scholarly journals Structural Characteristics of Multilayered Ni-Ti Nanocomposite Fabricated by High Speed High Pressure Torsion (HSHPT)

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1629
Author(s):  
Gheorghe Gurau ◽  
Carmela Gurau ◽  
Francisco Manuel Braz Fernandes ◽  
Petrica Alexandru ◽  
Vedamanickam Sampath ◽  
...  
Keyword(s):  
High Pressure ◽  
Shape Memory ◽  
High Speed ◽  
High Pressure Torsion ◽  
Structural Characteristics ◽  
Nickel Titanium ◽  
Martensitic Transition ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Electron Microscopes

It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength.

Phase Transformation in Ni-Ti Shape Memory and Superelastic Alloys Subjected to High Pressure Torsion

2010 ◽  
Vol 123-125 ◽  
pp. 1007-1010 ◽  
Author(s):  
Karimbi Koosappa Mahesh ◽  
Francisco M. Braz Fernandes ◽  
Gheorghe Gurau
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Shape Memory ◽  
High Pressure Torsion ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
One Stage ◽  
Heating And Cooling ◽  
Ti Alloys ◽  
M Phase

A systematic study on the phase transformation of Ni-Ti shape memory and superelastic alloys subjected to Severe Plastic Deformation (SPD) – High Pressure Torsion (HPT) technique has been carried out. Ni-Ti alloys of three compositions were chosen for the study. Specimens of these alloys in as-received (AR) condition and after HPT have been subjected to Differential Scanning Calorimetry (DSC) and X-ray Diffraction (XRD) analyses. In this study, while comparing the results of DSC thermograms and XRD spectra for the same sample conditions, some differences were observed. In the case of NiTi-H alloy after HPT, there appeared one stage phase transformation with DSC both while heating and cooling suggesting Martensite↔Austenite transformation but, with respect to XRD spectra while cooling, at the intermediate temperature of 55°C, the R-phase peaks corresponding to (1 1 2)R and (3 0 0)R planes appeared. In the thermogram obtained for the NiTi-B alloy subjected to HPT, it is observed that, while cooling, the Austenite to R-phase transformation is merged with R-phase to Martensite transformation. The results of the XRD obtained at -180°C show the presence of R-phase along with M-phase. The DSC curve of the NiTi-S alloy subjected to HPT corresponds to one stage phase transformation both while heating and cooling but, the diffractogram of the sample obtained at -180°C corresponds to the presence of both R-phase and M-phase.

scholarly journals Hardness-gradient reversion in FeMnSiCr shape memory alloy modules produced by high-speed high pressure torsion

2015 ◽  
Vol 33 ◽  
pp. 04001 ◽  
Author(s):  
Leandru-Gheorghe Bujoreanu ◽  
Viorel Goanță ◽  
Nicanor Cimpoeșu ◽  
Carmela Gurău ◽  
Marius-Gabriel Suru ◽  
...  
Keyword(s):  
High Pressure ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Speed ◽  
High Pressure Torsion ◽  
Hardness Gradient

Novel High-Speed High Pressure Torsion Technology for Obtaining Fe-Mn-Si-Cr Shape Memory Alloy Active Elements

2014 ◽  
Vol 23 (7) ◽  
pp. 2396-2402 ◽  
Author(s):  
Gheorghe Gurău ◽  
Carmela Gurău ◽  
Octavian Potecaşu ◽  
Petrică Alexandru ◽  
Leandru-Gheorghe Bujoreanu
Keyword(s):  
High Pressure ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Speed ◽  
High Pressure Torsion ◽  
Active Elements

Using High Speed High Pressure Torsion for Cu–13Al–4Ni Shape Memory Alloy Processing

2021 ◽  
Author(s):  
Gheorghe Gurau ◽  
Carmela Gurau ◽  
Francisco Manuel Braz Fernandes ◽  
Rui Jorge Cordeiro Silva ◽  
Florin Marin
Keyword(s):  
High Pressure ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Speed ◽  
High Pressure Torsion

Microstructural Evolution in Ultrafine Grained FeMnSiCr Shape Memory Alloy Modules

2017 ◽  
Vol 1143 ◽  
pp. 214-220 ◽  
Author(s):  
Gheorghe Gurau ◽  
Carmela Gurau ◽  
Mihaela Banu ◽  
Leandru Gheorghe Bujoreanu
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Pressure ◽  
Shape Memory Alloy ◽  
Severe Plastic Deformation ◽  
Shape Memory ◽  
High Speed ◽  
Structural Changes ◽  
High Pressure Torsion ◽  
Transmission Electron

