Elastic properties of NiTi

Brill, Thilo M.; Mittelbach, S.; Aßmus, W.; Müllner, M.; Lüthi, B.

doi:10.1088/0953-8984/3/48/004

Cited by 96 publications

(58 citation statements)

References 13 publications

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“…It has been shown that the Young's modulus for NiTi alloys decreases with temperature reaching a significant minimum at about the start of the reverse transformation followed by a steep increase once the reverse transformation is completed. [44][45][46][47] The Ni 49.9 Ti 50.1 alloy studied here exhibits similar compliance characteristics that were measured using a dynamic technique 48 and would definitely provide a mechanism for reverse reorientation to occur with increasing temperature.…”

Section: -3supporting

confidence: 64%

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Benafan

Padula

Noebe

et al. 2012

Journal of Applied Physics

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Deformation of a B19′ martensitic, polycrystalline Ni49.9Ti50.1 (at. %) shape memory alloy and its influence on the magnitude and stability of the ensuing two-way shape memory effect (TWSME) was investigated by combined ex situ mechanical experimentation and in situ neutron diffraction measurements at stress and temperature. The microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. With increasing uniaxial strain, it was observed that B19′ martensite deformed by reorientation and detwinning with preferred selection of the (1¯50)M and (010)M variants, (201¯)B19′ deformation twinning, and dislocation activity. These mechanisms were indicated by changes in bulk texture from the neutron diffraction measurements. Partial reversibility of the reoriented variants and deformation twins was also captured upon load removal and thermal cycling, which after isothermal deformation to strains between 6% and 22% resulted in a strong TWSME. Consequently, TWSME functional parameters including TWSME strain, strain reduction, and transformation temperatures were characterized and it was found that prior martensite deformation to 14% strain provided the optimum condition for the TWSME, resulting in a stable two-way shape memory strain of 2.2%. Thus, isothermal deformation of martensite was found to be a quick and efficient method for creating a strong and stable TWSME in Ni49.9Ti50.1.

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Section: -3supporting

confidence: 64%

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Benafan

Padula

Noebe

et al. 2012

Journal of Applied Physics

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“…1. Table 1 also shows predictions for the moduli using stiffness tensor values from ultrasonic measurements of NiTi single crystals from [20]. The polycrystal Young's moduli are predicted as a single-crystal average using Hashin-Shtrikman [21] [6,24] with elastic TiC data from [25].…”

Section: Neutron Diffraction Data Analysismentioning

confidence: 99%

Stress-induced martensitic transformations in NiTi and NiTi–TiC composites investigated by neutron diffraction

Vaidyanathan

Bourke

Dunand

1999

Materials Science and Engineering: A

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Superelastic NiTi (51.0 at.% Ni) specimens reinforced with 0, 10 and 20 vol.% TiC particles were deformed under uniaxial compression while neutron diffraction spectra were collected. The experiments yielded in-situ measurements of the thermoelastic stress-induced transformation. The evolution of austenite/martensite phase fractions and of elastic strains in the reinforcing TiC particles and the austenite matrix were obtained by Rietveld refinement [1] during the loading cycle as the austenite transforms to martensite (and its subsequent back transformation during unloading). Phase fractions and strains are discussed in terms of load transfer in composites where the matrix undergoes a stress-induced phase transformation.

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“…Unlike di usional transformations which are mainly controlled by con® gurational energies, a martensitic transformation involves only cooperative atomic displacement or lattice distortions without atom exchange or di usion, and thus lattice dynamics play a key role in MT, as manifested by recent neutron scattering experiments (Shapiro et al 1989, ManÄ osa et al 1993, Ohba et al 1994, elastic constant measurements (Mercier et al 1980, Khachin et al 1987, Brill et al 1991, and theoretical studies (Barsch andKrumhansl 1984, Krumhansl andGooding 1989). Therefore, the in¯uence of alloying element and lattice defect on MT should stem from their in¯uence on lattice dynamics.…”

