scholarly journals Features of the surface relief of TiNi alloy in coarse-grained and ultrafine-grained states at room and elevated temperatures

2018 ◽  
Vol 447 ◽  
pp. 012046
Author(s):  
A A Churakova ◽  
E F Gilmanova ◽  
D V Gunderov
Keyword(s):  
Surface Relief ◽  
Elevated Temperatures ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Ultrafine Grained

Nanostructured Shape Memory TiNi Alloy Processed by Severe Electroplastic Deformation

2008 ◽  
Vol 584-586 ◽  
pp. 507-512 ◽  
Author(s):  
Vladimir V. Stolyarov
Keyword(s):  
Cold Rolling ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Fracture Strain ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Current Effect ◽  
Electroplastic Rolling ◽  
Ultrafine Grained ◽  
A Current

Electropulse current effect during cold rolling on deformability, nanostructure formation and mechanical behavior in coarse-grained (CG) and ultrafine-grained (UFG) TiNi alloys enriched by nickel is investigated. The UFG sample subjected to cold rolling with current has a fracture strain (е = 1.91) which is higher than that without a current (е = 0.59). As a result of cold rolling with a current and a subsequent annealing at 400-450 °C, nanostructure is formed in both alloys, which leads to a significant enhancement of yield and ultimate stresses. It has been shown that the efficiency of electroplastic rolling depends on the purity of the alloys.

scholarly journals Giant Young’S Modulus Variations in Ultrafine-Grained Copper Caused by Texture Changes at Post-Spd Heat Treatment / Gigantyczne Zmiany Modułu Younga W Ultra Drobnoziarnistej Miedzi Spowodowane Przez Zmiany Tekstury W Trakcie Obróbki Cieplnej Po SPD

2015 ◽  
Vol 60 (4) ◽  
pp. 3073-3076 ◽  
Author(s):  
P. Pal-Val ◽  
L. Pal-Val ◽  
V. Natsik ◽  
A. Davydenko ◽  
A. Rybalko
Keyword(s):  
Heat Treatment ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Sharp Decrease ◽  
Coarse Grained ◽  
Total Change ◽  
Unusual Behavior ◽  
Axial Texture ◽  
Ultrafine Grained

The effect of annealing on dynamic Young’s modulus, E, of ultrafine-grained (UFG) copper obtained by combined severe plastic deformation (SPD) is investigated. It is established that Young’s modulus in the SPD-prepared samples exceeds that in the coarse-grained fully annealed (CGFA) samples by 10 to 20 %. Isothermal annealing at elevated temperatures between 90 and 630°С leads to a sharp decrease of Young’s modulus for annealing temperatures above 210°С. After annealing at 410°С, the value of E reaches its minimal value that is 35 % lower than E in CGFA samples (total change in E is about 47 % of the initial value). Further annealing at higher temperatures leads to an increase in Young’s modulus. It is shown, that the unusual behavior of Young’s modulus is caused by formation of the <111> axial texture in the SPD-treated samples which then is replaced by the <001> texture during the post-SPD heat treatment.

scholarly journals Mechanical behavior and fractographic analysis of a TiNi alloy with various thermomechanical treatment

2019 ◽  
Vol 298 ◽  
pp. 00019 ◽  
Author(s):  
Anna Churakova ◽  
Anna Yudahina ◽  
Elina Kayumova ◽  
Nikita Tolstov
Keyword(s):  
Dislocation Density ◽  
Thermal Cycling ◽  
Thermomechanical Treatment ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Phase Hardening ◽  
Cold Upsetting ◽  
Cycling Treatment ◽  
Ultrafine Grained

Influence of thermomechanical treatment (deformation, thermal cycling treatment in the temperature range of martensitic transformations B2-B19’) on the TiNi alloys’ mechanical behaviour and fracture was studied. Different states were considered, they are initial coarse-grained (CG), ultrafine-grained (UFG) after ECAP (with a grain size of 200 nm), the state after ECAP and cold upsetting by 30% - UFG state with high dislocation density. It was shown that thermal cycling causes some increase in dislocation density, strength and microhardness in all the states. Thermal cycling of UFG alloys allows forming the states with non-equilibrium grain boundaries, with additional dislocations of “phase hardening”. The nature of the fracture was analysed in the TiNi alloy in various states.

