Details
| Original language | English |
|---|---|
| Pages (from-to) | 4643-4657 |
| Number of pages | 15 |
| Journal | Acta materialia |
| Volume | 50 |
| Issue number | 18 |
| Publication status | Published - 28 Oct 2002 |
| Externally published | Yes |
Abstract
Results are presented on the cyclic deformation of single crystal NiTi containing Ti3Ni4 precipitates of various sizes. Mechanical cycling experiments reveal that the cyclic degradation resistance of NiTi is strongly dependent on crystallographic orientation. Under compression, orientations approaching the [100] pole of the stereographic triangle possess the highest fatigue resistance. Orientations approaching the [111] pole of the stereographic triangle demonstrate the lowest fatigue resistance. Aging to produce small coherent Ti3Ni4 precipitates (10 nm) improves the fatigue resistance of NiTi compared to the other heat treatments (solutionized or overaged) for nearly all orientations. NiTi with 10 nm Ti3Ni4 precipitates consistently showed stabilized martensite due to mechanical cycling, and an absence of dislocation activity. Samples with large incoherent Ti3Ni4 precipitates (500 nm) consistently showed significant dislocation activity due to mechanical cycling in addition to stabilized martensite colonies. The first cycle stress-strain hysteresis was found to correlate to the fatigue resistance of the material. Samples demonstrating large inherent hysteresis, with different heat treatments and orientations, showed poor fatigue performance. Rational for the observed behaviors is discussed in terms of operant deformation mechanisms and ramifications on modeling the cyclic deformation of NiTi are presented.
Keywords
- Dislocations, Fatigue, Martensite, Microstructure and cyclic stress-strain response, NiTi shape memory alloys, Precipitation, Single crystals, Transmission electron microscopy
ASJC Scopus subject areas
- Materials Science(all)
- Electronic, Optical and Magnetic Materials
- Materials Science(all)
- Ceramics and Composites
- Materials Science(all)
- Polymers and Plastics
- Materials Science(all)
- Metals and Alloys
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In: Acta materialia, Vol. 50, No. 18, 28.10.2002, p. 4643-4657.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Cyclic deformation mechanisms in precipitated NiTi shape memory alloys
AU - Gall, K.
AU - Maier, H. J.
N1 - Funding Information: The authors would like to gratefully thank Yuriy Chumlyakov for providing the single crystal material and Kevin Juntunen for conducting the mechanical tests. HJM acknowledges financial support by Deutsche Forschungsgemeinschaft.
PY - 2002/10/28
Y1 - 2002/10/28
N2 - Results are presented on the cyclic deformation of single crystal NiTi containing Ti3Ni4 precipitates of various sizes. Mechanical cycling experiments reveal that the cyclic degradation resistance of NiTi is strongly dependent on crystallographic orientation. Under compression, orientations approaching the [100] pole of the stereographic triangle possess the highest fatigue resistance. Orientations approaching the [111] pole of the stereographic triangle demonstrate the lowest fatigue resistance. Aging to produce small coherent Ti3Ni4 precipitates (10 nm) improves the fatigue resistance of NiTi compared to the other heat treatments (solutionized or overaged) for nearly all orientations. NiTi with 10 nm Ti3Ni4 precipitates consistently showed stabilized martensite due to mechanical cycling, and an absence of dislocation activity. Samples with large incoherent Ti3Ni4 precipitates (500 nm) consistently showed significant dislocation activity due to mechanical cycling in addition to stabilized martensite colonies. The first cycle stress-strain hysteresis was found to correlate to the fatigue resistance of the material. Samples demonstrating large inherent hysteresis, with different heat treatments and orientations, showed poor fatigue performance. Rational for the observed behaviors is discussed in terms of operant deformation mechanisms and ramifications on modeling the cyclic deformation of NiTi are presented.
AB - Results are presented on the cyclic deformation of single crystal NiTi containing Ti3Ni4 precipitates of various sizes. Mechanical cycling experiments reveal that the cyclic degradation resistance of NiTi is strongly dependent on crystallographic orientation. Under compression, orientations approaching the [100] pole of the stereographic triangle possess the highest fatigue resistance. Orientations approaching the [111] pole of the stereographic triangle demonstrate the lowest fatigue resistance. Aging to produce small coherent Ti3Ni4 precipitates (10 nm) improves the fatigue resistance of NiTi compared to the other heat treatments (solutionized or overaged) for nearly all orientations. NiTi with 10 nm Ti3Ni4 precipitates consistently showed stabilized martensite due to mechanical cycling, and an absence of dislocation activity. Samples with large incoherent Ti3Ni4 precipitates (500 nm) consistently showed significant dislocation activity due to mechanical cycling in addition to stabilized martensite colonies. The first cycle stress-strain hysteresis was found to correlate to the fatigue resistance of the material. Samples demonstrating large inherent hysteresis, with different heat treatments and orientations, showed poor fatigue performance. Rational for the observed behaviors is discussed in terms of operant deformation mechanisms and ramifications on modeling the cyclic deformation of NiTi are presented.
KW - Dislocations
KW - Fatigue
KW - Martensite
KW - Microstructure and cyclic stress-strain response
KW - NiTi shape memory alloys
KW - Precipitation
KW - Single crystals
KW - Transmission electron microscopy
UR - http://www.scopus.com/inward/record.url?scp=0037190899&partnerID=8YFLogxK
U2 - 10.1016/S1359-6454(02)00315-4
DO - 10.1016/S1359-6454(02)00315-4
M3 - Article
AN - SCOPUS:0037190899
VL - 50
SP - 4643
EP - 4657
JO - Acta materialia
JF - Acta materialia
SN - 1359-6454
IS - 18
ER -