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MATERIALS TRANSACTIONS Vol. 64 (2023), No. 4

ISIJ International
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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678
Publisher: The Japan Institute of Metals and Materials

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MATERIALS TRANSACTIONS Vol. 64 (2023), No. 4

Two-Directional Micro-Laue Diffraction Mapping to Observe Kink Deformation in Long-Period Stacking-Ordered Mg–Zn–Y Alloys under Compression

Shigeru Kimura, Kazushi Sumitani, Kentaro Kajiwara

pp. 716-719

DOI:

10.2320/matertrans.MT-MD2022001

Abstract

We modified a previously developed compact compression-test stage for synchrotron radiation micro-Laue diffraction mapping to investigate the deformation of the long-period stacking-ordered phase of a magnesium polycrystal. This modification made it possible to obtain grain-boundary images from two orthogonal directions, realizing to obtain depth information about the position of kink formation. Also, to compare bulk and surface images, a long-focus optical microscope, which can take photographs of the surface morphology of the sample, was introduced into the apparatus.

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Two-Directional Micro-Laue Diffraction Mapping to Observe Kink Deformation in Long-Period Stacking-Ordered Mg–Zn–Y Alloys under Compression

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Unified Understanding of Strengthening Mechanisms Acting in Mg/LPSO Two-Phase Extruded Alloys with Varying LPSO Phase Volume Fraction

Koji Hagihara, Toko Tokunaga, Kazuki Yamamoto, Michiaki Yamasaki, Tsuyoshi Mayama, Takumi Shioyama, Yoshihito Kawamura, Takayoshi Nakano

pp. 720-729

DOI:

10.2320/matertrans.MT-MD2022002

Abstract

The influence of the volume fraction of the long-period stacking ordered (LPSO) phase on the strengthening mechanisms acting in Mg/LPSO two-phase extruded alloys is discussed by focusing on compression tests of Mg94Zn2Y4 and Mg92Zn3Y5 alloys. An increase in the LPSO phase volume fraction increases the yield stress of these alloys, but the magnitude of the increase is not monotonic with the volume fraction. For deformation parallel to the extrusion direction, the rate of increase in the yield stress shows two large gaps between the Mg99.2Zn0.2Y0.6/Mg97Zn1Y2 and Mg92Zn3Y5/Mg89Zn4Y7 alloys. This is derived from the change in strengthening mechanisms. The upper gap between Mg92Zn3Y5/Mg89Zn4Y7 is derived from the change in the strengthening mechanism between short-fiber reinforcement and the simple rule of mixtures. The lower gap between Mg99.2Zn0.2Y0.6/Mg97Zn1Y2 corresponds to the existence of a short-fiber strengthening mechanism or not. As the volume fraction of the LPSO phase decreases, the magnitude of kink-band strengthening to the yield stress decreases; however, it is still effective even in alloys with a low volume fraction of the LPSO phase.

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Unified Understanding of Strengthening Mechanisms Acting in Mg/LPSO Two-Phase Extruded Alloys with Varying LPSO Phase Volume Fraction

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Microstructure Evolution and Local Hardness of Mg–Y–Zn Alloys Processed by ECAE

Motohiro Yuasa, Ryoichi Sato, Takao Hoshino, Daisuke Ando, Yoshikazu Todaka, Hiroyuki Miyamoto, Hidetoshi Somekawa

pp. 730-734

DOI:

10.2320/matertrans.MT-MD2022018

Abstract

Mg–9 at%Y–6 at%Zn and Mg–2 at%Y–1 at%Zn alloys were processed by equal-channel-angular extrusion (ECAE) to investigate their microstructure evolution and local hardness. The area fraction of the kink bands in the Mg–9 at%Y–6 at%Zn alloys increased with increasing the number of ECAE passes, resulting in higher hardness. In contrast, the number of kink boundaries in the local region near the indentation was almost constant. The relationship between the microstructure factors of the kink bands and the local hardness is discussed in comparison with the forged alloy. In the Mg–2 at%Y–1 at%Zn alloys, the microstructural evolution of the α-Mg matrix phase and long-period stacking ordered (LPSO) phase by 1-pass ECAE and the increase in local hardness were discussed.

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Microstructure Evolution and Local Hardness of Mg–Y–Zn Alloys Processed by ECAE

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Synchronized Formation of Kink Bands in Al/Al2Cu Mille-Feuille Structured Alloy

Takayuki Shiraiwa, Naoya Hamada, Fabien Briffod, Manabu Enoki, Koji Hagihara

pp. 735-743

DOI:

10.2320/matertrans.MT-MD2022005

Abstract

In this study, kink band formation behavior of an Al/Al2Cu eutectic alloy with a mille-feuille structure consisting of a hard Al2Cu phase and a soft Al phase was investigated under compression at room temperature. In-situ surface observations during compression tests revealed multiple micro kink-bands occurring simultaneously within a single lamellar colony. To analyze the formation behavior of micro kink-bands, the spatial distribution of the lamellar structure over a wide area of the specimen was quantitatively evaluated by performing image analysis using the Radon transform. The results showed that the micro kink-bands generated synchronously in one direction and rotated at a uniform angle. Such uniform and fine kink-bands are expected to contribute to the improvement of strength. To unravel the linkage between microstructure, kink band formation, and accompanying kink strengthening, an attempt was made to construct a model that predicts the spacing between micro kink-bands and critical stress for kinking from the features of the lamellar structure. The validity of the model to predict the spacing between kink bands was demonstrated by the experimental results.

