Details
| Original language | English |
|---|---|
| Pages (from-to) | 4287-4295 |
| Number of pages | 9 |
| Journal | Journal of materials research |
| Volume | 32 |
| Issue number | 23 |
| Publication status | Published - 14 Dec 2017 |
Abstract
Titanium-tantalum based alloys can demonstrate a martensitic transformation well above 100 °C, which makes them attractive for shape memory applications at elevated temperatures. In addition, they provide for good workability and contain only reasonably priced constituents. The current study presents results from functional fatigue experiments on a binary Ti-25Ta high-temperature shape memory alloy. This material shows a martensitic transformation at about 350 °C along with a transformation strain of 2 pct at a bias stress of 100 MPa. The success of most of the envisaged applications will, however, hinge on the microstructural stability under thermomechanical loading. Thus, light and electron optical microscopy as well X-ray diffraction were used to uncover the mechanisms that dominate functional degradation in different temperature regimes. It is demonstrated the maximum test temperature is the key parameter that governs functional degradation in the thermomechanical fatigue tests. Specifically, ω-phase formation and local decomposition in Ti-rich and Ta-rich areas dominate when T max does not exceed ≈430 °C. As T max is increased, the detrimental phases start to dissolve and functional fatigue can be suppressed. However, when T max reaches ≈620 °C, structural fatigue sets in, and fatigue life is again deteriorated by oxygen-induced crack formation.
Keywords
- functional degradation, martensite, memory metal, omega phase, phase transformation, shape memory effect, Ti
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: Journal of materials research, Vol. 32, No. 23, 14.12.2017, p. 4287-4295.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Microstructural evolution and functional fatigue of a Ti-25Ta high-temperature shape memory alloy
AU - Maier, Hans Jürgen
AU - Karsten, Elvira
AU - Paulsen, Alexander
AU - Langenkämper, Dennis
AU - Decker, Peer
AU - Frenzel, Jan
AU - Somsen, Christoph
AU - Ludwig, Alfred
AU - Eggeler, Gunther
AU - Niendorf, Thomas
PY - 2017/12/14
Y1 - 2017/12/14
N2 - Titanium-tantalum based alloys can demonstrate a martensitic transformation well above 100 °C, which makes them attractive for shape memory applications at elevated temperatures. In addition, they provide for good workability and contain only reasonably priced constituents. The current study presents results from functional fatigue experiments on a binary Ti-25Ta high-temperature shape memory alloy. This material shows a martensitic transformation at about 350 °C along with a transformation strain of 2 pct at a bias stress of 100 MPa. The success of most of the envisaged applications will, however, hinge on the microstructural stability under thermomechanical loading. Thus, light and electron optical microscopy as well X-ray diffraction were used to uncover the mechanisms that dominate functional degradation in different temperature regimes. It is demonstrated the maximum test temperature is the key parameter that governs functional degradation in the thermomechanical fatigue tests. Specifically, ω-phase formation and local decomposition in Ti-rich and Ta-rich areas dominate when T max does not exceed ≈430 °C. As T max is increased, the detrimental phases start to dissolve and functional fatigue can be suppressed. However, when T max reaches ≈620 °C, structural fatigue sets in, and fatigue life is again deteriorated by oxygen-induced crack formation.
AB - Titanium-tantalum based alloys can demonstrate a martensitic transformation well above 100 °C, which makes them attractive for shape memory applications at elevated temperatures. In addition, they provide for good workability and contain only reasonably priced constituents. The current study presents results from functional fatigue experiments on a binary Ti-25Ta high-temperature shape memory alloy. This material shows a martensitic transformation at about 350 °C along with a transformation strain of 2 pct at a bias stress of 100 MPa. The success of most of the envisaged applications will, however, hinge on the microstructural stability under thermomechanical loading. Thus, light and electron optical microscopy as well X-ray diffraction were used to uncover the mechanisms that dominate functional degradation in different temperature regimes. It is demonstrated the maximum test temperature is the key parameter that governs functional degradation in the thermomechanical fatigue tests. Specifically, ω-phase formation and local decomposition in Ti-rich and Ta-rich areas dominate when T max does not exceed ≈430 °C. As T max is increased, the detrimental phases start to dissolve and functional fatigue can be suppressed. However, when T max reaches ≈620 °C, structural fatigue sets in, and fatigue life is again deteriorated by oxygen-induced crack formation.
KW - functional degradation
KW - martensite
KW - memory metal
KW - omega phase
KW - phase transformation
KW - shape memory effect
KW - Ti
UR - http://www.scopus.com/inward/record.url?scp=85026921048&partnerID=8YFLogxK
U2 - 10.1557/jmr.2017.319
DO - 10.1557/jmr.2017.319
M3 - Article
AN - SCOPUS:85026921048
VL - 32
SP - 4287
EP - 4295
JO - Journal of materials research
JF - Journal of materials research
SN - 0884-2914
IS - 23
ER -