scholarly journals Effect of Ultrasonic Nanocrystal Surface Modification on the Microstructure and Martensitic Transformation of Selective Laser Melted Nitinol

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3068 ◽  
Author(s):  
C.A. Biffi ◽  
P. Bassani ◽  
M. Nematollahi ◽  
N. Shayesteh Moghaddam ◽  
A. Amerinatanzi ◽  
...  
Keyword(s):  
Surface Modification ◽  
Martensitic Transformation ◽  
Functional Properties ◽  
Electron Backscatter Diffraction ◽  
Scanning Calorimetry ◽  
Austenitic Phase ◽  
Production Route ◽  
Microhardness Profile ◽  
Novel Applications ◽  
Backscatter Diffraction

Nitinol has significant potential for biomedical and actuating-sensing devices, thanks to its functional properties. The use of selective laser melting (SLM) with Nitinol powder can promote novel applications aimed to produce 3D complex parts with integrated functional performances. As the final step of the production route, finishing processing needs to be investigated both for the optimization of the surface morphology and the limit alteration of the Nitinol functional properties. In this work, the effect of an advanced method of surface modification, ultrasonic nanocrystal surface modification (UNSM), on the martensitic transformation and microstructure of SLM built Ni50.8Ti49.2 (at.%) was investigated. Scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry indicated that the UNSM process can generate stress-induced martensite, at least partially suppressing the martensitic transformation. The microhardness profile indicates that the UNSM process can affect the mechanical properties of the SLMed Nitinol sample in a range of up to approximately 750 μm in depth from the upper surface, while electron backscatter diffraction analysis highlighted that the initial austenitic phase was modified within a depth below 200 μm from the UNSMed surface.

scholarly journals Microstructural and Mechanical Response of NiTi Lattice 3D Structure Produced by Selective Laser Melting

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 814 ◽  
Author(s):  
Carlo Alberto Biffi ◽  
Paola Bassani ◽  
Jacopo Fiocchi ◽  
Ausonio Tuissi
Keyword(s):  
Martensitic Transformation ◽  
Selective Laser Melting ◽  
Mechanical Response ◽  
Electron Backscatter Diffraction ◽  
Bulk Material ◽  
Niti Alloy ◽  
3D Structure ◽  
Lattice Structures ◽  
Laser Melting ◽  
Scanning Calorimetry

Nowadays, additive manufacturing (AM) permits to realize complex metallic structural parts, and the use of NiTi alloy, known as Nitinol, allows the integration of specific functions to the AM products. One of the most promising designs for AM is concerning the use of lattice structures that show lightweight, higher than bulk material deformability, improved damping properties, high exchange surface. Moreover, lattice structures can be realized with struts, having dimensions below 1 mm—this is very attractive for the realization of Nitinol components for biomedical devices. In this light, the present work regarded the experimental characterization of lattice structures, produced by selective laser melting (SLM), by using Ni-rich NiTi alloy. Differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), and compression testing were carried out for analyzing microstructure, martensitic transformation (MT) evolution, and superelasticity response of the SLMed lattice samples. The lattice microstructures were compared with those of the SLMed bulk material for highlighting differences. Localized martensite was detected in the nodes zones, where the rapid solidification tends to accumulate solidification stresses. An increase of martensitic transformation temperatures was also observed in lattice NiTi.

scholarly journals Novel −75°C SEM cooling stage: application for martensitic transformation in steel

Microscopy ◽  
2020 ◽  
Author(s):  
Kaneaki Tsuzazki ◽  
Motomichi Koyama ◽  
Ryosuke Sasaki ◽  
Keiichiro Nakafuji ◽  
Kazushi Oie ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Electron Backscatter Diffraction ◽  
Dislocation Slip ◽  
In Situ Observation ◽  
Contrast Imaging ◽  
Cooling Stage ◽  
Electron Channelling ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Abstract Microstructural changes during the martensitic transformation from face-centred cubic (FCC) to body-centred cubic (BCC) in an Fe-31Ni alloy were observed by scanning electron microscopy (SEM) with a newly developed Peltier stage available at temperatures to  −75°C. Electron channelling contrast imaging (ECCI) was utilized for the in situ observation during cooling. Electron backscatter diffraction analysis at ambient temperature (20°C) after the transformation was performed for the crystallographic characterization. A uniform dislocation slip in the FCC matrix associated with the transformation was detected at −57°C. Gradual growth of a BCC martensite was recognized upon cooling from −57°C to −63°C.

