Dynamic Recrystallization Mechanisms of Nickel Niobium Alloys during Hot Working

2021 ◽  
Vol 1016 ◽  
pp. 869-874
Author(s):  
Nadjoua Matougui ◽  
Mohamed Lamine Fares ◽  
David Piot
Keyword(s):  
Dynamic Recrystallization ◽  
Torsion Test ◽  
Large Strains ◽  
Strain Rates ◽  
Niobium Alloys ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Hot Torsion Test ◽  
Continuous Dynamic ◽  
Electron Back Scattered Diffraction

This present work examines the influence of niobium in solid solution on the microstructural evolution of pure nickel at various deformation conditions. On this purpose, high-purity nickel and six model nickel-niobium alloys (Ni–0.01, 0.1, 1, 2, 5 and 10 wt. % Nb) were subjected to hot torsion test to large strains within the temperature range from 800 to 1000 °C at strain rates of 0.03, 0.1 and 0.3 s–1. Microstructural analyses were carried out using both optical and scanning electron microscopy-based electron back-scattered diffraction technique. The overall results showed the key role played by the Nb amount when coupled with various DRX mechanisms involved, i.e. DDRX, CDRX, and GDRX with respect to the prescribed deformation conditions, in reducing grain size and retarding DRX kinetics from which the microstructures of the examined materials such as Ni 2 and 10 wt. % Nb were seen evolving in different ways. In all these deformed materials, a transition from discontinuous dynamic recrystallization to continuous dynamic recrystallization was observed at low temperature and high strain rate whereas only discontinuous dynamic recrystallization occurred at high temperature.

Dynamic Recrystallization of Zircaloy-4 during Working within the Upper α-Range

2004 ◽  
Vol 467-470 ◽  
pp. 1151-1156 ◽  
Author(s):  
Cédric Chauvy ◽  
Pierre Barbéris ◽  
Frank Montheillet
Keyword(s):  
Dynamic Recrystallization ◽  
Large Strain ◽  
Large Angle ◽  
Rate Sensitivity ◽  
Large Strains ◽  
Strain Rates ◽  
Compression Tests ◽  
Continuous Dynamic Recrystallization ◽  
Ebsd Technique ◽  
Continuous Dynamic

Compression tests were used to simulate simple deformation paths within the upper a-range of Zircaloy-4 (i.e. 500°C-750°C). The mechanical behaviour reveals two different domains : at low temperatures and large strain rates, strain hardening takes place before flow softening, whereas this first stage disappears at lower flow stress levels. Strain rate sensitivity and activation energy were determined for both domains. Dynamic recrystallization was investigated using the Electron BackScattering Diffraction (EBSD) technique. It appears that the mechanism involved here is continuous dynamic recrystallization (CDRX), based on the increasing misorientation of subgrain boundaries and their progressive transformation into large angle boundaries. At low strains (e £ 0.3), CDRX kinetics are similar whatever the deformation conditions, while higher temperatures and lower strain rates promote recrystallization at large strains.

scholarly journals In-situ characterization of continuous dynamic recrystallization during hot torsion of an Al–Si–Mg alloy

2020 ◽  
Vol 822 ◽  
pp. 153282 ◽  
Author(s):  
David Canelo-Yubero ◽  
Zsolt Kovács ◽  
J.F. Thierry Simonet Fotso ◽  
Domonkos Tolnai ◽  
Norbert Schell ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Mg Alloy ◽  
In Situ Characterization ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic

Microstructural Evolution of AA6082 with Small Aluminides under Hot Torsion and Friction Stir Processing

2013 ◽  
Vol 753 ◽  
pp. 263-266 ◽  
Author(s):  
Cecilia Poletti ◽  
Friedrich Krumphals ◽  
Stefan Mitsche ◽  
Zeng Gao
Keyword(s):  
Local Deformation ◽  
Large Strains ◽  
Fem Simulations ◽  
Friction Stir ◽  
Fine Grained ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic ◽  
Hot Rolled

The hot rolled AA6082 aluminium alloy with aluminide dispersoids is deformed up to large strains to obtain a fine grained microstructure. Friction stir spot welding (FSSW) is carried out on rolled plates by means of a device provided by MTS System Corporation. FEM simulations determine that the material can flow up to local strains between 10 and 50 when the material reaches temperatures between 300-500°C. With this information, hot torsion tests at constant temperatures are carried out in a Gleeble ® 3800 machine for different strain rates. In both cases, in situ water quenching is applied to freeze the microstructure and avoid any static recrystallization effect after hot deformation. Light optical microscopy is used to identify the evolution of the grains as a function of the local deformation parameters determined by FEM simulations. The microstructure development by FSSW as well as by torsion is then further characterized by means of EBSD. At small strains the material deforms mainly by dynamic recovery with small low angle grain boundary formation and boundary dragging by fine aluminides and Mg2Si. At large strains grain refinement by continuous dynamic recrystallization takes place heterogeneously as a function of the original crystallographic orientation and precipitation state of each grain.

scholarly journals Continuous dynamic recrystallization during hot torsion of an aluminum alloy.

