Influence of isothermal ageing on mechanical behaviour in Ni-rich Ti–Zr–Ni shape memory alloy

Sandu, Adrian Mihai; Tsuchiya, Koichi; Yamamoto, Shin; Todaka, Yoshikazu; Umemoto, Minoru

doi:10.1016/j.scriptamat.2006.08.033

Cited by 33 publications

(7 citation statements)

References 11 publications

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“…Previous studies on Ni-rich Ni-Ti-Hf and Ni-Ti-Zr alloys have ruled out the precipitation of Ni 4 Ti 3 phase and confirmed the formation of the H-phase in these ternary systems [4,5,16,17]. Thus, in analogy to the binary alloys and taking into account the effects observed by TEM (Fig.…”

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confidence: 58%

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Stability of a Ni-rich Ni-Ti-Zr high temperature shape memory alloy upon low temperature aging and thermal cycling

et al. 2016

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The thermal stability of Ni 50.3 Ti 29.7 Zr 20 with aging in austenite at 250 ºC has been studied for three distinctive microstructures obtained after selected thermal treatments: precipitate free and containing two different sizes and densities of H-phase nanoprecipitates. The martensitic transformation is suppressed after 1-3 weeks aging, depending on the initial microstructure, due to a B2 phase instability in the form of short range atomic reordering within the Ti+Zr sublattice, considered to be precursor to the H-phase precipitation. Thermal cycling leads to notable changes in the transformation temperatures, which strongly depends on the starting microstructure.

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confidence: 58%

“…More recently, the attention has moved to Ni-rich Ni-Ti-Hf and Ni-Ti-Zr as economical alternatives to the alloys containing precious metals. The functional properties of Ni-rich Ni-Ti-Hf/Zr can be modified by selected thermal treatments, particularly those inducing the precipitation of a new Ni-rich phase [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

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confidence: 99%

Stability of a Ni-rich Ni-Ti-Zr high temperature shape memory alloy upon low temperature aging and thermal cycling

et al. 2016

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“…Sandu and co-workers [28,29] reported on the effects of aging on the microstructure, martensitic transformation temperatures, and mechanical behavior of Ni-rich NiTiZr SMAs, in particular Ni 52 Ti 42 Zr 6 (at.%). They determined that fine nanosize Ni-rich precipitates were present in the microstructure after certain heat treatments, which increased the hardness of the alloy.…”

Section: On the Contrary Ni-rich Compositions Of Binary Niti Smas Camentioning

confidence: 99%

Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni50.3Ti34.7Zr15 shape memory alloy

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Караман

Pons

et al. 2016

Materials Science and Engineering: A

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The microstructure and shape memory characteristics of the Ni 50.3 Ti 34.7 Zr 15 shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure-property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformationprecipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni 50.3 Ti 34.7 Zr 15 alloy.

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“…The BF image also depicts a high density of dislocations introduced during the cyclic deformation. Since the sample exhibited only a small plastic strain, 14) it can be inferred that the most of the dislocations may be introduced during the forward/reverse transformation as a lattice invariant shear. This does not contradict with the aligned structure seen in Fig.…”

Section: Nmmentioning

confidence: 99%

Microstructural Evolution during Isothermal Aging in Ni-Rich Ti-Zr-Ni Shape Memory Alloys

et al. 2007

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Microstructural evolution during isothermal aging at temperatures ranging from 673 K to 773 K was investigated by transmission electron microscopy (TEM) for Ni-rich Ti-Zr-Ni alloys. It was revealed that the aging is a two-stage process: the first stage is characterized by circular diffuse scattering in electron diffraction patterns, most likely attributed to short range ordered structure with no significant microstructural change. Second stage is characterized by a fine coherent precipitation followed by the coarsening. The precipitates had a lenticular shape and their habit was f100g B2 . The electron diffraction pattern of the sample containing the precipitates exhibited satellite spots at 1=3h110i B2 and 1=4h210i B2 positions. High resolution TEM observations and fast Fourier transformation analysis revealed that the h100i B2 electron diffraction pattern was composed of the reflection from 4 variants of the precipitates. The two-stage microstructural evolutions coincide well with the previously reported changes in mechanical properties and martensitic transformation behavior.

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Influence of isothermal ageing on mechanical behaviour in Ni-rich Ti–Zr–Ni shape memory alloy

Cited by 33 publications

References 11 publications

Stability of a Ni-rich Ni-Ti-Zr high temperature shape memory alloy upon low temperature aging and thermal cycling

Stability of a Ni-rich Ni-Ti-Zr high temperature shape memory alloy upon low temperature aging and thermal cycling

Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni50.3Ti34.7Zr15 shape memory alloy

Microstructural Evolution during Isothermal Aging in Ni-Rich Ti-Zr-Ni Shape Memory Alloys

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