Improving product performance by forming surface compositions from shape memory effect materials with a gradient of properties and phase transformation temperatures

This project is investigates of NiTi shape memory alloy for simple smart application. The shape memory effect (SME) is attributed from the reversible phase transformation when subjected to stress and temperature. In this study, a small model of CAMAR logo was designed to mimic the shape memory effect. Three samples of wire were investigated; (i) Austenitic NiTi (ii) Martensitic NiTi and (iii) commercial plain carbon steel. The reversible austenite to martensite transformation of the NiTi wire was investigated by a differential scanning calorimetry (DSC) at temperatures ranging from -50 and 200oC. The wire was shaped into CAMAR logo using a mould and then heated at 500°C for 30 minutes in a high temperature furnace. To observe the shape effect recovery, the wire was straighten and reheated in warm water at different temperatures. Results showed that the austenitic wire exhibited complete shape memory recovery after heated at temperature approximately 35°C and 80°C. For the martensitic wire, complete recovery was only observed when the water temperature was ~ 80°C and no recovery was observed at ~30°C. This recovery effect was significantly influenced by the reversible phase transformation temperatures (PTTs) which attributed from the Austenite finish (Af) temperature.

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Phase Transformation and Microstructures in Ni and Cu Base Ferromagnetic Shape Memory Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.3157 ◽

2007 ◽

Vol 539-543 ◽

pp. 3157-3162 ◽

Cited By ~ 2

Author(s):

Takuro Kushima ◽

Koichi Tsuchiya ◽

Yasuyoshi Sho ◽

Takafumi Yamada ◽

Yoshikazu Todaka ◽

...

Keyword(s):

Phase Transformation ◽

Magnetic Property ◽

Chemical Composition ◽

Martensitic Transformation ◽

Curie Temperature ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Ferromagnetic Shape Memory Alloys ◽

Ferromagnetic Shape Memory

Effect of chemical composition was investigated on martensitic transformation temperatures, Curie temperature, magnetization and microstructures for Ni-(Mn, Fe, Co)-Ga and Cu-Mn-Ga systems. In the Ni-(Mn, Fe, Co)-Ga alloys, which is a modification of Ni-Mn-Ga systems, the Af and TC over 400 K were achieved. Cu-Mn-Ga alloy exhibited shape memory effect at temperatures above 373 K and had TC over 400 K. Furthermore, Cu-Mn-Ga exhibits good ductility even in polycrystalline condition unlike the case of Ni-Mn-Ga. Effect of addition of the fourth element to improve the magnetic property is under investigation.

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Phase transformation and structure of functionally graded Ni–Ti bi-layer thin films with two-way shape memory effect

Sensors and Actuators A Physical ◽

10.1016/j.sna.2015.03.014 ◽

2015 ◽

Vol 228 ◽

pp. 151-158 ◽

Cited By ~ 9

Author(s):

Maryam Mohri ◽

Mahmoud Nili-Ahmadabadi

Keyword(s):

Thin Films ◽

Phase Transformation ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Functionally Graded

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Martensitic Transformation Behavior and Shape Memory Effect of an Aged Ni-rich Ti-Ni-Hf High Temperature Shape Memory Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.138.399 ◽

2008 ◽

Vol 138 ◽

pp. 399-406 ◽

Cited By ~ 3

Author(s):

Xiang Long Meng ◽

Yu Dong Fu ◽

Wei Cai ◽

J.X. Zhang ◽

Qing Fen Li ◽

...

Keyword(s):

High Temperature ◽

Martensitic Transformation ◽

Shape Memory Alloy ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Aging Temperature ◽

Transformation Behavior ◽

Transformation Temperatures ◽

Solution Treated

The martensitic transformation behavior and shape memory effect (SME) have been investigated in a Ni-rich Ti29.6Ni50.4Hf20 high temperature shape memory alloy (SMA) in the present study. After aging, the transformation temperatures of Ti29.6Ni50.4Hf20 alloy increase obviously due to the precipitation of (Ti,Hf)3Ni4 particles. And the transformation sequence changes from one-step to two-step. When the experimental alloy is aged at different temperatures for 2h, the transformation temperatures increase rapidly with increasing the aging temperature and then change slightly with further increasing the aging temperature. Most of the martensite variants preferentially oriented in the aged Ti29.6Ni50.4Hf20 alloy. The aged Ti29.6Ni50.4Hf20 alloy shows the better thermal stability of transformation temperatures than the solution-treated one because the precipitates depress the introduction of defects during thermal cycling. In addition, the proper aged Ti29.6Ni50.4Hf20 alloy also shows the larger SME than the solution-treated one since the precipitates strengthen the matrix strongly.

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