NiTi and NiTi-TiC composites: Part 1. transformation and thermal cycling behavior

Mari, Daniele; Dunand, David C.

doi:10.1007/bf02669642

Cited by 50 publications

(14 citation statements)

References 34 publications

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“…In agreement with [3,18,19], no reaction was observed by optical microscopy between the NiTi matrix and the TiC particles, which were almost perfectly stoichiometric with a composition of 49.890.1 at.% C (as determined by combustion analysis with infrared detection). Given the inert nature of the TiC and the identical initial materials and processing routes for all samples, the matrix chemical composition can be assumed constant in all samples, suggesting that the differences in mechanical behavior observed in Fig.…”

Section: Resultssupporting

confidence: 76%

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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Section: Resultssupporting

confidence: 76%

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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“…From this table, it is seen that the transformation temperatures of NiTi are significantly altered by the addition of TiC particulates, as described in more detail in Refs. [3,4]. Density measurements show that NiTi, NiTi-10TiC, and NiTi-20TiC are 99.8, 99.7, and 99.4%, respectively, of their theoretical density.…”

Section: Resultsmentioning

confidence: 96%

“…The choice of TiC as reinforcement was motivated by the lack of reactivity with NiTi, which could otherwise adversely affect the shape-memory characteristics. The NiTi-TiC system's thermal transformation behavior [3,4], bulk mechanical properties in compression [5], and subsequent shape-memory recovery [6], and the study by neutron diffraction of twinning deformation and shape-memory recovery have been investigated [7,8]. More recently, their behavior in tension and two-way shape-memory response (wherein the transformation to martensite on cooling is biased) have been studied [9,10].…”

Section: Introductionmentioning

confidence: 99%

Fatigue crack-growth in shape-memory NiTi and NiTi–TiC composites

Vaidyanathan

Dunand

Ramamurty

2000

Materials Science and Engineering: A

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“…The additional step is associated with the internal elastic stresses, which facilitate the transformation to the intermediate R-phase with a lower transformation shear. [2,4,5,8,10,[13][14][15] The transformation sequences that are not as well described are those that include greater than two steps on cooling or heating. They are referred to here as multiple-step transformations (MSTs) and include sequences such as three-step/two-step and threestep/three-step transformations, for example.…”

Section: Introductionmentioning

confidence: 98%

Analysis of multistep transformations in single-crystal NiTi

Johnson

Hamilton

Şehitoğlu

et al. 2005

Metall Mater Trans A

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The effects of composition and heat treatment on the thermally induced phase-transformation behavior of single-crystal NiTi with compositions of 50. 1, 50.4, 50.8, and 51.5 at. pct Ni are presented in this article. Differential scanning calorimetry (DSC) experiments reveal that a heat-treated 50.1 at. pct Ni alloy exhibits an unprecedented multiple-step transformation (MST) on both heating and cooling, with up to four peaks. This behavior is absent in the higher-Ni-content alloys. In polycrystalline NiTi alloys, MSTs have been attributed to microstructure heterogeneities such as grain boundaries and dislocations, which influence precipitation. In-situ scanning electron microscopy (SEM) results show that the MST in the 50.1 at. pct Ni alloy is associated with single-crystal defects such as dendrites and low-angle boundaries. A heterogeneous precipitate distribution is observed in transmission electron microscopy (TEM) images of the same low-Ni alloy, also associated with the defects, creating conditions that have been shown in other studies to promote the MST in polycrystals. These MSTs are not observed for high-Ni single-crystal alloys containing the same defects. In this article, we describe the origin of the extraordinary forward and reverse MSTs in the low-Ni alloy and the absence of the MST in high-Ni alloys. Transformation sequences are proposed based on the contrasting precipitate microstructures.

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NiTi and NiTi-TiC composites: Part 1. transformation and thermal cycling behavior

Cited by 50 publications

References 34 publications

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

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

Fatigue crack-growth in shape-memory NiTi and NiTi–TiC composites

Analysis of multistep transformations in single-crystal NiTi

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