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Latest 30 articles

Smart Materials in Manufacturing (Elsevier) published a paper as OA on the unique microstructure and hardness variation of Ti-6Al-2Sn-4Zr-6Mo alloys by metal additive manufacturing.

Prince Valentine Cobbinah*, Sae Matsunaga, Yoshiaki Toda, Ryosuke Ozasa, Masayuki Okugawa, Takuya Ishimoto, Yuheng Liu, Yuichiro Koizumi, Pan Wang, Takayoshi Nakano*, Yoko Yamabe-Mitarai*:
Peculiar microstructural evolution and hardness variation depending on laser powder bed fusion-manufacturing condition in Ti-6Al-2Sn-4Zr-6Mo,
Smart Materials in Manufacturing, 2, (2024), 100050, 1-10.
https://doi.org/10.1016/j.smmf.2024.100050

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Abstract
This study aims to comprehensively analyze the phase and microstructure evolution and related hardness variations of the Ti-6Al-2Sn-4Zr-6Mo wt.% (Ti6246) alloy produced by laser powder bed fusion (LPBF) under various laser conditions and to gain insight into the mechanisms of these changes using numerical thermal analysis. Higher laser volumetric densities (VEDs) resulted in a finer α/α' microstructure and increased hardness, exhibiting a positive correlation with the VED, except under extremely high conditions. This contrary trend, reported for the first time, is attributed to the solid-phase transformation from the β phase to metastable α' martensite during LPBF induced by rapid cooling. Despite the finer microstructure, the samples under very high VED conditions showed lower hardness, deviating from the overall trend. The X-ray diffraction peaks in the high-VED samples suggested a partial decomposition of α' to α + β owing to laser-induced reheating of the underlying layers, which is considered a contributing factor to the hardness reduction. The numerical analysis showed that the underlying layer was exposed to high temperatures for a relatively long time under high-VED conditions. It was revealed that the hardness of LPBF-fabricated Ti6246 was influenced by unique thermal processes: rapid cooling and reheating of the pre-solidified part, leading to the formation of a metastable α' phase and partial decomposition into α + β. These findings provide insights for tailoring Ti6246 with desired physical properties via LPBF.

Keywords
LPBF; Ti6246; Polycrystalline microstructure; Metastable phase; Rapid cooling; Thermal history

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A paper proposing the world's first (R≥2.0) super high entropy alloy (SHEA) was published as OA in Materials Chemistry and Physics (IF=4.6).

Tadaaki Matsuzaka, Akira Hyakubu, Yong Seong Kim, Aira Matsugaki, Takeshi Nagase, Takuya Ishimoto, Ryosuke Ozasa, Hyoung Seop Kim, Tomoji Mizuguchi, Ozkan Gokcekaya, Takayoshi Nakano:
Development of an equiatomic octonary TiNbTaZrMoHfWCr super high-entropy alloy for biomedical applications,
Materials Chemistry and Physics, 316, (2024), 129120; 1-7.
DOI: https://doi.org/10.1016/j.matchemphys.2024.129120
 
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Abstract
A super-high-entropy alloy (SHEA) with ΔSmix ≥ 2.0R (where R is the gas constant) was designed to produce metallic materials with superior mechanical properties to conventional alloys. As an alternative to conventional quinary high-entropy alloys (HEAs), herein, octonary SHEAs for biomedical applications (BioSHEAs) are proposed for the first time, and the TiNbTaZrMoHfWCr BioSHEA was fabricated. Arc-melted BioSHEA exhibited an extremely high yield strength of 1953 ± 84 MPa, which was approximately 550 MPa higher than that of the quinary TiNbTaZrMo BioHEA. This yield strength is considerably higher than that estimated by the rule of mixtures for pure metals, confirming the achievement of significant solid-solution strengthening induced by a supermulticomponent solid solution composed of elements with different atomic radii. Its biocompatibility was comparable to that of pure Ti and the quinary BioHEA, and superior to that of SUS316L. This study demonstrates the validity of a novel entropy-based guideline for increasing the mixing entropy to achieve metallic materials with ultrahigh strength.
 
Keywords
Super-high-entropy alloys (SHEAs); Octonary system; Supermulticomponent; Solid-solution strengthening; BioSHEAs

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An international collaborate research on the microstructure of pure Cr produced by L-PBF and the effect of HIP on wear has been published in the International Journal of Refractory Metals and Hard Materials (IF=3.6).

Asli Gunay Bulutsuz*, Buse Gulec, Ozkan Gokcekaya*, Johannes Gardstam, Takayoshi Nakano, Hakan Yilmazer:
An investigation over microstructure and HIP processing effects on wear performance of pure chromium parts fabricated by laser powder bed fusion,
International Journal of Refractory Metals and Hard Materials, 120, (2024), 106616, 1-10.
DOI: https://doi.org/10.1016/j.ijrmhm.2024.106616

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Abstract
Chromium (Cr) and its alloys have long been valued for their exceptional properties, including corrosion resistance and high-temperature stability, rendering them indispensable in industrial applications such as chemical processing, energy production, and aerospace. However, due to the difficulties in Cr-based alloy manufacturing, there is a need for novel manufacturing methodologies. Additive Manufacturing (AM) emerges as a promising approach, particularly Laser Powder Bed Fusion (LPBF), which allows for intricate designs, reduced material waste, and simplified assembly. However, certain issues still need to be addressed, including defects like cracks and porosities in the manufactured parts. Post-processing techniques such as Hot Isostatic Pressing (HIP) have gained prominence for enhancing the material properties and quality of AM parts, including those produced using LPBF. HIP treatments are effective in eliminating internal pores, although some challenges remain, notably the presence of trapped argon and grain coarsening side effects of HIP process parameters. This study focuses on LPBF-processed pure chromium parts with crystallographic texture and investigates their properties after HIP treatment, including microstructure, hardness, and tribological performance. According to the obtained results: the HIP process reduced cracks, especially in the center region, but increased gaps in the side region. HIP also hindered grain realignment, limiting grain growth, and resulting in high HAGB density and low MUD values. Elevated HIP processing pressure negatively affected tribological performance due to increased grain size, and reduced hardness. This study, for the first time, realized the effect of HIP conditions on the microstructure and tribological performance of LPBF-processed pure Cr.