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Synchronized Formation of Kink Bands in Al/Al2Cu Mille-Feuille Structured Alloy

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Kink Formation and Strengthening Effects in TiNi–V Eutectic Alloys with Mille-Feuille Structure

Naoya Maki, Yoji Miyajima, Kazuhiro Ishikawa

pp. 744-749

DOI:

10.2320/matertrans.MT-MD2022008

Abstract

Kink formation by rolling and its strengthening effects on the mechanical properties of TiNi–V alloy were investigated. The as-cast TiNi–V alloy had a eutectic lamellar structure consisting of B2-TiNi and bcc-V phases. When the alloy was rolled, kinks were formed in the layered structure. The Vickers hardness of the alloy increased after it was subjected to 30% rolling reduction, and then decreased with increasing annealing temperature. After the rolled alloy was annealed at 973 K, its hardness recovered to the original value; however, the layer structure and kinks remained in the alloy. Thus, both dislocations and kinks were introduced into the alloy by rolling, but only dislocations disappeared upon annealing. Therefore, a layered TiNi–V alloy with only kinks but no dislocations was obtained. A comparison of the yield stresses of as-cast, 30% rolled, and annealed alloy specimens revealed that the magnitude of strengthening by dislocations and kinks was about 170 and 40 MPa, respectively. Therefore, kink formation and kink strengthening effects similar to those observed in Mg-based long-period stacking ordered (LPSO) alloys were observed.

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Kink Formation and Strengthening Effects in TiNi–V Eutectic Alloys with Mille-Feuille Structure

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Local Structural Analysis around Solute-Element in Annealed Mg99.2Zn0.2Y0.6 Alloy Using X-ray Fluorescence Holography

Koji Kimura, Daisuke Egusa, Koji Hagihara, Naohisa Happo, Naomi Kawamura, Hiroo Tajiri, Kouichi Hayashi, Eiji Abe

pp. 750-755

DOI:

10.2320/matertrans.MT-MD2022009

Abstract

X-ray fluorescence holography was applied to dilute Mg99.2Zn0.2Y0.6 alloy annealed at 520°C for 5 h to obtain atomic images around Zn atom. In spite of the extremely low concentration of the solute-element, clear hologram patterns were obtained. The reconstructed atomic images revealed that the Zn atom in this annealed Mg99.2Zn0.2Y0.6 alloy mainly occupy the hcp Mg site. This finding is consistent with the transmission electron microscope image, where fcc-type stacking faults are hardly observed. These results are in contrast to the previous report that Zn and Y form short-range-ordered solute clusters at the fcc-type stacking fault in Mg–Zn–Y alloy. The effect of heat treatment on the atomic arrangement of solute-elements in this dilute alloy is discussed in relation to the previously reported mechanical properties.

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Local Structural Analysis around Solute-Element in Annealed Mg99.2Zn0.2Y0.6 Alloy Using X-ray Fluorescence Holography

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Relationship between Cluster-Arranged Nanoplate Formation and Mechanical Properties of Dilute Mg–Y–Zn Alloys Prepared by Combination of Low-Cooling-Rate Solidification and Extrusion Techniques

Seitaro Ishizaki, Michiaki Yamasaki, Koji Hagihara, Soya Nishimoto, Taisuke Nakamura, Yoshihito Kawamura

pp. 756-765

DOI:

10.2320/matertrans.MT-MD2022015

Abstract

High-strength dilute Mg–Y–Zn alloys with cluster-arranged layer/nanoplate (CAL/CANaP) precipitates were developed via combined processes of low-cooling-rate solidification and extrusion techniques. The effects of CANaP morphology and deformation kink bands installation on the tensile properties of the extruded Mg–Y–Zn alloys were investigated. A slow-cooling solidification process with a cooling rate range of 0.1–0.01 K·s−1 produces a CAL-aggregated region in the α-Mg matrix. The CAL-aggregated region comprises long-period stacking ordered (LPSO) nanoplates with an intergrowth structure and the solo-CAL precipitates. The area fraction of the CAL-aggregated region increased with decreasing cooling rate. The microstructure of the extruded Mg99.2Y0.6Zn0.2 alloys prepared from low cooling rate-solidified ingots consisted of three characteristic regions: (i) dynamically recrystallized (DRXed) fine α-Mg grains, (ii) worked coarse α-Mg grains with a CAL-aggregated region, and (iii) worked blocky LPSO grains. The strength and ductility of the extruded Mg–Y–Zn alloys may be controlled by the volume fractions of the worked and DRXed grains, respectively. It is desirable to control the CANaP thickness and spacing to ∼1 µm and ∼0.8 µm or more, respectively, to promote DRX. Conversely, it is necessary to control the CANaP thickness and spacing to ∼1 µm and ∼0.8 µm or less, respectively, to form the worked grains in which kink bands are introduced.

