Effect of microstructure on fatigue of superelastic NiTi wires

[Display omitted] •Samples with small grains show stable superelastic behavior but low fatigue life.•Larger 250 nm grains exhibit unstable behavior, however the best fatigue life.•Large grains are prone to the deformation twinning leading to their refinement.•Microstructure refinement correlates wit...

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Veröffentlicht in:	International journal of fatigue 2021-11, Vol.152, p.106400, Article 106400
Hauptverfasser:	Tyc, Ondřej, Molnárová, Orsolya, Šittner, Petr
Format:	Artikel
Sprache:	eng
Schlagworte:	Crack propagation Crystal defects Deformation effects Fatigue Fatigue cracks Fatigue failure Fatigue life Fatigue tests Grains Heat treatment Intermetallic compounds Martensitic transformation Materials fatigue Microstructure Nickel titanides NiTi Plastic deformation Shielding Superelasticity Temperature dependence Twinning
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Zusammenfassung:	[Display omitted] •Samples with small grains show stable superelastic behavior but low fatigue life.•Larger 250 nm grains exhibit unstable behavior, however the best fatigue life.•Large grains are prone to the deformation twinning leading to their refinement.•Microstructure refinement correlates with a significant decrease in fatigue life.•400 °C/1 h aging shifts superelastic temperature window by 30 °C at constant d~75 nm. NiTi wires, having different nanocrystalline microstructures, were subjected to superelastic fatigue tests in a wide temperature range, and lattice defects accumulating during tensile cycling were analyzed. NiTi wires with the smallest grains displayed stable stress-strain response and the lowest fatigue life (Nf
ISSN:	0142-1123 1879-3452
DOI:	10.1016/j.ijfatigue.2021.106400