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Material shaping and joining are the two fundamental processes that lie at the core of many forms of metal manufacturing techniques, including additive manufacturing. Current metal additive manufacturing processes such as laser/e-beam powder bed fusion and Directed Energy Deposition predominantly use heat and subsequent melt–fusion and solidification to achieve shaping and joining. The energy efficiency of these processes is severely limited due to energy conversion losses before energy is delivered at the point of melt–fusion for shaping and joining, and due to losses through heat transfer to the surrounding environment. This manuscript demonstrates that by using the physical phenomenon of lowered yield stress of metals and enhanced diffusion in the presence of low amplitude high frequency oscillatory strain, metal shaping and joining can be performed in an energy-efficient way. The two performed simultaneously enable a metal additive manufacturing process, namely Resonance-Assisted Deposition (RAD), that has several unique capabilities, like the ability to print net-shape components from hard-to-weld alloys like Al6061 and the ability to print components with a very high aspect ratio. In this study, we show this process's capabilities by printing solid components using aluminum-based metal alloys. [ABSTRACT FROM AUTHOR]

Metal 3D printing is revolutionizing the industry by enabling rapid and cost‐effective production of complex metal 3D products with intricate geometries, attracting significant attention in recent years. Particularly, metal 3D‐printed catalysts have emerged as a cutting‐edge fusion technology that serves as both catalysts and reactors, referred to as self‐catalytic reactors (SCRs). Therefore, this concept article aims to introduce the recent advancements in metal 3D printing technology in the catalyst and reactor field, and illustrate the various aspects for the rational design of self‐catalytic reactors. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing (AM) is a layer-by-layer process that makes the direct manufacturing of various industrial parts possible. This method facilitates the design and fabrication of complex industrial, advanced, and fine parts that are used in different industry sectors, such as aerospace, medicine, turbines, and jewelry, where the utilization of other fabrication techniques is difficult or impossible. This method is advantageous in terms of dimensional accuracy and fabrication speed. However, the parts fabricated by this method may suffer from faults such as anisotropy, micro-porosity, and defective joints. Metals like titanium, aluminum, stainless steels, superalloys, etc., have been used—in the form of powder or wire—as feed materials in the additive manufacturing of various parts. The main criterion that distinguishes different additive manufacturing processes from each other is the deposition method. With regard to this criterion, AM processes can be divided into four classes: local melting, sintering, sheet forming, and electrochemical methods. Parameters affecting the properties of the additive-manufactured part and the defects associated with an AM process determine the method by which a certain part should be manufactured. This study is a survey of different additive manufacturing processes, their mechanisms, capabilities, shortcomings, and the general properties of the parts manufactured by them. [ABSTRACT FROM AUTHOR]

Despite the variety of different methods of metal 3D printing on Earth, only a few of them can be realized in space. Processes that employ electron beam as a heat source and wire as a consumable material is among the most promising methods for these applications. But to date, such processes still have not been implemented in actual space operation, mainly due to the low accuracy and resolution of these 3D printed products that require significant post-processing for their intended use. Large and heavy hardware employed in these processes is another significant problem. xBeam 3D Metal Printing is the electron beam DED-wire additive manufacturing technology that has already demonstrated the capability to produce high-quality parts with high productivity on terrestrial relatively lightweight and compact hardware. xBeam process employs a profile electron beam generated by low-voltage gas-discharge electron beam guns combined with the coaxial wire feed to provide excellent control of metallurgy processes in the melt pool and around it during deposition. Realized metallurgy conditions are the crucial factor in providing the combination of high accuracy and resolution with good metal structure and properties. Moreover, maintaining such metallurgy conditions does not require gravity—only cohesion/adhesion forces and surface tension forces are involved. This fact suggests good prospects for using the xBeam 3D Metal Printing in space applications. In addition, the method opens several unique technological opportunities that are important in space exploration, including the nonstick deposition technique allowing the production of "ready-to-use" parts, surface glazing able to substitute machining, recycling of the metal waste directly into wire for 3D printing, and others. The article presents technical solutions for implementing 3D printing and related processes in space conditions and analyzes the metallurgical aspects of the technology using titanium alloy Ti-6Al-4V as an example. [ABSTRACT FROM AUTHOR]

3D printing technology can rapidly transform digital model into physical realization, and has been widely studied in many fields. However, its developments are very slow in the fields of catalysis and reaction engineering, due to harsh application environments. Here, we report that metal 3D printing is used to prepare Nickel‐based Self‐Catalytic Reactor (Ni‐SCR) for COx methanation. The optimized Ni‐SCR samples exhibit unique surface properties. The catalytic results reveal that they also possess premium methanation performance. This work will facilitate the developments both in 3D printing technologies and novel catalytic systems. [ABSTRACT FROM AUTHOR]