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Relationship between Cluster-Arranged Nanoplate Formation and Mechanical Properties of Dilute Mg–Y–Zn Alloys Prepared by Combination of Low-Cooling-Rate Solidification and Extrusion Techniques

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Effect of Extrusion Ratio in Hot-Extrusion on Kink Deformation during Compressive Deformation in an αMg/LPSO Dual-Phase Magnesium Alloy Monitored by In Situ Neutron Diffraction

Stefanus Harjo, Wu Gong, Kazuya Aizawa, Takuro Kawasaki, Michiaki Yamasaki, Tsuyoshi Mayama, Yoshihito Kawamura

pp. 766-773

DOI:

10.2320/matertrans.MT-MD2022004

Abstract

To elucidate the effect of extrusion ratio in hot-extrusion on the deformation behavior during compression of Mg97Zn1Y2 alloy containing about 25-vol% long-period stacking ordered phase (LPSO) in the HCP structured α matrix (αMg), in situ neutron diffraction measurements were performed under compressive loading using four types of samples: as-cast and after hot extrusion at 623 K with extrusion ratios of 5.0, 7.5 and 12.5. The macroscopic yielding was observed to appear by the occurrence of basal slip of αMg in the as-cast sample and at the onset of twinning in the hot extruded samples. The applied stress to initiate slip, twinning, and kinking increased by hot extrusion and then decreased with increasing extrusion ratio. LPSO shared higher stress than αMg and the ratio to the strength increased as the extrusion ratio increased. In the extruded samples, the phase stress levels in LPSO when kinking initiated were almost the same for the hot-extruded samples, around 580 MPa, regardless of the extrusion ratio.

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Effect of Extrusion Ratio in Hot-Extrusion on Kink Deformation during Compressive Deformation in an αMg/LPSO Dual-Phase Magnesium Alloy Monitored by In Situ Neutron Diffraction

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Effects of High-Pressure Press on the Tensile Properties and Morphology of Polypropylene

Yukino Ito, Shotaro Nishitsuji, Hironari Sano, Masaru Ishikawa, Takashi Inoue, Hiroshi Ito

pp. 774-779

DOI:

10.2320/matertrans.MT-MD2022014

Abstract

In the field of metals, especially in magnesium alloys, a new concept has been reported that introducing a kink by applying compression or other deformation to a material with an LPSO structure, in which hard and soft layers are alternately stacked, results in higher strength. Because crystalline polymers are alternately layered with a crystalline phase, the hard layer, and an amorphous phase, the soft layer, it is expected that crystalline polymers can be made stronger if kinks can be introduced by applying compression or other deformation. In this study, the effects of a high-pressure press on the tensile properties and morphology of polypropylene (PP) were investigated. We found that a high-pressure press reduced the strain at break but increased the tensile modulus and the stress at break in the stress–strain curves. Thus, we succeeded in developing high-strength PP using a high-pressure press. In addition, it is found that the tensile properties were isotropic with no directional dependence after press. This implies that the tensile strength can be increased isotropically. Observing the morphology parallel to the press direction by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS), it was found that the crystal lamellae spread isotropically. Conversely, observation of the morphology perpendicular to the press direction by optical microscopy (OM) and transmission electron microscopy (TEM) revealed the formation of a shear band where deformation was concentrated owing to pressure. In the shear band, it was found that lamella fragmentation occurred and a kinked structure was formed. In this region, the molecular chains may be constrained by pressure, and become a tension state, which leads to the improvement of the mechanical properties.

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Effects of High-Pressure Press on the Tensile Properties and Morphology of Polypropylene

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Microstructure Evolution in Mg98.6Y1Zn0.4 Alloys and the Development by Hot Deformation Examined by Synchrotron Radiation Small- and Wide-Angle Scattering

Hiroshi Okuda, Yoshiaki Maegawa, Kento Shimotsuji, Shin-ichi Inoue, Yoshihito Kawamura, Shigeru Kimura

pp. 780-784

DOI:

10.2320/matertrans.MT-MD2022007

Abstract

Synchrotron radiation small- and wide-angle scattering measurements have been performed for Mg98.6–Y1–Zn0.4 alloys. In the early stage of phase transformation from supersaturated solid solutions, isotropic scattering suggesting segregation at grain boundaries was observed. It grew with temperature during heating the sample at a constant rate of 0.133 K/s. Above 600 K where introduction of stacking faults is expected, needle-like scattering became visible, which represents platelet shape segregation of cluster layers called cluster arranged layer (CAL). The layer eventually developed to form multiple layers, cluster arranged nano plates (CANaP) at higher temperatures. Microstructure change by hot rolling after the heat treatments has been examined from a viewpoint of kink-deformed microstructures.

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Microstructure Evolution in Mg98.6Y1Zn0.4 Alloys and the Development by Hot Deformation Examined by Synchrotron Radiation Small- and Wide-Angle Scattering

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Kink Modeling and Simulations Based on Field Theory of Multiscale Plasticity (FTMP) Part I: Explicit Kink Model and Double Compression Test

Kota Mizutani, Yuta Nawa, Tadashi Hasebe

pp. 785-794

DOI:

10.2320/matertrans.MT-MD2022016

Abstract

This study describes the basic capabilities of an “Explicit” kink model based on Field Theory of Multiscale Plasticity (FTMP), where the incompatibility tensor-incorporated additional degrees of freedom (DOFs), mediated by the Rank-1 connectivity-based projection direction with variable shear measure, directly drives the kink field evolutions in addition to the conventional slip mode. Not only inhomogeneous but realistic kink morphologies but also slightly improved energy releasing characteristics are shown to be reproduced. Furthermore, virtual double compression tests are performed on thus obtained kinked samples, demonstrating the kink strengthening that qualitatively agrees with experiments. Further enrichment of the model via the incompatibility-based DOFs introduced also in the slip model is shown to be able to simulate even more realistic kink morphologies and the attendant rotation angle distributions accurately.