scholarly journals Decoupling the Impacts of Strain Rate and Temperature on TRIP in a Q&P Steel

JOM ◽  
2022 ◽  
Author(s):  
Christopher B. Finfrock ◽  
Diptak Bhattacharya ◽  
Brady N. L. McBride ◽  
Trevor J. Ballard ◽  
Amy J. Clarke ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Strain Rate ◽  
Strain Hardening ◽  
Electron Backscatter Diffraction ◽  
Dislocation Slip ◽  
Transformation Induced Plasticity ◽  
High Strain Rate Deformation ◽  
The Individual ◽  
Backscatter Diffraction ◽  
Strain Hardening Rate

AbstractThe individual effects of strain rate and temperature on the strain hardening rate of a quenched and partitioned steel have been examined. During quasistatic tests, resistive heating was used to simulate the deformation-induced heating that occurs during high-strain-rate deformation, while the deformation-induced martensitic transformation was tracked by a combination of x-ray and electron backscatter diffraction. Unique work hardening rates under various thermal–mechanical conditions are discussed, based on the balance between the concurrent dislocation slip and transformation-induced plasticity deformation mechanisms. The diffraction and strain hardening data suggest that the imposed strain rate and temperature exhibited dissonant influences on the martensitic phase transformation. Increasing the strain rate appeared to enhance the martensitic transformation, while increasing the temperature suppressed the martensitic transformation.

scholarly journals Stress-induced detwinning and martensite transformation in an austenite Ni–Mn–Ga alloy with martensite cluster under uniaxial loading

IUCrJ ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 366-372 ◽  
Author(s):  
Long Hou ◽  
Ying Niu ◽  
Yanchao Dai ◽  
Lansong Ba ◽  
Yves Fautrelle ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Electron Backscatter Diffraction ◽  
Uniaxial Loading ◽  
Compression Stress ◽  
Compression Axis ◽  
Comprehensive Understanding ◽  
Training Process ◽  
The Hierarchical Structure ◽  
Schmid Factor ◽  
Backscatter Diffraction

Stress-induced martensitic detwinning and martensitic transformation during step-wise compression in an austenite Ni–Mn–Ga matrix with a martensite cluster under uniaxial loading have been investigated by electron backscatter diffraction, focusing on the crystallographic features of microstructure evolution. The results indicate that detwinning occurs on twins with a high Schmid factor for both intra-plate and inter-plate twins in the hierarchical structure, resulting in a nonmodulated (NM) martensite composed only of favourable variants with [001]NM orientation away from the compression axis. Moreover, the stress-induced martensitic transformation occurs at higher stress levels, undergoing a three-stage transformation from austenite to a twin variant pair and finally to a single variant with increasing compressive stress, and theoretical calculation shows that the corresponding crystallographic configuration is accommodated to the compression stress. The present research not only provides a comprehensive understanding of martensitic variant detwinning and martensitic transformation under compression stress, but also offers important guidelines for the mechanical training process of martensite.

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.

Laser shape setting of superelastic nitinol wires: Functional properties and microstructure

2017 ◽  
Vol 10 (01) ◽  
pp. 1740008 ◽  
Author(s):  
Ausonio Tuissi ◽  
Mauro Coduri ◽  
Carlo Alberto Biffi
Keyword(s):  
Laser Beam ◽  
Shape Memory ◽  
Functional Properties ◽  
High Energy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Production Route ◽  
Thin Wires ◽  
The Wire

Shape setting is one of the most important steps in the production route of Nitinol Shape Memory Alloys (SMAs), as it can fix the functional properties, such as the shape memory effect and the superelasticity (SE). The conventional method for making the shape setting is performed at 400–500[Formula: see text]C in furnaces. In this work, a laser beam was adopted for performing straight shape setting on commercially available austenitic Nitinol thin wires. The laser beam, at different power levels, was moved along the wire length for inducing the functional performances. Calorimetric, pseudo-elastic and microstructural features of the laser annealed wires were studied through differential scanning calorimetry, tensile testing and high energy X-ray diffraction, respectively. It can be stated that the laser technology can induce SE in thin Nitinol wires: the wire performances can be modulated in function of the laser power and improved functional properties can be obtained.