In Situ Testing and Heterogeneity of UFG Cu at Elevated Temperatures

2015 ◽  
Vol 1127 ◽  
pp. 67-72
Author(s):  
Martin Petrenec ◽  
Petr Král ◽  
Jiří Dvořák ◽  
Milan Svoboda ◽  
Vàclav Sklenička
Keyword(s):  
Elevated Temperature ◽  
Tensile Test ◽  
Grain Growth ◽  
Elevated Temperatures ◽  
Tensile Deformation ◽  
Constant Strain Rate ◽  
Electron Back Scatter Diffraction ◽  
Coarse Grained ◽  
Ultrafine Grained

Experiments were conducted to investigate deformation-induced processes during in-situ tensile test at elevated temperature. Consequently the microstructure after creep loading was examined by 3D Electron Back Scatter Diffraction (EBSD) technique. The billets of coarse-grained copper were processed by equal-channel angular pressing (ECAP) at room temperature using a die that had an internal angle of 90° between the two parts of the channel and an outer arc of curvature of ~ 20°, where these two parts intersect. The pressing speed was 10 mm/min. To obtain an ultrafine-grained (UFG) material, the billets were subsequently pressed by route Bc by 8 ECAP passes to give the mean grain size ~ 0.7 μm. The constant strain-rate test in tension was performed at 473 K using testing GATAN stage Microtest 2000EW with EH 2000 heated grips which is configured for in-situ electron back scatter diffraction (EBSD) observations. Microstructure was examined by FEG-SEM TESCAN MIRA 3 XM equipped by EBSD detector HKL NordlysMax from OXFORD INSTRUMENT. The tensile test was interrupted by fast stress reductions after different deformation step and observation of microstructure changes was performed. Despite of a considerable interest in ECAP processing method, there are not many works documenting microstructure evolution and changes during creep testing and determining creep mechanisms of ultrafine-grained materials processed by ECAP. It was found that creep resistance of UFG pure Al and Cu is considerably improved after one ECAP pass in comparison with coarse grained material, however, further repetitive pressing leads to a noticeable deterioration in creep properties of ECAP material. Recently it was observed the coarsening of the grains in microstructure of ECAP copper during creep at elevated temperature. It was suggested that creep behaviour is controlled by storage and dynamic recovery of dislocations at high-angle boundaries. In the present work was found that ultrafine-grained microstructure is instable and significant grain growth has already occurred during heating to the testing temperature. Static recrystallization during heating led to the formation of high fraction of special boundaries Σ3 and Σ9. The tensile deformation at 473 K led to the additional grain growth and formation of new grains. Microstructure was investigated also by 3D EBSD.

scholarly journals Comparison of the corrosion behavior of the TiNi alloy in the coarse-grained and ultrafine-grained state

2021 ◽  
Vol 2124 (1) ◽  
pp. 012026
Author(s):  
E M Kayumova ◽  
A A Churakova ◽  
O R Latypov
Keyword(s):  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Volume Fraction ◽  
Significant Proportion ◽  
Gravimetric Method ◽  
Corrosion Products ◽  
Coarse Grained ◽  
Tini Alloy ◽  
Ultrafine Grained ◽  
Coarse Grained State

Abstract This article studies the corrosion behavior of the TiNi alloy in the coarse-grained and ultrafine-grained states. The study of the influence of the initial microstructure on the corrosion behavior of the TiNi alloy was carried out by the gravimetric method in the NaCl and H2SO4 solution for a month. Studies was shown that as a result of the action of a corrosive medium from a sample in a coarse-grained state, it undergoes greater destruction, pitting corrosion was observed, at the same time, in an ultrafine-grained sample only traces of corrosion products are observed on the surface of the samples. Investigations with an inverted light microscope in a dark field made it possible to observe corrosion products and determine their volume fraction. Evaluation of the corrosion rate showed that in the coarse-grained state it is 126 times higher than the corrosion rate in the ultrafine-grained state. Analysis of X-ray phase analysis showed that in the coarse-grained state after corrosion tests, a significant proportion of the TiNiH1.4 phase is observed, while in the ultrafine-grained state all phases correspond only to the TiNi phases. The TiNi alloy contains an Ti2Ni phase enriched Ti both in the coarse-grained state and in the ultrafine-grained state. Moreover, in a coarse-grained state, its share is 2 times higher.

