Low temperature crystallised Ti-rich NiTi shape memory alloy films for microactuators

Seguin, Jean-Luc; Bendahan, Marc; Isalgué, A.; Esteve-Cano, Vicente; Carchano, H.; Torra, V.

doi:10.1016/s0924-4247(98)00304-5

Cited by 56 publications

(17 citation statements)

References 9 publications

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“…Despite the high substrate temperature during sputtering, the as-deposited films were amorphous. This is consistent [16] with the fact that the film composition was slightly Ni-rich, as determined using x-ray fluorescence and energy dispersive x-ray spectroscopy.…”

Section: Methodssupporting

confidence: 88%

The effects of process-induced stress on the microstructures and the phase transformation characteristics of sputtered titanium-nickel thin-film shape-memory alloys

Wang

Zohar

Wong

2001

J. Micromech. Microeng.

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The microstructures and the phase transformation temperatures of sputtered titanium-nickel (TiNi) thin films, both free-standing and attached on different underlying multi-layer substrates, have been studied. Differences in the microstructures, such as the lattice constants and relative concentrations of TiNi, Ti 2 Ni and TiNi 3 phases, have been observed among the free-standing and the attached films, among the films attached on different underlying multi-layers and among the films with different relative orders of ageing and release. Not surprisingly, the corresponding phase transformation temperatures are also different. It is proposed that both process-and substrate-induced stresses affect the microstructures, hence the phase transformation characteristics, of the resulting shape-memory thin films.

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Section: Methodssupporting

confidence: 88%

The effects of process-induced stress on the microstructures and the phase transformation characteristics of sputtered titanium-nickel thin-film shape-memory alloys

Wang

Zohar

Wong

2001

J. Micromech. Microeng.

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“…This capacity has made NiTi a desirable material for many applications including MEMS, [1] biomedical devices, [2,3] and civil infrastructure. [4±6] One of the first mainstream uses of NiTi was in orthodontics, in which drawn NiTi wires were used as arc wires to apply a constant force to a patient's teeth.…”

mentioning

confidence: 99%

Cast NiTi Shape‐Memory Alloys

et al. 2005

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Shape-memory alloys, such as nickel-titanium (NiTi), have the unique ability to recover an applied inelastic strain either through the removal of the applied stress (pseudoelasticity) or the application of heat (shape-memory). This capacity has made NiTi a desirable material for many applications including MEMS, [1] biomedical devices, [2,3] and civil infrastructure. [4±6] One of the first mainstream uses of NiTi was in orthodontics, in which drawn NiTi wires were used as arc wires to apply a constant force to a patient's teeth. [2,3] To date, nearly all applications of NiTi employ a deformation processed and machined material. However, due to NiTi's poor workability, especially at higher Ni content, [7] and machinability, [8] fabrication of NiTi is expensive. High cost can make the selection of NiTi an unreasonable choice for many promising applications. Although direct casting could eliminate these costly steps, little work has been done to examine the structure and properties of NiTi in its cast state, limiting the possibility of its use in potential applications.The desire for a method of near net-shape production of NiTi parts has motivated the research of powder metallurgy as a fabrication technique. [9,10] Several methods, including self propagating high temperature synthesis (SHS), [11,12] Hot Isostatic Pressing (HIP), [9,10,13±16] and Metal Injection Molding (MIM) [10,16] are being considered for the production of shapememory materials. Recent attention has been given to HIP due to the achievement of near theoretical densities [10,13] and to MIM for its promising attribute of near net-shape production. [10,13,16] Although the work done by Johansen et al. [9] showed promising results, demonstrating tensile strains larger than 10 % for HIPed NiTi, the majority of the remaining studies demonstrate lower fracture strains under tensile loading (0.6 %±5.1 % [10,13,16] ). The study by McNeese et al. [15] revealed HIPed NiTi with recoverable tensile strains of up to 2 % and recoverable compressive strains of 4.5 %. However, despite progress being made in powder metallurgy, the search for an ideal method for net-shape processing of NiTi that would maintain its unique shape-memory properties is still underway. This was the driving motivation of this study, which aims to correlate processing, structure, and properties of cast NiTi. The link between structure and properties of cast NiTi builds a foundation for the design of net-shape NiTi castings.In general, net-shape casting is a good method for producing parts with complex geometries and is one of the simplest and most direct ways to fabricate a metal component. [17] Typical problems that can arise with a cast material include compositional segregation, porosity, inclusions (oxides, sulfides and nitrides), and shrinkage. [18±21] The solidification of a metal is a thermodynamically driven process that is dependent on such things as initial compositions, temperature, and pressure. [22] For cast alloys, thermodynamics drives the solidification path and co...

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“…In-situ or ex-situ heat treatment is carried out at about 500°C-700°C for 1 to 4 h in a high vacuum, such as 10 −5 Pa, in order to avoid the formation of oxides [13][14][15]. In recent studies, efforts have been exerted to achieve directly in-situ crystalline form shape memory films to avoid the drawbacks of heat treatment [16][17][18][19][20]. For this purpose, substrate temperatures were raised above 450°C-500°C at the deposition process to obtain crystalline structure.…”

Section: Introductionmentioning

confidence: 99%

A low temperature in-situ crystalline TiNi shape memory thin film deposited by magnetron sputtering

Çiçek

Efeoğlu

Totık

et al. 2015

Surface and Coatings Technology

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Low temperature crystallised Ti-rich NiTi shape memory alloy films for microactuators

Cited by 56 publications

References 9 publications

The effects of process-induced stress on the microstructures and the phase transformation characteristics of sputtered titanium-nickel thin-film shape-memory alloys

The effects of process-induced stress on the microstructures and the phase transformation characteristics of sputtered titanium-nickel thin-film shape-memory alloys

Cast NiTi Shape‐Memory Alloys

A low temperature in-situ crystalline TiNi shape memory thin film deposited by magnetron sputtering

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