Details
| Original language | English |
|---|---|
| Article number | 139373 |
| Journal | Materials Science and Engineering A |
| Volume | 792 |
| Early online date | 19 Apr 2020 |
| Publication status | Published - 5 Aug 2020 |
Abstract
Nickel Titanium (NiTi) alloys have been used for many years based on their unique ability to exhibit the shape-memory and pseudoelastic effects. The indentation-induced two-way shape memory effect (TWSME) is a specific sub-capability of this alloy such that a repeatably switchable surface can be created by “training” the material through mechanical indentation and activated through temperature transitions between the austenitic and martensitic phases. This study sought to observe the effect Ti3Ni4 precipitate aging would have on the indentation-induced TWSME. Ti3Ni4 has previously been shown as an effective method to alter NiTi transformation temperatures, yet it was unclear what effect localized stress fields around precipitates would have on the TWSME. The results presented here indicate that growth of precipitates in the alloy before training suppresses the resultant indentation-induced TWSME, and small precipitates, which cause minimal lattice mismatch to the matrix (i.e. highest coherency), have the strongest role in suppressing the effect. It is suggest that lattice coherency acts to inhibit plastic deformation, suppressing the creation of the preferred microstructure under the indent required to guide the TWSME. Therefore, precipitate aging is not a recommended alternative to precise alloying in order to alter transformation temperatures with the goal of maximizing the indentation-induced TWSME effect within a targeted temperate transformation regime.
Keywords
- Indentation, NiTi, Nitinol, Shape-memory alloy, Two-way shape-memory effect
ASJC Scopus subject areas
- Materials Science(all)
- General Materials Science
- Physics and Astronomy(all)
- Condensed Matter Physics
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
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In: Materials Science and Engineering A, Vol. 792, 139373, 05.08.2020.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Influence of Ti3Ni4 precipitates on the indentation-induced two-way shape-memory effect in Nickel-Titanium
AU - Laursen, Christopher M.
AU - Peter, Nicolas J.
AU - Gerstein, Gregory
AU - Maier, Hans-Jürgen
AU - Dehm, Gerhard
AU - Frick, Carl P.
N1 - Funding Information: C.P.F. and C.M.L. gratefully acknowledge support from the National Science Foundation (NSF) CAREER award (Grant no. DMR-1255603).
PY - 2020/8/5
Y1 - 2020/8/5
N2 - Nickel Titanium (NiTi) alloys have been used for many years based on their unique ability to exhibit the shape-memory and pseudoelastic effects. The indentation-induced two-way shape memory effect (TWSME) is a specific sub-capability of this alloy such that a repeatably switchable surface can be created by “training” the material through mechanical indentation and activated through temperature transitions between the austenitic and martensitic phases. This study sought to observe the effect Ti3Ni4 precipitate aging would have on the indentation-induced TWSME. Ti3Ni4 has previously been shown as an effective method to alter NiTi transformation temperatures, yet it was unclear what effect localized stress fields around precipitates would have on the TWSME. The results presented here indicate that growth of precipitates in the alloy before training suppresses the resultant indentation-induced TWSME, and small precipitates, which cause minimal lattice mismatch to the matrix (i.e. highest coherency), have the strongest role in suppressing the effect. It is suggest that lattice coherency acts to inhibit plastic deformation, suppressing the creation of the preferred microstructure under the indent required to guide the TWSME. Therefore, precipitate aging is not a recommended alternative to precise alloying in order to alter transformation temperatures with the goal of maximizing the indentation-induced TWSME effect within a targeted temperate transformation regime.
AB - Nickel Titanium (NiTi) alloys have been used for many years based on their unique ability to exhibit the shape-memory and pseudoelastic effects. The indentation-induced two-way shape memory effect (TWSME) is a specific sub-capability of this alloy such that a repeatably switchable surface can be created by “training” the material through mechanical indentation and activated through temperature transitions between the austenitic and martensitic phases. This study sought to observe the effect Ti3Ni4 precipitate aging would have on the indentation-induced TWSME. Ti3Ni4 has previously been shown as an effective method to alter NiTi transformation temperatures, yet it was unclear what effect localized stress fields around precipitates would have on the TWSME. The results presented here indicate that growth of precipitates in the alloy before training suppresses the resultant indentation-induced TWSME, and small precipitates, which cause minimal lattice mismatch to the matrix (i.e. highest coherency), have the strongest role in suppressing the effect. It is suggest that lattice coherency acts to inhibit plastic deformation, suppressing the creation of the preferred microstructure under the indent required to guide the TWSME. Therefore, precipitate aging is not a recommended alternative to precise alloying in order to alter transformation temperatures with the goal of maximizing the indentation-induced TWSME effect within a targeted temperate transformation regime.
KW - Indentation
KW - NiTi
KW - Nitinol
KW - Shape-memory alloy
KW - Two-way shape-memory effect
UR - http://www.scopus.com/inward/record.url?scp=85087590394&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2020.139373
DO - 10.1016/j.msea.2020.139373
M3 - Article
AN - SCOPUS:85087590394
VL - 792
JO - Materials Science and Engineering A
JF - Materials Science and Engineering A
SN - 0921-5093
M1 - 139373
ER -