Phase transformation characteristics and mechanical characterization of nitinol synthesized by laser direct deposition

Halani, Pratik R.; Kaya, İrfan; Shin, Yung C.; Karaca, H.E.

doi:10.1016/j.msea.2012.09.031

Cited by 91 publications

(39 citation statements)

References 32 publications

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“…The reverse transition was reflected on cooling down, where more than one peak was observed. A similar effect was observed during the NiTi ageing process [32,34,35]. It could also be caused by the presence of multi-compositions of NiTi, slightly differing in their transformation temperatures.…”

Section: Resultssupporting

confidence: 67%

“…During cooling three peaks were present, which were respectively attributed to the transition from austenite to the R-phase, and others to inhomogeneities. Based on the literature, the R-phase creation during transformation can be attributed to the Ni4Ti3 particles' presence for the high nickel [32][33][34] and Ti2Ni for the high titanium alloys [35,36]. The reverse transition was reflected on cooling down, where more than one peak was observed.…”

Section: Resultsmentioning

confidence: 99%

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Properties of NiTi Shape Memory Alloy Micro-Foils Obtained by Pulsed-Current Sintering of Ni/Ti Foils

Prendota

Goc

Strączek

et al. 2019

Metals

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Successful one-step manufacturing of micro-foils of NiTi shape memory compound by pulsed-current sintering of nickel and titanium is reported. Sandwich-like starting configurations of Ni/Ti/Ni (ST1, ST4), Ti/Ni/Ti (ST3), and a simple Ni/Ti (ST2) one, were used. XRD and differential scanning calorimetry (DSC) measurements revealed multistep martensitic transformation, much more pronounced for ST1 than for ST2 and ST3. SEM/energy dispersive X-ray spectrometer (EDS) measurements showed the predominant NiTi phase in ST1, ST4, and other intermetallic compounds in addition to it, for ST2 and ST3. The temperature dependence of the electrical resistance for ST4 shows a peak corresponding to the R-phase and a high residual resistivity. The shape memory effect of 100% was obtained for ST1 and ST4, with the temperature range of its recovery dependent on the initial strain. The ST2 and ST3 materials revealed brittleness and a lack of plasticity due to the dominancy of the austenite phase and/or the intermetallic compound content.

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Properties of NiTi Shape Memory Alloy Micro-Foils Obtained by Pulsed-Current Sintering of Ni/Ti Foils

Prendota

Goc

Strączek

et al. 2019

Metals

View full text Add to dashboard Cite

show abstract

“…For processing NiTi, the entire process is usually done in an enclosed chamber filled with Argon to minimize oxidation. While in principle it is possible to use elemental powder mixtures [137,138,[152][153][154], the majority of published results are from pre-alloyed NiTi powder [137-146, 148, 150, 151].…”

Section: Additive Manufacturing Of Nitimentioning

confidence: 99%

Metals for bone implants. Part 1. Powder metallurgy and implant rendering

et al. 2014

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“…LENS can even be used to fabricate graded materials with composition and porosity gradient across sections. [31,33] Fabrication of Ti, Ti-Al-V [34] and recently superelastic TiNi alloys [35] have been demonstrated using LENS. There have been many reports of SMAs fabricated using additive manufacturing, but to date there has not been investigation of elastocaloric properties of additive manufactured SMAs.…”

Section: Introductionmentioning

confidence: 99%

Elastocaloric cooling of additive manufactured shape memory alloys with large latent heat

Hou¹,

Simsek²,

Stasak³

et al. 2017

J. Phys. D: Appl. Phys.

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The stress-induced martensitic phase transformation of shape memory alloys (SMAs) is the basis for elastocaloric cooling. Here we employ additive manufacturing to fabricate TiNi SMAs, and demonstrate compressive elastocaloric cooling in the TiNi rods with transformation latent heat as large as 20 J g −1 . Adiabatic compression on as-fabricated TiNi displays cooling DT as high as −7.5 °C with recoverable superelastic strain up to 5 %. Unlike conventional SMAs, additive manufactured TiNi SMAs exhibit linear superelasticity with narrow hysteresis in stress-strain curves under both adiabatic and isothermal conditions. Microstructurally, we find that there are Ti 2 Ni precipitates typically one micron in size with a large aspect ratio enclosing the TiNi matrix. A stress transfer mechanism between reversible phase transformation in the TiNi matrix and mechanical deformation in Ti 2 Ni precipitates is believed to be the origin of the unique superelasticity behavior. Abstract:The stress-induced martensitic phase transformation of shape memory alloys (SMAs) is the basis for elastocaloric cooling. Here we employ additive manufacturing to fabricate TiNi SMAs, and demonstrate compressive elastocaloric cooling in the TiNi rods with transformation latent heat as large as 20 J g −1 . Adiabatic compression on as-fabricated TiNi displays cooling ∆T as high as −7.5 °C with recoverable superelastic strain up to 5 %. Unlike conventional SMAs, additive manufactured TiNi SMAs exhibit linear superelasticity with narrow hysteresis in stress-strain curves under both adiabatic and isothermal conditions. Microstructurally, we find that there are Ti2Ni precipitates typically one micron in size with a large aspect ratio enclosing the TiNi matrix.A stress transfer mechanism between reversible phase transformation in the TiNi matrix and mechanical deformation in Ti2Ni precipitates is believed to be the origin of the unique superelasticity behavior.

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Phase transformation characteristics and mechanical characterization of nitinol synthesized by laser direct deposition

Cited by 91 publications

References 32 publications

Properties of NiTi Shape Memory Alloy Micro-Foils Obtained by Pulsed-Current Sintering of Ni/Ti Foils

Properties of NiTi Shape Memory Alloy Micro-Foils Obtained by Pulsed-Current Sintering of Ni/Ti Foils

Metals for bone implants. Part 1. Powder metallurgy and implant rendering

Elastocaloric cooling of additive manufactured shape memory alloys with large latent heat

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