Keywords
Laser powder bed fusion; Pure Cr; Crystallographic texture; Hot isostatic pressing; Wear performance

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Research on the development of low elasticity antimicrobial Ti-Nb-Cu alloys for biological applications was published in Materials Today Communications (IF=3.8).

Qiang Li*, Qizhen Peng, Qi Huang, Mitsuo Niinomi, Takuya Ishimoto, Takayoshi Nakano:
Development and characterizations of low-modulus Ti-Nb-Cu alloys with enhanced antibacterial activities,
Materials Today Communications, 38, (2024), 108402, 1-8.
DOI: https://doi.org/10.1016/j.mtcomm.2024.108402
 
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Abstract
Avoiding infection is a requirement for the long-term stability and safety of implants, but most Ti alloys for implantation hardly inhibit the bacterial proliferations. Cu works as a β stabilizer in Ti alloys, and Cu ion can kill bacteria. To obtain antibacterial activities in low-modulus Ti alloys, Ti-35Nb-(0, 1, 2, 3, 4)Cu (wt%) alloys were prepared by non-consumable arc melting following by homogenization, hot rolling, and solution treatment. They were then subjected to phase analysis, microstructure observation, tensile test and dynamic polarization. The cytotoxicity and antibacterial activities were finally evaluated. The results show that Cu stabilizes the β phase and inhibits the generation of α" phase during quenching. Ti-35 Nb and Ti-35Nb-1Cu consist of β and α" phases, and Ti-35Nb-(2, 3, 4)Cu alloys have a single β phase. The Ti-Nb-Cu alloys exhibit the Young's moduli ranging from 57 to 72 GPa. All the alloys show passivation behavior with a low passive current density. Cytotoxicity is hardly observed in the alloys. The antibacterial rates of Ti-35Nb-(1, 2, 3, 4)Cu alloys against E. coli are 62.8%, 68.9%, 70.9% and 73.2%, respectively, and the antibacterial rates against S. aureus are 63.4%, 69.7%, 72.8% and 74.7%, respectively. The developed β-type Ti-35Nb-4Cu alloy shows a relatively low Young's modulus and good antibacterial properties, and is a candidate for biomedical applications.
 
Keywords
Biomedical Ti alloys, Mechanical properties, Corrosion resistance, Cytotoxicity, Antibacterial properties

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Bone (IF=4.1) published an OA article showing that bone matrix orientation has a stronger effect on bone mechanical function adaptation than bone density.

Jun Wang, Takuya Ishimoto, Tadaaki Matsuzaka, Aira Matsugaki, Ryosuke Ozasa, Takuya Matsumoto, Mikako Hayashi, Hyoung Seop Kim, Takayoshi Nakano*:
Adaptive Enhancement of Apatite Crystal Orientation and Young's Modulus Under Elevated Load in Rat Ulnar Cortical Bone,
Bone, 181, (2024), 117024: 1-10.
https://doi.org/10.1016/j.bone.2024.117024

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Abstract
Functional adaptation refers to the active modification of bone structure according to the mechanical loads applied daily to maintain its mechanical integrity and adapt to the environment. Functional adaptation relates to bone mass, bone mineral density (BMD), and bone morphology (e.g., trabecular bone architecture). In this study, we discovered for the first time that another form of bone functional adaptation of a cortical bone involves a change in bone quality determined by the preferential orientation of apatite nano-crystallite, a key component of the bone. An in vivo rat ulnar axial loading model was adopted, to which a 3-15 N compressive load was applied, resulting in approximately 440-3200 μɛ of compression in the bone surface. In the loaded ulnae, the degree of preferential apatite c-axis orientation along the ulnar long axis increased in a dose-dependent manner up to 13 N, whereas the increase in BMD was not dose-dependent. The Young's modulus along the same direction was enhanced as a function of the degree of apatite orientation. This finding indicates that bone has a mechanism that modifies the directionality (anisotropy) of its microstructure, strengthening itself specifically in the loaded direction. BMD, a scalar quantity, does not allow for load-direction-specific strengthening. Functional adaptation through changes in apatite orientation is an excellent strategy for bones to efficiently change their strength in response to external loading, which is mostly anisotropic.

Keywords
Functional adaptation; Bone strength; Apatite orientation; Bone quality: In vivo loading

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An international collaborate research on improving the antimicrobial properties of Ti by Zn coating with improved adhesion has been published in Materials Today Communications (IF=3.8).

Ming Li, Qiang Li*, Jiawei Yang, Mitsuo Niinomi, Takayoshi Nakano:
Preparation and Antibacterial Activity of Zn Coating on Pure Ti with Enhanced Adhesion,
Materials Today Communications, 38, (2024), 1-10
https://doi.org/10.1016/j.mtcomm.2024.108149

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Abstract
A titania nanotubes layer was prepared as an intermediate layer on pure Ti via anodic oxidation, and subsequently, a Zn-containing coating was electrochemically deposited. The influence of the deposition parameters on the Zn content was studied using an orthogonal experiment. The obtained coatings were characterized using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and their adhesion was measured using a scratch test. The deposition time had the greatest effect on the Zn content of the electrodeposited samples, whereas the deposition temperature had the smallest effect. After the electrodeposition, Zn was uniformly distributed on the surface and existed mainly as a simple substance. The adhesion was only 10.9 N in the Zn-free sample; it increased with increasing Zn content of the samples, and reached a maximum value of 22.4 N in the sample with a Zn content of approximately 16%. The samples with Zn-containing coatings exhibited strong antibacterial effects against E. coli and S. aureus, and the antibacterial effect increased with increasing Zn content. Cell viability was above 80%, indicating that the Zn-containing coating is a good candidate as an antibacterial coating for biomedical applications.

Keywords
Zn-containing coating; Electrochemical deposition; Orthogonal experiment; Adhesion; Antibacterial property; Pure Ti

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A paper was published as OA in The International Journal of Advanced Manufacturing Technology (IF=3.4).

