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

Sandu, Adrian Mihai; Tsuchiya, Koichi; Tabuchi, Masayuki; Yamamoto, Shinya; Todaka, Yoshikazu; Umemoto, Minoru

doi:10.2320/matertrans.48.432

Cited by 26 publications

(5 citation statements)

References 15 publications

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“…The diffuse streaks could be attributed to the formation of very small precipitates during the slow furnace cooling process from the homogenisation temperature. Sandu et al 63 also observed similar diffuse streaks in an aged Ni-rich NiTiZr alloy. The SAD pattern taken from the martensite phase (Fig.…”

Section: Crystal Structure and Microstructure Of Nitihf-based Alloysmentioning

confidence: 65%

NiTiHf-based shape memory alloys

Karaca

Acar

Tobe

et al. 2014

Materials Science and Technology

160

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NiTiHf-based shape memory alloys have been receiving considerable attention for high temperature, high strength and two-way shape memory applications since they could have transformation temperatures above 100°C, shape memory effect under high stress (above 500 MPa) and superelasticity above 100°C. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf-based alloys have some drawbacks such as low ductility and high slope in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. It has been revealed that microstructural control is crucial to govern the shape memory properties (e.g. transformation temperatures, matrix strength, shape recovery strain, twinning type, etc.) of NiTiHf-based alloys. A summary of the most recent improvements on selected NiTiHf-based systems is presented to point out their significant shape memory properties, effects of alloying, aging and microstructure of transforming phases and precipitates.

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Section: Crystal Structure and Microstructure Of Nitihf-based Alloysmentioning

confidence: 65%

NiTiHf-based shape memory alloys

Karaca

Acar

Tobe

et al. 2014

Materials Science and Technology

160

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“…Based on the hardness data, it also appeared that Ti 3 Ni 4 precipitates achieved better strengthening of the matrix compared to Ti 2 Ni precipitates; however, no mechanical or shape memory properties were reported. 87 Ni rich compositions have also been examined for Ni-Ti-Zr alloys, 145,146 and similar formation of (Ti-Zr) 3 Ni 4 type precipitates during aging was found. However, these experiments were conducted in low Zr alloys and again no mechanical or shape memory property data were available.…”

Section: Iii1?2 Ni-ti-hf and Ni-ti-zrmentioning

confidence: 86%

High temperature shape memory alloys

Ma¹,

Караман²,

Noebe³

2010

International Materials Reviews

830

371

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Shape memory alloys (SMAs) with high transformation temperatures can enable simplifications and improvements in operating efficiency of many mechanical components designed to operate at temperatures above 100uC, potentially impacting the automotive, aerospace, manufacturing and energy exploration industries. A wide range of these SMAs exists and can be categorised in three groups based on their martensitic transformation temperatures: group I, transformation temperatures in the range of 100-400uC; group II, in the range of 400-700uC; and group III, above 700uC. In addition to the high transformation temperatures, potential high temperature shape memory alloys (HTSMAs) must also exhibit acceptable recoverable transformation strain levels, long term stability, resistance to plastic deformation and creep, and adequate environmental resistance. These criteria become increasingly more difficult to satisfy as their operating temperatures increase, due to greater involvement of thermally activated mechanisms in their thermomechanical responses. Moreover, poor workability, due to the ordered intermetallic structure of many HTSMA systems, and high material costs pose additional problems for the commercialisation of HTSMAs. In spite of these challenges, progress has been made through compositional control, alloying, and the application of various thermomechanical processing techniques to the point that several likely applications have been demonstrated in alloys such as Ti-Ni-Pd and Ti-Ni-Pt. In the present work, a comprehensive review of potential HTSMA systems are presented in terms of physical and thermomechanical properties, processing techniques, challenges and applications.

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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

Evirgen

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

Cited by 26 publications

References 15 publications

NiTiHf-based shape memory alloys

NiTiHf-based shape memory alloys

High temperature shape memory alloys

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

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