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Kink Modeling and Simulations Based on Field Theory of Multiscale Plasticity (FTMP) Part I: Explicit Kink Model and Double Compression Test

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Kink Modeling and Simulations Based on Field Theory of Multiscale Plasticity (FTMP) Part II: Implicit Kink Model and Scale-Free Treatment

Tadashi Hasebe, Kota Mizutani

pp. 795-804

DOI:

10.2320/matertrans.MT-MD2022017

Abstract

We discuss not only kink formations but also the attendant primary strengthening taken place during the formation processes, by proposing anew an “Implicit” kink model based on Field Theory of Multiscale Plasticity (FTMP) only by utilizing the incompatibility tensor-incorporated Rank-1 degrees of freedom in the hardening law of the slip constitutive equation. Demonstrated is either realistically inhomogeneous kink field morphologies and successfully-raised flow stress level throughout the deformation, with the help of prescribed soft/hard structure accompanied by initial misorientations. A preliminary attempt is also made for identifying the critical roles of the empirically-found “scale-free” nature in the AE characteristics, based on the proposed model combined with the interaction field formalism in FTMP, resulting in further improved kink morphologies as well as slightly increased flow stress level.

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Kink Modeling and Simulations Based on Field Theory of Multiscale Plasticity (FTMP) Part II: Implicit Kink Model and Scale-Free Treatment

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Orientation Dependence of High Temperature Compressive Behavior of Textured Ti3SiC2

Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka

pp. 805-812

DOI:

10.2320/matertrans.MT-MD2022012

Abstract

In order to clarify the orientation dependent deformation behavior of the MAX phase ceramics, compressive deformation behavior was examined in a textured Ti3SiC2 (TSC) at a high temperature of 1200°C. Depending on the relationship between the texture and loading directions, both the deformation behavior and microstructure were strongly influenced, and the resultant basal slip, kink formation and delamination affected the compression behavior of the textured TSC. When the stress was loaded parallel or perpendicular to the basal plane (0TSC and 90TSC), the stress-strain (S-S) curves showed higher peak stresses followed by the reduction in the flow stress. When the stress was loaded 45° to the basal plane (45TSC), the S-S curve showed strain hardening after yielding, but did not show peak stress. Although the strength was higher both in 0TSC and 90TSC than in 45TSC, both 0TSC and 90TSC showed the formation of cracks and delamination, resulting to the large drop in the flow stress. In contrast to 0TSC and 90TSC, although 45TSC did not exhibit the peak stress, it exhibited work hardening due to the kink boundary formation, irrespective of the formation of delamination. It is reasonable to conclude from the deformation behavior and the deformed microstructures that for the TSC, the kink boundary plays an important role for attaining both deformability and strength.

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Orientation Dependence of High Temperature Compressive Behavior of Textured Ti3SiC2

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DFT Calculation of High-Angle Kink Boundary in 18R-LPSO Alloy

Mitsuhiro Itakura, Masatake Yamaguchi, Daisuke Egusa, Eiji Abe

pp. 813-816

DOI:

10.2320/matertrans.MT-MD2022010

Abstract

Kink boundaries formed in Mg-based long period stacking order (LPSO) alloys play a key role in strengthening of these materials. As the kink structure grows, many high-angle kink boundaries are eventually formed which has inclination angle close to 34 degrees. We show that this peculiar structure is a result of irreversible structural transformation and is energetically stable. We also calculate segregation energies of alloying elements Y and Zn to this boundary. Finally, the critical resolved shear stress for the migration of kink boundary is estimated for a pure-Mg kink and that with saturated with segregation. We show that segregated kink boundary requires very high shear stress about 700 MPa for migration.

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DFT Calculation of High-Angle Kink Boundary in 18R-LPSO Alloy

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Numerical Analysis of Disclinations in Connecting Kink Bands Formed by Multiple Basal Shear

Ryutaro Matsumura, Yuri Shinohara, Tomonari Inamura

pp. 817-826

DOI:

10.2320/matertrans.MT-MD2022020

Abstract

We analyzed the kinematic (geometric) aspects of kink bands with multiple basal shear using rank-1 connection to investigate the type of disclination and annihilation of disclinations in kink microstructures. We found that wedge disclinations occur in connecting kink bands for realistic magnitude of shear that can occur, regardless of the shear direction. The normal vector of the junction plane between kink bands and Frank vector of the resulting wedge-disclination varied continuously with respect to the changes in the magnitude and direction of the basal shear. Annihilation of disclinations is possible even between the kinks which are formed by multiple basal shears. Kinematical model of the three-dimensional wavy kinks are proposed using the obtained results.

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Numerical Analysis of Disclinations in Connecting Kink Bands Formed by Multiple Basal Shear

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Effects of a Preannealing Process on the Morphology of Developed Kinks in Mille-Feuille Structured Cu/A5052 Alloy Fabricated by Accumulative Roll Bonding: Criteria for Kink Formation

Moeko Yamazaki, Kazuhiro Ishikawa, Toshiyuki Fujii, Yoji Miyajima

pp. 827-834

DOI:

10.2320/matertrans.MT-MD2022003

Abstract

Cu/A5052 dissimilar metal laminates (DMLs) were fabricated by an accumulative roll bonding process. The Cu/A5052 DML consisted of hard and soft layers, in other words, high and low shear modulus layers, which is called a mille-feuille structure (MFS). The Cu/A5052 DML with the MFS showed kink deformation during monotonic compression. Kink formation was analyzed by in-situ optical microscopy and digital image correlation. The development behavior and morphology of the ortho-type kink depended on the annealing conditions prior to the compression tests. Based on the observations and measurements, criteria for kink formation in the DML with the MFS were proposed.

