Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


Dissertation-Keyvan Safaei2.pdf (9.55 MB)

ETD Abstract Container

Abstract Header

Thermomechanical Properties of NiTi Shape Memory Alloy Processed by Laser Powder Bed Fusion (LPBF) Under Compression,Tension, and Torsion: A Strategy for Texture Management via Controlling the Build Orientation and Scanning Strategy

Safaei Baghbaderani, Keyvan
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659706827496354

Abstract Details

2022, Doctor of Philosophy, University of Toledo, Engineering.
At the early stages of research on additive manufacturing (AM), most of the research efforts were spent on optimizing the process parameters to obtain practical parts with minimum to no defects, while the performance of such components remained a lesser priority. Although the physical properties are the key factor in manufacturing, the final thermo-mechanical properties are of importance when it comes to applications. From a metallurgical point of view, the thermo-mechanical properties of materials are linked to their microstructure. Thus, for altering or enhancing the mechanical performance of a component, it is necessary to tailor/alter the microstructure. On the other hand, the microstructure is directly influenced by the manufacturing process, thus it creates Process-Microstructure-Property-Performance (PMPP) linkage. Besides the capability of making the components with complex shapes, additive manufacturing also provides high flexibility to control the process compared to conventional manufacturing methods by leveraging a large number of parameters (i.e., heat source power, scan speed, etc.) that allow better control over the process and the microstructure. Thus, additive manufacturing not only is able to fabricate complex geometries that may not be possible with conventional methods but also empowers the enhancement of the material properties. It is well reported that crystallographic orientation plays a key role in the thermomechanical behavior of the single crystal NiTi-based SMAs. That notable effect has also been observed in strongly textured SMAs. Such a high dependency of NiTi-based SMAs on crystallographic texture highlights the importance of developing an approach to control the AM process and obtain the preferred crystallographic textures. On the other hand, despite the growing demand for SMAs rotary actuators, the existing literature focuses mostly on assessing the compression and tension behaviors of AM-fabricated NiTi SMAs, while the torsional behavior of AM-processed NiTi alloys is less available. To fill the gaps highlighted earlier, we propose a practical strategy to control the crystallographic texture through controlling the build orientation in the laser powder bed fusion (LPBF) method. The LPBF parameters play a key role in tailoring the microstructure of the as-fabricated parts. In NiTi alloys, the high thermal gradient toward the build-up direction leads to epitaxial grain growth with the preferred crystallographic orientation of <001>. Columnar grain structure with a strong texture is the main source of the anisotropy in the LPBF-processed NiTi. The capability of controlling the microstructure and texture of the alloy through the process opens new doors to alter or enhance the properties of the parts. In this study, a practical approach was developed for controlling the texture of NiTi alloy by altering the building parameters. It is shown that the build orientation and scanning strategy are key parameters that can tailor the texture of the material toward the loading direction. To this end, NiTi coupons were fabricated using the LPBF method with different build parameters for multiaxial mechanical testing. The resulted textures were correlated with the thermomechanical behavior of the samples under compression, tension, and torsion to highlight the texture dependency of NiTi alloy’s properties.
Mohammad Elahinia (Committee Chair)
Othmane Benafan (Committee Co-Chair)
Behrang Poorganji (Committee Co-Chair)
Meysam Haghshenas (Committee Member)
Ala Qattawi (Committee Member)
235 p.
Engineering; Materials Science; Mechanical Engineering
Shape memory alloy; NiTi; Laser powder bed fusion; Crystallographic texture; Thermomechanical behavior; Controlling texture; Build orientation; Scanning strategy;

Recommended Citations

Citations

  • Safaei Baghbaderani, K. (2022). Thermomechanical Properties of NiTi Shape Memory Alloy Processed by Laser Powder Bed Fusion (LPBF) Under Compression,Tension, and Torsion: A Strategy for Texture Management via Controlling the Build Orientation and Scanning Strategy [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659706827496354

    APA Style (7th edition)

  • Safaei Baghbaderani, Keyvan. Thermomechanical Properties of NiTi Shape Memory Alloy Processed by Laser Powder Bed Fusion (LPBF) Under Compression,Tension, and Torsion: A Strategy for Texture Management via Controlling the Build Orientation and Scanning Strategy. 2022. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659706827496354.

    MLA Style (8th edition)

  • Safaei Baghbaderani, Keyvan. "Thermomechanical Properties of NiTi Shape Memory Alloy Processed by Laser Powder Bed Fusion (LPBF) Under Compression,Tension, and Torsion: A Strategy for Texture Management via Controlling the Build Orientation and Scanning Strategy." Doctoral dissertation, University of Toledo, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1659706827496354

    Chicago Manual of Style (17th edition)

toledo1659706827496354
65
© 2022, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.