Ozkan Gokcekaya*, Ali Günen, Ferhat Ceritbinmez, Abdollah Bahador, Takayoshi Nakano, Melik Çetin:
Wire-EDM performance and surface integrity of Inconel 718 with unique microstructural features fabricated by laser powder bed fusion,
The International Journal of Advanced Manufacturing Technology, (2024), 1-16
https://doi.org/10.1007/s00170-023-12924-7
 
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Abstract
Inconel 718 alloy is difficult to machine using conventional methods due to its physical properties. Thereby, additive manufacturing (AM) of IN718 components with near-net shapes has been extensively studied. Even though AM processes provide shape and size accuracy, there is still the need for the machining of the AM-processed components to achieve the final shape of a component. Laser powder bed fusion (LPBF) has been successfully utilized to fabricate near-net shape IN718 components; moreover, the microstructure of LPBF-IN718 was unique owing to the AM processing, resulting in differences in grain size, grain boundary characteristics, and grain orientations. Furthermore, these microstructural characteristics are expected to alter the machining performance of IN718. Therefore, this study investigated the wire electro-discharge machining (WEDM) performance of LPBF-718 samples compared to wrought IN718 while focusing on the unique microstructure characteristics of LPBF-IN718 samples (lamella, single-crystal, ploy-crystal). Three different cutting strategies (rough, semi-finish, and finish) were implemented to understand the performance of the multi-pass cutting phenomenon and its effect on the surface of IN718. For all samples, rough (single pass) cutting displayed high roughness, while finish (three passes) cutting exhibited good surface quality. Compositional analyses on the machined surface showed debris formation including Zn and Cu-containing recast material, indicating wire erosion. The surface of single-crystal LPBF-IN718 after the WEDM process was smooth owing to its large grain size and less amount of grain boundary, resulting in slow cutting speed but a good surface finish. Thus, this study, for the first time, investigated the effect of unique microstructural characteristics of LPBF-fabricated IN718 on WEDM performance and machined surface quality.

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The Journal of the Mechanical Behavior of Biomedical Materials (IF=3.9) published the results of our collaborate research with Shanghai University of Science and Technology and Dr. Niinomi on the suppression of infection by surface deposition of iodine.

Qiang Li*, Shuaishuai Li, Hao Sun, Mitsuo Niinomi, Takayoshi Nakano:
Preparation and Characterizations of Antibacterial Iodine-containing Coatings on Pure Ti,
Journal of the Mechanical Behavior of Biomedical Materials, 151, (2024), 106366, 1-8.
https://doi.org/10.1016/j.jmbbm.2023.106366

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Abstract
Iodine-containing coatings were prepared on pure Ti surfaces via electrochemical deposition to enhance their antibacterial properties. The factors influencing iodine content were analyzed using an orthogonal experiment. The electrochemically deposited samples were characterized using scanning electron microscopy with energy dispersive spectroscopy and X-ray photoelectron spectroscopy, and their antibacterial properties and cytotoxicity were evaluated. The results showed that changing the deposition time is an effective way to control the iodine content. The iodine content, coating thickness, and adhesion of the samples increased with deposition time. Iodine in the coatings mainly exists in three forms, which are I2, I3−, and pentavalent iodine. For samples with iodine-containing coatings, the antibacterial ratios against E. coli and S. aureus were greater than 90% and increased with increasing iodine content. Although the samples with iodine-containing coatings showed some inhibition of the proliferation of MC3T3-E1 cells, the cell viabilities were all higher than 80%, suggesting that iodine-containing coatings are biosafe.

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Metals and Materials International (IF=3.5) has published a study of beta-containing TiAl alloys as an OA paper.

Sung-Hyun Park, Ozkan Gokcekaya, Ryosuke Ozasa, Myung-Hoon Oh, Young-Won Kim, Hyoung Seop Kim, Takayoshi Nakano:
Microstructure and crystallographic texture evolution of β-solidifying γ-TiAl alloy during single- and multi-track exposure via laser powder bed fusion,
Metals and Materials International, (2023), 1-15
https://doi.org/10.1007/s12540-023-01579-4

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Abstract
The microstructural evolution and crystallographic texture formation of β-solidifying Ti-44Al-6Nb-1.2Cr alloy were identified under single- and multi-track exposures via laser powder bed fusion (L-PBF) for various process parameters. Under single-track exposure, the microstructure of the melt pool was divided into the band-like α2 phase in the melt pool boundary and β phase in the melt pool center. Numerical and thermodynamic simulations revealed that the underlying mechanism of phase separation was related to the variation in the cooling rate in the melt pool, whereas microsegregation induced a shift in the solidification path. Meanwhile, the crystallographic texture of the α2 phase region was identical to that of the substrate owing to the epitaxial growth of the β phase and subsequent α phase nucleation. In contrast, the β phase exhibited a ± 45° inclined <100> alignment in the melt pool, which was tilted to align along the build direction toward the center of the melt pool corresponding to the simulated thermal gradient direction. Furthermore, the narrow hatch space condition maintained the crystallographic texture to the subsequent scan, forming a continuous band-like α2 phase with a strong selection. However, the crystallographic texture in a wide hatch space condition manifested a random distribution and constituted a fine mixture of the β and α2 phases. For the first time, these results will offer an understanding of an anisotropic microstructure control via the L-PBF process and ensure the tailoring of the mechanical properties in the β-solidifying γ-TiAl-based alloys by approaching hatch spacing control.

Keywords
γ-TiAl alloy, Microstructural evolution, Crystallographic texture, Laser powder bed fusion

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A study on microstructural changes after heat treatment of beta TiAl powder for AM has been published as an OA article in Crystals (IF=2.7).

Sung-Hyun Park, Ozkan Gokcekaya, Ryosuke Ozasa, Ken Cho, Hiroyuki Y. Yasuda, Myung-Hoon Oh, Takayoshi Nakano*:
Microstructure evolution of gas-atomized β-solidifying γ-TiAl alloy powder during subsequent heat treatment,
Crystals, 13, (2023), 1629; 1-10.
https://doi.org/10.3390/cryst13121629

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Abstract
To promote the use of γ-TiAl alloys in various domains, such as the aerospace industry, it is pivotal to investigate the unusual phase transformation from rapidly solidified and metastable γ-TiAl toward the equilibrium state. In this study, the microstructure characteristics of gas-atomized β-solidifying Ti-44Al-6Nb-1.2Cr alloy powder, in terms of the effect of rapid solidification on microstructure evolution, were explored in comparison with cast materials. The phase constitution, morphology, and crystallographic orientation between phases were noted to be distinct. Furthermore, subsequent heat treatment was conducted at different temperatures using gas-atomized powder. The transition from the metastable to equilibrium state was observed, wherein firstly, the γ phase precipitated from the retained α2 phase, forming an α2/γ lamellar microstructure. In intensified heat-treatment conditions adequate for cellular reaction, β/γ cells were formed at the grain boundaries of α2/γ lamellar colonies. The findings highlight the overall phase transformation during rapid solidification and continuous microstructural evolution from the nonequilibrium to the equilibrium state. This research can bridge the gap in understanding the effect of the solidification rate on microstructural evolution and contribute to enhanced comprehension of the microstructure in other domains involving rapid solidification, such as the additive manufacturing of γ-TiAl alloys.

