Positive and negative two-way shape memory effect in [111]-oriented Ni51Ti49 single crystals

I. Kaya; H. Tobe; H. E. Karaca; M. Nagasako; R. Kainuma; Y. Chumlyakov

doi:10.1016/j.msea.2015.04.087

Positive and negative two-way shape memory effect in [111]-oriented Ni₅₁Ti₄₉ single crystals

I. Kaya, H. Tobe, H. E. Karaca, M. Nagasako, R. Kainuma, Y. Chumlyakov

Research output: Contribution to journal › Article › peer-review

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Abstract

This study investigates the effect of precipitates and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]-oriented Ni₅₁Ti₄₉ single crystal shape memory alloy. The single crystals were either solution-treated or aged at 500°C for 1.5h to form Ni₄Ti₃ precipitates, and then deformed to obtain TWSME. When the solution-treated or aged specimens were loaded at low temperature in martensitic phase, positive (compressive) TWSME was observed. After compressive loading at high temperature in austenitic phase, the solution-treated specimen did not show TWSME while the aged specimen revealed negative (tensile) TWSME. TEM investigation revealed that the negative TWSME strain is produced by the selection of martensite variants due to the back stress created by the dislocation formation around Ni₄Ti₃ precipitates that affects the R-phase formation. A maximum negative TWSME strain of 1.9% was obtained in the aged specimen after compressive deformation of 6% at 200°C.

Original language	English
Pages (from-to)	42-53
Number of pages	12
Journal	Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
Volume	639
DOIs	https://doi.org/10.1016/j.msea.2015.04.087
Publication status	Published - 2015 Jul 5

Keywords

Microstructure
NiTi
Precipitation
Shape memory alloys
Two-way shape memory effect

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title = "Positive and negative two-way shape memory effect in [111]-oriented Ni51Ti49 single crystals",

abstract = "This study investigates the effect of precipitates and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]-oriented Ni51Ti49 single crystal shape memory alloy. The single crystals were either solution-treated or aged at 500°C for 1.5h to form Ni4Ti3 precipitates, and then deformed to obtain TWSME. When the solution-treated or aged specimens were loaded at low temperature in martensitic phase, positive (compressive) TWSME was observed. After compressive loading at high temperature in austenitic phase, the solution-treated specimen did not show TWSME while the aged specimen revealed negative (tensile) TWSME. TEM investigation revealed that the negative TWSME strain is produced by the selection of martensite variants due to the back stress created by the dislocation formation around Ni4Ti3 precipitates that affects the R-phase formation. A maximum negative TWSME strain of 1.9% was obtained in the aged specimen after compressive deformation of 6% at 200°C.",

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author = "I. Kaya and H. Tobe and Karaca, {H. E.} and M. Nagasako and R. Kainuma and Y. Chumlyakov",

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T1 - Positive and negative two-way shape memory effect in [111]-oriented Ni51Ti49 single crystals

AU - Kaya, I.

AU - Tobe, H.

AU - Karaca, H. E.

AU - Nagasako, M.

AU - Kainuma, R.

AU - Chumlyakov, Y.

PY - 2015/7/5

Y1 - 2015/7/5

N2 - This study investigates the effect of precipitates and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]-oriented Ni51Ti49 single crystal shape memory alloy. The single crystals were either solution-treated or aged at 500°C for 1.5h to form Ni4Ti3 precipitates, and then deformed to obtain TWSME. When the solution-treated or aged specimens were loaded at low temperature in martensitic phase, positive (compressive) TWSME was observed. After compressive loading at high temperature in austenitic phase, the solution-treated specimen did not show TWSME while the aged specimen revealed negative (tensile) TWSME. TEM investigation revealed that the negative TWSME strain is produced by the selection of martensite variants due to the back stress created by the dislocation formation around Ni4Ti3 precipitates that affects the R-phase formation. A maximum negative TWSME strain of 1.9% was obtained in the aged specimen after compressive deformation of 6% at 200°C.

AB - This study investigates the effect of precipitates and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]-oriented Ni51Ti49 single crystal shape memory alloy. The single crystals were either solution-treated or aged at 500°C for 1.5h to form Ni4Ti3 precipitates, and then deformed to obtain TWSME. When the solution-treated or aged specimens were loaded at low temperature in martensitic phase, positive (compressive) TWSME was observed. After compressive loading at high temperature in austenitic phase, the solution-treated specimen did not show TWSME while the aged specimen revealed negative (tensile) TWSME. TEM investigation revealed that the negative TWSME strain is produced by the selection of martensite variants due to the back stress created by the dislocation formation around Ni4Ti3 precipitates that affects the R-phase formation. A maximum negative TWSME strain of 1.9% was obtained in the aged specimen after compressive deformation of 6% at 200°C.

KW - Microstructure

KW - NiTi

KW - Precipitation

KW - Shape memory alloys

KW - Two-way shape memory effect

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Positive and negative two-way shape memory effect in [111]-oriented Ni₅₁Ti₄₉ single crystals

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