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Published in: Shape Memory and Superelasticity 2/2019

03-04-2019 | ICOMAT 2017

Ni-Concentration Dependence of Directed Energy Deposited NiTi Alloy Microstructures

Authors: Beth A. Bimber, Reginald F. Hamilton, Todd A. Palmer

Published in: Shape Memory and Superelasticity | Issue 2/2019

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Abstract

Localized re-melting and re-heating in regions between overlapping passes and layers drive localized microstructure development during laser-based additive manufacturing processes. Ti-rich (Ti52.1Ni47.9 at.%) and Ni-rich (Ni53Ti47 at.%) alloy builds were fabricated using a laser-based directed energy deposition (LDED) process and sectioned in three orthogonal cross-sections to provide a 3-dimensional view of the grain and precipitate morphologies in the interpass and interlayer regions. Fine equiaxed grains, which were an order of magnitude smaller than the columnar grains in the bulk regions, were observed in the interfacial regions. While these columnar grains showed preferential orientation in the highest heat flow direction corresponding to the build height, the fine equiaxed grain structures in the interfacial regions showed no orientation preferences. In addition to these changes in grain structures, precipitation of second phases is also impacted in these regions. The re-melting and re-heating characteristic of the interfacial regions produces precipitates in the Ni-rich alloys with fine oriented morphologies different from those observed in the bulk regions.
Literature
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go back to reference Elahinia MH, Moghaddam NS, Andani MT, Amerinatanzi A, Bimber BA, Hamilton RF (2016) Fabrication of NiTi through additive manufacturing: a review. Prog Mater Sci 83:630–663CrossRef Elahinia MH, Moghaddam NS, Andani MT, Amerinatanzi A, Bimber BA, Hamilton RF (2016) Fabrication of NiTi through additive manufacturing: a review. Prog Mater Sci 83:630–663CrossRef
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go back to reference Hamilton RF, Bimber BA, Palmer TA (2018) Correlating microstructure and superelasticity of directed energy deposition additive manufactured Ni-rich NiTi alloys. J Alloy Compd 739:712–722CrossRef Hamilton RF, Bimber BA, Palmer TA (2018) Correlating microstructure and superelasticity of directed energy deposition additive manufactured Ni-rich NiTi alloys. J Alloy Compd 739:712–722CrossRef
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go back to reference Hamilton RF, Bimber BA, Andani MT, Elahinia MH (2017) Multi-scale shape memory effect recovery in NiTi alloys additive manufactured by selective laser melting and laser directed energy deposition. J Mater Process Technol 250:55–64CrossRef Hamilton RF, Bimber BA, Andani MT, Elahinia MH (2017) Multi-scale shape memory effect recovery in NiTi alloys additive manufactured by selective laser melting and laser directed energy deposition. J Mater Process Technol 250:55–64CrossRef
Metadata
Title
Ni-Concentration Dependence of Directed Energy Deposited NiTi Alloy Microstructures
Authors
Beth A. Bimber
Reginald F. Hamilton
Todd A. Palmer
Publication date
03-04-2019
Publisher
Springer US
Published in
Shape Memory and Superelasticity / Issue 2/2019
Print ISSN: 2199-384X
Electronic ISSN: 2199-3858
DOI
https://doi.org/10.1007/s40830-019-00215-8

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