There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Additive manufacturing of metallic components – Process, structure and properties

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Additive manufacturing of metals

Selective Electron Beam Melting of Oxide Dispersion Strengthened Copper

Bulk metallic glasses (BMGs), due to their amorphous structure, exhibit remarkable mechanical properties, and there is an increasing interest in their commercialization. For the industrial fabrication of BMG, knowledge about the isothermal crystallization kinetics of industrial-grade BMG is required. Previous investigations on isothermal crystallization kinetics are mainly based on high-purity samples with very good glass forming ability and/or mainly limited to the low temperature regime. In the present study, a systematic investigation on the isothermal crystallization kinetics of an industrial-grade Zr-based BMG (Zr 59.3 Cu 28.8 Al 10.4 Nb 1.5 at.%, trade name: AMZ4) has been performed using conventional and flash differential scanning calorimetry. We report the time-temperature-transformation (TTT) diagrams of the AMZ4 with two different oxygen levels. The diagrams cover the temperature range from glass transition temperature up to liquidus temperature, that have the typical “C-shaped” noses. Faster crystallization of the higher oxygen level AMZ4 was observed, and the underlying mechanisms were investigated. The universal isothermal Johnson-Mehl-Avrami-Kolmogorov (JMAK) model was employed to model the isothermal crystallization kinetics. Satisfactory match was achieved between the experimental facts and the JMAK model, and the interfacial energies between the crystalline phase and liquid were determined as ∼ 0.04 J/ m 2 for the industrial-grade AMZ4. The crystallization fraction dependence of Avrami index and activation energy is studied and found to be neglectable in the JMAK modeling. The critical casting thicknesses were estimated based on the TTT diagrams.

Isothermal crystallization kinetics of an industrial-grade Zr-based bulk metallic glass

Our contribution demonstrates that the combination of additive manufacturing and electrophoretic deposition offers great potential for the future manufacturing of tailor-made catalytic structures for continuous flow applications. A new protocol for the controlled and homogeneous coating of both electrodes of interpenetrating porous open cell structures (interPOCS) with layers of boehmite is presented. Moreover, it has been found that by applying different coating voltages in an electrophoretic deposition (EPD) process, the properties of the obtained coating can be fine-tuned with respect to layer thickness, density, and porosity. This offers very interesting options for optimizing the catalysis-relevant properties from two sides by the use of the special interPOCS support design and by adjusting the coating through the parameters of the EPD coating process.

Electrophoretic deposition of boehmite on additively-manufactured, interpenetrating periodic open cellular structures for catalytic applications

Using suitable scanning strategies, even single crystals can emerge from powder during additive manufacturing. In this paper, a full microstructure map for additive manufacturing of technical single crystals is presented using the conventional single crystal Ni-based superalloy CMSX-4. The correlation between process parameters, melt pool size and shape, as well as single crystal fraction, is investigated through a high number of experiments supported by numerical simulations. Based on these results, a strategy for the fabrication of high fraction single crystals in powder bed fusion additive manufacturing is deduced.

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A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy.

In the present paper criteria are presented for precision machining with laser beams. It is outlined that a copper vapour laser system (CVL) consisting of an unstable resonator, subsequent amplifiers, a suitable synchronizing unit, an optical system for beam forming and guiding and an CNC-handling system fulfills most of these requirements. Machining speeds are given for different materials. Finally, examples are shown for possible applications of CVL-processing.

Carolin Körner

Papers

Selective Electron Beam Melting of Oxide Dispersion Strengthened Copper

Isothermal crystallization kinetics of an industrial-grade Zr-based bulk metallic glass

Electrophoretic deposition of boehmite on additively-manufactured, interpenetrating periodic open cellular structures for catalytic applications

A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy.

Precision Machining with Copper Vapour Lasers