2019 ◽  
Vol 1270 ◽  
pp. 012049 ◽  
Author(s):  
M C Poletti ◽  
T Simonet-Fotso ◽  
D Halici ◽  
D Canelo-Yubero ◽  
F Montheillet ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Dynamic Recrystallization ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic

Microstructure Evolution of Ti-5Al-5V-5Mo-3Cr after Hot Deformation at Large and Moderate Strains

2018 ◽  
Vol 941 ◽  
pp. 1443-1449 ◽  
Author(s):  
María Cecilia Poletti ◽  
Ricardo Buzolin ◽  
Sanjev Kumar ◽  
Peng Wang ◽  
Thierry Franz Jules Simonet-Fotso
Keyword(s):  
Hot Deformation ◽  
Beta Phase ◽  
Internal Variable ◽  
Alpha Phase ◽  
Large Strains ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Wide Range ◽  
Hot Torsion ◽  
Continuous Dynamic

This work deals with the analysis and modelling of the microstructural evolution of the metastable titanium alloy Ti-5Al-5V-5Mo-3Cr during hot deformation up to moderate and large strains. Experimental flow curves and deformed samples are obtained by hot compression and hot torsion tests using a Gleeble ® 3800 device. The samples are deformed above and below the beta transus temperature and in a wide range of strain rates. Microstructures are characterized after deformation and in-situ water quenching using light optical and scanning electron microscopy and electron back scattered diffraction (EBSD). Dynamic recovery of the beta phase is found to be the main deformation mechanism up to moderated strains. By increasing the strain, continuous dynamic recrystallization (cDRX) is confirmed by the progressive conversion of low angle boundaries into high-angle boundaries. Alpha phase plays a secondary role in the deformation of the material by pinning the movement of beta high angle grain boundaries (HAGB). The evolution of the microstructure is modelled using dislocation density as internal variable in the single β field.

Geometric Dynamic Recrystallization in an AA2219 Alloy Deformed to Large Strains at an Elevated Temperature

2004 ◽  
Vol 467-470 ◽  
pp. 1199-1204 ◽  
Author(s):  
Rustam Kaibyshev ◽  
I. Mazurina ◽  
Oleg Sitdikov
Keyword(s):  
Dynamic Recrystallization ◽  
Equal Channel Angular Extrusion ◽  
Large Strains ◽  
Specific Process ◽  
Continuous Dynamic Recrystallization ◽  
Aa2219 Alloy ◽  
Continuous Dynamic ◽  
The Stability ◽  
Average Size ◽  
Zr Alloy

The mechanism of new grain evolution during equal channel angular extrusion (ECAE) up to a total strain of ~12 in an Al-Cu-Mn-Zr alloy at a temperature of 475oC (0.75Tm) was examined. It was shown that the new grains with an average size of about 15 µm result from a specific process of geometric dynamic recrystallization (GRX) which can be considered as a type of continuous dynamic recrystallization (CDRX). This process involves three elementary mechanisms. At moderate strains, extensive elongation of initial grains takes place; old grain boundaries become progressively serrated. Upon further ECAE processing, transverse low-angle boundaries (LAB) with misorientation ranging from 5 to 15o are evolved between grain boundary irregularities subdividing the initial elongated grains on crystallites with essentially equiaxed shape. The misorientation of these transverse subboundaries rapidly increases with increasing strain, resulting in the formation of true recrystallized grains outlined by high-angle boundaries from all sides. In the same time, the average misorientation of deformation-induced boundaries remains essentially unchanged during ECAE. It is caused by the fact that the evolution of LABs with misorientation less than 4o occurs continuously during severe plastic deformation. The mechanism maintaining the stability of the transverse subboundaries that is a prerequisite condition for their further transformation into highangle boundaries (HABs) is discussed.

scholarly journals Review on Dynamic Recrystallization of Martensitic Stainless Steels during Hot Deformation: Part I—Experimental Study

