In powder bed fusion (PBF)-based additive manufacturing, three-dimensional products are fabricated by the accumulation of minute solidified sections based on tiny melt pools, each of which has dimensions of about 100 μm. Therefore, the solidification structure of PBF-fabricated material is characterized by periodic repetitions on a scale smaller than the melt pool size. This is quite different from casting, in which solidification progresses more macroscopically and transitions of, for example, segregation and grain characteristics occur on a macroscopic scale. In other words, it is possible to obtain a product with a homogeneous microstructure throughout by homogeneously controlling solidification behavior in each melt pool in a PBF. This article reviews the relationship between solidification behavior in the melt pools and melt pool geometry, and evolved microstructure, especially crystallographic texture. It also discusses how such texture control contributes to mechanical properties of metallic materials from view points of an environment and energy.

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 In recent years, in order to achieve carbon neutrality, improving the fuel efficiency of aircraft jet engines has become an important issue in the field of air transportation. TiAl alloys have received considerable attention for aircraft engine application due to their low density and excellent high temperature strength. However, the poor ductility and high reactivity of the alloys hinder their precise manufacturing, resulting in large amounts of material waste and high manufacturing costs. Thus, it is necessary to establish an innovative manufacturing process for the alloys. Recently, electron beam powder bed fusion （EB-PBF） has attracted much attention to fabricate TiAl alloys since the process can build 3D objects with complex shape. Recently, our research group has revealed that EB-PBF is a tool that can control the microstructure and mechanical properties of the alloys. In this article, we describe the microstructural control of β-containing TiAl alloys through EB-PBF. In particular, we illustrate the influences of heat input/ extraction on microstructure, as well as latest developments and efforts in optimizing process conditions using a machine learning.

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 Biomedical materials used for reconstructing bone function lost due to trauma or disease include artificial joints, bone fixation materials, and bone replacement materials, which are indispensable medical devices in the treatment of orthopedic-related diseases. Their roles are not limited to physically replacing a defective site and acting as a scaffold for bone regeneration. In recent years, medical devices that work on the molecular and cellular level to realize functional repair of tissues and organs through integration with the living body have been developed. The design of biocompatible and biofunctional surfaces requires a spatial and temporal hierarchy of interface phenomena between non-living materials and living organisms. The control of the properties of these artificial materials through their design, processing methods, and surface treatment techniques is closely related to local cell adhesion, tissue regeneration, and systemic metabolic reactions. Bone engineering research, including the creation of such materials, is indispensable in supporting bone medicine, as it affects from molecular adsorption at the bio/material interface to the control of cell adhesion, bacterial adhesion, and immune response, from biochemical reactions occurring in milliseconds to bone connectivity over a period of years. In addition, advances in technologies, including additive manufacturing, can establish surface property control targeting selective activation of biomolecules, from advanced nanoscale structural control to single-molecule chemical modification. In particular, additive manufacturing is a promising technology that can achieve high spatial resolution for micrometer-order cell control and high corrosion resistance that leads to a reconstruction of tissues and organs through controlling the bio/materials interfacial reactions. The control of bio functions through the molding of external and internal shapes and the control of their crystallographic organization is expected to make a significant contribution to the realization of bone quality-targeted medicine, which has been difficult to achieve with conventional materials technology alone. Furthermore, it is expected to play a significant role in the future development of ultra early disease prediction and digital medical technology. The elucidation of atomic-scale phenomena at the interface between non-living organisms and living organisms will make it possible to realize bone treatment tailored to the pathology and skeletal structure of each patient by accumulating fundamental knowledge and understanding it from a multilevel perspective.

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 Solute segregation significantly af fects material properties and is an essential issue in powder-bed fusion （PBF） type additive manufacturing of Ni-based superalloys. This paper introduces the computational studies of solute segregations in the Hastelloy-X Ni-based superalloy under the PBF process predicted by the multi-phase field and Scheil-Gulliver models. These studies suggest that significant solute segregation occurs under rapid cooling conditions and increases the liquation crack susceptibility.

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 Laser-based powder bed fusion of metals （PBF-LB/M） method, a type of additive manufacturing （AM）, is generally known as a technology that enables fabrication of arbitrary three-dimensional shapes with layer-by-layer melting and solidification of metallic powders using laser as a heat source. In recent years, we proposed that the PBF-LB/M method can create a unique temperature field that achieves a directional and rapid solidification, leading to enhance functionality in various metallic materials. Such a control of material properties and functionality could not be realized with conventional fabrication methods. This paper reviews the control of material properties and functionality of the products developed by the PBF-LB/M method with focus on extremely high cooling rate （~10⁷ K/s） originated from a large thermal gradient and solidification rate.

