The structure of NiTiCu shape memory alloys

Bricknell, R.H.; Melton, K.N.; Mercier, O.

doi:10.1007/bf02658390

Cited by 91 publications

(31 citation statements)

References 25 publications

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“…The convergence tolerance of energy, maximum force, maximum stress and maximum displacement were set to be 5. The martensite crystal structures of TiNiCu alloys with different Cu contents have been reported [21,[29][30][31][32][33] and are listed in Table 1. The B19 and B19′ phases were observed in experiments, while the BCO structure was obtained from computational calculations.…”

Section: Computation Methodologymentioning

confidence: 99%

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Gou

Liu

2015

Metals

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Abstract:The study of crystal structures in shape memory alloys is of fundamental importance for understanding the shape memory effect. In order to investigate the mechanism of how Cu content affects martensite crystal structures of TiNiCu alloys, the present research examines the atomic displacement of Ti50Ni50−xCux (x = 0, 5, 12.5, 15, 18.75, 20, 25) shape memory alloys using density functional theory (DFT). By the introduction of Cu atoms into TiNi martensite crystal to replace Ni, the displacements of Ti and Ni/Cu atoms along the x-axis are obvious, but they are minimal along the y-and z-axes. It is found that along the x-axis, the two Ti atoms in the unit cell move in opposite directions, and the same occurred with the two Ni/Cu atoms. With increasing Cu content, the distance between the two Ni/Cu atoms increases while the Ti atoms draw closer along the x-axis, leading to a rotation of the (100) plane, which is responsible for the decrease in the monoclinic angle. It is also found that the displacements of both Ti atoms and Ni/Cu atoms along the x-axis are progressive, which results in a gradual change of monoclinic angle and a transition to B19 martensite crystal structure.

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Section: Computation Methodologymentioning

confidence: 99%

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Gou

Liu

2015

Metals

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“…By introducing porosity into NiTi-based SMAs, it is possible to tailor the stiffness and microstructure to more closely match that of bone as well as improve tissue and bone ingrowth [4,5]. The addition of Cu, which substitutes for Ni in NiTi SMAs, such as Ni 40 Ti 50 Cu 10 , improves the stability of the phase transformation temperatures responsible for the shape memory effect and pseudoelasticity (up to 8 % reversible strain) and narrows the phase transformation hysteresis [6][7][8][9][10][11][12]. Heat treatments can be used to enhance the mechanical properties, increase the phase transformation temperatures, and likely decrease Ni release, and thus, decrease toxic, allergic, and carcinogenic effects [13] by forming Ni 4 Ti 3 precipitates, which also improve the phase transformation recovery.…”

Section: Introductionmentioning

confidence: 99%

“…Bricknell et al [7] showed that the substitution of Cu for Ni in NiTi SMAs decreases the lattice distortion needed to form the martensite phase from the austenite phase, while still maintaining the ordered CsCl type structure at high temperature. Gil et al [14,15] showed that NiTiCu SMAs exhibit a much more narrow stress hysteresis, based on transformation stresses, as compared to binary NiTi SMAs.…”

Section: Introductionmentioning

confidence: 99%

“…Sehitoglu et al [18,19] and Biscarini et al [20] investigated the mechanical properties of NiTiCu single crystal SMAs under compression loading, and reported that the slip resistance increases when Ni-rich precipitates are present. To date, the mechanical behavior of bulk NiTiCu SMA is well established [7,[14][15][16][17][18][19][21][22][23][24]; however, few studies have focused on the effect of porosity on NiTiCu SMAs [25][26][27][28]. Goryczka et al [26,27] examined powder processing methods for producing homogenous NiTiCu SMAs.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical Properties of NiTi-Based Foam with High Porosity for Implant Applications

Qiu

Young

2015

Shap. Mem. Superelasticity

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In order to better understand NiTi-based shape memory alloy foams for implant applications, Ni 40 Ti 50 Cu 10 foams were heat treated and then deformed under incremental and cyclic compression loading. After heat treatment, the microstructure consists of a (Ni,Cu)Ti matrix with small (Ni,Cu) 4 Ti 3 precipitates and a large Ti 2 (Ni,Cu) secondary phase. The heat-treated Ni 40 Ti 50 Cu 10 foam exhibits a two-step transformation, involving B19 0 ? B19 and B19 ? B2 on heating and B2 ? B19 and B19 ? B19 0 on cooling, respectively. One Ni 40 Ti 50 Cu 10 foam was compression loaded for 10 cycles at each subsequent strain level, i.e., 1, 2, 3, 4, 5, and 6 % strain. In each set of compressive stress-strain loops, the maximum stress level decreases due to plastic damage accumulation and/or retention of transformed martensite. Cross-sectional images from micro-computed tomography were collected during compression loading, which shows very uniform deformation without severe structural damage even up to 5 % strain. Localized deformation is visible at 6 % strain.

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“…1) Substituting Cu for Ni in binary Ti-Ni SMAs can lower the transformation hysteresis, the superelasticity hysteresis, and the flow stress level in the martensite state. [2][3][4][5][6] However, when the Cu substitution is more than 10 at.%, the alloy becomes brittle and reduces seriously the workability and shape recovery strain, 2,7) which restrains the applications of high Cu-content Ti-Ni-Cu ternary SMAs. In recent years, melt-spinning techniques have been utilized to fabricate high Cu-content Ti-Ni-Cu ternary SMAs to avoid the aforementioned shortage of workability.…”

Section: Introductionmentioning

confidence: 99%

Crystallization Kinetics of Ti50Ni25Cu25 Melt-Spun Amorphous Ribbons

Chang

Kimura

2006

Mater. Trans.

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The Avrami exponent n of Ti 50 Ni 25 Cu 25 amorphous ribbons during isothermal annealing derived from the Johnson-Mehl-Avrami equation is about 3.0 and shows good agreement with that obtained by Schloßmacher et al. This indicates that the main crystallization mechanism of Ti 50 Ni 25 Cu 25 ribbons is interface-controlled three-dimensional isotropic growth with early nucleation-site saturation. According to the Arrhenius relation, the activation energy for crystallization is 314 kJ/mol. This value is similar to that obtained using the Kissinger method, which implies that the crystallization during continuous heating or isothermal annealing follows a similar crystallization mechanism.

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The structure of NiTiCu shape memory alloys

Cited by 91 publications

References 25 publications

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Effect of Cu Content on Atomic Positions of Ti50Ni50−xCux Shape Memory Alloys Based on Density Functional Theory Calculations

Mechanical Properties of NiTi-Based Foam with High Porosity for Implant Applications

Crystallization Kinetics of Ti<SUB>50</SUB>Ni<SUB>25</SUB>Cu<SUB>25</SUB> Melt-Spun Amorphous Ribbons

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