Details
Original language | English |
---|---|
Pages (from-to) | 288-295 |
Number of pages | 8 |
Journal | Journal of alloys and compounds |
Volume | 633 |
Publication status | Published - 7 Feb 2015 |
Abstract
Due to its transformation behavior, Co-Ni-Ga represents a very promising high temperature shape memory alloy (HT SMA) for applications at elevated temperatures. Co-Ni-Ga single crystals show a fully reversible pseudoelastic shape change up to temperatures of 400 °C. Unfortunately, polycrystalline Co-Ni-Ga suffers from brittleness and early fracture mainly due to intergranular constraints. In the current study, different thermo-mechanical processing routes produced various microstructures which differ in grain size and texture. A bicrystalline bamboo-like grain structure results in the highest reversible transformation strains and excellent cyclic stability. Moreover, solution-annealed and hot-rolled conditions also showed cyclic stability. Using in situ high-resolution electron microscopy, the elementary processes, which govern the microstructural evolution during pseudoelastic cycling were investigated and the mechanisms that govern structural and functional degradation were identified. The observations documented in the present work suggest that the formation of the ductile γ-phase on and near grain boundaries as well as the activation of multiple martensite variants at grain boundaries are beneficial for improved cyclic performance of polycrystalline Co-Ni-Ga HT SMAs.
Keywords
- Crack formation, In situ testing, Martensitic transformation, Microstructure, Superelasticity
ASJC Scopus subject areas
- Engineering(all)
- Mechanics of Materials
- Engineering(all)
- Mechanical Engineering
- Materials Science(all)
- Metals and Alloys
- Materials Science(all)
- Materials Chemistry
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In: Journal of alloys and compounds, Vol. 633, 07.02.2015, p. 288-295.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Damage evolution in pseudoelastic polycrystalline Co-Ni-Ga high-temperature shape memory alloys
AU - Vollmer, Malte
AU - Krooß, Philipp
AU - Segel, Christian
AU - Weidner, Anja
AU - Paulsen, Alexander
AU - Frenzel, Jan
AU - Schaper, Mirko
AU - Eggeler, Gunther
AU - Maier, Hans Jürgen
AU - Niendorf, Thomas
N1 - Funding information: Financial support by Deutsche Forschungsgemeinschaft (DFG) within the Research Unit Program “Hochtemperatur-Formgedächtnislegierungen” (Contract Nos. NI1327/3-1; MA1175/34-1; FR2675/3-1) is gratefully acknowledged.
PY - 2015/2/7
Y1 - 2015/2/7
N2 - Due to its transformation behavior, Co-Ni-Ga represents a very promising high temperature shape memory alloy (HT SMA) for applications at elevated temperatures. Co-Ni-Ga single crystals show a fully reversible pseudoelastic shape change up to temperatures of 400 °C. Unfortunately, polycrystalline Co-Ni-Ga suffers from brittleness and early fracture mainly due to intergranular constraints. In the current study, different thermo-mechanical processing routes produced various microstructures which differ in grain size and texture. A bicrystalline bamboo-like grain structure results in the highest reversible transformation strains and excellent cyclic stability. Moreover, solution-annealed and hot-rolled conditions also showed cyclic stability. Using in situ high-resolution electron microscopy, the elementary processes, which govern the microstructural evolution during pseudoelastic cycling were investigated and the mechanisms that govern structural and functional degradation were identified. The observations documented in the present work suggest that the formation of the ductile γ-phase on and near grain boundaries as well as the activation of multiple martensite variants at grain boundaries are beneficial for improved cyclic performance of polycrystalline Co-Ni-Ga HT SMAs.
AB - Due to its transformation behavior, Co-Ni-Ga represents a very promising high temperature shape memory alloy (HT SMA) for applications at elevated temperatures. Co-Ni-Ga single crystals show a fully reversible pseudoelastic shape change up to temperatures of 400 °C. Unfortunately, polycrystalline Co-Ni-Ga suffers from brittleness and early fracture mainly due to intergranular constraints. In the current study, different thermo-mechanical processing routes produced various microstructures which differ in grain size and texture. A bicrystalline bamboo-like grain structure results in the highest reversible transformation strains and excellent cyclic stability. Moreover, solution-annealed and hot-rolled conditions also showed cyclic stability. Using in situ high-resolution electron microscopy, the elementary processes, which govern the microstructural evolution during pseudoelastic cycling were investigated and the mechanisms that govern structural and functional degradation were identified. The observations documented in the present work suggest that the formation of the ductile γ-phase on and near grain boundaries as well as the activation of multiple martensite variants at grain boundaries are beneficial for improved cyclic performance of polycrystalline Co-Ni-Ga HT SMAs.
KW - Crack formation
KW - In situ testing
KW - Martensitic transformation
KW - Microstructure
KW - Superelasticity
UR - http://www.scopus.com/inward/record.url?scp=84923608347&partnerID=8YFLogxK
U2 - 10.1016/j.jallcom.2015.01.282
DO - 10.1016/j.jallcom.2015.01.282
M3 - Article
AN - SCOPUS:84923608347
VL - 633
SP - 288
EP - 295
JO - Journal of alloys and compounds
JF - Journal of alloys and compounds
SN - 0925-8388
ER -