A study of an amorphous-crystalline structured Ti–25Ni–25Cu (at.%) shape memory alloy

Rösner, Harald; Shelyakov, A. V.; Глезер, А. М.; Feit, K.; Schloßmacher, P.

doi:10.1016/s0921-5093(99)00406-2

Cited by 70 publications

(46 citation statements)

References 7 publications

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“…For all samples, a fine plate-like precipitation parallel to {001 }B2 planes is visible as shown in Figure 8. Selected area diffraction patterns are similar to those already reported by Rosner et al [8]. In order to make the identification of these precipitates easier, long time of annealing, up to 100 hrs, have been carried out to make them grow.…”

Section: Annealingsupporting

confidence: 81%

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Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

et al. 2001

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Addition of Zr up to 10 at% to Tiso-xNiasCuaZr* alloys has been used to elaborate melt spun ribbons. It has been found that low Zr content increase the glass forming ability of the alloy with a maximum at 2.5 % where the ribbon is almost fully amorphous. Above 2.5 at% a second crystalline phase occur which prevent martensitic transformation even in thermal treated samples. After crystallization, bimodal grain size distribution in low Zr content ribbons lead to a two-stage martensitic transformation. A decrease of the transformation temperature is observed with increasing Zr content. The increase of the martensitic transformation temperatures during aging is attributed to a plate-like precipitation.

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Section: Annealingsupporting

confidence: 81%

“…Additionally, copper does not change significantly transformation temperature range [3]. Copper addition decreases also liquidus temperature of TiNi alloys and improves quality of melt spun ribbons causing partial amorphization of ribbons [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

et al. 2001

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“…Twins are frequently observed in the martensitic grains. A few thin plate-like precipitates inside the matrix grains are found at higher magnifications and are assumed to be of the same nature as those recently observed in a similar melt-spun ribbon [6]. No dislocations are detected not even in the ribbon "AN07" cycled for N=5230.…”

Section: Microstructural Characterization By Temsupporting

confidence: 71%

Microstructure and properties of crystallized melt-spun Ti₅₀Ni₂₅Cu₂₅ ribbons after current-driven thermal cycling

et al. 2001

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The influence of thermal cycling driven by electrical current under a small and constant applied stress of 50 MPa on martensitic transformation, microstructure and electrical resistance of crystallized melt-spun ribbons of a Ti 5 oNi25Cu 2 5 (at.%) shape memory alloy is investigated. Cycled specimens and uncycled ones as a reference are characterized by various methods like differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and electrical resistance. After thermal cycling DSC curves during cooling exhibit two transformation peaks whereas the reverse transformation proceeds in only one step. The separation of the two peaks and also their maximum remains stable during cycling but the peak shapes become broader. The reason for the two-stage transformation is found in a crystalline surface layer already present in the as-spun state. A heat treatment between 700°C and 800°C for 600s is able to recrystallize the surface layer. Only minor changes of the microstructure due to current-driven thermal cycling could be observed. The average grain size is about 500 nm in both cycled and uncycled specimens. A few plate-like precipitates are present created during the crystallization process. Twins are frequently observed. Dislocations, however, are never observed not even in the cycled specimens.

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“…The process of rapid solidification provide very fine grains and microscopically homogeneous substructure with minimum processing steps, thereby reducing the cost and improving the shape memory characteristics. [10][11][12][13][14][15] Although many reports have been published on rapid solidification process of shape memory alloys in recent years, most of the authors have been devoted to Cu-based alloys. 13,15,16) Very few reports devoted to Ti-Ni alloys are available, 11,12) so that the texture and microstructure of Ti-Ni ribbons have not been well clarified.…”

Section: Introductionmentioning

confidence: 99%

Texture and Microstructure of Ti-Ni Melt-Spun Shape Memory Alloy Ribbons

2004

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The shape memory behavior, texture and microstructure were studied for Ti-Ni ribbons fabricated by a melt-spinning method where the Ni contents were designed to be 49.0 at%, 50.0 at% and 51.0 at%. The texture of the parent B2 phase was determined by X-ray diffraction pole figures. A strong h100i fiber texture was found in both pole figures and orientation distribution functions (ODF). TEM observation revealed that all the ribbons are fully crystallized and that disk-type precipitates of about 10 nm in length locate on {100} of B2 phase uniformly. The thermal cyclic tests under various constant stresses showed shape recoverable strains exceeding 5% and critical stresses for plastic deformation being higher than 400 MPa for Ti-49.0 at%Ni and Ti-50.0 at%Ni as-spun ribbons. These excellent shape memory characteristics of the melt-spun ribbons are due to the formation of these disk-type precipitates. In addition, Ti 2 Ni precipitates of 25 nm in diameter appeared along grain boundaries of Ti-51.0 at%Ni as-spun ribbon. Since the Ni content of the matrix is condensed due to the formation of Ti 2 Ni precipitates, no shape memory effect was observed in Ti-51.0 at%Ni as-spun ribbon under the experimental conditions.

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A study of an amorphous-crystalline structured Ti–25Ni–25Cu (at.%) shape memory alloy

Cited by 70 publications

References 7 publications

Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

Microstructure and properties of crystallized melt-spun Ti₅₀Ni₂₅Cu₂₅ ribbons after current-driven thermal cycling

Texture and Microstructure of Ti-Ni Melt-Spun Shape Memory Alloy Ribbons

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A study of an amorphous-crystalline structured Ti–25Ni–25Cu (at.%) shape memory alloy

Cited by 70 publications

References 7 publications

Martensitic transformation and microstructure of rapidly solidified Ti50-xNi25Cu25Zrx shap memory alloys

Martensitic transformation and microstructure of rapidly solidified Ti50-xNi25Cu25Zrx shap memory alloys

Microstructure and properties of crystallized melt-spun Ti50Ni25Cu25 ribbons after current-driven thermal cycling

Texture and Microstructure of Ti-Ni Melt-Spun Shape Memory Alloy Ribbons

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Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

Martensitic transformation and microstructure of rapidly solidified Ti_50-xNi₂₅Cu₂₅Zr_x shap memory alloys

Microstructure and properties of crystallized melt-spun Ti₅₀Ni₂₅Cu₂₅ ribbons after current-driven thermal cycling