scholarly journals What EBSD and TKD Tell Us about the Crystallography of the Martensitic B2-B19′ Transformation in NiTi Shape Memory Alloys

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 562 ◽  
Author(s):  
Cyril Cayron
Keyword(s):  
Shape Memory ◽  
Electron Backscatter Diffraction ◽  
Niti Alloy ◽  
Phenomenological Theory ◽  
Alternative Approach ◽  
Nickel Titanium Alloys ◽  
Crystallographic Characteristics ◽  
Backscatter Diffraction ◽  
Niti Shape Memory Alloys ◽  
Good Agreement

The complex and intricate microstructure of B19′ martensite in shape memory nickel titanium alloys is generally explained with the Phenomenological Theory of Martensitic Crystallography (PTMC). Over the last decade, we have developed an alternative approach that supposes the existence of a “natural” parent–daughter orientation relationship (OR). As the previous TEM studies could not capture the global crystallographic characteristics of the B2→B19′ transformation required to discriminate the models, we used Electron BackScatter Diffraction (EBSD) and Transmission Kikuchi Diffraction (TKD) to investigate a polycrystalline NiTi alloy composed of B19′ martensite. The EBSD maps show the large martensite plates and reveal the coexistence of different ORs. The TKD maps permit us to image the “twins” and confirm the continuum of orientations suspected from EBSD. The results are interpreted with the alternative approach. The predominant OR in EBSD is the “natural” OR for which the dense directions and dense planes of B2 and B19′ phases are parallel—i.e., (010)B19′//(110)B2 and [101]B19′//[ 1 ¯ 11]B2. The natural OR was used to automatically reconstruct the prior parent B2 grains in the EBSD and TKD maps. From the distortion matrix associated with this OR, we calculated that the habit plane could be (1 1 ¯ 2)B2//(10 1 ¯ )B19′. The traces of these planes are in good agreement with the EBSD maps. We interpret the other ORs as “closing-gap” ORs derived from the natural OR to allow the compatibility between the distortion variants. Each of them restores a parent symmetry element between the variants that was lost by distortion but preserved by correspondence.

scholarly journals Validation of three-dimensional diffraction contrast tomography reconstructions by means of electron backscatter diffraction characterization

2013 ◽  
Vol 46 (4) ◽  
pp. 1145-1150 ◽  
Author(s):  
Melanie Syha ◽  
Andreas Trenkle ◽  
Barbara Lödermann ◽  
Andreas Graff ◽  
Wolfgang Ludwig ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
Data Reconstruction ◽  
Characterization Methods ◽  
Diffraction Contrast ◽  
Ebsd Data ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Tomography Data ◽  
Good Agreement

Microstructure reconstructions resulting from diffraction contrast tomography data of polycrystalline bulk strontium titanate were reinvestigated by means of electron backscatter diffraction (EBSD) characterization. Corresponding two-dimensional grain maps from the two characterization methods were aligned and compared, focusing on the spatial resolution at the internal interfaces. The compared grain boundary networks show a remarkably good agreement both morphologically and in crystallographic orientation. Deviations are critically assessed and discussed in the context of diffraction data reconstruction and EBSD data collection techniques.

scholarly journals Biocompatibility of Nanoporous TiO2Coating on NiTi Alloy Prepared via Dealloying Method

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Jin Huang ◽  
Junqiang Wang ◽  
Xiangdong Su ◽  
Weichang Hao ◽  
Tianmin Wang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Shape Memory ◽  
Biomedical Application ◽  
Niti Alloy ◽  
Treatment Method ◽  
Niti Shape Memory Alloy ◽  
Contact Method ◽  
Biological Compatibility ◽  
Before And After ◽  
Niti Shape Memory Alloys

This paper investigated the biocompatibility of nanoporous TiO2coating on NiTi shape-memory alloy (SMA) prepared via dealloying method. Our previous study shows that the dealloying treatment at low temperature leads to 130 nm Ni-free surface titania surface layer, which possesses good bioactivity because of the combination of hydroxyl (OH−) group in the process of dealloying treatment simultaneously. In this paper, the biological compatibility of NiTi alloy before and after dealloying treatment was evaluated and compared by direct contact method with dermal mesenchymal stem cells (DMSCs) by the isolated culture way. The interrelation between the biological compatibility and surface change of material after modification was systematically analyzed. As a consequence, the dealloying treatment method at low temperature could be of interest for biomedical application, as it can avoid sensitization and allergies and improve biocompatibility of NiTi shape-memory alloys. Thus it laid the foundation of the clinical trials for surface modification of NiTi memory alloy.

