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Abstract/Details

Processing and characterization of Nickel-base superalloy micro-components and films for MEMS applications

Burns, Devin E. The Johns Hopkins University. ProQuest Dissertations Publishing, 2013. 3572711.

Abstract (summary)

Microelectromechanical (MEMS) devices are not capable of withstanding harsh operating environments, which may include high temperatures, pressures and corrosive agents. Ni-base superalloys have been used successfully in the hot stages of jet turbine engines despite the presence of these conditions. In my thesis work, I developed two techniques compatible with micro-processing methods to produce Ni-base superalloy micro-components for MEMS applications. The mechanical properties of these materials were accessed at room and elevated temperatures. Microstructural studies were performed, linking microstructural features to mechanical properties.

The first technique modified LIGA Ni (LIGA is a German acronym for lithography, electroplating and molding) microtensile specimens using a vapor phase aluminization process. A subsequent homogenization heat treatment produced a two phase Ni-Ni3A1 microstructure characteristic of modern Ni-base superalloys. Al composition was used to tailor both the precipitate size and volume fraction. Aluminized LIGA Ni micro-components exhibited room temperature yield and ultimate strengths 3 to 4 times LIGA Ni micro-components subject to the same heat treatment.

The second technique involved sputtering a commercial Ni-base superalloy, Haynes 718, to produce thick sputtered foils (up to 20 gam) on silicon and brass substrates. The as-deposited foils were nanocrystalline solid solutions with chemical compositions similar to the bulk material. Foils subject to ageing heat treatments exhibited unique precipitation mechanisms and good thermal stability. Strengths as high as 750 MPa at 700°C were observed with several percent ductility. This is a significant improvement over state of the art metallic MEMS materials.

Furthermore, a new high temperature microtensile testing technique was developed. The technique embeds a displacement based force sensor into the hot zone of a furnace. This arrangement ensures temperature uniformity during testing, while permitting friction along the loading axis by measuring force locally. Load and displacement are measured simultaneously with a single camera using digital image correlation techniques. Initial results, using Al 6061-T6 as a reference material, were promising.

Indexing (details)


Subject
Mechanical engineering;
High Temperature Physics;
Materials science
Classification
0548: Mechanical engineering
0597: High Temperature Physics
0794: Materials science
Identifier / keyword
Pure sciences; Applied sciences; Alloy 718; Aluminization; Films; High temperature testing; Micro-components; Nickel-base superalloy; Sputtering
Title
Processing and characterization of Nickel-base superalloy micro-components and films for MEMS applications
Author
Burns, Devin E.
Number of pages
206
Degree date
2013
School code
0098
Source
DAI-B 74/12(E), Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
978-1-303-39299-3
Advisor
Hemker, Kevin
Committee member
El-wady, Irafar; Weihs, Timothy
University/institution
The Johns Hopkins University
Department
Mechanical Engineering
University location
United States -- Maryland
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3572711
ProQuest document ID
1433867221
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
https://www.proquest.com/dissertations/docview/1433867221/A7AF5D6759DB4986PQ/1