scholarly journals Understanding the Machinability of Austempered Ductile Iron (ADI)

2018 ◽  
Vol 925 ◽  
pp. 311-317 ◽  
Author(s):  
Dika Handayani ◽  
Robert C. Voigt ◽  
Kathy Hayrynen
Keyword(s):  
Plastic Deformation ◽  
Martensitic Transformation ◽  
Severe Plastic Deformation ◽  
Ductile Iron ◽  
Cutting Tool ◽  
Electron Backscatter Diffraction ◽  
Austempered Ductile Iron ◽  
Finish Machining ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Guidelines for production milling, turning and drilling of the standard grades of austempered ductile irons (ADI) have been established. Electron Backscatter Diffraction (EBSD) characterization has clearly shown that severe plastic deformation in the machining-affected-zone, ahead of and beneath the cutting tool, will cause strain-induced martensitic transformation of the austenite in the ausferrite structure that inhibits machinability. This phenomenon is particularly of concern during finish machining where small depths of cut are strongly influenced by surface martensite from prior machining passes.

scholarly journals Effect of Trace Elements on the Crystallization Temperature Interval and Properties of 5xxx Series Aluminum Alloys

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 483 ◽  
Author(s):  
Qianqian Li ◽  
Mengjia Li ◽  
Guangxi Lu ◽  
Shaokang Guan ◽  
Engui Zhang ◽  
...  
Keyword(s):  
Trace Elements ◽  
Temperature Interval ◽  
Crystallization Temperature ◽  
Electron Backscatter Diffraction ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Goss Texture ◽  
Mechanical Properties And Corrosion ◽  
Backscatter Diffraction

The influence of alloying elements Er, Zr, Cu, Si and Zn on the crystallization temperature interval, microstructure, mechanical properties and corrosion behavior of Al-Mg-Mn alloy were studied by differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), tensile testing, electrochemical measurements and nitric acid mass loss test (NAMLT). The results show that the crystallization temperature range of Al-Mg-Mn alloy with addition of Zn decreased 4.7 °C. Cold rolled alloys mainly contain S texture, Copper texture, Brass texture, and Goss texture; the content of the S texture is the highest. With the addition of trace elements, the second phase Al3Er, Al3Zr, Al2CuMg, Mg2Si and MgZn2 can be formed, which can improve the tensile strength and yield strength of Al-Mg-Mn alloy. The addition of the alloying element Zn can also improve the intergranular corrosion resistance of the Al-Mg-Mn alloy.

scholarly journals Crystallographic orientation relationships in the α→γ′ martensitic transformation in an Fe–Mn–Al–Ni system

2018 ◽  
Vol 51 (4) ◽  
pp. 990-997 ◽  
Author(s):  
Juan Manuel Vallejos ◽  
César Enrique Sobrero ◽  
Martina Ávalos ◽  
Javier Walter Signorelli ◽  
Jorge Alberto Malarría
Keyword(s):  
Martensitic Transformation ◽  
Electron Backscatter Diffraction ◽  
Parent Phase ◽  
Product Phase ◽  
Orientation Relationships ◽  
Transformation Mechanism ◽  
Thermally Activated ◽  
Type Transformation ◽  
Wide Range ◽  
Backscatter Diffraction

The Fe43.5Mn34Al15Ni7.5 (at.%) alloy exhibits outstanding pseudoelastic behaviour over a wide range of temperatures. This alloy undergoes an unusual martensitic transformation from a disordered body-centred cubic (α) parent phase to a face-centred cubic (γ′) product phase. In the present work, the orientations of the parent and product phases for quenched samples were analysed by electron backscatter diffraction. Bain, Kurdjumow–Sachs, Pitsch, Nishiyama–Wassermann and Greninger–Troiano orientation relationships between the parent and product phases were compared with experimental results. The Pitsch relationship appears to be the most suitable to describe the α→γ′ martensitic transformation. This result provides experimental support to the dislocation-based heterogeneous Bogers–Burgers type transformation mechanism. No indications of variant selection were detected in the thermally activated transformations.

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