Determination of microstructure and twinning relationship between martensitic variants in 53 at.%Ni–25 at.%Mn–22 at.%Ga ferromagnetic shape memory alloy

2006 ◽  
Vol 39 (5) ◽  
pp. 723-727 ◽  
Author(s):  
D. Y. Cong ◽  
Y. D. Zhang ◽  
Y. D. Wang ◽  
C. Esling ◽  
X. Zhao ◽  
...  
Keyword(s):  
High Resolution ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Electron Backscatter Diffraction ◽  
Ferromagnetic Shape Memory Alloy ◽  
Resolution Electron ◽  
Ferromagnetic Shape Memory ◽  
Backscatter Diffraction ◽  
Martensitic Variants

A recent study by high-resolution neutron powder diffraction provided accurate crystallographic information for the newly developed ferromagnetic shape memory alloy 53 at.%Ni–25 at.%Mn–22 at.%Ga. This made it possible to study by high-resolution electron backscatter diffraction the local microstructures and the twinning relationships between martensitic variants. The twin interfaces were also investigated and they are found to be coherent on the {112} planes.

A non-local implicit gradient-enhanced model for thermomechanical behavior of shape memory alloys

2018 ◽  
Vol 29 (9) ◽  
pp. 1818-1834 ◽  
Author(s):  
Hojjat Badnava ◽  
Mohammad Mashayekhi ◽  
Mahmoud Kadkhodaei ◽  
Ahmad Amiri-Rad
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Finite Element Software ◽  
Non Local ◽  
Niti Shape Memory Alloys ◽  
Temperature Responses ◽  
Fully Coupled ◽  
Good Agreement

A three-dimensional, implicit gradient-enhanced, fully coupled thermomechanical constitutive model is developed within the framework of thermodynamic principles for NiTi shape memory alloys. This work focuses on unstable behaviors of NiTi samples under different thermomechanical loading conditions. Temperature variation and its coupling effect on non-local behavior of a shape memory alloy during a loading–unloading cycle at different strain rates are considered. The proposed constitutive equations are implemented into the finite element software ABAQUS, and the numerical investigations indicate that the used procedure is an effective computational tool for simulation of several behaviors of NiTi samples including phase front nucleation and propagation, stress–strain–temperature responses, and transformation-induced stress relaxation. The obtained results are shown to be in a good agreement with available experimental and numerical findings in the literature. The effectiveness of the model in removing mesh sensitivity is evaluated by investigating the mesh-dependence issue for the low strain rate problems through numerical examples.

Grain Rotation during Twin-Detwin Deformation of Mg AZ31 Alloy Using In Situ XRD and EBSD

2019 ◽  
Vol 793 ◽  
pp. 17-22
Author(s):  
Hong Jia Zhang ◽  
Enrico Salvati ◽  
Chrysanthi Papadaki ◽  
Kai Soon Fong ◽  
Xu Song ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Az31 Alloy ◽  
High Energy ◽  
Intensity Change ◽  
X Ray Diffraction ◽  
Grain Rotation ◽  
Backscatter Diffraction ◽  
Tension Loading ◽  
Good Agreement

To investigate grain rotation caused by twinning-detwinning during plastic deformation, experiments using synchrotron high energy X-ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD) are carried out under in situ compression-tension loading. Comparison between the XRD and EBSD data confirms that the intensity change of diffraction rings in XRD experiment is caused by twining and detwinning. A good agreement of twin fraction values obtained from XRD and EBSD is achieved. This demonstrates that the grains and texture are homogeneously distributed along the normal direction of the sample. In the meantime, it is observed that detwinning can only be activated in a large quantity when the loading reverses into tension from compression in the first loading stage.