High speed high pressure torsion (HSHPT) processing technology, engineered to achieving (ultra) fine bulk metallic structure under high pressure (~ GPa) and torsion by applying supplementary elevated rotation speed of superior anvil. Coned-disk spring shape modules were processed from an as cast Fe-28Mn-6Si-5Cr (mass %) shape memory alloy (SMA). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed that the structure of modules became submicron as an effect of HSHPT processing. After severe plastic deformation, a grain size gradient was obtained along the truncated cone generator, increasing from inner to outer areas, due to different deformation degrees in these zones. The mechanical and shape memory properties was performed in order to relate the structural changes caused by severe plastic deformation.

scholarly journals The Effect of the In-Situ Heat Treatment on the Martensitic Transformation and Specific Properties of the Fe-Mn-Si-Cr Shape Memory Alloys Processed by HSHPT Severe Plastic Deformation

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4621
Author(s):  
Carmela Gurau ◽  
Gheorghe Gurau ◽  
Felicia Tolea ◽  
Bogdan Popescu ◽  
Mihaela Banu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Speed ◽  
High Pressure Torsion ◽  
Electron Interaction ◽  
Sudden Increase ◽  
Neel Temperature ◽  
Néel Temperature

This work focuses on the temperature evolution of the martensitic phase ε (hexagonal close packed) induced by the severe plastic deformation via High Speed High Pressure Torsion method in Fe57Mn27Si11Cr5 (at %) alloy. The iron rich alloy crystalline structure, magnetic and transport properties were investigated on samples subjected to room temperature High Speed High Pressure Torsion incorporating 1.86 degree of deformation and also hot-compression. Thermo-resistivity as well as thermomagnetic measurements indicate an antiferromagnetic behavior with the Néel temperature (TN) around 244 K, directly related to the austenitic γ-phase. The sudden increase of the resistivity on cooling below the Néel temperature can be explained by an increased phonon-electron interaction. In-situ magnetic and electric transport measurements up to 900 K are equivalent to thermal treatments and lead to the appearance of the bcc-ferrite-like type phase, to the detriment of the ε(hcp) martensite and the γ (fcc) austenite phases.

Nickel–titanium shape memory alloy mechanical components produced by investment casting

2018 ◽  
Vol 29 (19) ◽  
pp. 3748-3757 ◽  
Author(s):  
Jackson de Brito Simões ◽  
Carlos José de Araújo
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Investment Casting ◽  
Mechanical Characterization ◽  
Nickel Titanium ◽  
Compression Tests ◽  
Thermoelastic Martensitic Transformation ◽  
Scanning Calorimetry ◽  
Helical Springs ◽  
Mechanical Components

This work aimed to produce mechanical components of nickel–titanium shape memory alloys using investment casting processes. Then, in order to validate processing, different designs of nickel–titanium shape memory alloy components as staple implants, Belleville springs, meshes, helical springs, screws and hexagonal honeycombs were produced and submitted to thermal and mechanical characterization. Thermoelastic martensitic transformation of the nickel–titanium shape memory alloy parts was determined by differential scanning calorimetry and electrical resistance with temperature, while the superelastic behaviour was verified by cyclic tensile and compression tests. It has been demonstrated that the employed investment casting processes are suitable to manufacture nickel–titanium shape memory alloy mechanical components with simple and complicated designs as well as functional properties related to phase transformation and superelasticity.

scholarly journals Crystallization of Cu60Zr20Ti20 bulk metallic glass by high pressure torsion

2019 ◽  
Vol 58 (1) ◽  
pp. 304-312
Author(s):  
Ádám Révész ◽  
András Horváth ◽  
Gábor Ribárik ◽  
Erhard Schafler ◽  
David J. Browne ◽  
...  
Keyword(s):  
High Pressure ◽  
Metallic Glass ◽  
Crystallite Size ◽  
Bulk Metallic Glass ◽  
High Pressure Torsion ◽  
Average Crystallite Size ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Microstructural Parameters ◽  
Profile Fitting

Abstract Bulk metallic glass of Cu60Zr20Ti20 composition has been synthesized by copper mold casting. Slices of the as-cast glass has been subjected to severe plastic deformation by high-pressure torsion for different whole turns. The microstructure and the thermal behavior of the deformed disks have been investigated by X-ray diffraction and differential scanning calorimetry. It was confirmed that the initial compression preceding the high pressure torsion induces crystallized structure, which shows only minor further changes upon the severe plastic shear deformation achieved by twisting the sample. The X-ray line profiles have been evaluated by the Convolutional Whole Profile Fitting algorithm in order to determine the evolution of the microstructural parameters, such as the median and variance of the crystallite size distribution, average crystallite size and dislocation density as a function of the number of revolutions. Hardness measurements by nanoindentation have also been carried out on the as-cast alloys and the deformed disks.

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