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 Titanium and magnesium alloys have been applied as structural and biological materials because of their superior high specific strength. However, since they are thermodynamically immiscible, effective bonding methods have not been established. We have recently designed a dealloying bonding method to join thermodynamically immiscible metals. In the dealloying method using metallic melt, only specific components are selectively leached from the precursor alloy into the metallic melt by differences in chemical interactions, while the remaining components self-assemble into a porous form. When the metal melts solidifies, bicontinuous microstructure of the residual phase and the solidified phase is formed, which mechanically bonds the immiscible phase. We have already succeeded in bonding pure Fe and pure Mg by this method, and here we report the extension of the usefulness of this technique to joining pure Ti and pure Mg in dissimilar materials. To avoid melting the entire Mg matrix, eutectic melting of Cu and Mg was used to locally generate liquid metal dealloying at the bonding interface. Although precursor layers and by-products of the dealloying can remain at the bonding interface, these can be eliminated by optimizing the bonding conditions, such as bonding temperature, time, precursor layer thickness, and pressure. When these brittle layers are eliminated from the bonding interface, the tensile fracture strength is highest, yielding a strong mechanical bonding strength that fractures with the Mg base metal. This study offers the possibility of joining other two immiscible metals, and in addition may provide fundamental knowledge for overcoming difficult bonding of practical alloys.

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 This paper introduces the Particle Homogenization Modeling （PHM） method to purpose of manufacturing structural ceramics. This is an improved approach of the binder jetting method. Through the modeling, sintering, and evaluation of parts with thicknesses of 10 to 30 mm, which have been difficult to produce with existing techniques, the characteristics and behavior of this technique during modeling will be explained.

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 Additive manufacturing is a 3D printing technology that creates objects by layering materials based on data from 3D models. Due to improvements in the accuracy of layered modeling and diversification of materials used, it is now used in various fields such as aerospace, automobiles, home appliances, and medicine. In the field of dentistry, the introduction of additive manufacturing has led to significant innovations in treatment in some cases. This paper describes the history of the development of digital and additive technologies and their clinical use in the field of dentistry.

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 Additive manufacturing is a popular manufacturing technique for fabrication of complex geometries that are difficult to form by traditional methods. Geometries such as fractal patterns and various types of lattices can be designed and moulded by layer-wise manufacturing techniques, but also pose certain challenges to overcome, such as complex channels or voids and overhangs. This paper discusses the current state of the art in additive manufacturing of these complex geometries and explores the challenges that must be overcome to enable accurate fabrication with a focus on the use of vat photopolymerisation methods to process ceramic materials.

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  With the advance of nanotechnology, gold nanoparticles (AuNPs) with interesting optical and chemical properties are attracting attention. The reduction reaction of soluble Au precursors such as chloroauric acid (HAuCl₄ ) in an aqueous solution is widely used as the synthetic route of AuNPs. However, coexisting ionic species, especially Cl−, can negatively affect the application of AuNPs, so an additional removal process is necessary. Herein, we report the synthesis of AuNPs using almost insoluble gold hydroxide (Au(OH)₃ ) as the Au precursor in aqueous media. AuNPs were successfully synthesized under mild conditions (pH ～7, 60℃ and 80℃) in the presence of a non-toxic triblock copolymer acting as a reducing and stabilizing agent. The sizes of the AuNPs were 39.3±11.7 nm and 51.0±12.9 nm at 60℃ and 80℃, respectively. The resulting colloidal dispersions of the AuNPs obtained under neutral conditions and without the influence of coexisting the ionic species are expected to apply to catalytic and biological applications where surface activity plays an important role.

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 We performed the comparative studies for the synthesis of high-entropy rare earth (Y_0.2 La_0.2 Nd_0.2 Sm_0.2 Gd_0.2 )BO₄ (B = Cr, Mo, W) oxide powders using the polyol process, co-precipitation process, and solid-state reactions. Zircon-type RECrO₄ powders and scheelite-type REMoO₄ and REWO₄ powders were obtained through the polyol process after being post heated at 600 °C and 800 °C, respectively. The powders synthesized from the co-precipitation process and solid-state reactions were not single-phase high entropy oxides, except that the scheelite-type REWO₄ powders were obtained through the co-precipitation process. This work demonstrated that the polyol process outperforms co-precipitation and solid-state reaction methods in synthesizing single-phase high-entropy rare earth compounds with group 6 elements.

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 Short fiber-reinforced composites (SFRP) are being expanded for use as a material with high specific strength and specific stiffness, and SFRP has good moldability by injection molding. However, the strength and other properties decrease depending on the molding conditions, it is necessary to set optimal molding conditions. Experimental evaluations have been conducted using various shapes, such as flat plates and T-shaped molds, but analytical evaluations are also necessary from an economic and time perspective. In this study, the MPS (Moving Particle Semi-implicit) method was applied to a T-shape mold because of its ability to track the behavior of fibers and resin. As a result, the analysis confirmed the accelerated resin and the resin accelerating after deceleration that was observed in the experiment. In the rib part, it was confirmed that the resin temperature in the center was lower due to the shift of the cooled resin in the plate part. In addition, most of the fibers in the rib part were oriented in the direction of flow due to the acceleration that occurred during the flow into the rib part, but some fibers were found were oriented perpendicular to the flow direction.

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