Keywords
gas atomization; rapid solidification; nonequilibrium state; β-solidifying γ-TiAl alloy; recrystallization

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Journal of Materials Research and Technology (IF=6.4) published an OA paper on the unique properties of double arrowhead structures fabricated by electron beam additive manufacturing.

Zana Eren*, Ozkan Gokcekaya*, Takayoshi Nakano, Zahit Mecitoğlu:
In-plane quasi-static compression deformation of Ti6Al4V double arrow-headed lattices fabricated by electron beam powder bed fusion process: Build orientation, scan speed and failure mechanism,
Journal of Materials Research and Technology, 27, (2023), 6192-6210.
https://doi.org/10.1016/j.jmrt.2023.11.027

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Abstract
The 2D double arrow-headed (DAH) lattice structures, which are promising cellular structures for impact mitigation, remain relatively unexplored in terms of their compression response when manufactured using the powder bed fusion process with Ti6Al4V (Ti64) alloy. This study aims to investigate the effects of build orientation and beam scan speed of Electron Beam Powder Bed Fusion (PBF-EB) process on the energy absorption of 2D Ti64 DAH lattice structures. Additionally, potential microstructural variations due to adjusted process parameters can be linked to different levels of energy absorption. For the compressions, the lattice structures were manufactured at two build orientations (0° and 45°), using three different beam scan speeds: speed function (SF), low speed (LS), high speed (HS). In micro-characterizations, the unit cells of 0deg-LS exhibited the lowest micro-porosity level at 0.12 . Based on KAM values, thin struts at unit cells had higher residual stresses than thick struts, contributing to the initiation of failure locations. The compressions revealed that the 0deg-LS group absorbed 21.6 and 24 more energy than 0deg-SF and 0deg-HS groups, respectively, at compressions of 33 . 45° samples absorbed approximately 10 % more energy than 0° samples except HS groups. The lowest micro-porosity of 0deg-LS contributed to having the highest energy absorption among 0deg samples. As the residual stresses in KAM values did not differ strongly with varying beam speed, varied energy absorptions were not linked to them. An optimization of the numerical compressions helped obtain designs with higher energy absorption and less relative volume. This study provides valuable insights into Ti64 cellular applications constrained with 2D-type designs.

Keywords
Mechanical metamaterials
Electron beam powder bed fusion process
Double arrow-headed lattice
Compression deformation
Microstructure

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Our paper on lightweight MEA Fe47Mn25Al13Cr7Ni5C3 in collaboration with Prof. Hyoung Seop Kim's group at POSTECH has been published in Materials Science and Engineering A (IF=6.4).

Gang Hee Gu, Hyeonseok Kwon, Jae Heung Lee, Takayoshi Nakano, Hyoung Seop Kim*:
Lightweight Fe47Mn25Al13Cr7Ni5C3 medium-entropy alloy with enhanced mechanical properties,
Materials Science and Engineering A, 890, (2024), 145924: 1-8.
https://doi.org/10.1016/j.msea.2023.145924

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Abstract
In this study, we designed a lightweight Fe47Mn25Al13Cr7Ni5C3 medium-entropy alloy (MEA) (calculated density of 6.803 g/cm3) with enhanced mechanical properties. The MEA samples were produced in three conditions with varying microstructures via thermomechanical processing. They achieved excellent tensile properties through strengthening mechanisms such as partial recrystallization, ultrafine grains, and M23C6 and B2 precipitates. Different strengthening mechanisms were applied depending on the annealing heat treatment conditions, resulting in three different strength-elongation combinations. Furthermore, the MEA, under all designed conditions, exhibited superior specific yield strength-uniform elongation and specific ultimate tensile strength-uniform elongation combinations compared to previously studied lightweight high-entropy alloys (HEAs) and lightweight steel. This was primarily attributed to the combination of benefits obtained from the low proportion of iron (47 at%) as a principal element and the large amount of aluminum addition (13 at%). The proposed MEA and its design strategy can satisfy the requirements for lightweight, cost-effective, strong, and ductile metallic materials, making a great contribution to the automotive industry in terms of crash resistance and fuel efficiency.

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A paper demonstrating that bone matrix orientation has strong resistance to bacterial infection has been published in Biomaterials Advances.

Ryota Watanabe, Aira Matsugaki, Ozkan Gokcekaya, Ryosuke Ozasa, Takuya Matsumoto, Hiroyuki Takahashi, Hidekazu Yasui, Takayoshi Nakano:
Host bone microstructure for enhanced resistance to bacterial infections,
Biomaterials Advances, 154, (2023), 213633, 1-9
https://doi.org/10.1016/j.bioadv.2023.213633

Abstract
Postoperative bacterial infection is a serious complication of orthopedic surgery. Not only infections that develop in the first few weeks after surgery but also late infections that develop years after surgery are serious problems. However, the relationship between host bone and infection activation has not yet been explored. Here, we report a novel association between host bone collagen/apatite microstructure and bacterial infection. The bone-mimetic-oriented micro-organized matrix structure was obtained by prolonged controlled cell alignment using a grooved-structured biomedical titanium alloy. Surprisingly, we have discovered that highly aligned osteoblasts have a potent inhibitory effect on Escherichia coli adhesion. Additionally, the oriented collagen/apatite micro-organization of the bone matrix showed excellent antibacterial resistance against Escherichia coli. The proposed mechanism for realizing the antimicrobial activity of the micro-organized bone matrix is by the controlled secretion of the antimicrobial peptides, including β-defensin 2 and β-defensin 3, from the highly aligned osteoblasts. Our findings contribute to the development of anti-infective strategies for orthopedic surgeries. The recovery of the intrinsically ordered bone matrix organization provides superior antibacterial resistance after surgery.

