A Kinetic Study on the Evolution of Martensitic Transformation Behavior and Microstructures in Ti–Ta High-Temperature Shape-Memory Alloys During Aging

Paulsen, Alexander; Frenzel, Jan; Langenkämper, Dennis; Rynko, Ramona; Kadletz, Peter M.; Grossmann, Lukas; Schmahl, Wolfgang W.; Somsen, Christoph; Eggeler, Gunther

doi:10.1007/s40830-018-00200-7

Cited by 8 publications

(12 citation statements)

References 65 publications

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“…7a and b, which look very different from what is typically observed for Ni-Ti SMAs, can only be appreciated when one considers the effect of the formation, dissolution and re-precipitation of x-phase [41,[43][44][45]. The smaller irregular peak 3 which follows represents the transformation from austenite to martensite, hampered by the formation of the x-phase which forms quickly [30,32,34]. From the experiment shown in Fig.…”

Section: Dsc Chartsmentioning

confidence: 89%

“…Note that this temperature is significantly higher than the temperatures which are typically considered for the shape setting for Ni-Ti-based SMA spring actuators. It was chosen to avoid the formation of a-Ti and x-phase, which downgrade the functional performance of Ti-Ta HTSMAs [20][21][22][31][32][33][34].…”

Section: Thermo Mechanical Treatments and Wire Drawingmentioning

confidence: 99%

“…The start and finish temperatures of the martensitic transformation (M S and M F ) and of the reverse transformation (A S and A F ) were determined using the tangent method. All details on DSC sample preparation and test procedures are given in [34]. The cyclic functional performance of the Ti-Ta spring actuators was characterized using a test rig design which was described by Grossmann et al [35,36].…”

Section: Phase Transition Temperatures and Spring Actuator Testingmentioning

confidence: 99%

“…Atomistic calculations on the stability of phases, especially the x-phase, were performed [28][29][30]. Special emphasis was placed on the role of the x-phase during functional fatigue of Ti-Ta alloys [31][32][33][34] and it has been shown that by controlling the temperature during heating and cooling one can counteract fast functional degradation by x-phase precipitation. Functional fatigue was so far studied using uniaxial specimens.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory-Scale Processing and Performance Assessment of Ti–Ta High-Temperature Shape Memory Spring Actuators

Paulsen

Dumlu

Piorunek

et al. 2021

Shap. Mem. Superelasticity

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Ti75Ta25 high-temperature shape memory alloys exhibit a number of features which make it difficult to use them as spring actuators. These include the high melting point of Ta (close to 3000 °C), the affinity of Ti to oxygen which leads to the formation of brittle α-case layers and the tendency to precipitate the ω-phase, which suppresses the martensitic transformation. The present work represents a case study which shows how one can overcome these issues and manufacture high quality Ti75Ta25 tensile spring actuators. The work focusses on processing (arc melting, arc welding, wire drawing, surface treatments and actuator spring geometry setting) and on cyclic actuator testing. It is shown how one can minimize the detrimental effect of ω-phase formation and ensure stable high-temperature actuation by fast heating and cooling and by intermediate rejuvenation anneals. The results are discussed on the basis of fundamental Ti–Ta metallurgy and in the light of Ni–Ti spring actuator performance.

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Section: Dsc Chartsmentioning

confidence: 89%

Section: Thermo Mechanical Treatments and Wire Drawingmentioning

confidence: 99%

Section: Phase Transition Temperatures and Spring Actuator Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Laboratory-Scale Processing and Performance Assessment of Ti–Ta High-Temperature Shape Memory Spring Actuators

Paulsen

Dumlu

Piorunek

et al. 2021

Shap. Mem. Superelasticity

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“…Transformation temperatures of conventional shape memory alloys (SMAs), such as Ni-Ti and Cu-based alloys, generally do not exceed 200 o C and shape memory alloys with transformation temperatures above 200 o C are required for many applications in advanced technological fields, such as automotive, robotics and space industries [1][2][3]. Many different SMAs are currently being studied for these purposes [4][5][6] and the intermetallic Ni3Ta compound, which exhibits shape memory behaviour with a martensitic transformation temperature above 300 o C, has become a candidate material in these areas [7]. Thus, in recent years, many researchers have tried to determine the mechanism of shape memory behaviour exhibited by the Ni3Ta compound and to examine how different factors, such as third element addition, have an influence on its shape memory behaviour and structural properties.…”

Section: Introductionmentioning

confidence: 99%

Effect of Heat Treatment on the Structural Properties and Martensitic Transformation of Ni-26.5at. %Ta High Temperature Shape Memory Alloy

Yildiz

2020

Gazi University Journal of Science

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On the Importance of Structural and Functional Fatigue in Shape Memory Technology

Frenzel

2020

Shap. Mem. Superelasticity

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The present work provides a brief overview on structural and functional fatigue in shape memory alloys (SMAs). Both degenerative processes are of utmost technological importance because they limit service lives of shape memory components. While our fundamental understanding of these two phenomena has improved during the last two decades, there are still fields which require scientific attention. NiTi SMAs are prone to the formation of small cracks, which nucleate and grow in the early stages of structural fatigue. It is important to find out how these micro-cracks evolve into engineering macro-cracks, which can be accounted for by conventional crack growth laws. The present work provides examples for the complexity of short crack growth in pseudoelastic SMAs. The importance of functional fatigue has also been highlighted. Functional fatigue is related to the degeneration of specific functional characteristics, such as actuator stroke, recoverable strain, plateau stresses, hysteresis width, or transformation temperatures. It is caused by the accumulation of transformation-induced defects in the microstructure. The functional stability of SMAs can be improved by (1) making phase transformations processes smoother and (2) by improving the material’s resistance to irreversible processes like dislocation plasticity. Areas in need of further research are discussed.

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A Kinetic Study on the Evolution of Martensitic Transformation Behavior and Microstructures in Ti–Ta High-Temperature Shape-Memory Alloys During Aging

Cited by 8 publications

References 65 publications

Laboratory-Scale Processing and Performance Assessment of Ti–Ta High-Temperature Shape Memory Spring Actuators

Laboratory-Scale Processing and Performance Assessment of Ti–Ta High-Temperature Shape Memory Spring Actuators

Effect of Heat Treatment on the Structural Properties and Martensitic Transformation of Ni-26.5at. %Ta High Temperature Shape Memory Alloy

On the Importance of Structural and Functional Fatigue in Shape Memory Technology

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