–Si equilibrium phase diagram near 1200 K was drawn.

This study investigated the effects of potassium amyl xanthate (KAX) and oxidation treatment using hydrogen peroxide (H₂O₂) on the selective flotation of copper concentrates containing arsenic-bearing copper minerals. The mineralogical analysis revealed that enargite and chalcopyrite were the main arsenic-bearing copper and copper sulfide minerals, respectively, in the copper concentrate. KAX treatment at pH 9 improved the recoveries of copper sulfide and arsenic-bearing copper minerals. However, arsenic-bearing copper minerals floated more rapidly than copper sulfide minerals, indicating better separation selectivity. The separation selectivity of the KAX treatment was significantly improved at pH 10. H₂O₂ treatment was found to selectively improve the recovery of arsenic-bearing copper minerals. A combination treatment using 0.1 M H₂O₂ and 60 g/t of KAX at pH 9 enhanced the separation selectivity in the selective flotation of copper sulfide and arsenic-bearing copper minerals by producing a copper concentrate with the lowest arsenic grade and highest copper grade in tailings compared to those obtained from separated KAX and H₂O₂ treatments.

The in situ scratch test inside the scanning electron microscope (SEM) could provide more detailed information about the dynamic contact process between the indenter and material surface. However, most of the current in situ scratch testers can only perform qualitative tests, and the normal and lateral forces could not be measured. Accordingly, an in situ scratch tester with the ability to observe the scratching region inside the SEM and simultaneously measure the normal and lateral forces, was developed. It mainly consisted of three identical stick-slip piezoelectric actuators, a specially designed two-axis force sensor and a force feedback control system. The z-directional piezoelectric actuator was used to apply the scratch load and the x-directional piezoelectric actuator was used to realize the scratch motion. The normal and lateral forces were measured by the two-axis force sensor, and the force feedback control system was used to control the normal force for achieving the constant load scratching and linear load scratching modes. The compact structure made it easy to integrate with the SEM. By experiments, the main performances and functions of the proposed in situ scratch tester were characterized. The experimental results indicated that the noises of the normal and lateral forces were both less than 0.1 mN, and the minimum single-step displacements in the indentation and scratch directions were about 8 nm and 34 nm, respectively. The in situ scratch test of Ti6Al4V confirmed the ability of the scratch tester to simultaneously observe the scratching region and measure the normal and lateral forces, by which the correlation between the scratch morphology and lateral/normal forces could be established. Accordingly, this study provides a new tool for the investigation of material flow, chip formation and tool adhesion during ultra-precision machining.

The image analysis tensile test method was applied to obtain true stress–true strain curves at elevated temperature in Ti–6Al–4V alloy. A CCD camera successfully captured the profile change of a specimen during the tensile test. Minimum radius and neck curvature can be calculated from the profile, then used to determine true strain and true stress after necking using Bridgman’s equation. True stress–true strain curves up to a strain of 0.8 were obtained in the high temperature tensile test at 850°C. The true stress–true strain curves show work hardening at a strain rate of 0.2 s⁻¹ and dynamic restoration at a strain rate of 0.01 s⁻¹ in the tensile test at 850°C. On the other hand, in compression tests, the true stress–true strain curves show steep decrease in true stress after yielding. This might be due to the effect of barreling of the specimen, rather than any metallurgical structural change. The image analysis tensile test method is applicable to obtain accurate high–temperature true stress–true strain curves at elevated temperature up to large strain extent.

This Paper was Originally Published in Japanese in J. JSTP 62 (2021) 177–182.

Iridium is one of the most refractory platinum group metals (PGMs) used in crucibles, catalysts, and ignition tips for spark plugs. Refining and recycling of iridium are energy-intensive processes with high environmental impacts; therefore, a novel recycling process is desirable to expand the utilization of iridium.

Previously, we established a novel process for recycling platinum and palladium using “dry aqua regia”, which is a molten salt consisting of iron(III) chloride and potassium chloride. This process can recycle PGMs more easily than conventional recycling processes.

In this study, we employed “dry aqua regia” for the recycling of iridium. Iridium was dissolved in molten salt and recovered by precipitation using ammonium chloride as the precipitant and nitric acid or hydrogen peroxide as the oxidant. Consequently, it was dissolved by dry aqua regia treatment at 630–670 K, and the dissolved iridium was recovered by precipitation using ammonium chloride and hydrochloric acid with oxidants. The recovery ratio reached 28.3% and 45.7% using nitric acid and hydrogen peroxide, respectively, as oxidants. Based on these findings, we established the fundamental process of recycling iridium using “dry aqua regia”.