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Effects of a Preannealing Process on the Morphology of Developed Kinks in Mille-Feuille Structured Cu/A5052 Alloy Fabricated by Accumulative Roll Bonding: Criteria for Kink Formation

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Morphology and Thermoelectric Properties of Mg3+δSb2 Foams Manufactured Using Combustion Synthesis

Takashi Koga, Takashi Itoh

pp. 835-840

DOI:

10.2320/matertrans.MT-Y2022005

Abstract

Magnesium antimonide (Mg3Sb2) is a promising thermoelectric compound utilized for thermoelectric power generation. We have found out that the Mg3Sb2 compound can be made from Mg and Sb powder mixture via the combustion synthesizing reaction. In this study, we manufactured the compounds from the compacted bodies with different Mg fractions between 60.0 and 75.0 at% in an argon gas flow at 650°C for 1 hour via the combustion synthesis process. Morphology, porosity, phases and thermoelectric properties (electrical resistivity and Seebeck coefficient at room temperature to 500°C) were investigated for the manufactured samples. All samples manufactured with different Mg fractions mainly consisted of Mg3Sb2 and became foamed bodies with a porosity between 50 and 70%. The thermoelectric properties changed with the Mg fraction. The maximum power factor of 42.1 µW/mK2 at 488°C was obtained in the foamed body with the Mg fraction of 64 at%. The dimensionless figure of merit (ZT) of the sample was also estimated using the thermal conductivity, which was calculated considering its large porosity. The maximum dimensionless figure of merit (ZTmax) would be 0.13 at 488°C.

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Morphology and Thermoelectric Properties of Mg3+δSb2 Foams Manufactured Using Combustion Synthesis

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Fe20Mo20Ni20Rh20Ru20 and Fe14Mo35Ni15Rh15Ru21 Ultrahigh-Mixing-Entropy Alloys with Single Hexagonal Close-Packed Structure

Akira Takeuchi, Takeshi Wada, Kenji Amiya, Hidemi Kato, Takeshi Nagase

pp. 841-848

DOI:

10.2320/matertrans.MT-M2022213

Abstract

Mo35Ni15Rh15Ru35, Fe14Mo35Ni15Rh15Ru21, Mo25Ni25Rh25Ru25, and Fe20Mo20Ni20Rh20Ru20 (at%) alloys were designed by referring to hexagonal close-packed (hcp) Nb–Mo–Ru–Rh–Pd high-entropy alloys (HEAs) reported by Liu et al., with the help of Pearson’s Crystal Data. X-ray diffraction profiles of the Fe20Mo20Ni20Rh20Ru20 and Fe14Mo35Ni15Rh15Ru21 alloys prepared via the conventional arc-melting and subsequent annealing at 1700 K for 1 h show an hcp structure. Further scanning electron microscopy observations combined with elemental mapping via energy-dispersive X-ray spectroscopy confirmed the single hcp structure. The Fe20Mo20Ni20Rh20Ru20 HEA annealed at 1700 K for 1 h exhibited a mixing entropy (Smix) normalized by the gas constant (R) of 1.846, 14% higher than the configuration entropy (Sconfig) normalized by R (Sconfig/R = ln 5). This study reveals two new ultrahigh-mixing-entropy alloys (UHMixEAs) that satisfy Smix > Sconfig, the Fe20Mo20Ni20Rh20Ru20 and Fe14Mo35Ni15Rh15Ru21 alloys. The evaluation of Smix/Sconfig for the present UHMixEAs and referential Co-containing HEAs from early studies revealed that Smix/Sconfig of the former are constant whereas those of the latter increase at the magnetic transition (Curie) temperature or below.

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Fe20Mo20Ni20Rh20Ru20 and Fe14Mo35Ni15Rh15Ru21 Ultrahigh-Mixing-Entropy Alloys with Single Hexagonal Close-Packed Structure

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Influence of Cu Concentration on Structure, Mechanical Properties and Corrosion Resistance of Ti–Ni–Cu Shape Memory Alloy Ribbons

Kieu Xuan Hau, Nguyen Hai Yen, Nguyen Huy Ngoc, Truong Viet Anh, Pham Thi Thanh, Nguyen Van Toan, Nguyen Huy Dan

pp. 849-854

DOI:

10.2320/matertrans.MT-M2022161

Abstract

The paper presents the results of investigating the influence of Cu concentration on structure, mechanical properties and corrosion resistance of Ti50Ni50−xCux (x = 0, 5, 10, 15 and 20) alloy ribbons. The ribbons with a thickness of about 25 µm were prepared by using melt-spinning method with a tangential velocity of copper wheel of 40 m.s−1. All the ribbons reveal a single crystalline phase of (Ni,Cu)Ti with the martensitic-B19 structure at room temperature when Cu substitutes for Ni. The structural transformations temperature, tensile strain and elastic modulus increase with increasing Cu concentration whereas the hardness and dislocation density trendly decrease. The corrosion potential Ecorr in 3.5% NaCl aqueous solution increases from −0.67 V (for x = 0) to −0.46 V (for x = 20) indicating the better resistance against electrochemical corrosion by Cu addition.

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Influence of Cu Concentration on Structure, Mechanical Properties and Corrosion Resistance of Ti–Ni–Cu Shape Memory Alloy Ribbons

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Study on Machinability of Lead-Free α + β Brass 62.5Cu–1Si–Zn Alloy

Koichi Suzaki, Hiroki Goto, Tomokazu Tabuchi, Hiroyuki Mori, Keiichiro Oishi

pp. 855-860

DOI:

10.2320/matertrans.MT-D2022007

Abstract

Free-cutting brass contains 3% lead to obtain excellent machinability, but because lead is harmful to the human body, lead regulations are being tightened in Europe, starting with the 2010 and 2014 lead control laws for drinking water-related equipment in the United States, and including RoHS regulations, ELV regulations, and the 4MS Positive List. Being affected by these increasingly strict lead regulations in Europe and the United States, demand for brass with significantly reduced lead content is on the rise.

