Grain Nucleation and Growth in Deformed NiTi Shape Memory Alloys: An In Situ TEM Study

A novel approach in determining the transition temperatures of NiTi shape memory alloys was investigated and compared with conventional techniques. The technique is based on microthemal analysis using a scanning thermal microscope (SThM). In particular, this method has the potential to allow the transformation temperatures of thin films to be investigated in situ. Thin film shape memory alloys have potential applications, such as microactuators, where conventional analysis techniques are either not directly applicable to such samples or are difficult to perform.

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Martensitic Nucleation on Dislocations in Cu-Al-Ni Shape Memory Alloys Studied by in Situ Tem

ICOMAT ◽

10.1002/9781118803592.ch9 ◽

2013 ◽

pp. 71-76

Author(s):

M. L. No ◽

D. Caillard ◽

J. San Juan

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

In Situ Tem ◽

Martensitic Nucleation

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In situ TEM study of irradiation-induced transformation in TiNi shape memory alloys

MRS Proceedings ◽

10.1557/proc-792-r1.10 ◽

2003 ◽

Vol 792 ◽

Author(s):

X. T. Zu ◽

F.R. Wan ◽

S. Zhu ◽

L. M. Wang

Keyword(s):

Phase Transformation ◽

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Electron Irradiation ◽

Room Temperature ◽

Critical Voltage ◽

In Situ Tem ◽

In Situ Observation

ABSTRACTTiNi shape memory alloy (SMA) has potential applications for nuclear reactors and its phase stability under irradiation is becoming an important topic. Some irradiation-induced diffusion-dependent phase transformations, such as amorphization, have been reported before. In the present work, the behavior of diffusion-independent phase transformation in TiNi SMA was studied by electron irradiation at room temperature. The effect of irradiation on the martensitic transformation of TiNi shape memory alloys was studied by Transmission Electron Microscopy (TEM) with in-situ observation and differential scanning calorimeter (DSC). The results of TEM and DSC measurements show that the microstructure of samples is R phase at room temperature. Electron irradiations were carried out using several different TEM with accelerating voltage of 200 kV, 300 kV, 400 kV and 1000 kV. Also the accelerating voltage in the same TEM was changed to investigate the critical voltage for the effect of irradiation on phase transformation. It was found that a phase transformation occurred under electron irradiation above 320 kV, but never appeared at 300 kV or lower accelerating voltage. Such phase transformation took place in a few seconds of irradiation and was independent of atom diffusion. The mechanism of Electron-irradiation-induced the martensitic transformation due to displacements of atoms from their lattice sites produced by the accelerated electrons.

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In Situ Structural Characterization of Laser Welded NiTi Shape Memory Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.738-739.338 ◽

2013 ◽

Vol 738-739 ◽

pp. 338-343 ◽

Cited By ~ 2

Author(s):

Francisco Manuel Braz Fernandes ◽

Karimbi Koosappa Mahesh ◽

Corneliu Marius Crăciunescu ◽

João Pedro Oliveira ◽

Norbert Schell ◽

...

Keyword(s):

Mechanical Properties ◽

Synchrotron Radiation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Mechanical Behaviour ◽

State Of The Art ◽

Structural Characteristics ◽

Niti Shape Memory Alloys

The demand of emerging joining techniques for shape memory alloys (SMA) has become of great importance, as their functional properties, namely shape memory effect (SME) and superelasticity (SE) present unique solutions for state-of-the-art applications. Literature shows that significant efforts have been conducted on laser welding of these alloys, although very limited results concerning mechanical properties are repeatedly achieved. A better understanding of the mechanical behaviour of these welded joints may be got through a detailed analysis of the structural characteristics of the material from the base metal to the weld bead. Such studies have been carried out on a series of Ni-rich Ni-Ti SMA laser welded plates using synchrotron radiation.

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