Crystal structure and crystallographic characteristics of martensite in Ni50Mn38Sb12 alloys

2016 ◽  
Vol 49 (2) ◽  
pp. 513-519 ◽  
Author(s):  
Chunyang Zhang ◽  
Haile Yan ◽  
Yudong Zhang ◽  
Claude Esling ◽  
Xiang Zhao ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Electron Backscatter Diffraction ◽  
Type I ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
Fundamental Information ◽  
Orientation Variant ◽  
Crystallographic Characteristics ◽  
Backscatter Diffraction ◽  
Atomic Coordinates

For Ni–Mn–Sb ferromagnetic multifunctional alloys, the crystal structures of martensite variants and the orientation relationships between them are decisive factors for their magnetic field-induced behaviours and are hence of importance. Such information has rarely been reported in the literature. In the present work, the crystal structure, microstructure and orientation relationships of Ni–Mn–Sb martensite were thoroughly investigated by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). Through XRD analyses, the crystal structure of the martensite, including the crystal system, the space group, the lattice parameters and the atomic coordinates, was fully resolved. The structure is orthorhombic and can be represented with a 4O superstructure. EBSD analyses show that the Ni–Mn–Sb martensite has a lamellar form. One martensite lamella corresponds to one orientation variant. The lamellae are organized in long plate-shaped colonies. Within each colony, four distinct orientation variants (A, B, C and D) appear repeatedly and extend in roughly the same direction. The four variants are twin related to one another, with variants A and C (or variants B and D) forming a type I twin, variants A and B (or C and D) a type II twin, and variants A and D (or B and C) a compound twin. The complete twinning elements for each twin relation were thus fully determined. The interfaces between the variants were identified to be their corresponding twinning planes. All these results provide fundamental information for Ni–Mn–Sb alloys that is useful for interpreting their magnetic and mechanical characteristics.

scholarly journals Functionalization of the NiTi Shape Memory Alloy Surface by HAp/SiO2/Ag Hybrid Coatings Formed on SiO2-TiO2 Glass Interlayer

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1648 ◽  
Author(s):  
Karolina Dudek ◽  
Mateusz Dulski ◽  
Bożena Łosiewicz
Keyword(s):  
Heat Treatment ◽  
Shape Memory ◽  
Electrochemical Impedance ◽  
Niti Alloy ◽  
Composite Coatings ◽  
Energy Dispersive Spectrometer ◽  
Weight Ratio ◽  
Hybrid Coatings ◽  
Niti Shape Memory Alloy ◽  
Niti Shape Memory Alloys

The surface modification of NiTi shape memory alloys is a method for increasing their multi-functionalities. In our solution, hydroxyapatite powder was mixed with a chemically synthesized silicon dioxide/silver (nSiO2/Ag) nanocomposite in a different weight ratio between components (1:1, 5:1, and 10:1) and then electrophoretically deposited on the surface of the NiTi alloy, under various time and voltage conditions. Subsequently, uniform layers were subjected to heat treatment at 700 °C for 2 h in an argon atmosphere to improve the strength of their adhesion to the NiTi substrate. A change in linear dimensions of the co-deposited materials during the sintering process was also analyzed. After the heat treatment, XRD, Raman, and Scanning Electron Microscopy (SEM) + Energy Dispersive Spectrometer (EDS) studies revealed the formation of completely new composite coatings, which consisted of rutile and TiO2-SiO2 glass with silver oxide and HAp particles that were embedded into such coatings. It was found that spalling characterized the 1:1 ratio coating, while the others were crack-free, well-adhered, and capable of deformation to 3.5%. Coatings with a higher concentration of nanocomposite were rougher. Electrochemical impedance spectroscopy (EIS) tests in Ringer’s solution revealed the capacitive behavior of the material with high corrosion resistance. The kinetics and susceptibility to pitting corrosion was the highest for the NiTi electrode that was coated with a 5:1 ratio HAp/nSiO2/Ag hybrid coating.