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Study on Machinability of Lead-Free α + β Brass 62.5Cu–1Si–Zn Alloy

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Research on Sound Absorption Properties of Tri-Periodic Minimal Surface Sandwich Structure of Selective Laser Melting Titanium Alloy

Kong Xiang-nan, Liu Bin, Li Zhong-Hua, Zhang Peng-Fei, Shi Chao

pp. 861-868

DOI:

10.2320/matertrans.MT-M2022164

Abstract

Triply Periodic Minimal Surface (TPMS) sandwich structure has the characteristics of lightweight, high specific strength, specific stiffness, vibration, and noise reduction. There is relatively little research on its sound absorption performance. TPMS sandwich structure based on selective laser melting (SLM) technology can achieve precise control of structure type, porosity, and so on, and has broad prospects in noise control applications. In this paper, the sandwich structure is designed based on tri-periodic minimal surface implicit function, and the titanium alloy sandwich structure is formed by SLM technology, and the sound absorption performance of titanium alloy TPMS sandwich structure is studied. The effects of volume fraction, panel thickness, and cell layer number on the sound absorption performance of the two TPMS structures were systematically analyzed using the transfer function method. The results show that: The GP10 sandwich structure with the volume fraction of 20%, the thickness of the panel is 1.0 mm, and the number of cell layers is 3C parameter combination has better sound absorption performance and higher sound absorption bandwidth, and the sound absorption coefficient is 0.36. For Ti6Al4V sandwich sound absorption structure, it is not suitable to design too thick panels. When the volume fraction is lesser, the increase of the tortuosity factor τ improves the sound absorption performance of the two structures, and excessive volume fraction leads to a decrease of sound absorption performance. The increase of cell layers can broaden the sound absorption bandwidth of the two structures, and the sound absorption capacity increases and then decreases in the range of 150–6400 Hz. The Gyroid structure mostly exhibits resonance sound absorption mechanism, while the Diamond structure exhibits resonance sound absorption mechanism combined with the viscous loss of sound wave. The work done in this paper can provide a theoretical basis for the study of the sound absorption characteristics of TPMS sandwich structure.

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Research on Sound Absorption Properties of Tri-Periodic Minimal Surface Sandwich Structure of Selective Laser Melting Titanium Alloy

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Mechanical Characteristics of Boron and Cerium Added NiCrMo Non-Precious Dental Casting Alloys

Ali Haider, Syed Husain Imran Jaffery, Aamir Nusair Khan, Najam Ulqadir, Xiubing Jing

pp. 869-876

DOI:

10.2320/matertrans.MT-M2022170

Abstract

Nickel–Chromium–Molybdenum (Ni–Cr–Mo) alloys are widely used for dental applications. This research was aimed to investigate improvement in the mechanical properties of Ni–Cr–Mo alloy through Boron and Cerium doping. These alloys were doped with boron and boron+cerium alloying elements. The mechanical testing of the samples revealed that minor addition of these alloying elements significantly improved the ultimate tensile strength and yield strength. Moreover, the melting points of the doped samples, determined by differential thermal analysis, decreased appreciably with doping elements. Furthermore, detailed wear testing was carried out to analyze the in-situ behavior of the alloys. Significant improvement in wear rate was noted for the boron and boron+cerium added alloy samples. Also biocompatibility for the three alloys in cytotoxicity test proved the suitability for the use of these alloys in dental prostheses.

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Mechanical Characteristics of Boron and Cerium Added NiCrMo Non-Precious Dental Casting Alloys

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Stabilization of Equiatomic Solutions Due to High-Entropy Effect

Taichi Abe, Kwangsik Han, Yumi Goto, Ikuo Ohnuma, Toshiyuki Koyama

pp. 877-884

DOI:

10.2320/matertrans.MT-M2022167

Abstract

The stability of solid-solution phases in FCC and BCC lattices was examined in multi-component alloys based on the CALPHAD technique using the compound energy formalism and regular solution model. From the thermodynamic calculations, it was found in ternary systems that the single solid-solution phase became stable around the equiatomic composition where the configurational entropy was the largest value. The transition temperature from the disordered phase to ordered phase(s) or miscibility gap(s) decreased with the increasing number of elements in the system. The order-disorder transition temperature on the FCC lattice was affected by the end member of the ordered phases existing at the equiatomic composition, whereas it was not significant for the order-disorder transition in the BCC lattice. The single solid-solution phase region at equiatomic compositions was affected by variations in the interaction parameters. In multi-component systems, the variations were averaged with increasing the number of elements in the system. This suggests that high-entropy alloys can afford a variety of elements. This study shows that the disordered state can be formed in multicomponent systems around the equiatomic composition and suggests clearly that due to the high-entropy effect, the solution phases are stabilized.

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Stabilization of Equiatomic Solutions Due to High-Entropy Effect

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Real-Time Imaging of Brass Cross-Section with Dezincification Corrosion by Electrochemical Measurement Combined with Video Observation

Yoshinao Hoshi, Yoshiyuki Otake, Yukihiro Uchisawa, Hikari Watanabe, Isao Shitanda, Masayuki Itagaki

pp. 885-888

DOI:

10.2320/matertrans.MT-D2022009

Abstract

A real-time imaging electrochemical measurement system was developed for an in-situ observation of brass dezincification corrosion. This system allows for a video recording of brass cross-section under galvanostatic polarization. The progress of erosion associated with the dezincification corrosion in the depth direction on the brass cross-section was successfully observed from the video recording during the measurement. The erosion depth at each measurement time could be estimated from the cross-section images, indicating that the erosion depth was drastically increased at arbitrary time under galvanostatic polarization. It suggested that the erosion rate in the depth direction is strongly related to the dissolution behavior of zinc and copper from brass surface, namely, the preferential dissolution and the simultaneous dissolution. The relation between the dissolution behavior and the electrode potential of brass under galvanostatic polarization was discussed.

