Origin of 2-stage R-phase transformation in low-temperature aged Ni-rich Ti–Ni alloys

Zhou, Yumei; Zhang, J.; Fan, Genlian; Ding, Xiangdong; Sun, Jun; Ren, Xiaobing; Otsuka, Kazuhiro

doi:10.1016/j.actamat.2005.08.013

Cited by 110 publications

(71 citation statements)

References 12 publications

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“…Therefore transformations during cooling occur in two steps B2 → R → B19 . In the recent literature a tree-stage or multistage martensitic transformation in aged Ni-rich NiTi alloys were reported [10][11][12][13]. Generally, the occurrence of the multiple stage transformations is attributed to precipitation-induced inhomogeneity of the matrix, both in terms of composition and internal stress fields.…”

Section: Introductionmentioning

confidence: 99%

X-Ray Diffraction Studies of the Reversible Phase Transformation in NiTi Shape Memory Alloy

Lekston

Zubko

2016

Acta Phys. Pol. A

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In the present paper the phase transformations occurring in hot worked and heat-treated Ni-rich NiTi shape memory alloy were studied using X-ray diffraction, differential scanning calorimetry and bend and free recovery measurements. Based on conducted measurements it can be seen that in the studied alloy two-step B2 ↔ R ↔ B19 phase transitions occurred. Due to the fact that during heating the phase transition B2 → R and R → B19 occurs in a very narrow temperature range and differential scanning calorimetry peaks overlap additional X-ray diffraction measurements were performed. Obtained characteristic temperatures from applied different experimental methods are in good agreement. The optimum heat-treatment was selected to obtain rods with a shape recovery temperature A f below 37• C to prepare prototypes of medical implants activated by patients body heat.

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Section: Introductionmentioning

confidence: 99%

X-Ray Diffraction Studies of the Reversible Phase Transformation in NiTi Shape Memory Alloy

Lekston

Zubko

2016

Acta Phys. Pol. A

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“…19 The martensitic transformation evolution on aging is consistent with previous study. 20 Previous studies show that the size of the precipitates in NCATB alloys increases with the aging time monotonically, and meanwhile, the density of the precipitates decreases. 21,22 For TiNi alloys, a similar trend was reported.…”

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confidence: 99%

Phase diagram of FeNiCoAlTaB ferrous shape memory alloy on aging time

2017

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Ferrous shape memory alloy, Fe41Ni28Co17Al11.5Ta2.5B0.05, has shown large superelastic strain and strength in previous study. In the fabrication of this alloy, aging process is crucial for the formation of shape memory effect/superelasticity. However, its phase evolution on aging time is not clearly known. In this study, we systematically studied the phase diagram of this alloy on aging time. It is found that the unaged alloy shows a strain glass transition. With the aging time proceeding, the martensitic transformation gradually emerges. The phase diagram can be explained by the formation of coherent precipitates induced by aging. The heterogeneous strain between coherent precipitates and matrix is the driving force responsible for the emerging martensitic transformation. The generic explanation is supposed to be useful in martensitic transformation engineering for developing novel shape memory alloys from non-transforming materials.

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“…On the other hand, many previous studies have reported that heterogeneous precipitation reaction happens preferentially around the grain boundaries and the grain interior regions are free of precipitates (Ref [13][14][15][16][17][18][19][20][21]. These inhomogeneities bring about multistage transformations in DSC curves of aged samples in the present study.…”

Section: Dsc Curves Of Heat-treated Wiresmentioning

confidence: 63%

The Mechanical and Thermal Behaviors of Heat-Treated Ni-Rich NiTi Orthodontic Archwires

Aghamiri

Nili‐Ahmadabadi

Raygan

et al. 2009

J. of Materi Eng and Perform

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The near equiatomic nickel-titanium alloy is an outstanding intermetallic compound exhibiting distinctive properties associated with characteristic thermal and stress-induced martensitic transformations. The process of producing orthodontic wires has been modified to obtain the optimal shape memory behaviors. Phase transformation temperatures and load-deflection characteristics of this binary alloy are very significant variables in the performance of this alloy and can be manipulated by different thermomechanical treatments via inducing precipitation or dislocation networks in the matrix. In this study, one brand of commercial heat-activated nickel-titanium archwire (3 M Unitek) was selected and solution treated. Then, the wires annealed at 400°C for 10, 30, and 60 min. Thermal transformation temperatures were determined using differential scanning calorimeter. It was showed that these temperatures increased with increasing the time of heat treatment and multistage transformation occurred as the result of inhomogeneities. In order to evaluate mechanical parameters of heat-treated archwires, they were placed on an archform fixture simulating maxillary dentition and load-deflection curves were obtained by three-point bending test at 37°C. The results compared to as-received archwires and the best superelasticity was observed after 30 min aging.

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Origin of 2-stage R-phase transformation in low-temperature aged Ni-rich Ti–Ni alloys

Cited by 110 publications

References 12 publications

X-Ray Diffraction Studies of the Reversible Phase Transformation in NiTi Shape Memory Alloy

X-Ray Diffraction Studies of the Reversible Phase Transformation in NiTi Shape Memory Alloy

Phase diagram of FeNiCoAlTaB ferrous shape memory alloy on aging time

The Mechanical and Thermal Behaviors of Heat-Treated Ni-Rich NiTi Orthodontic Archwires

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