Effect of thermal cycling on the thermomechanical behaviour of NiTi shape memory alloys

Urbina, C.; Flor, Silvia De la; Ferrando, Francesc

doi:10.1016/j.msea.2008.10.026

Cited by 57 publications

(35 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[12,[15][16][17] This has led to speculation that the stability of the R phase can be increased by the introduction of defects during early thermal cycles, thus altering the transformation sequence from B2 fi B19¢ to B2 fi R fi B19¢. [12,14,15,18] Such a hypothesis would appear to be consistent with electron microscopy observations, which showed the nucleation of the R phase on dislocations in Ti 50 Ni 48 Al 2 . [19] Typically, SMAs are annealed following cold work operations to reduce the dislocation density.…”

Section: Introductionmentioning

confidence: 58%

“…The R start temperature (R s ) was found to remain constant, at~52°C, throughout thermal cycling, which is in agreement with the results of other studies. [14,15] The depression of B19¢ s with each thermal cycle in Ti 50.2 Ni 49.8 would suggest that after a given number of cycles, R s would occur at a higher temperature than B19¢ s , as shown in Figure 10(b). The close proximity of the R s and B19¢ s points during early cycles in Figure 10(b) could lead to difficulty in differentiating between the two transformations if using an indirect measurement technique such as electrical resistance.…”

Section: Resultsmentioning

confidence: 98%

“…The B2 phase formed a rhombohedral structured phase (R), prior to the formation of the B19¢. The occurrence of this phase has since formed the subject of many research efforts, [8,14] particularly with respect to its influence on stabilizing the transformation temperatures during thermal cycling. [10,15,16] Several studies of binary TiNi alloys (either equiatomic or slightly Ti rich in composition) have observed the R phase following five to eight thermal cycles, when it had not been evident in earlier cycles.…”

Section: Introductionmentioning

confidence: 99%

“…Measurement techniques such as differential scanning calorimetry (DSC), electrical resistivity (ER), and internal friction have been used in many studies to investigate the behaviour of SMAs during cycling. [12,14,15,20,21] While these techniques can provide data points during cyclic regimes, they can only indicate a change in the material rather than characterize the evolution of crystal structure, phase fraction, texture, etc. Additionally, the sensitivity of these techniques is not always sufficient to provide a true picture of what is actually occurring in the material.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

In-Situ Synchrotron Characterization of Transformation Sequences in TiNi-Based Shape Memory Alloys during Thermal Cycling

Jones

Raghunathan

Dye

2010

Metall Mater Trans A

View full text Add to dashboard Cite

In-situ synchrotron radiation has been used to provide direct analysis of the transformation sequences in TiNi-based shape memory alloys during thermal cycling. The high resolution, narrow peak width Debye-Scherrer diffraction spectra enabled positive identification and quantification of the phase transformation sequences, which is not possible through normal laboratory studies. The results facilitate a clearer understanding of the development and influence of intermediate phases such as R or B19 on sequential martensitic transformations. Ti 50.2 Ni 49.8 transformed predominately via a single-step B2 M B19¢ transformation, although evidence of the R phase was found during cooling in every cycle. The martensitic start temperature was depressed by~0.6°C per cycle, while the R-phase start temperature was found to be unaffected. Ti 50 Ni 41 Cu 9 transformed through a two-step B2 M B19 M B19¢ sequence, with the B2 fi B19 transformation reaching completion prior to the formation of any B19¢. The transformation temperatures of Ti 50 Ni 41 Cu 9 were found to be insensitive to thermal cycling, remaining constant over the studied cycle range.

show abstract

Section: Introductionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

In-Situ Synchrotron Characterization of Transformation Sequences in TiNi-Based Shape Memory Alloys during Thermal Cycling