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Real-Time Imaging of Brass Cross-Section with Dezincification Corrosion by Electrochemical Measurement Combined with Video Observation

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Effect of Microwave Irradiation to Kinetics of Carbothermic Reduction of NiO

Kazuhiro Nagata, Shin-ichiro Fukada

pp. 889-895

DOI:

10.2320/matertrans.MT-M2022121

Abstract

The carbothermic reduction of NiO was carried out by microwave irradiation at 2.45 GHz under a constant rate of temperature rise. The state of reaction was analyzed by means of non-equilibrium thermodynamics. The rates of the dominant reaction was the Boudouard reaction followed by NiO + CO → Ni + CO2, differing from that by conventional radiant heating. The uncompensated heat of reactions and the enthalpy change of reactions were almost same amount. The activation energy was 141 kJ/mol for the carbothermic reduction of NiO, 115 kJ/mol for the NiO reduction by CO gas and 166 kJ/mol for the Boudouard reaction. The former two values were smaller than conventional radiant heating.

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Effect of Microwave Irradiation to Kinetics of Carbothermic Reduction of NiO

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Role of KMnO4–NaF Treatment in Galvanic Corrosion Resistance of AA5083 Coupled to Steel

Takumi Kosaba, Izumi Muto, Masashi Nishimoto, Yu Sugawara

pp. 896-903

DOI:

10.2320/matertrans.MT-L2022021

Abstract

The role of KMnO4–NaF conversion treatment in the galvanic corrosion resistance of AA5083 aluminum alloy coupled to AISI 1045 carbon steel in synthetic seawater (diluted 100 times) was investigated. The 10 min-treated AA5083 was observed to reduce the period of high current density during the early stage of coupling and decrease the number of localized corrosion damages on the AA5083. The 10 min conversion treatment significantly reduced the electrode potential of bulk Al6(Fe, Mn), and it was concluded that the Al6(Fe, Mn) particles on the conversion-treated AA5083 no longer acted as a local cathode at the electrode potential when the AA5083 was in contact with AISI 1045 carbon steel. The decrease in cathodic activity of Al6(Fe, Mn) was attributed to the removal of Fe from the surface film of Al6(Fe, Mn), addition of Mn by the conversion treatment, and thickening of the film.

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Role of KMnO4–NaF Treatment in Galvanic Corrosion Resistance of AA5083 Coupled to Steel

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Production of Titanium Hydride Powder from Titanium Tetrachloride Using Magnesium Metal in Hydrogen Gas Atmosphere

Sung-Hun Park, So-Yeong Lee, Dae-Hyeon Lee, Jungshin Kang, Ho-Sang Sohn

pp. 904-913

DOI:

10.2320/matertrans.M-M2023802

Abstract

The development of titanium (Ti) powder production process is important because Ti powder metallurgy (PM) is a promising method that can result in large cost savings by reducing material loss and the number of steps in the conventional manufacturing process of Ti metal and its alloys. This study investigated the process of producing Ti hydride powder directly from titanium tetrachloride (TiCl4) using magnesium (Mg) metal and hydrogen gas (H2). The experiments were conducted at 1073–1173 K when the TiCl4 feeding rate was in the range of 19.16–57.42 g·min−1 with the use of cooling gas as Ar or H2 gas. A mixture of Ti and Ti hydride (TiH1.5) was obtained in an iron (Fe) crucible by the dehydrogenation of Ti hydride as the TiCl4 reduction proceeded. The concentration of oxygen (O) decreased with a decrease in the specific surface area and/or an increase in the proportion of TiH1.5 in the powder. As a result, the concentration of O of the mixture of Ti and TiH1.5 decreased to 0.116 mass% under a certain condition.

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Production of Titanium Hydride Powder from Titanium Tetrachloride Using Magnesium Metal in Hydrogen Gas Atmosphere

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High-Temperature Oxidation Behavior of Ni/Al2O3 Composites with Various Ni Content

Phanuwat Khlaisongkhram, Yen-Ling Kuo, Makoto Nanko, Daisuke Maruoka

pp. 914-919

DOI:

10.2320/matertrans.MT-M2022111

Abstract

Al2O3 composites dispersed with 1, 5, 10, and 15 vol% nickel particles were prepared using a pulsed electric current sintering technique. High-temperature oxidation was conducted at temperatures ranging from 1200°C to 1350°C for 6–24 h in air. After oxidation, the sample surface mainly consisted of NiAl2O4 oxide. The growth of the oxidized zone in all sample groups followed a parabolic pattern. The influence of the Ni content on the high-temperature oxidation behavior of Ni/Al2O3 is discussed. A kinetic model was proposed to explain the growth of the oxidized zone. The diffusion coefficient of oxygen ions through the grain boundaries of the Al2O3 matrix can be obtained using the proposed model, which is in agreement with those in the literature.