Counter electrodes of Carbon Aerogel with Silver Sulfide Structures (CA/Ag₂S) were synthetized by cathodic deposition and solid vapor reactions. Their optical and electrical properties were determined, and they were tested as counter electrodes in dye-sensitized solar cells instead of the conventional Pt. It was found that the Ag₂S presence improves the optical and electrical conductivity of the counter electrodes. However, the impedance electrochemical spectra indicated increased resistivity (ERS) and charge transfer resistance (Rp) with increased Ag₂S structures; this suggests that the interface (CA/Ag₂S) may act as a barrier to electron transfer. Furthermore, the W1-R values decreased as the amount of Ag₂S increased, indicating a higher catalytic activity for these samples. DSSC efficiencies range from 1 to 2.5%, lower than those reported for platinum. They are a consequence of a poor fill factor (FF) that can be explained by the electrolyte loss that occurs during cell testing due to the counter electrodes’ high absorption and catalytic properties. While the performance is not ideal, the high initial Jsc values (21 mA/cm²) suggest that this system may present an opportunity as a material for energy devices.

Scandium (Sc) lacks commercially viable independent deposits and is mainly recovered as a by-product of the smelting of other ores. In the process of recovering nickel from laterite ores, Sc is recovered from leaching solutions. The recovery of Sc requires its efficient separation and purification from other impurities. This study proposes a process for the selective separation and recovery of Sc from other trivalent cations in sulfuric acid solutions using an iminodiacetic acid chelating resin, Diaion™ CR11. The adsorption behaviors of trivalent ions Sc(III), Cr(III), Al(III), and Fe(III) onto CR11 in single- and multiple-metal systems were investigated to determine the appropriate Sc separation conditions. In systems containing single metal ions, pseudo-first-order and pseudo-second-order kinetic models were used to fit the data. Linear and nonlinear methods were used for fitting. The activation energies were calculated from the rate constants at a pH of 2.0 and at three different temperatures of 23°C, 60°C, and 80°C and followed the order: Cr(III) > Fe(III) > Sc(III) > Al(III). In binary systems including Sc(III), the simultaneous adsorption of Sc(III) and other trivalent ions onto CR11 was investigated. Previously adsorbed Sc(III) on CR11 was displaced by the subsequent adsorption of Fe(III) or Cr(III) from the solution. The affinity of the metal ions to iminodiacetic acid and the adsorption reaction rate were critical factors for suitable selective Sc separation, indicating that prior removal of Fe(III) was necessary. Column experiments at 23°C using a synthetic solution without Fe(III) showed that Cr(III) adsorption was suppressed, and that Sc(III) was efficiently adsorbed. Scandium can be efficiently recovered from a solution containing Sc(III) after prior removal of Fe(III) by adsorption at low temperature using CR11.

Iridium is a platinum-group metal with unique catalytic properties and chemical stability. Because of these characteristics, the metal is used in the form of iridium–tantalum oxides in the catalytic layer of oxygen evolution electrodes. Recovering Ir from end-of-life products is important because of its low production volume, the uneven geographical distribution of Ir sources, and high supply risks. However, Ir recovery requires its dissolution in aqueous solution using a strong acid, making the procedure not only dangerous but also hazardous to the environment. Moreover, if metals other than Ir are dissolved in the aqueous solution during its recovery, harmful effluents and gases could be generated. Separating Ir from such other metals would be difficult. Accordingly, we developed a method to extract Ir only from the catalyst layer and, simultaneously, recover Ir as a Ca–Ir composite oxide that is soluble in hydrochloric acid. Only iridium oxide was volatilized from the catalyst layer of the oxygen evolution electrodes and brought into contact with CaO in the gas phase. The composite oxide obtained was dissolved in hydrochloric acid and subsequently analyzed. The result revealed that Ir is highly soluble in hydrochloric acid, and the composite oxide does not contain Ta.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 87 (2023) 243–248.

