In-situ modification of thermal, microstructural, and mechanical responses by altering scan lengths in laser powder bed fusion additive manufacturing of Ti-6Al-4V

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Publication Details

Author list: Patcharapit Promoppatum, Bralee Chayasombat, Aung Nyein Soe, Atikom Sombatmai, Yuji Sato, Tetsuo Suga, Masahiro Tsukamoto;

Publisher: Elsevier

Publication year: 2023

Journal: Optics & Laser Technology (0030-3992)

Volume number: 164

ISSN: 0030-3992

eISSN: 1879-2545

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85153962808&doi=10.1016%2fj.optlastec.2023.109525&partnerID=40&md5=2c8473b79495183871257abee8a2a6fa

Languages: English-Great Britain (EN-GB)

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Abstract

Although a laser powder bed fusion (LPBF) process involves a complex laser-material interaction, it allows the possibility of designing the process conditions to achieve a distinct thermal history. Thus, in-situ control of microstructures and mechanical properties is feasible. Among many process parameters, the scan length has been regarded as an important variable, which can have a strong effect on thermal responses. Therefore, the present study performed a numerical and experimental assessment of the effect of scan lengths on thermal, microstructural, and mechanical behaviors on the LPBF of Ti-6Al-4V. Four scan lengths of 0.25, 0.5, 1, and 2 mm were used. Overall, it was found that shortening scan lengths can result in a more rapid cooling. As a result, even though the phase fraction was indifferent in each sample, a lath size refinement was observed for the sample with a short scan length. By changing the scan length from 2 to 0.25 mm, the lath size changed from 1.05 to 0.76 µm, and the yield stress increased from 1031 MPa to 1125 MPa. Nonetheless, the ductility reduction was also observed, which was mainly driven by a significant void escalation at 0.25 mm scan length. In addition, not only was the void fraction higher with shorter scan lengths, but it also become more highly localized at the hatch interface, especially at a scan length of 0.25 mm. Therefore, the gain of yield stress with the loss of ductility at the short scan length was noted. Ultimately, the present work revealed comprehensively the interaction between thermal, microstructural, and mechanical responses under different built conditions. These understandings could be used further toward process optimization in the LPBF technology. © 2023 Elsevier Ltd

Keywords

Additive manufacturing