• Removable partial denture frameworks prepared by three methods. • Digital evaluation tool for internal discrepancy assessment of denture frameworks. • Metal 3D printed partial denture frameworks meet the clinical standards. To evaluate the accuracy of metal 3D printed frameworks (MEP group) for removable partial dentures (RPDs) by digital superimposition, in comparison to that of frameworks produced by the conventional (CON group) and resin printing/casting (RPC group) workflows. A partially edentulous maxillary dentiform was prepared with rest seats and guiding planes on the right canine, left first premolar, and left second molar. Thirty master casts were prepared via repeated impressions of the dentiform. Frameworks were fabricated by three different workflows (n = 10 for each group). The internal discrepancies of the frameworks were assessed at 12 points by digital scanning with an optical triangulation principle-based tabletop scanner and superimposition using a reference best-fit alignment method. First, the master cast was scanned alone. Subsequently, a thin silicone material was applied to the framework and fitted onto the master cast, after which the framework was removed. Finally, the master cast with the silicone material attached was rescanned. The data from the two scans were matched, with the reference being the area not occupied by the silicone. For the CON, MEP, and RPC groups, respectively, the mean overall internal discrepancies (279.72 µm, 241.02 µm, and 331.70 µm), and the mean internal discrepancies on palate areas (292.92 µm, 250.72 µm, and 355.84 µm) and rest seat areas (240.12 µm, 211.91 µm, and 259.26 µm) did not significantly differ among the three fabrication methods (p = 0.558, 0.542, and 0.774). The reference best-fit alignment of scan datasets is a useful approach to evaluate the internal discrepancy of frameworks. Metal 3D printing produces RPD frameworks that are comparable to conventional frameworks and meet clinical standards. [ABSTRACT FROM AUTHOR]

Currently, the Republic of Korea operates a total of 28 nuclear power plants, including those under construction. Although every part of a nuclear power plant is important for safe operation, most attention is paid to the nuclear fuel assembly. The assembly is divided into fuel rods containing fuel assembly fuel and spacer grids. The spacer grid is an important component for core cooling by keeping the fuel rods protected and spaced apart. The spacer grid is produced from a strap bar, which is the base plate, and by spot welding eight edges of the strap bar. However, the spot welding machine has a large capacity and power supply such that the welding quality varies depending on the weld metal and surface conditions. As a result, the welding point may be defective. Therefore, this study aims to analytically verify the performance of a newly designed spacer grid for metal 3D AM as well as present analytical criteria for product development. [ABSTRACT FROM AUTHOR]

The objective of this work is to establish a volumetric metal 3-dimensional (3D) printing system based on material extrusion method and to fabricate metal patterns by investigating various process variables. Numerical heat transfer simulation was conducted to design the nozzle system with a minimized heat loss at the nozzle tip. Based on the simulation results, a metal 3D printing system with X, Y, and Z stages was constructed. The effects of lead content in molten metals and printing conditions such as stage speed and flow rate were investigated. The line formation like bulged, uniform, and dashed lines was evaluated using an optical microscope, and the variation in line widths of uniform lines was investigated with the process variables. Various types of 2-dimensional (2D) patterns were fabricated with an optimized process variable. A simple 3D structure was obtained to demonstrate the feasibility of the proposed system and procedure. [ABSTRACT FROM AUTHOR]

Additive manufacturing technologies based on metal are evolving into an essential advanced manufacturing tool for constructing prototypes and parts that can lead to complex structures, dissimilar metal-based structures that cannot be constructed using conventional metallurgical techniques. Unlike traditional manufacturing processes, the metal AM processes are unreliable due to variable process parameters and a lack of conventionally acceptable evaluation methods. A thorough understanding of various diagnostic techniques is essential to improve the quality of additively manufactured products and provide reliable feedback on the manufacturing processes for improving the quality of the products. This review summarizes and discusses various ex-situ inspections and in-situ monitoring methods, including electron-based methods, thermal methods, acoustic methods, laser breakdown, and mechanical methods, for metal additive manufacturing. [ABSTRACT FROM AUTHOR]

We present a fundamental study on the development of trimming dies at room temperature for the hot-stamping process using directed energy deposition. Specimens of G and F materials were fabricated by machining 3D-printed blocks. The hardness of G-layered specimens was slightly higher than that of F-layered specimens, reaching approximately 700 HV at the surface. The G-layered specimens consisted of columnar and equiaxed dendrites, whereas the F-layered specimens mainly consisted of equiaxed dendrites. Spherical pores were observed inside the layered cross section, whereas relatively large irregular-shaped cavities were observed in layered boundaries. The tensile strengths of the G-layered and F-layered specimens were approximately 1800 and 1650 MPa, respectively. During bonding strength tests on an area bonded with S45C base metal, a fracture occurred in one case because of the lack of fusion at the boundary, and the F-layered specimens showed a lower strength than the G-layered ones. During wear tests on a quenched 1.5 GPa-grade aluminized steel plate, the F-layered specimens showed lower wear loss. However, the G-layered specimens showed better wear resistance during wear tests on a 1.5 GPa-grade electrogalvanized steel plate. These findings serve as fundamental data for additive manufacturing processes using tool steels of high-strength materials with high melting points. [ABSTRACT FROM AUTHOR]