A study on the mechanical behavior and microstructure of NiTiHf shape memory alloy under hot deformation

Belbasi, Majid; Salehi, Mohammad Taghi; Mousavi, S.A.A. Akbari; Ebrahimi, Seyed Mohammad

doi:10.1016/j.msea.2012.09.039

Cited by 30 publications

(5 citation statements)

References 25 publications

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“…poor workability and/or high amounts of noble metals. 8,9,11 Titanium-tantalum SMAs represent a promising alternative to overcome all these issues if one can avoid the cyclic degradation due to the formation of the !-phase. The current study investigates the functional fatigue behavior of Ti-Ta and introduces a new concept providing pronounced fatigue life extension.…”

mentioning

confidence: 99%

On the functional degradation of binary titanium–tantalum high-temperature shape memory alloys — A new concept for fatigue life extension

Niendorf

Krooß

Batyrsina

et al. 2014

Funct. Mater. Lett.

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High-temperature shape memory alloys are promising candidates for actuator applications at elevated temperatures. Ternary nickeltitanium-based alloys either contain noble metals which are very expensive, or suffer from poor workability. Titanium-tantalum shape memory alloys represent a promising alternative if one can avoid the cyclic degradation due to the formation of the omega phase. The current study investigates the functional fatigue behavior of Ti-Ta and introduces a new concept providing for pronounced fatigue life extension.Keywords: Omega phase; martensite; phase transformation; microstructure; shape memory effect.Conventional shape memory alloys (SMAs) have been intensely investigated over the last decades due to their extraordinary properties. 1-6 Different metallic alloys can show a shape memory effect, e.g. Cu-based 5 and Fe-based systems, 6 but Ni-Ti is still the most widely used conventional SMA 3 due to good functional and structural properties. Unfortunately, the transformation temperatures of Ni-Ti are limited to below 100 ○ C, thus hindering applications in elevated and high-temperature regimes. 7 As shape memory actuators allow for designing devices characterized by high compactness and efficiency, a large effort has been spent to develop high-temperature shape memory alloys (HTSMAs). For actuation in a medium temperature range of about 100-400 ○ C, mainly Ni-Ti based ternary (Ni-Ti-X) systems have been proposed. [8][9][10] These alloys show promising shape memory characteristics, i.e. actuation strain and microstructural stability, but at the same time suffer from two main drawbacks, i.e. poor workability and/or high amounts of noble metals. 8,9,11 Titanium-tantalum SMAs represent a promising alternative to overcome all these issues if one can avoid the cyclic degradation due to the formation of the !-phase. The current study investigates the functional fatigue behavior of Ti-Ta and introduces a new concept providing pronounced fatigue life extension. The cyclic deformation behavior of a polycrystalline titanium-tantalum (Ti-Ta) alloy containing 30 at.% Ta under iso-stress loading during thermal cycling employing temperatures ranging from 50 ○ C to 600 ○ C was investigated. In order to reveal the most detrimental factor leading to a change of transformation temperatures and a loss of transformation strain, fatigue tests were conducted with differing heating and cooling rates and aging treatments. Using X-ray diffraction (XRD) it could be clearly shown that stabilization of the high-temperature parent phase (β-phase) and the concomitant evolution of the !-phase led to functional degradation. The results of the current study suggest that both phases are mainly induced through aging during high temperature exposure and not by martensitic transformation events during cycling. A new concept employing single-step short-time annealing for regeneration of the initial transformation behavior is introduced.As shown and intensively discussed in a series of studies published by Buenconsejio et al.,[12]...

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confidence: 99%

On the functional degradation of binary titanium–tantalum high-temperature shape memory alloys — A new concept for fatigue life extension

Niendorf

Krooß

Batyrsina

et al. 2014

Funct. Mater. Lett.

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“…For NiTi alloys, replacing titanium or nickel with Zr or Pd above 10 at.% can increase the transformation temperatures [12,13]. There are many reports on the crystal structures [11,[14][15][16][17], phase transformations [18][19][20][21][22][23][24], shape-memory behaviors [12,[25][26][27][28][29], and precipitate phases [30][31][32][33][34] in NiTiX (X = Pd, Hf, and Zr) alloys.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Study of Martensitic Transformation in NiTiPt High Temperature Shape Memory Alloys

Yang

Shang

2021

Applied Sciences

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The crystal structures and martensitic transformation of Ti50Ni50−xPtx alloys (x = 0, 6.25, 8.33, 10.42, 12.5, 18.75, 25) were studied by means of density functional theory (DFT). The computational results indicate that the lattice parameters of Ti-Ni-Pt alloys continuously increase with increasing the Pt content. It is found that at ≤ 12.5 at.% Pt, the martensite structure is monoclinic B19′ phase, and the energy differences between parent and martensite phases (ΔE) decrease slightly with a minimum observed at 6.25 at.% Pt. However, when the Pt content is increased to around 15 at.%, the most stable martensite phase is the orthorhombic B19 structure, and the ΔE increases sharply with Pt concentration. It was found that the phase transition temperatures are closely related to the energy differences ΔE between parent and martensite phases. The electronic structures of martensite B19 and B19′ phases are also discussed.

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“…Of these alloys, NiTiHf is a promising alloy system due to the low cost compared to the other additions while still exhibiting a moderate ductility [18]. To date, several studies have been conducted on phase transformation [19], shape memory properties [20], martensitic transformation [21] and mechanical behavior under hot deformation [22] of NiTiHf alloys. To the best of the authors' knowledge, there are no studies reporting on machining performance of this NiTiHf next generation high temperature SMA.…”

Section: Introductionmentioning

confidence: 99%

Machinability of Ni-rich NiTiHf high temperature shape memory alloy

Kirmacioglu¹,

Kaynak²,

Benafan³

2019

Smart Mater. Struct.

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Machining of Ni-rich Ni 50.3 Ti 29.7 Hf 20 (at%) high temperature shape memory alloys was evaluated under flood cooling conditions. Effects of various cutting speeds (between 20 and 120 m min −1 ), depth of cuts (between 0.4 and 1 mm), and the associated cutting forces on the work-piece surface quality and tool wear of this alloy are presented. Experimental data demonstrates that abrasion and adhesion were the predominant wear mechanisms leading to extreme wear in a short machining time. Thermal softening mechanism dominated the trend of cutting forces until 95 m min −1 cutting speed. Beyond this speed, force components sharply increased resulting from extreme tool wear. Chip breakability of this alloy is much better when compared to NiTi shape memory alloy.

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A study on the mechanical behavior and microstructure of NiTiHf shape memory alloy under hot deformation

Cited by 30 publications

References 25 publications

On the functional degradation of binary titanium–tantalum high-temperature shape memory alloys — A new concept for fatigue life extension

On the functional degradation of binary titanium–tantalum high-temperature shape memory alloys — A new concept for fatigue life extension

Ab Initio Study of Martensitic Transformation in NiTiPt High Temperature Shape Memory Alloys

Machinability of Ni-rich NiTiHf high temperature shape memory alloy

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