Jones

Raghunathan

Dye

2010

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…[9,14] Introduction of slip is expected to create shape memory fatigue [8,9,14,[23][24][25][26][27][28][29][30][31][32][33][34][35] : changes in transformation temperature, reduction/loss of memory or introducing irreversible strains, loss of pseudoelasticity, etc. The simplest form of shape memory fatigue is achieved through thermal cycling, [8,14,[25][26][27][29][30][31][32][33][34][35] which is observed to increase dislocation density, depress transformation temperatures, and affect the R-phase and martensite transformation behavior. However, no study exists linking thermal cycling with direct microstructural observations: changes in grain size/shape, in-grain misorientations, retained martensite, etc.…”

Section: Introductionmentioning

confidence: 99%

Origin of Microstructural Irreversibility in Ni-Ti Based Shape Memory Alloys during Thermal Cycling

Basu

Jain

Maji

et al. 2011

Metall Mater Trans A

View full text Add to dashboard Cite

Different microstructures of Ni-Ti-and Ni-Ti-Fe-based shape memory alloys were subjected to thermal cycling: dipping in liquid nitrogen, for approximately 5 minutes, and then bringing it back to room temperature or austenite (cubic: B2) M martensite (monoclinic: B19¢) reversible solid-state phase transformation. Direct electron backscattered diffraction (EBSD) observations could bring out aspects of microstructural irreversibilities: namely, changes in grain size, misorientation buildup, and presence of retained martensite. The average changes in grain size (Dd) differed by almost 2 to 4 times between different microstructures. The highest Dd was typically observed in structures having maximum clustering of fine (d < 5 lm) grains. The sample with highest Dd was also subjected to multiple thermal cycling. Although Dd scaled linearly with d after the first thermal cycle, the scatter increased during subsequent thermal cycles. Grain or orientations deviating from the linear behavior were clearly anisotropic crystallographically. With repeated thermal cycling, the patterns of changes in Dd, austenite misorientation, and retained martensite content were similar. A phenomenological model or hypothesis, based on 40 deg 001 h i orientation relationship between austenite and martensite phases, was proposed to address the observed patterns of microstructural irreversibility.

show abstract

Improvement of NiTi Shape Memory Actuator Performance Through Ultra‐Fine Grained and Nanocrystalline Microstructures

et al. 2011

View full text Add to dashboard Cite

Due to their combination of good thermomechanical properties, corrosion resistance, and biocompatibility, nearstoichiometric NiTi alloys are the shape memory alloys (SMAs) that have had the greatest commercial success. [1][2][3][4][5] Their shape memory effect is derived from a diffusionless transformation in the solid state known as the martensitic transformation. On cooling from high temperatures, the material undergoes a transformation from the austenite phase to the martensite phase that begins at the martensite start temperature (M S ) and is completed at the martensite finish temperature (M F ). Upon reheating, the reverse transformation occurs between the austenite start temperature (A S ) and the austenite finish temperature (A F ). Martensitic transformations are typically associated with a thermal and/or mechanical hysteresis: [6][7][8][9] The forward transformation starts at a lower temperature (in the case of a thermal transformation) or at a higher stress (in the case of a stress-induced transformation) than the reverse transformation. Upon heating or unloading, the martensite begins to transform back to austenite at a relatively higher temperature than was required to induce the transformation upon cooling or mechanical loading of the material. [6][7][8][9] Ball and James [6,7] and others [8,9] have shown that the width of the hysteresis depends on the crystallographic compat- COMMUNICATION[*] Dr.

show abstract

Effect of thermal cycling on the thermomechanical behaviour of NiTi shape memory alloys

Cited by 57 publications

References 44 publications

In-Situ Synchrotron Characterization of Transformation Sequences in TiNi-Based Shape Memory Alloys during Thermal Cycling

In-Situ Synchrotron Characterization of Transformation Sequences in TiNi-Based Shape Memory Alloys during Thermal Cycling

Origin of Microstructural Irreversibility in Ni-Ti Based Shape Memory Alloys during Thermal Cycling

Improvement of NiTi Shape Memory Actuator Performance Through Ultra‐Fine Grained and Nanocrystalline Microstructures

Contact Info

Product

Resources

About