Keywords
Postoperative infection; Laser powder bed fusion; Titanium alloy; Surface topography; Bone matrix anisotropy; Antimicrobial activity

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ACS Applied Materials & Interfaces (IF=10.4) published online a study on a proposed metal catalytic flow reactor made of MOF-based metal 3D printers.

Kohsuke Mori*, Tatsuya Fujita, Hiroto Hata, Hyo-Jin Kim, Takayoshi Nakano, Hiromi Yamashita:
Surface Chemical Engineering of a Metal 3D-Printed Flow Reactor Using a Metal-Organic Framework for Liquid-Phase Catalytic H2 Production from Hydrogen Storage Materials,
ACS Applied Materials & Interfaces, (2023), online.
https://doi.org/10.1021/acsami.3c10945

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Abstract
The accurate positioning of metal-organic frameworks (MOFs) on the surface of other materials has opened up new possibilities for the development of multifunctional devices. We propose here a postfunctionalization approach for three-dimensional (3D)-printed metallic catalytic flow reactors based on MOFs. The Cu-based reactors were immersed into an acid solution containing an organic linker for the synthesis of MOFs, where Cu2+ ions dissolved in situ were assembled to form MOF crystals on the surface of the reactor. The resultant MOF layer served as a promising interface that enabled the deposition of catalytically active metal nanoparticles (NPs). It also acted as an efficient platform to provide carbonous layers via simple pyrolysis under inert gas conditions, which further enabled functionalization with organic modifiers and metal NPs. Cylindrical-shaped catalytic flow reactors with four different cell densities were used to investigate the effect of the structure of the reactors on the catalytic production of H2 from a liquid-phase hydrogen storage material. The activity increased with an increasing internal surface area but decreased in the reactor with the smallest cell size despite its high internal surface area. The results of fluid dynamics studies indicated that the effect of pressure loss becomes more pronounced as the pore size decreases.

KEYWORDS:
metal 3D printing, flow reactor, metal−organic framework, postfunctionalization, hydrogen

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Materials (IF=3.4) published a paper on the creation of shape memory alloys by electron beam coating.

Lei Wang, Masayuki Okugawa*, Hirokazu Konishi, Yuheng Liu, Yuichiro Koizumi*, Takayoshi Nakano:
Fusion of Ni Plating on CP-Titanium by Electron Beam Single-Track Scanning: Toward a New Approach for Fabricating TiNi Self-Healing Shape Memory Coating,
Materials, 16(15), (2023), 5449; 1-15.
https://doi.org/10.3390/ma16155449

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Abstract
The limited wear resistance of commercially pure titanium (CP-Ti) hinders its use in abrasive and erosive environments, despite its good strength-weight ratio and corrosion resistance. This paper reports the first study proposing a novel method for wear-resistant TiNi coating through Ni plating and electron beam (EB) irradiation in an in situ synthetic approach. Single-track melting experiments were conducted using the EB to investigate the feasibility of forming a TiNi phase by fusing the Ni plate with the CP-Ti substrate. Varying beam powers were employed at a fixed scanning speed to determine the optimal conditions for TiNi phase formation. The concentration of the melt region was found to be approximate as estimated from the ratio of the Ni-plate thickness to the depth of the melt region, and the region with Ni-48.7 at.% Ti was successfully formed by EB irradiation. The study suggests that the mixing of Ti atoms and Ni atoms was facilitated by fluid flow induced by Marangoni and thermal convections. It is proposed that a more uniform TiNi layer can be achieved through multi-track melting under appropriate conditions. This research demonstrates the feasibility of utilizing EB additive manufacturing as a coating method and the potential for developing TiNi coatings with shape memory effects and pseudoelasticity.

Keywords: commercially pure Ti; TiNi coating; shape memory alloy; pseudoelasticity; wear resistance; electron beam melting

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Additive Manufacturing Letters published an OA paper on that the presence of Mo prevents the freezing of thermal equilibrium vacancies in a beta Ti-15Mo-5Zr-3Al alloy fabricated via laser lithography by positron annihilation and computer simulation.

Masataka Mizuno*, Kazuki Sugita, Kousuke Do, Takuya Ishimoto, Takayoshi Nakano, Hideki Araki:
Stability of vacancies in β-type Ti-15Mo-5Zr-3Al alloy fabricated via laser powder bed fusion,
Additive Manufacturing Letters, 7, (2023), 100162; 1-7.
https://doi.org/10.1016/j.addlet.2023.100162

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Abstract
The structural instability in the β-type titanium alloys could affect the stability of vacancies. The stability of vacancies in a β-type Ti-15Mo-5Zr-3Al alloy, fabricated via laser powder bed fusion (LPBF), was investigated using positron annihilation spectroscopy and first-principles calculations. The observed positron lifetimes were close to the experimental and calculated bulk lifetime of Ti-15Mo-5Zr-3Al, which indicates that vacancies were not detected in Ti-15Mo-5Zr-3Al by positron lifetime measurements. Therefore, for the first time, it has been confirmed that quenched-in vacancies are not introduced in the LPBF-manufactured β-type Ti-15Mo-5Zr-3Al despite the fast cooling rate in LPBF process. This feature is preferable for the structural stability in biomedical and industrial applications. The calculated atomic displacement from the ideal bcc lattice positions decreased in β-type Ti-Mo alloys with increasing Mo concentration, indicating that the bcc structure was stabilized by the added Mo. The calculated vacancy formation energies of Ti atoms in β-type Ti-14.5Mo and Ti-27.0Mo alloys exhibited an increasing trend with an increasing number of neighboring Mo atoms. Mo atoms also increased the migration energies of the neighboring paths of vacancies. The calculated results for Ti-15Mo-5Zr-3Al suggest that, while the bcc structure was stabilized by the Mo atoms in Ti-15Mo-5Zr-3Al, the migration and formation energies were still low enough for the diffusion of vacancies.

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A paper determining the quantification of thresholds for auditory brainstem responses has been published as an OA article in the International Journal of Molecular Sciences (IF=5.6).

