Microstructure of selective laser melted nickel–titanium
No Thumbnail Available
Authors
Author (Corporation)
Publication date
2014
Typ of student thesis
Course of study
Type
01A - Journal article
Editors
Editor (Corporation)
Supervisor
Parent work
Materials Characterization
Special issue
DOI of the original publication
Link
Series
Series number
Volume
94
Issue / Number
Pages / Duration
189-202
Patent number
Publisher / Publishing institution
Elsevier
Place of publication / Event location
Edition
Version
Programming language
Assignee
Practice partner / Client
Abstract
In selective laser melting, the layer-wise local melting of metallic powder by means of a scanning focused laser beam leads to anisotropic microstructures, which reflect the pathway of the laser beam. We studied the impact of laser power, scanning speed, and laser path onto the microstructure of NiTi cylinders. Here, we varied the laser power from 56 to 100 W and the scanning speed from about 100 to 300 mm/s. In increasing the laser power, the grain width and length increased from (33 ± 7) to (90 ± 15) μm and from (60 ± 20) to (600 ± 200) μm, respectively. Also, the grain size distribution changed from uni- to bimodal. Ostwald-ripening of the crystallites explains the distinct bimodal size distributions. Decreasing the scanning speed did not alter the microstructure but led to increased phase transformation temperatures of up to 40 K. This was experimentally determined using differential scanning calorimetry and explained as a result of preferential nickel evaporation during the fabrication process. During selective laser melting of the NiTi shape memory alloy, the control of scanning speed allows restricted changes of the transformation temperatures, whereas controlling the laser power and scanning path enables us to tailor the microstructure, i.e. the crystallite shapes and arrangement, the extent of the preferred crystallographic orientation and the grain size distribution.
Keywords
Shape memory alloy, NiTi, Selective laser melting, Differential scanning calorimetry, Electron rackscatter diffraction, Anisotropic grain
Subject (DDC)
600 - Technik, Medizin, angewandte Wissenschaften
Event
Exhibition start date
Exhibition end date
Conference start date
Conference end date
Date of the last check
ISBN
ISSN
1044-5803
1873-4189
1873-4189
Language
English
Created during FHNW affiliation
Yes
Strategic action fields FHNW
Publication status
Published
Review
Peer review of the complete publication
Open access category
Closed
License
Citation
BORMANN, Therese, Bert MÜLLER, Michael SCHINHAMMER, Anja KESSLER, Peter THALMANN und Michael DE WILD, 2014. Microstructure of selective laser melted nickel–titanium. Materials Characterization. 2014. Bd. 94, S. 189–202. DOI 10.1016/j.matchar.2014.05.017. Verfügbar unter: https://irf.fhnw.ch/handle/11654/45838