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 572
Author(s):  
Hamed Aghajani Derazkola ◽  
Eduardo García Gil ◽  
Alberto Murillo-Marrodán ◽  
Damien Méresse
Keyword(s):  
Dynamic Recrystallization ◽  
Stainless Steels ◽  
Hot Deformation ◽  
Large Strains ◽  
Microstructural Changes ◽  
Ultrafine Grains ◽  
Microstructure Changes ◽  
Continuous Dynamic Recrystallization ◽  
Martensitic Stainless Steels ◽  
Continuous Dynamic

The evolution of the microstructure changes during hot deformation of high-chromium content of stainless steels (martensitic stainless steels) is reviewed. The microstructural changes taking place under high-temperature conditions and the associated mechanical behaviors are presented. During the continuous dynamic recrystallization (cDRX), the new grains nucleate and growth in materials with high stacking fault energies (SFE). On the other hand, new ultrafine grains could be produced in stainless steel material irrespective of the SFE employing high deformation and temperatures. The gradual transformation results from the dislocation of sub-boundaries created at low strains into ultrafine grains with high angle boundaries at large strains. There is limited information about flow stress and monitoring microstructure changes during the hot forming of martensitic stainless steels. For this reason, continuous dynamic recrystallization (cDRX) is still not entirely understood for these types of metals. Recent studies of the deformation behavior of martensitic stainless steels under thermomechanical conditions investigated the relationship between the microstructural changes and mechanical properties. In this review, grain formation under thermomechanical conditions and dynamic recrystallization behavior of this type of steel during the deformation phase is discussed.

Analysis of Large Strain Hot Torsion Textures Associated With “Continuous” Dynamic Recrystallization

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
S. M. Lim ◽  
C. Desrayaud ◽  
F. Montheillet
Keyword(s):  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Large Strain ◽  
Texture Evolution ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Shear Direction ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic

The development of ideal orientations within the steady-state region of hot torsion flow curves of fcc and bcc metals undergoing “continuous” dynamic recrystallization is analyzed. It is well known that in fcc metals, e.g., Al deformed at 400°C and above, the experimentally observed end texture consists of the twin-symmetric B(112¯)[11¯0]/B¯(1¯1¯2)[1¯10] component, whereby the (hkl)[uvw] indices correspond to the shear plane z and the shear direction θ, respectively. In bcc iron however, only one of the self-symmetric D1(112¯)[111] and D2(1¯1¯2)[111] components dominates (the former in the case of positive shear or clockwise rotation about the r-axis, and the latter during negative shear). The tendency toward a single end orientation imposes certain limitations on grain refinement, as this would ultimately imply the coalescence of subgrains of or close to this orientation, and therefore the disappearance of existing high angle boundaries (≥15 deg). It is believed that the preference of D1 over D2, or vice versa, could be related to phenomena other than glide-induced rotations, e.g., grain boundary migration resulting from differences in work hardening rates. In this paper, the standard Taylor model is first used to predict the texture evolution in simple shear under the full-constraint rate-sensitive scheme. This is then coupled with an approach that takes into account grain boundary migration resulting from differences in dislocation densities within grains of varying orientations. The preliminary results are in agreement with experimental findings, i.e., grains with initial orientations close to D2 grow at the expense of neighboring grains during negative shear and vice versa.

scholarly journals Flow modelling of Ti6Al4V under large strains

2020 ◽  
Vol 321 ◽  
pp. 12028
Author(s):  
HOGREFE Katharina ◽  
BUZOLIN Ricardo ◽  
POLETTI María Cecilia
Keyword(s):  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Large Strain ◽  
Microstructural Characterization ◽  
Internal Variables ◽  
Large Strains ◽  
Continuous Dynamic Recrystallization ◽  
Flow Modelling ◽  
Continuous Dynamic

This work uses flow stresses obtained experimentally at different strain rates and temperatures to validate flow modelling results. Flow curves of Ti6Al4V are measured via torsion experiments with a Gleeble® 3800 up to effective strains of 8. A physically based model that describes the evolutions of microstructure and the flow stress in the β-phase field was developed. A model of continuous dynamic recrystallization (CDRX) based on the work of Gourdet and Montheillet [1] for aluminium alloys is combined in this work with elements taken from Kocks and Mecking [2]. The model consists of a detailed description of the microstructure, based on different dislocation density populations and grain boundaries. All these internal variables evolve according to a production and a recovery term correlated mathematically with the temperature and the strain rate. The modelled output variables besides the flow stress are the total, the interior and the wall dislocation densities as well as the subgrain and grain sizes developed by continuous dynamic recrystallization. The model describes the softening occurring during large strain deformations, which is partly produced by the formation of new high angle grain boundaries (HAGB). The fraction of HAGB was used to determine the recrystallization grade, validated with microstructural characterization.

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