Kenji Tanaka, Shuma Ohara, Tadaaki Matsuzaka, Aira Matsugaki*, Takuya Ishimoto, Ryosuke Ozasa, Yukiko Kuroda, Koichi Matsuo, Takayoshi Nakano*:
Quantitative threshold determination of auditory brainstem responses in mouse models,
International Journal of Molecular Sciences, 24(14), (2023), 11393; 1-12.
https://doi.org/10.3390/ijms241411393

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Abstract
The auditory brainstem response (ABR) is a scalp recording of potentials produced by sound stimulation, and is commonly used as an indicator of auditory function. However, the ABR threshold, which is the lowest audible sound pressure, cannot be objectively determined since it is determined visually using a measurer, and this has been a problem for several decades. Although various algorithms have been developed to objectively determine ABR thresholds, they remain lacking in terms of accuracy, efficiency, and convenience. Accordingly, we proposed an improved algorithm based on the mutual covariance at adjacent sound pressure levels. An ideal ABR waveform with clearly defined waves I-V was created; moreover, using this waveform as a standard template, the experimentally obtained ABR waveform was inspected for disturbances based on mutual covariance. The ABR testing was repeated if the value was below the established cross-covariance reference value. Our proposed method allowed more efficient objective determination of ABR thresholds and a smaller burden on experimental animals.

Keywords:
auditory brainstem responses (ABR); auditory function; ABR threshold; correlation coefficient; cross-covariance

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A collaborate research paper with Tokyo Dental College on alveolar bone microstructure around orthodontic anchor screws was published as an OA article in Journal of Functional Biomaterials (IF=4.901).

Keisuke Okawa, Satoru Matsunaga*, Norio Kasahara, Masaaki Kasahara, Chie Tachiki, Takayoshi Nakano, Shinichi Abe, Yasushi Nishii:
Alveolar Bone Microstructure Surrounding Orthodontic Anchor Screws with Plasma Surface Treatment in Rats,
Journal of Functional Biomaterials, 14(7), (2023), 356: 1-12.
https://doi.org/10.3390/jfb14070356

click here for this paper.

Abstract
A lateral load was applied to anchor screws that had undergone surface treatment, and the structure, cellular dynamics, and quality of the bone surrounding anchor screws were analyzed to investigate the effect of this surface treatment on the peri-implant jawbone. In addition, bone microstructural characteristics were quantitatively evaluated for each site of loading on the bone around the anchor screw. Rats were euthanized after observation on days 3, 5, or 7, and bone quality analyses were performed. Bone-implant contact rate increased more rapidly at an early stage in the treated surface group than in the untreated surface group. Bone lacuna morphometry showed that the measured values adjacent to the screw at the screw neck on the compressed side (A) and at the screw tip on the uncompressed side (D) were significantly lower than those at the screw tip on the compressed side (B) and at the screw neck on the uncompressed side ©. Collagen fiber bundle diameter showed that the measured values adjacent to regions A and D were significantly higher than those at regions B and C. Anchor screw surface activation facilitates initial bone contact of the screw, suggesting that early loading may be possible in clinical practice.

Keywords
bone quality; biological apatite orientation; collagen fiber; miniscrews; horizontal loading

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A paper on guidelines for controlling the crystal aggregation structure of metastable beta Ti alloys by LPBF has been published as an OA paper in Materials Letters (IF=3.574).

Takuya Ishimoto, Ryoya Suganuma and Takayoshi Nakano*:
Tailoring the crystallographic texture of biomedical metastable β-type Ti-alloy produced via laser powder bed fusion using temperature-field simulations,
Materials Letters, 349, (2023), 134835; 1-4.
https://doi.org/10.1016/j.matlet.2023.134835

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Abstract
Recently, the use of laser powder bed fusion (LPBF) to create crystallographic textures, such as single-crystal-like and polycrystalline textures, has attracted attention. However, the relationship between the LPBF conditions and the resulting texture is unclear. This study investigates the effects of the LPBF conditions (laser power and scanning speed) on the texture by estimating the solidification behavior using temperature-field simulations. Herein, we show for the first time that laser power and scanning speed negatively and positively affect the so1lidification rate R, respectively, and do not affect the thermal gradient G significantly. Thus, when the laser power decreases and scanning speed increases, the G/R ratio decreases and polycrystal formation is enhanced. This is consistent with practical observations.

Keywords
Laser powder bed fusion, Crystallographic texture, Single crystal, Polycrystal, Temperature simulation

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Next-generation catalysts with high activity, high selectivity, and high temperature durability were successfully prepared by laser metal 3D printing and published as an OA paper in Advanced Functional Materials (IF=19.9).

Hyo-Jin Kim, Kohsuke Mori*, Takayoshi Nakano, Hiromi Yamashita:
Robust Self-Catalytic Reactor for CO2 Methanation Fabricated by Metal 3D Printing and Selective Electrochemical Dissolution,
Advance Functional Materials, (2023), 2303994; 1-21.
https://doi.org/10.1002/adfm.202303994

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Abstract
The methanation of CO2 has been actively pursued as a practical approach to mitigating global climate change. However, the complexity of the catalyst development process has hindered the development of new catalysts for CO2 methanation; as a result, few catalysts are commercially available. Herein, a multifunctional self-catalytic reactor (SCR) is prepared via metal 3D printing and selective electrochemical dissolution as a method to not only simplify the catalyst development process but also fabricate active catalysts for CO2 methanation. The combination of metal 3D printing and selective electrochemical dissolution is demonstrated as a feasible method to prepare active catalysts for the methanation of CO2 in a short time. In addition, the use of an electrochemical method enables the formation of galvanic cells on the SCR; these cells continuously generate active sites via self-dissolution during a simple refresh process, resulting in high reusability of the SCR. The proposed method represents a new facile technique to fabricate highly reusable catalysts that exhibit superior performance for CO2 methanation, and the results provide a guideline for preparing metal 3D-printed catalysts that will satisfy industrial demand.

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Metals (IF=2.695) published a paper on soluble intermetallic compounds as an OA paper.

