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10. Microstructure and Mechanical Properties of Ti-6Al-4V In Situ Alloyed with 3 wt% Cr by Laser Powder Bed Fusion.

Author

Goettgens, Valerie Sue, Weber, Luca, Braun, Jakob, Kaserer, Lukas, Letofsky-Papst, Ilse, Mitsche, Stefan, Schimbäck, David, and Leichtfried, Gerhard

Subjects
MICROSTRUCTURE, TENSILE strength, POWDERS, SPECIFIC gravity, ALLOYS
Abstract

This work studied the microstructure and mechanical properties of Ti-6Al-4V in situ alloyed with 3 wt% Cr by laser powder bed fusion (LPBF). Specimens with a relative density of 99.14 ± 0.11% were produced, showing keyhole and lack of fusion pores. Due to incomplete mixing of the components during melting, chemical inhomogeneities were observed in the solidified material. The addition of Cr promoted thermal supercooling during solidification and induced a reduction in the primary β grain size in the longitudinal direction and a weakening of the otherwise strong 〈100〉β texture, both typical issues for Ti-6Al-4V produced by LPBF. The primary β at first transformed martensitically to α', but by preheating the substrate plate to 500 °C and cyclically reheating the material by melting subsequent layers, in situ martensite decomposition was achieved, resulting in a fine lamellar α + β microstructure. In addition, the B19 phase was detected in the β matrix, presumably caused by Fe impurities in the Cr powder feedstock. Specimens exhibited a hardness of 402 ± 18 HV10, and an excellent ultimate tensile strength of 1450 ± 22 MPa at an elongation at break of 4.5 ± 0.2%. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Evolutionary optimized 3D WiFi antennas manufactured via laser powder bed fusion

Author

Mair, Dominik, Renzler, Michael, Kovář, Stanislav, Martínek, Tomáš, Kadavý, Tomáš, Bergmueller, Simon, Horn, Andrada, Braun, Jakob, Kaserer, Lukas, Mair, Dominik, Renzler, Michael, Kovář, Stanislav, Martínek, Tomáš, Kadavý, Tomáš, Bergmueller, Simon, Horn, Andrada, Braun, Jakob, and Kaserer, Lukas

Abstract

The swift and automated design of antennas remains a challenging aspect in research due to the specific design needs for individual applications. Alterations in resonance frequency or boundary conditions necessitate time-consuming re-designs. Though the application of evolutionary optimization and generative methods in general to antenna design has seen success, it has been mostly restricted to two-dimensional structures. In this work, we present an approach for designing three-dimensional antennas using a genetic algorithm coupled with a region-growing algorithm - to ensure manufacturability - implemented in Matlab manufactured via laser powder bed fusion (LPBF). As a simulation tool for optimization CST is used. The antenna has been optimized in a completely automated manner and was produced using the metal 3D printing technology LPBF and aluminium based AlSi10Mg powder. The presented concept, which builds upon previous two-dimensional techniques, allows for significant flexibility in design, adapting to changing boundary conditions, and avoiding the geometric restrictions seen in prior methods. The optimized antenna has a size of 3.01 cm × 3.43 cm × 1.67 cm and was measured in an anechoic chamber. According to measurements a minimum reflection coefficient of -19.95 dB at 2.462 GHz and a bandwidth of 308.8 MHz are observed. CST simulation results predict an efficiency of 98.91% and the maximum antenna gain is measured at 2.45 GHz to be 3.27 dB i. Simulations made with CST and Ansys HFSS and measurements are in excellent agreement with a deviation of the resonance frequency of only 0.13% , thus further establishing genetic algorithms as a highly viable option for the design of novel antenna structures.

Published
2023

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