The Aspects of Practical Application of Ultrafine-Grained Titanium Alloys Produced by Severe Plastic Deformation

2010 ◽  
Vol 667-669 ◽  
pp. 1183-1187 ◽  
Author(s):  
Evgeny V. Naydenkin ◽  
Ilya V. Ratochka ◽  
Galina P. Grabovetskaya
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Titanium Alloys ◽  
Elevated Temperatures ◽  
Acoustic Properties ◽  
Coarse Grained ◽  
Medical Implants ◽  
Ultrafine Grained ◽  
Mechanical And Physical Properties ◽  
Ultrasound System

The mechanical and physical properties of ultrafine-grained titanium alloys produced by severe plastic deformation are considered. It is found that the formation of ultrafine-grained structure in these materials causes a significant enhancement in their mechanical properties at room temperature and in their resistance to hydrogen embrittlement as well as a change in their acoustic properties. Moreover, superplasticity is realized in these materials at less elevated temperatures relative to the respective coarse grained counterparts. It is shown that the above changes in material properties permit optimization of conditions by the production of items from the titanium alloys, e.g. medical implants having the requisite strength and stepped waveguides having long life even in the high power density conditions of an ultrasound system.

scholarly journals The Investigation of Microstructure and Mechanical Behavior and the Fractographic Analysis of the Ti49.1Ni50.9 Alloy in States with Different Activation Deformation Volumes

2021 ◽  
Vol 11 (7) ◽  
pp. 3052
Author(s):  
Anna Churakova ◽  
Dmitry Gunderov ◽  
Elina Kayumova
Keyword(s):  
Mechanical Behavior ◽  
Test Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Fractographic Analysis ◽  
Coarse Grained ◽  
Ultrafine Grained ◽  
Coarse Grained State ◽  
Different Temperatures

In this article, the microstructure and mechanical behavior of the Ti49.1Ni50.9 alloy with a high content of nickel in a coarse-grained state, obtained by quenching, ultrafine-grained (obtained through the equal-channel angular pressing (ECAP) method) and nanocrystalline (high pressure torsion (HPT) + annealing), were investigated using mechanical tensile tests at different temperatures. Mechanical tests at different strain rates for determining the parameter of strain rate sensitivity m were carried out. Analysis of m showed that with an increase in the test temperature, an increase in this parameter was observed for all studied states. In addition, this parameter was higher in the ultrafine-grained state than in the coarse-grained state. The activation deformation volume in the ultrafine-grained state was 2–3 times greater than in the coarse-grained state at similar tensile temperatures. Fractographic analysis of samples after mechanical tests was carried out. An increase in the test temperature led to a change in the nature of fracture from quasi-brittle–brittle (with small pits) at room temperature to ductile (with clear dimples) at elevated temperatures. Microstructural studies were carried out after the tensile tests at different temperatures, showing that at elevated test temperatures, the matrix was depleted in nickel with the formation of martensite twins.

Description of the Superplastic Flow Process by Deformation Mechanism Maps in Ultrafine-Grained Materials

2016 ◽  
Vol 838-839 ◽  
pp. 51-58 ◽  
Author(s):  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Deformation Mechanism ◽  
Elevated Temperatures ◽  
High Pressure Torsion ◽  
Processing Technique ◽  
Superplastic Flow ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Flow Process ◽  
Ultrafine Grained ◽  
Wide Range

The synthesis of ultrafine-grained (UFG) materials is very attractive because small grains lead to excellent creep properties including superplastic ductility at elevated temperatures. Severe plastic deformation (SPD) is an attractive processing technique for refining microstructures of metallic materials to have ultrafine grain sizes within the submicrometer to even the nanometer level. Among the SPD techniques, most effective processing is conducted through equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) and there are numerous reports demonstrating the improved tensile properties at elevated temperature. This report demonstrates recent results on superplasticity in metals after ECAP and HPT. Moreover, superplastic flow of the UFG materials is evaluated by using flow mechanisms developed earlier for coarse-grained materials and depicted by plotting deformation mechanism maps which provide excellent visual representations of flow properties over a wide range of testing conditions.

scholarly journals New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

2015 ◽  
Vol 60 (2) ◽  
pp. 605-614 ◽  
Author(s):  
T. Kvačkaj ◽  
A. Kováčová ◽  
J. Bidulská ◽  
R. Bidulský ◽  
R. Kočičko
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Tensile Tests ◽  
Coarse Grained ◽  
Wear Behaviour ◽  
Ofhc Copper ◽  
Strain Rates ◽  
Ultrafine Grained ◽  
Reduction Of Area ◽  
Pin On Disk

AbstractIn this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates$({\dot \varepsilon} \sim 10^2 \;{\rm{s}}^{ - 1} )$. However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.

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