Occurrence and origin of non-martensitic acicular artifacts on NiTi

Undisz, Andreas; Reuther, K.; Reuther, H.; Rettenmayr, Markus

doi:10.1016/j.actamat.2010.09.026

Cited by 18 publications

(6 citation statements)

References 10 publications

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“…To obtain a representative surface condition, the samples were ground using SiC abrasive (600, 1200, 2500, and 4000 grid). The last grinding step sufficed in producing a surface with mirror finish 33. After grinding, all samples were rinsed with deionized water and ethanol.…”

Section: Methodsmentioning

confidence: 99%

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Mechanism of oxide layer growth during annealing of NiTi

Undisz

Schrempel

Wesch

et al. 2012

J Biomedical Materials Res

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After annealing at 540°C, NiTi is covered by a characteristic oxide layer with an Ni-containing outer and an Ni-free inner titanium oxide region. To elucidate details of the yet unclear formation process, samples were annealed in an atmosphere containing different oxygen isotopes at a time and analyzed by nondestructive ion beam techniques at different stages of the oxidation. During the heating stage, an oxygen permeable "low Ni" titanium oxide forms, and the oxide layer grows inward. Subsequently, when the annealing temperature of 540°C is reached, Ni-free stoichiometric titanium oxide forms and inhibits the transport of oxygen toward the bulk. Thus, the oxide layer growth changes to outward, and the final location of the reaction front between O and Ti is inside the oxide layer at the transition of "low Ni" oxide to "Ni-free" oxide. Consequently, the annealing conditions during inward oxide layer growth govern the surface properties, whereas the conditions during outward oxide layer growth are uncritical with respect to the surface properties. The findings are directly applicable to set the amount of surface Ni of NiTi devices, provide basis for detailed interpretation of experimental results involving annealing of NiTi, and can further respective modeling.

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Section: Methodsmentioning

confidence: 99%

“…The last grinding step sufficed in producing a surface with mirror finish. 33 After grinding, all samples were rinsed with deionized water and ethanol.…”

Section: Niti Samples and Pretreatmentmentioning

confidence: 99%

Mechanism of oxide layer growth during annealing of NiTi

Undisz

Schrempel

Wesch

et al. 2012

J Biomedical Materials Res

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“…A Jeol JSM-6460 scanning electron microscope (SEM) equipped with an INCA X-Sight 350 energy dispersive x-ray (EDX) analysis aperture was used for microscopy and chemical analysis of the BM-LPZ interface. As per a recent study by Undisz et al [15], a dilute HF etchant was used for microstructure analysis to limit surface pitting and avoid the formation of surface artifacts. Crystallographic data were collected from the BM and LPZ structures using micro-x-ray diffraction (XRD) analysis.…”

Section: Methodsmentioning

confidence: 99%

Enhanced thermomechanical functionality of a laser processed hybrid NiTi–NiTiCu shape memory alloy

Daly¹,

Pequegnat²,

Zhou³

et al. 2012

Smart Mater. Struct.

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The exciting thermomechanical behavior of NiTi shape memory alloys (SMAs) has sparked significant research effort seeking to exploit their exotic properties. The performance capabilities of conventional NiTi offerings are limited, however, by current fabrication technologies. In this study, a high power density laser source was implemented to locally alloy Cu into a conventional NiTi material. The effects of laser processing created a localized NiTiCu ternary material domain which possessed a set of unique thermomechanical properties. The combined active responses of the laser processed hybrid NiTi-NiTiCu SMA represent an enhanced material functionality, which permits a multi-stage thermomechanical recovery and allows for unprecedented novel applications to be realized.

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“…48 swabs for Dt5, 60 swabs for Dt12, and 72 swabs for Dt25. We used aqueous etching solution as suggested in (Undisz et al, 2011): 7.4% HF, 18.5% HNO 3 and 74.1% H 2 0. According to the manufacturer of the acids, the concentrations of HNO 3 and HF acids are 65% and 40%, respectively.…”

Section: Appendix B Microstructure Of Tubesmentioning

confidence: 97%