Shape Recovery and ε - γ Transformation in Fe29Mn7Si5Cr SMA

2008 ◽  
Vol 59 ◽  
pp. 86-91 ◽  
Author(s):  
Nele Van Caenegem ◽  
Kim Verbeken ◽  
Roumen H. Petrov ◽  
N.M. van der Pers ◽  
Yvan Houbaert
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Recovery ◽  
Electron Backscatter Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Backscatter ◽  
Shape Memory Behaviour ◽  
Backscatter Diffraction

The shape memory behaviour of a Fe29Mn7Si5Cr based alloy has been investigated. Characterization of the martensitic transformation and the different structural constituents was performed using optical microscopy, X-ray diffraction (XRD) methods and electron backscatter diffraction (EBSD). The transformation temperatures and the shape recovery were determined by dilatometry on prestrained samples.

A Study on Grinding Performance of Porous NiTi Shape Memory Alloy

2007 ◽  
Vol 359-360 ◽  
pp. 143-147
Author(s):  
Yi Yi Tao ◽  
Jiu Hua Xu ◽  
Wen Feng Ding
Keyword(s):  
Shape Memory ◽  
Mechanical Performance ◽  
Niti Alloy ◽  
Surface Characteristics ◽  
Niti Shape Memory Alloy ◽  
Machining Performance ◽  
Experimental Conditions ◽  
Porous Niti ◽  
Force Ratio ◽  
Niti Shape Memory Alloys

The machining performance of porous NiTi shape memory alloys prepared using powder metallurgical production technique has been investigated experimentally in the grinding operation. Grinding force ratio, specific grinding energy, surface characteristics were detected. The result reveals that, much difference of grinding characteristics exists among three kinds of NiTi alloy because of the pore rate and the mechanical performance induced by TiH2. Under the experimental conditions, the integrated effects of predominant plastic flow and slight brittle fracture were taken for porous NiTi alloy during grinding. Additionally, the grinding parameters should be chosen carefully, otherwise the surface quality deteriorates and even the microcrack perhaps appears.

scholarly journals Crystallography of γ′-Fe4N formation in single-crystalline α-Fe whiskers

2020 ◽  
Vol 53 (4) ◽  
pp. 865-879
Author(s):  
Helge Schumann ◽  
Gunther Richter ◽  
Andreas Leineweber
Keyword(s):  
Orientation Relationship ◽  
Electron Backscatter Diffraction ◽  
Phenomenological Theory ◽  
Mechanical Constraints ◽  
Gaseous Nitriding ◽  
Iron Whiskers ◽  
Backscatter Diffraction ◽  
Fatigue Endurance ◽  
Habit Planes ◽  
Shear System

Gaseous nitriding of steel and iron can significantly improve their properties, for example corrosion resistance, fatigue endurance and tribological properties. In order to obtain a better understanding of the early stages of formation of the initial cubic primitive γ′-Fe4N, the mechanism and crystallography of the α–γ′ phase transformation was investigated under simplified conditions. Single-crystal α-Fe whiskers were nitrided at 823 K and a nitriding potential of 0.7 atm−1/2 for 20 min. The resulting microstructure and phases, as well as the crystallographic orientation of crystallites belonging to a particular phase, were characterized by scanning electron microscopy coupled with electron backscatter diffraction. The habit planes were investigated by single- and two-surface trace analysis. The α-Fe whiskers partly transform into γ′-Fe4N, where γ′ grows mainly in a plate-like morphology. An orientation relationship close to the rational Pitsch orientation relationship and {0.078 0.432 0.898}α and {0.391 0.367 0.844}γ′ as habit planes were predicted by the phenomenological theory of martensite crystallography (PTMC), adopting a {101}α〈101〉α shear system for lattice invariant strain, which corresponds to a {1 1 1}γ′〈1 12〉γ′ shear system in γ′. The encountered orientation relationship and the habit planes exhibit excellent agreement with predictions from the PTMC, although the transformation definitely requires diffusion. The γ′ plates mainly exhibit one single internally untwinned variant. The formation of additional variants due to strain accommodation, as well as the formation of a complex microstructure, was suppressed to a considerable extent by the fewer mechanical constraints imposed on the transforming regions within the iron whiskers as compared to the situation at the surface of bulk samples.

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