Toward understanding the effect of remelting on the additively manufactured NiTi
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ORIGINAL ARTICLE
Toward understanding the effect of remelting on the additively manufactured NiTi Parisa Bayati 1 & Keyvan Safaei 1 & Mohammadreza Nematollahi 1 & Ahmadreza Jahadakbar 2 & Aref Yadollahi 3 & Mohammad Mahtabi 4 & Mohammad Elahinia 1 Received: 10 July 2020 / Accepted: 9 November 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract By advancing additive manufacturing (AM) techniques for nitinol (NiTi), a shape memory alloy, more researchers investigate this tool for a wide range of applications. AM-fabricated NiTi parts may contain micropore/voids and have a rough surface due to the nature of the fabrication. As a solution, we proposed a modification to the NiTi-selective laser melting/SLM approach that could possibly reduce the internal micropores/voids and improve the relative density and surface roughness of the parts. In this approach, here referred to as remelting, the laser rescans each layer followed by the main laser scan and prior to the powder deposition for the next layer. To this end, we fabricated AM NiTi coupons with combinations of power and scanning speed with the same hatch spacing for evaluating the effect of remelting. SEM analysis, density and surface roughness measurements, and Xray CT, as well as DSC and compression tests were utilized for characterization. It was revealed that the remelting procedure in each layer homogenizes the surface, reduces the defects, and improves the powder bed quality of the next layer. It was found that using proper combinations of remelting process parameters, it is possible to fabricate NiTi components with increased density, fewer defects, and smoother top surfaces, which are important factors in fatigue life and functionality of the parts. Although the transformation temperatures and compression response were not significantly affected by the remelting procedure, the process is expected to improve the fatigue life of the SLM NiTi samples, which will be investigated in the future studies. Keywords Additive manufacturing . Selective laser melting . Remelting . Shape memory alloys . NiTi
1 Introduction Selective laser melting (SLM/LBPF) is a laser-based powderbed additive manufacturing procedure which allows fabricating parts and components in a layer-by-layer approach from the pre-alloyed or pre-mixed material powder [1]. With the Parisa Bayati, Keyvan Safaei, Mohammadreza Nematollahi and Ahmadreza Jahadakbar contributed equally to this work. * Mohammad Elahinia [email protected] 1
Department of Mechanical, Industrial, and Manufacturing Engineering, The University of Toledo, Toledo, OH 43606, USA
2
Thermomorph, LLC, 2600 Dorr St, Toledo, OH 43606, USA
3
William B. Burnsed, Jr. Department of Mechanical, Aerospace, and Biomedical Engineering, University of South Alabama, Mobile, AL 36688, USA
4
Department of Mechanical Engineering, The University of Tennessee at Chattanooga, Chattanooga, TN 37403, USA
use of additive manufacturing (AM) methods, there is almost no limitation for the geometry and material selec
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