NiTi-Based High-Temperature Shape-Memory Alloys

Noebe, Ronald D.; Biles, Tiffany; Padula, Santo

doi:10.1201/9781420017465.ch7

Cited by 21 publications

(16 citation statements)

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“…Of the known NiTi-based HTSMAs (alloys containing one or more of the alloying elements Au, Pd, Pt, Hf, or Zr), NiTiPd has been one of the most extensively studied [1] and is considered a prime candidate for use as a solid-state actuator in the aerospace, automotive, and energy exploration industries, where space is generally limited, the environment can be harsh, and alloys with a high transformation temperature are a necessity. [2] Originally investigated in 1980 by Boriskina and Kenina, (Ni,Pd)Ti was identified as a stoichiometric pseudobinary system between NiTi and TiPd.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Bigelow

Padula

Garg

et al. 2010

Metall Mater Trans A

130

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While NiTiPd alloys have been extensively studied for proposed use in high-temperature shapememory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd) 49.5 Ti 50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

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Section: Introductionmentioning

confidence: 99%

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Bigelow

Padula

Garg

et al. 2010

Metall Mater Trans A

130

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“…Ternary high-temperature Ti-Ni-based SMAs (TiNiX), where X is a precious metal, such as Pd, Pt, etc., or where X is Zr or Hf, are actively developed and studied [ 12 , 13 , 14 , 15 ]. However, the first group of alloys are too expensive due to the use of precious metals as alloying elements, and the second group exhibits insufficient deformability.…”

Section: Introductionmentioning

confidence: 99%

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

et al. 2023

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In the present work, the possibility of manufacturing long-length TiNiHf rods with a lowered Hf content and a high-temperature shape memory effect in the range of 120–160 °C was studied. Initial ingots with 1.5, 3.0 and 5.0 at.% Hf were obtained by electron beam melting in a copper water-cooled stream-type mold. The obtained ingots were rotary forged at the temperature of 950 °C, with the relative strain from 5 to 10% per one pass. The obtained results revealed that the ingots with 3.0 and 5.0 at.% Hf demonstrated insufficient technological plasticity, presumably because of the excess precipitation of (Ti,Hf)2Ni-type particles. The premature destruction of ingots during the deformation process does not allow obtaining high-quality long-length rods. A long-length rod with a diameter of 3.5 mm and a length of 870 mm was produced by rotary forging from the ingot with 1.5 at.% Hf. The obtained TiNiHf rod had relatively high values of mechanical properties (a dislocation yield stress σy of 800 MPa, ultimate tensile strength σB of 1000 MPa, and elongation to fracture δ of 24%), functional properties (a completely recoverable strain of 5%), and a required finishing temperature of shape recovery of 125 °C in the as-forged state and of 155 °C after post-deformation annealing at 550 °C for 2 h.

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“…Approach (ii), additions of carbon or oxygen do not have a direct effect on transformation temperature, rather both elements preferentially combine with Ti to form stable compounds leaving the matrix Ni rich and therefore resulting in reduction in transformation temperatures [8]. The restriction over compositional stoichiometry to remain in vicinity of equiatomic composition observed in binary NiTi is also extended to certain NiTi based ternary alloys [17,18] via the formation of pseudo binaries [19]. Therefore, in ternary and quaternary alloys (approach iii) it is desirable to maintain the (Ni,X 1 ):(Ti,X 2 ) ratio in vicinity of 1:1, where X 1 and X 2 are third and/or fourth element substitutions for Ni and Ti respectively.…”

Section: Introductionmentioning

confidence: 99%

In situ evaluation of the transformation behaviour of NiTi-based high temperature shape memory alloys

Azeem¹,

Dye²

2014

Intermetallics

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Fine grained polycrystalline NiTi shape memory alloys containing 15 at.% Hf and Zr and zero or 3 at.% Cu fabricated by ingot metallurgy were investigated using in situ synchrotron X-ray diffraction in order to examine the viability of producing stable and affordable high temperature shape memory alloys. The alloys produced had a high thermal hysteresis, in excess of 70 • C but A f temperatures of over 250 • C were obtained for Ni 50 Ti 35 Hf 15. 3 at.% Cu additions did not significantly reduce the per-cycle degradation of transformation temperatures but did reduce the transformation temperatures. The evolution of the lattice parameters during the first five thermal cycles was observed. Negative thermal expansion was found in the b B19 cell direction in all the alloys examined and significant deviations in the lattice parameters in the region of transformation were found. A per-cycle evolution in the end-point B19 lattice parameters was observed, but no such evolution was found for the B2 phase, which is rationalised by appealing to the increase in population of interface dislocations.

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NiTi-Based High-Temperature Shape-Memory Alloys

Cited by 21 publications

References 0 publications

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

Production, Mechanical and Functional Properties of Long-Length TiNiHf Rods with High-Temperature Shape Memory Effect

In situ evaluation of the transformation behaviour of NiTi-based high temperature shape memory alloys

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