Section: §1 Introductionmentioning

confidence: 99%

“…However, there have been only a few elastic constant measurements on TiNi to date (Mercier et al 1980, Khachin et al 1987, Brill et al 1991, and no elastic constants are known for the ternary alloy TiNiCu. This is mainly due to the di culty in growing single crystals of these alloys.…”

Section: §1 Introductionmentioning

confidence: 99%

Elastic constants of Ti₅₀Ni₃₀Cu₂₀alloy prior to martensitic transformation

Ren

Taniwaki

Otsuka

et al. 1999

Philosophical Magazine A

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Elastic constants of Ti 50 Ni 30 Cu 20 alloy prior to the martensitic transformation B2 B19 was measured for the ® rst time by using the rectangular parallelepiped resonance method. The softening in both shear modulus c and c 44 was found with approaching transformation temperature. As a result of soft c 44 , the anisotropy factor shows a low value of 2.8 in the vicinity of the transformation temperature. c 11 , c 12 , and bulk modulus were found to show little temperature dependence in the vicinity of the transformation temperature. Compared with the binary Ti 50 Ni 50 alloy, Ti 50 Ni 30 Cu 20 alloy exhibits a 40% higher and increasing anisotropy with approaching transformation temperature. Based on the experimental results, we explained why Ti 50 Ni 30 Cu 20 transforms into B19 martensite, while Ti 50 Ni 50 transforms into a strange monoclinic B19 martensite. §1. Introduction Despite the fact that Ti± Ni is the most important shape memory alloy for various technological applications (for example, Otsuka and Shimizu (1986)), its martensitic transformation (MT) mechanism, which governs its properties, has remained poorly understood for many years compared with other shape memory alloys. The central problem is how to explain the abnormal structure of TiNi martensite B19 .In contrast to other martensites of b (B2) phase alloys which are invariably formed by di erent ways of basal plane stacking (see Nishiyama (1978) for a review), B19 martensite exhibits a large and strange non-basal distortion ({001} 110 B2 shear) to the well-known basal plane structure B19 (Heheman and Sandrock 1971, Kudoh et al. 1985). This non-basal shear gives a monoclinic distortion to B19 structure and lowers the orthorhombic symmetry of B19 to monoclinic, thus the distorted martensite is named as B19 . The reason for such a non-basal distortion is unclear. On the other hand, the addition of 20 at.% Cu into Ti 50 Ni 50 alloy changes the transformation product into common B19 martensite for Ti 50 Ni 30 Cu 20 alloy (Nam et al. 1990b), although the parent phase for both alloys has the same B2 (CsCl) structure. Accompanying such a change of transformation product, the

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Elastic properties of NiTi

Abstract: Physikalisches hstitut. UniversitZt F r d m t , D-6000 F t d u r t am Main, Federal Republic of Germany $ Institut fiu Kernphysik, UniversitHt E t d u r t , D-6000 Frankfurt a m Main, Federal Republic of Germany

Cited by 96 publications

References 13 publications

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Stress-induced martensitic transformations in NiTi and NiTi–TiC composites investigated by neutron diffraction

Elastic constants of Ti₅₀Ni₃₀Cu₂₀alloy prior to martensitic transformation

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Elastic properties of NiTi

Abstract: Physikalisches hstitut. UniversitZt F r d m t , D-6000 F t d u r t am Main, Federal Republic of Germany $ Institut fiu Kernphysik, UniversitHt E t d u r t , D-6000 Frankfurt a m Main, Federal Republic of Germany

Cited by 96 publications

References 13 publications

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Stress-induced martensitic transformations in NiTi and NiTi–TiC composites investigated by neutron diffraction

Elastic constants of Ti50Ni30Cu20alloy prior to martensitic transformation

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Elastic constants of Ti₅₀Ni₃₀Cu₂₀alloy prior to martensitic transformation