In situ EBSD investigations of the asymmetric stress-induced martensitic transformation in TiNi shape memory alloys under bending

2008 ◽  
Vol 498 (1-2) ◽  
pp. 278-282 ◽  
Author(s):  
S.C. Mao ◽  
X.D. Han ◽  
Y.B. Tian ◽  
J.F. Luo ◽  
Z. Zhang ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Asymmetric Stress

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

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.

Martensitic Transformation in Submicron Cu-Al-Ni Pillar

2013 ◽  
Vol 1581 ◽  
Author(s):  
Lifeng Liu ◽  
Yumei Zhou ◽  
Lan Lv
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Single Crystal ◽  
Shape Memory ◽  
Sample Size ◽  
Small Scale ◽  
Bulk Materials ◽  
Stress Curve ◽  
Strain Stress

ABSTRACTThe transformation plateau on the strain-stress curve is the characteristic of superelasticity of bulk shape memory alloys upon tension/compression loading. However, recent studies show that such transformation plateau is hard to see when the sample size of shape memory alloys decreases to submicrons. In order to see what happened in such small scale samples during loading, in-situ compression test has been done with single crystal Cu-14.2Al-4.0Ni (wt %) submicron pillars. Our in-situ observation during compression demonstrates that the stress-induced martensitic transformation indeed occurs in submicron pillars, but is not suppressed. Furthermore, the transformation proceeds in a sequential nucleation-growth-nucleation dominated mode, but not the transient way like that in bulk materials. As a result, the stress keeps increasing throughout the transformation and no obvious transformation plateau can be detected. However, the underlying reason for such contrast transformation behaviors between our submicron pillars and bulk materials still needs further investigation.

Atomic Order and Martensitic Transformation in Cu-Al-Be Shape Memory Alloys

1995 ◽  
Vol 05 (C8) ◽  
pp. C8-973-C8-978
Author(s):  
M. Jurado ◽  
Ll. Mañosa ◽  
A. González-Comas ◽  
C. Stassis ◽  
A. Planes
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Atomic Order

scholarly journals Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

2021 ◽  
Author(s):  
A. Bauer ◽  
M. Vollmer ◽  
T. Niendorf
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Grain Orientations ◽  
High Degree

AbstractIn situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

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