In this study, cracks formed on the surface of Al–Mg alloy strips cast using a high-speed unequal-diameter twin-roll caster were observed. In addition, the effects of the roll load and the molten metal pouring method on the crack were investigated. Four types of Al–Mg alloys (AC7A, AC7B, Al–3%Mg, and Al–7%Mg) were cast into strips at roll speed of 30 m/min. The crack size decreased with decreasing roll load, and when the roll load was 4 N/mm, no cracks formed. However, the strips did not completely solidify under this low load, and conveyance was difficult due to the insufficient strength of as-cast strips. To reduce the load in the inner area along the width direction of the strips, the thickness of the solidification layer in this area was made shorter than that at the edges by modifying the molten metal pouring method. In the modified pouring method, the molten metal was poured onto the roll using a launder placed against the roll at a small angle. With this method, the edges completely solidified and had enough strength for conveyance. Moreover, cracking substantially improved, and when the distance between the edge of the molten metal pool and the pouring point was set, crack formation was almost completely eliminated. The band region at the center in the thickness direction of the strips was widened using the proposed pouring method. The tensile strength and limiting drawing ratio of strips cast using the proposed pouring method were both greater than those of the strips cast using the conventional pouring method.

This Paper was Originally Published in Japanese in J. JFS 94 (2022) 282–289. The main text in p. 82 was slighly modified.

An increase in the volume fraction of pores in aluminum alloys causes a decrease in the elongation and the strength of alloys. To improve the mechanical properties of aluminum alloys, it is important to understand the growth and shrinkage behavior of pores. In this study, we analyzed the relationship between hydrogen desorption behavior and the growth/shrinking behavior of pores in A6061 alloys and pure aluminum using thermal desorption analysis and synchrotron radiation X-ray tomography. In pure aluminum, the fine pores began to annihilate at temperatures above 500°C and the relatively large pores coarsened. In contrast, the pores shrank with increasing temperature in A6061 alloy. The influence of second-phase particles has been discussed as a possible explanation for the difference in the nature of pores at elevated temperatures in pure aluminum and A6061 alloys. As in the A6061 alloy, much of the hydrogen desorbed from the pores due to heating is released externally from the second-phase particles on the aluminum surface, resulting in pore shrinkage due to the internal pressure drop of pores.

This Paper was Originally Published in Japanese in J. JILM 73 (2023) 212–217.

A new method for strengthening Mg alloy rod is proposed. AZ80Mg alloy rods were forged along the longitudinal axis (LA) at extremely high pressures beyond fracture stress under a condition where plastic deformation was eliminated in a die, i.e., deformation-restricted forging (DRFing), followed by cold extrusion. Although the ultimate tensile strength (UTS) and hardness were gradually raised with DRFing stress, the yield strength (YS) was lowered by sharp basal texture evolution on the plane normal to the LA and tensile axis. However, the extrusion after DRFing drastically changed the texture to (0001) || LA, causing a large increase in YS. Consequently, a superior balance of mechanical properties: YS of 376 MPa, UTS of 417 MPa, and ductility of 10%, could be achieved after the combined processes of DRFing and extrusion.

In order to verify the validity of the rank-1 connection model of kink band, a comparison between the kink described by the rank-1 connection and the kink actually formed in LPSO-Mg alloy was made in this study. Crystal rotation and kink interface (v_k) of kink bands formed by almost single basal slip were analyzed by EBSD and double trace analysis. Theoretical kink interface (n_α) was computed using the experimentally acquired crystal rotation of the kink bands using the rank-1 connection model. A comparison was made between n_α and v_k. Theory and experiment showed agreement within 4°, indicating that the geometry of the kink band is well described by the rank-1 connection.

In order to determine a factor of kink strengthening, spatial distribution of crystal rotation, kink interface rotation and plastic strain in deformed kink bands was investigated. Fine mesh was drawn on kink microstructure using focused-ion beam to map the plastic strain caused by the further deformation. Results clearly showed the existence of local deformation in the opposite direction of the external stress. This opposing plastic deformation was explained well the observed crystal rotation and rotation of the kink interface, provided that the rank-1 connection was maintained during deformation. The constraint between connected kink bands was suggested to be the origin of this opposite deformation and one of the factors leading to kink strengthening.

In order to clarify a strengthening principle due to the presence of the kink band, the geometry of the intersection of slip deformation and kink interface was analyzed in a situation where there is only one slip system and no cracking or delamination occurs. When the kink interface is penetrated by slip deformation while maintaining the continuity of deformation, disclinations are always formed at the intersection, and the migration of kink interface is required (cooperative deformation). The disclination and the cooperative deformation always increase the stress for deformation, regardless of how small the penetrating slip is. In layered structures such as long-period stacking ordered (LPSO) Mg alloys, there is a mismatch in the number of layers at the intersection of the kink interface and the slip deformation, which necessitates cutting of the layers. This means that the 〈c〉-dislocation is necessary for the cooperative deformation in LPSO-Mg. It is suggested that when the Peierls stress of 〈c〉-dislocation is much higher than that of basal slip (easy slip), the presence of kink interface leads to a dramatic increase in the stress for plastic deformation.