Effect of SHS conditions on microstructure of NiTi shape memory alloy

Novák, Pavel; Mejzlíková, Lucie; Michalcová, Alena; Čapek, Jaroslav; Béran, P.; Vojtěch, Dalibor

doi:10.1016/j.intermet.2013.05.015

Cited by 59 publications

(29 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As mentioned above, the structure appearing to result from SHS reaction was observed in the NiTi alloy already at 900°C using a heating rate of approximately 300°C/min, 17 even though other references state that the SHS reaction is triggered by the melt formation by eutectic reaction at 942°C. To prove the possibility to initiate the SHS reaction under these conditions and to describe the reaction mechanism, the following steps were carried out:…”

Section: Methodsmentioning

confidence: 89%

“…The heating rate was the same as in our previous paper, where the structure corresponding to the SHS reaction was observed after the process at 900°C. 17 • In-situ XRD analysis during heating from the laboratory temperature to 900°C with the heating rate of 60°C/min. The heating rate was limited by the capabilities of the device.…”

Section: Methodsmentioning

confidence: 99%

“…15 However, in our previous paper about the optimization of the conditions for the reaction synthesis of the NiTi shape memory alloy the structure corresponding to the SHS reaction was observed already after heating to 900°C, being very similar to the material processed at 1100°C. 17 This paper aims to explain how it is possible to initiate the SHS reaction in NiTi alloy at 900°C. To prove it, the mechanism and kinetics of the Ni+Ti reactions were studied by thermal analysis, in-situ XRD analysis and an experimental model.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Formation of Ni-Ti intermetallics during reactive sintering at 800–900 °C

Novák¹,

Vojtěch²,

Pecenová³

et al. 2017

Mater. Tehnol.

View full text Add to dashboard Cite

In this work the formation of intermetallics in the Ni-Ti system by reactive sintering at 800-900°C was studied. The mechanism and kinetics of the reactions, which led to Ni-Ti phases, were determined by thermal analysis, in-situ XRD and the application of an experimental model consisting of nickel-plated titanium. It was found that the formation of Ni-Ti phases below the transformation temperature of titanium is controlled by diffusion. Above this temperature, the reactions switch to the rapid Self-propagating High-temperature Synthesis (SHS) mode. Keywords: reactive sintering, powder metallurgy, NiTi V delu je bil raziskan nastanek intermetalnih zlitin v sistemu NiTi pri reaktivnem sintranju na 800-900°C. S termi~no analizo, XRD-in situ analizo in uporabo eksperimentalnega modela, nikljanega s titanom, sta bila dolo~ena mehanizem in kinetika reakcij, ki sta vodila k NiTi fazam. Ugotovljeno je bilo, da je tvorba NiTI faze pod transformacijsko temperaturo titana, nadzorovana z difuzijo. Nad to temperaturo se reakcije spremenijo na hitro rasto~i temperaturno -sintezni na~in (SHS). Klju~ne besede: reaktivno sintranje, metalurgija prahov, NiTi

show abstract

Section: Methodsmentioning

confidence: 89%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Formation of Ni-Ti intermetallics during reactive sintering at 800–900 °C

Novák¹,

Vojtěch²,

Pecenová³

et al. 2017

Mater. Tehnol.

View full text Add to dashboard Cite

show abstract

“…1 Intermetallic compounds are promising materials for structural and non-structural high-temperature applications (heat resistance, corrosion resistance, electronic devices, magnets, super conductors). 2,3 Especially NiTi alloys are some of the most technologically important shape-memory alloys 4,5 which find extensive applications in the mechanical, medical, electronic, chemical and aerospace industries due to their excellent shape-memory effect, high erosion resistance, high damping capacity and biocompatibility. These properties make them suitable candidates for various engineering applications.…”

Section: Introductionmentioning

confidence: 99%

“…These properties make them suitable candidates for various engineering applications. [2][3][4][5][6][7] Nickel titanium is a near-equiatomic intermetallic exhibiting distinctive and desirable thermo-mechanical properties, namely, the thermal shape-memory effect and super elasticity. 8 Up to now, a number of processes including self-propagating high-temperature synthesis (SHS), thermal explosion, laser-melting deposition, casting and mechanical alloying techniques 2,5,9,10 have been used for manufacturing ýntermetallics.…”

Section: Introductionmentioning

confidence: 99%

Effect of electric current on the production of NiTi intermetallics via electric-current-activated sintering

Yener¹

2015

Mater. Tehnol.

View full text Add to dashboard Cite

This study focuses on investigating the fabrication of in-situ intermetallic NiTi composites from a powder mixture containing the mass fractions 50 % nickel powder and 50 % titanium powder. The elemental powders were mixed in the stoichiometric ratio corresponding to the NiTi intermetallic molar proportion of 1 : 1, ball-milled and uniaxially compressed under a pressure of 170 MPa. Sintering was then carried out for 15 min in a steel mold using the electric-current-activated sintering method. Electric-current values of 1000 A, 1300 A and 2000 A were used for the sintering while keeping the voltage in the range of 0.9 V to 1.2 V. The phases in the samples were analyzed with XRD and their Vickers hardness was measured as (701 ± 166) HV0.05. Energy dispersive X-ray spectroscopy carried out with a scanning electron microscope (SEM-EDS) showed that the microstructures of the samples consist of different phases such as Ti, Ni2Ti3, NiTi2, Ni3Ti and TiO2 as a function of electric current. The XRD analysis also supported the SEM-EDS results. The nano-indentation technique was used to determine the elastic modulus of different phases. Keywords: NiTi intermetallics, electric-current-activated sintering (ECAS), nano-indentation Ta {tudija je usmerjena v preiskavo in situ izdelave intermetalnega NiTi-kompozita iz me{anice prahov z masnima dele`ema 50 % niklja v prahu in 50 % titana v prahu. Obe vrsti prahu sta bili zme{ani v stehiometri~nem razmerju, ki ustreza molskemu razmerju NiTi 1 : 1, zmleti v kroglastem mlinu in enoosno stisnjeni pri tlaku 170 MPa. Petnajstminutno sintranje je bilo izvr{eno v jeklenem kalupu s sintranjem, aktiviranim z elektri~nim tokom. Pri sintranju so bili uporabljeni elektri~ni tokovi 1000 A, 1300 A in 2000 A, medtem ko je bila napetost v obmo~ju med 0,9 V in 1,2 V. Faze v vzorcih so bile dolo~ene z rentgenom (XRD) in izmerjena je bila trdota po Vickersu (701 ± 166) HV0,05. Energijska disperzijska rentgenska spektroskopija (EDS), izvr{ena na vrsti~nem elektronskem mikroskopu (SEM-EDS), je pokazala, da je mikrostruktura vzorcev sestavljena iz razli~nih faz, kot so Ti, Ni2Ti3, NiTi2, Ni3Ti in TiO2, odvisno od elektri~nega toka. XRD-analiza je podprla rezultate, dobljene s SEM-EDS. Elasti~ni modul razli~nih faz je bil dolo~en z nanovtiski. Klju~ne besede: intermetalna zlitina NiTi, sintranje, aktivirano z elektri~nim tokom (ECAS), nanovtiski

show abstract