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High-Temperature Oxidation Behavior of Ni/Al2O3 Composites with Various Ni Content

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Effect of Mn Content on Fatigue Limit of Various Flake Graphite Cast Irons

Yilagaqi, Kazumichi Shimizu, Kenta Kusumoto, Ken Sasaki, Koji Sato, Hiroshi Horie

pp. 920-924

DOI:

10.2320/matertrans.F-M2023801

Abstract

In recent years, with the active use of Mn-containing high-tensile strength steels as an automotive body material, it has become increasingly difficult to recycle Mn-containing high tensile strength steel scrap as raw material to produce cast iron, due to the fact that Mn is known as an element promoting the chilling tendency of cast iron melt. Therefore, in this study, the effect of Mn on the fatigue limit of flake graphite cast iron was investigated for the purpose of increasing the strength of cast iron and recycling high tensile strength steel. Flake graphite cast irons with different Mn contents (0.5 mass% and 2.0 mass%, the carbon equivalent corresponding to FC200, FC300 and FC400 of JIS specification (G 5501)) were prepared for plane bending fatigue test.

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Effect of Mn Content on Fatigue Limit of Various Flake Graphite Cast Irons

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Acceptable Concentrations of Cu and Ni in Corrosion Resistance of Mg–6 mass% Zn Alloy

Taiki Morishige, Koki Ezumi, Masato Ikoma, Tetsuo Kikuchi, Ryuichi Yoshida, Toshihide Takenaka

pp. 925-930

DOI:

10.2320/matertrans.MT-M2022171

Abstract

Cu and Ni impurities in Mg alloys are deleterious contaminants that reduce the corrosion resistance of the alloy. Mg2Cu and Mg2Ni precipitates can cause significant anodic dissolution of the Mg matrix, owing to their potential difference. Suppression of these phases can prevent the deterioration of corrosion resistance. The neutralization of these impurities through the formation of Mg–Zn intermetallic phases has been studied, because the atomic radii of Cu and Ni are similar to that of Zn. As a result, the MgZn2 phase may precipitate during the rapid cooling that occurs during the solidification of the Mg–6 mass% Zn alloy, and introduce substitutional impurity atoms in the crystal lattice. Mg(Zn, Cu)2 and Mg(Zn, Ni)2 phases can be formed instead of Mg2Cu and Mg2Ni, in the presence of both of Zn and these impurities. The microstructures and corrosion properties of the Mg–6 mass% Zn alloy with various Cu or Ni concentrations are investigated in this work. The Cu and Ni impurities are concentrated into MgZn2 phase in the Mg–6 mass% Zn alloy without Mg2Cu or Mg2Ni formation when the concentrations of these impurities are within acceptable limits. Consequently, the corrosion rate of the Mg–6 mass% Zn alloy with 1.4 mass% Cu or 0.25 mass% Ni is almost the same as that of the alloy without Cu and/or Ni contaminations.

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Acceptable Concentrations of Cu and Ni in Corrosion Resistance of Mg–6 mass% Zn Alloy

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Low-Temperature Oxidation-Sintering Behaviors of Cu Fine Particles

Nobuaki Takeuchi, Daisuke Ando, Koike Junichi, Yuji Sutou

pp. 931-938

DOI:

10.2320/matertrans.MT-M2022219

Abstract

Cu fine-particle paste is a promising material to form a low-cost interconnect for flexible electronics devices. It has been reported that Cu particles can be sintered at low temperature (well below the half of the melting point) through two-step heat treatment processes of oxidation and reduction. However, the mechanism of the low temperature sintering is not clear yet. In this study, we investigated the oxidation sintering process of Cu fine particles by thermal gravimetric analysis (TGA) in the temperature range of 200°C∼300°C, X-ray diffraction (XRD), and microstructural observation. It was found from TGA that the oxidation process was initially rate-controlled by surface reaction and then by Cu diffusion at grain boundaries of Cu2O. Transmission electron microscopy observation revealed the formation of a core (Cu)-shell (Cu2O) structure during the oxidation process. The adjacent Cu2O shells were bonded to each other resulting in a cross-linked structure. The subsequent reduction process led to the formation of a porous structure by oxygen removal, but the cross-linked structure was maintained, which would make the low-temperature sintered Cu body as robust as solidified solder and sintered Ag paste.

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Low-Temperature Oxidation-Sintering Behaviors of Cu Fine Particles

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Mechanical Properties of Solderable Polymer Composites with Low- and High-Melting-Point Solder Mixed Filler

Min Jeong Ha, Sangil Kim, Won Chul Cho, Jong-Min Kim, Byung-Seung Yim

pp. 939-942

DOI:

10.2320/matertrans.MT-M2022200

Abstract

A solderable polymer composite (SPC) with a low-melting-point solder (LMPS)/high-melting-point solder (HMPS) mixed filler was formulated to solve the bonding property and reliability problems in an SPC system with an LMPS filler. In addition, the possibility of enhancing the mechanical bonding properties of SPC with LMPS/HMPS mixed fillers was investigated. Three types of SPCs (mixing ratios for LMPS and HMPS: 100:0, 50:50, and 0:100) were prepared, and two types of mechanical property investigations (i.e., ball shear and microhardness tests) were performed to measure the mechanical bonding properties of SPCs according to the LMPS/HMPS mixing ratios. The SPC with an LMPS/HMPS mixed filler exhibited enhanced mechanical bonding properties compared with the Sn–58Bi solder paste and SPC with LMPS or HMPS only due to the change in composition and subsequent microstructure transformation of the solder joint after adding HMPS.

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Erratum

MATERIALS TRANSACTIONS Vol.64(2023), No.4

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Mechanical Properties of Solderable Polymer Composites with Low- and High-Melting-Point Solder Mixed Filler

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