Koji Hagihara*, Shuhei Shakudo, Toko Tokunaga, Takayoshi Nakano:
Development of Zn-Mg-Ca biodegradable dual-phase alloys,
Metals, 13 [6], (2023), 1095; 1-13.
https://doi.org/10.3390/met13061095

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Abstract
In this paper, in order to achieve the development of a novel biodegradable dual-phase alloy in a Ca-Mg-Zn system, the establishment of the control strategy of degradation behavior of alloys composed of two phases was attempted by the control of alloy composition, constituent phases, and microstructure. By combining two phases with different dissolution behavior, biodegradable alloys are expected to exhibit multiple functions. For example, combining a suitable slow dissolving phase with a faster dissolving second phase may allow for dynamical concavities formation during immersion on the surface of the alloy, assisting the invasion and establishment of bone cells. Without the careful control of the microstructure, however, there is a risk that such dual-phase alloy rapidly collapses before the healing of the affected area. In this study, ten two-phase alloys consisting of various different phases were prepared and their degradation behaviors were examined. Consequently, it was found that by combining the IM3 and IM1 intermetallic phases with the compositions of Ca2Mg5Zn13 and Ca3Mg4.6Zn10.4, the expected degradation behavior can be obtained.
Keywords: biodegradable metallic material; dual-phase alloy; intermetallic compound; degradation behavior

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Frontiers in Earth Science-Paleontology (IF=3.661) has published an article on "Life history evolution of insular dwarfism" as an OA article.

Shoji Hayashi*, Mugino O. Kubo*, Marcelo R Sanchez, Hiroyuki Taruno, Masako Izawa, Tsunehiro Shiroma, Takayoshi Nakano and Masaki Fujita:
Variation and process of life history evolution in insular dwarfism as revealed by a natural experiment,
Frontiers in Earth Science-Paleontology, (2023), in press.
https://doi.org/10.3389/feart.2023.1095903

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A paper on X-scan 3D image construction of SUS316L stainless steel formed by AM was published in Journal of Imaging.

Keiya Sugiura, Toshio Ogawa, Yoshitaka Adachi*, Fei Sun, Asuka Suzuki, Akinori Yamanaka, Nobuo Nakada, Takuya Ishimoto, Takayoshi Nakano, Yuichiro Koizumi:
Big-Volume SliceGAN for Improving a Synthetic 3D Microstructure Image of Additive-Manufactured TYPE 316L Steel,
Journal of Imaging, 9 [5], (2023), 90; 1-12.
DOI: https://doi.org/10.3390/jimaging9050090

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Abstract: A modified SliceGAN architecture was proposed to generate a high-quality synthetic three-dimensional (3D) microstructure image of TYPE 316L material manufactured through additive methods. The quality of the resulting 3D image was evaluated using an auto-correlation function, and it was discovered that maintaining a high resolution while doubling the training image size was crucial in creating a more realistic synthetic 3D image. To meet this requirement, modified 3D image generator and critic architecture was developed within the SliceGAN framework.

Keywords: SliceGAN; generative adversarial network; synthetic 3D image; additive manufacturing; autocorrelation function

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A collaborate research paper with Northeastern University on beta-titanium alloys containing high concentrations of Zr has been published as an OA paper in the Journal of Alloys and Compounds (JALCOM) (IF=6.371).

Xiaoli Zhao*, Rongxin Zhu, Wenke Song, Lei Meng, Mitsuo Niinomi, Takayoshi Nakano, Nan Jia, Deliang Zhang:
A strategy to regulate the yield ratio of a metastable high Zr-containing β titanium alloy: Synergistic effects of the β domain, β stability and β/α interfaces by varying the α phase content,
Journal of Alloys and Compounds, 952, (2023), 170024; 1-13.
https://doi.org/10.1016/j.jallcom.2023.170024

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Abstract
To meet the demands of both processing and serving, to the best of our knowledge, this is the first report exhibiting large range control of the yield ratio from 0.31 to 0.96 with decent elongations over 10% in the same alloy with low-cost thermal treatments. The yield ratio of the metastable Ti-30Zr-5Mo alloy was regulated via adjusting trigger stress of the stress-induced phase transformation and work-hardening ability through changing the α phase content. Materials with acicular α phase of different contents were successfully prepared via low-cost thermal treatment. The effects of the α phase content on the stress-induced α' martensite phase transformation and work hardening behavior were then investigated. In the Ti-30Zr-5Mo alloy with dual phases, due to the crystal difference and element partitioning, the hardness of the α phase is higher than that of the β matrix, and the hardness difference between the phases increases with increasing α phase. In addition to Mo, Zr plays an important role in stabilizing the β phase in high-Zr-containing alloys. Deformation initiates in the β phase of both single-phase and duplex-phase alloys. The deformation mechanism of the β phase is dependent on both the β domain and β stability. Due to the low trigger stress and excellent work hardening ability, stress-induced α' martensite phase transformation is helpful to lower the yield ratio. As the α phase content increases, the trigger stress increases, and when the α phase content increases to 40%, dislocation slip dominates rather than stress-induced α' martensite phase transformation, and a high yield strength of 944 MPa is obtained. The α/β phase interfaces act as effective obstacles to hinder dislocation movement and provide working hardening, and the obstruction effect is more significant with an increase in the hardness difference between the α and β phases. The stress-induced α' phase transformation and/or the deformation coordination between the α and β phases guarantee decent elongations of no less than 10% in the large control of the yield ratio from 0.31 to 0.96 with a yield strength from 254 to 1013 MPa. It paves the way to develop "Unititaniam" alloys for wide possible applications.

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A paper on the demonstration of intervertebral spacers capable of inducing bone orientation has been published as an OA article in The Spine Journal.

Aira Matsugaki, PhD, Manabu Ito, MD, PhD, Yoshiya Kobayashi, Meng, Tadaaki Matsuzaka, Meng, Ryosuke Ozasa, PhD, Takuya Ishimoto, PhD, Hiroyuki Takahashi, PhD, Ryota Watanabe, Meng, Takayuki Inoue, PhD, Katsuhiko Yokota, BA, Yoshio Nakashima, Meng, Takashi Kaito, MD, PhD, Seiji Okada, MD, PhD, Takao Hanawa, PhD, Yukihiro Matsuyama, MD, PhD, Morio Matsumoto, MD, PhD, Hiroshi Taneichi, MD, PhD, Takayoshi Nakano*, PhD:
Innovative design of bone quality-targeted intervertebral spacer: Accelerated functional fusion guiding oriented collagen/apatite microstructure without autologous bone graft,
The Spine Journal, 23, (2023), 609-620.
DOI: https://doi.org/10.1016/j.spinee.2022.12.011

[Abstract]
●BACKGROUND CONTEXT
Although autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting.
●PURPOSE
We developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure.
●STUDY DESIGN
This was an in vivo animal study.
●METHODS
Intervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2-L3 or L4-L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests.
●RESULTS
The spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The push-out load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix.
●CONCLUSIONS
The developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft.
●CLINICAL SIGNIFICANCE
Our results provide a foundation for designing future spacers for interbody fusion in human.

