Step-wise martensite to austenite reversible transformation stimulated by temperature or stress: a comparison in NiTi alloys

Airoldi, G.; Corsi, Alana; Riva, G.

doi:10.1016/s0921-5093(97)00494-2

Cited by 60 publications

(41 citation statements)

References 11 publications

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“…The opened position refers to the shape in the martensitic state while the closed position corresponds to the shape in the austenitic state. No SMART-effect (Step-wise Martensite to Austenite Reversible Transformation) as described by G. Airoldi et al [6] have been observed.…”

Section: Resultsmentioning

confidence: 71%

Effects of perturbations on a trained shape memory micro-actuator

2001

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The so-called Two-Way-Shape-Memory Effect (TWSME) introduced using a training process has been used to produce a reversible motion in a small actuator. It is usually noted that the TWSME induces a preferred oriented martensite which results, during the reverse transformation, in a spontaneous shape change on cooling. While heating up, the material transforms to austenite and recovers its original shape. However, if the material is mechanically deformed in martensite, in order to modify the martensite variants distribution induced by the TWSME, a two-step transformation occurs: when heating up, the material first transforms into the low-temperature shape, -i.e. the "memorized" shape induced by the training process"-and then to the high-temperature shape. This two-step transformation has been observed in a SMA micro-device. These experiments are presented in details and possible interpretations will be discussed.

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Section: Resultsmentioning

confidence: 71%

Effects of perturbations on a trained shape memory micro-actuator

2001

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“…Madangopal et al [2] proposed that M2 could store more elastic strain energy than M1 in a global transformation; therefore the reverse transformation of M2 could be somehow pre-positioned. Airoldi et al [4] explained the TME in terms of the lack of elastic strain energy in M2. Therefore, a higher temperature is necessary to finish the transformation of M2 and to start the transformation of M1.…”

Section: Discussionmentioning

confidence: 99%

“…Previously this phenomenon was also named thermal arrest memory effect [2] or step-wise martensite to austenite reversible transformation [3,4]. The TME was firstly reported in thermally induced phase transformation in TiNi alloys [5], but then the TME has been reported in many other types of shape memory alloys [6][7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…However, a recent report showed that a repeatable TME can be introduced into a TiNi alloy by a pre-deformation larger than 12% [16]. The TME phenomenon has also been found in stress-induced transformations [4]. However, the TME in the stress-induced transformation cannot be erased by conducting complete mechanical-thermal cycles, but can be erased through an appropriate thermal treatment [4].…”

Section: Introductionmentioning

confidence: 99%

“…The TME phenomenon has also been found in stress-induced transformations [4]. However, the TME in the stress-induced transformation cannot be erased by conducting complete mechanical-thermal cycles, but can be erased through an appropriate thermal treatment [4]. The TME can be observed in the SMAs using many types of characterization methods, such as calorimetric measurements [6,7], the electrical resistance method [13], dilatometry [17] and the wafer curvature method [18].…”

Section: Introductionmentioning

confidence: 99%

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Review on the temperature memory effect in shape memory alloys

Wang

2011

International Journal of Smart and Nano Materials

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Shape memory alloys (SMAs) are well known for their unique shape memory effect (SME) and superelasticity (SE) behavior. The SME and SE have been extensively investigated in past decades due to their potential use in many applications, especially for smart materials. The unique effects of the SME and SE originate from martensitic transformation and its reverse transformation. Apart from the SME and SE, SMAs also exhibit a unique property of memorizing the point of interruption of martensite to parent phase transformation. If a reverse transformation of a SMA is arrested at a temperature between reverse transformation start temperature (A s ) and reverse transformation finish temperature (A f ), a kinetic stop will appear in the next complete transformation cycle. The kinetic stop temperature is a 'memory' of the previous arrested temperature. This unique phenomenon in SMAs is called temperature memory effect (TME). The TME can be wiped out by heating the SMAs to a temperature higher than A f . The TME is a specific characteristic of the SMAs, which can be observed in TiNi-based and Cu-based alloys. TME can also occur in the R-phase transformation. However, the TME in the R-phase transformation is much weaker than that in the martensite to parent transformation. The decrease of elastic energy after incomplete cycle on heating procedure and the motion of domain walls have significant contributions to the TME. In this paper, the TME in the TiNi-based and Cu-based alloys including wires, slabs and films is characterized by electronic-resistance, elongation and DSC methods. The mechanism of the TME is discussed.Keywords: temperature memory effect; shape memory alloys IntroductionShape memory alloys (SMAs) have attracted considerable interest as potential candidates for novel engineering and mechanical applications owing to their excellent functional properties, i.e. shape memory effect (SME) and superelasticity (SE) behavior. The unique effects of SME and SE originate from martensitic transformation and its reverse transformation. SMAs also exhibit a unique property of memorizing the point of interruption during transformation from martensite to parent phase. An incomplete thermal cycle upon heating of SMAs (arrested at a temperature T s between austenite transformation start and finish temperatures, A s and A f ) induced a kinetic stop in the next complete thermal cycle. The kinetic stop temperature is closely related to the previous arrested temperature. Therefore, this phenomenon is named the temperature memory effect (TME) [1].

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