[Keywords]
Bone quality, Collagen and apatite orientation, Intervertebral spacer, Push-out strength, Spinal fusion, Through-pore grooved surface structure

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A paper on the control of crystal orientation structure by gas flow direction and the elucidation of the mechanism has been accepted for publication as an OA paper in Virtual and Physical Prototyping (IF=10.962).

Hiroki Amano, Takuya Ishimoto, Koji Hagihara, Ryoya Suganuma, Keisuke Aiba, Shi-Hai Sun, Pan Wang, Takayoshi Nakano*:
Impact of gas flow direction on the crystallographic texture evolution in laser powder bed fusion,
Virtual and Physical Prototyping, (2023), in press.

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The paper was published as an OA article in MDPI's Materials (IF=3.748).

Kazuhisa Sato*, Shunya Takagi, Satoshi Ichikawa, Takuya Ishimoto, Takayoshi Nakano:
Microstructure and Solute Segregation Around the Melt Pool Boundary of Orientation-Controlled 316L Austenitic Stainless Steel Produced by Laser Powder Bed Fusion,
Materials, 16(1), (2023), 218; 1-10.
DOIhttps://doi.org/10.3390/ma16010218

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A paper on an international collaborative study that found boronated hydroxyapatite to have a strong affinity with osteoblasts was published as an OA article in Ceramics International (IF=5.532).

Ozkan Gokcekaya, Celaletdin Ergun*, Thomas J. Webster, and Takayoshi Nakano:
Influence of precursor deficiency sites for borate incorporation on the structural and biological properties of boronated hydroxyapatite,
Ceramics International, (2022),
DOI: https://doi.org/10.1016/j.ceramint.2022.10.232

Abstract
The biological properties of hydroxyapatite (HA) are significantly influenced by its compositional characteristics especially doping elements and/or Ca/P ratio, which can be altered by precursor chemistry. In this study, a group of boronated (B-incorporated) hydroxyapatite (BHA) was synthesized using a precipitation method by setting the Ca/P ratio to the stoichiometric value of HA (1.67), while altering the precursor chemistry by adjusting either (Ca + B)/P (Ca-deficient precursor, BC) or Ca/(P + B) (P-deficient precursor, BP). After heat-treatment, the partial decomposition of the BC was observed, forming tricalcium phosphate as the byproduct, however, the BP showed phase stability at all temperatures. The B-ionic species in the form of (BO2)− and (BO3)3− were incorporated into the HA structure at the (PO4)3− and (OH)− positions, respectively. The incorporation of the B species also facilitated the incorporation of (CO3)2− groups specifically in the BPs. This is the first finding on BHA reporting that preferential (CO3)2− incorporation depends on the precursor chemistry used. As a result, osteoblast adhesion was superior on the BPs compared to pure HA owing to the carbonated structure, increasing cell spreading area. As such, this in vitro study highlighted that the present P-deficient precursor approach for synthesizing BHA improved biocompatibility properties and should, thus, be further considered for the next-generation of improved orthopedic applications.

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A paper elucidating how to control tissue and mechanical properties based on Scalmalloy(R) scanning strategies has been published as an OA paper in Crystals (IF=2.670).

Yusufu Ekubaru, Ozkan Gokcekaya, Takayoshi Nakano*,
Effects of Scanning Strategy on the Microstructure and Mechanical Properties of Sc-Zr-Modified Al-Mg Alloy Manufactured by Laser Powder Bed Fusion,
Crystals, 12, (2022), 1348; 1-13.
DOI: https://doi.org/10.3390/cryst12101348

Abstract
Laser powder bed fusion (LPBF)-manufactured Sc-Zr-modified Al-Mg alloy (Scalmalloy) has a bimodal microstructure comprising coarse grains (CGs) in the hot melt pool area and ultrafine grains (UFGs) along the melt pool boundaries (MPBs). Owing to these microstructural features, an increase in the MPBs can increase the UFGs, leading to enhanced mechanical properties. However, the effects of the LPBF process parameters, especially the laser scan strategy, on the microstructure and mechanical properties of Scalmalloy are still unclear. Here, a comparative study was conducted between X- and XY-mode laser scan strategies, with the same volumetric energy, based on the melt pool configuration, grain size distribution, and precipitation behaviors. The X-scan exhibited mechanical properties superior to those exhibited by the XY-scan, attributed to the higher volume fraction (VF) of UFGs. An increase in the VF of UFGs was observed, from 46% for the XY-scan to 56% for the X-scan, owing to an increase in MPBs. Consequently, the tensile strength of the X-scan was higher than that of the XY-scan. The maximum yield strength (271.5 ± 2.7 MPa) was obtained for the X-scan strategy, which was approximately twice that obtained for casting. The results of this study demonstrate that the microstructure and mechanical properties of Scalmalloy can be successfully tuned by a laser scanning strategy.

Keywords: laser powder bed fusion; Scalmalloy; ultrafine grain; precipitation; melt pool

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The following four commentary papers will be published as OA papers in Materials Transactions.

Ryosuke Ozasa, Aira Matsugaki, Takuya Ishimoto, Takayoshi Nakano*:
Review - Research and development of titanium-containing biomedical high entropy alloys (BioHEAs) utilizing rapid solidification via laser-powder bed fusion,
Materials Transactions, (2022), in press.

Ishimoto Takuya, Takayoshi Nakano*:
Review - Microstructural control and functional enhancement of light metal materials via metal additive manufacturing,
Materials Transactions, (2022), in press.

Aira Matsugaki*, Tadaaki Matsuzaka, Takayoshi Nakano:
Review - Metal additive manufacturing of titanium alloys for control of hard tissue compatibility,
Materials Transactions, (2022), in press.

Hiroki Amano*, Takuya Ishimoto, Takayoshi Nakano
Review - Importance of Atmospheric Gas Selection in Metal Additive Manufacturing: Effects on Spatter, Microstructure, and Mechanical Properties,
Materials Transactions, (2022), in press.

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