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.

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 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.

scholarly journals A Physically Based Constitutive Model and Continuous Dynamic Recrystallization Behavior Analysis of 2219 Aluminum Alloy during Hot Deformation Process

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1443 ◽  
Author(s):  
Lei Liu ◽  
Yunxin Wu ◽  
Hai Gong ◽  
Shuang Li ◽  
A. S. Ahmad
Keyword(s):  
Constitutive Model ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Hot Deformation ◽  
Flow Behavior ◽  
Large Strains ◽  
Al Alloy ◽  
Continuous Dynamic Recrystallization ◽  
Physically Based ◽  
Continuous Dynamic

The isothermal compression tests of the 2219 Al alloy were conducted at the temperature and the strain rate ranges of 623–773 K and 0.01–10 s−1, respectively, and the deformed microstructures were observed. The flow curves of the 2219 Al alloy obtained show that flow stress decreases with the increase in temperature and/or the decrease in strain rate. The physically based constitutive model is applied to describe the flow behavior during hot deformation. In this model, Young’s modulus and lattice diffusion coefficient are temperature-dependent, and the creep exponent is regarded as a variable. The predicted values calculated by the constitutive model are in good agreement with the experimental results. In addition, it is confirmed that the main softening mechanism of the 2219 Al alloy during hot deformation is dynamic recovery and incomplete continuous dynamic recrystallization (CDRX) by the analysis of electron backscattered diffraction (EBSD) micrographs. Moreover, CDRX can readily occur under the condition of high temperatures, low strain rates, and large strains. Meanwhile, the recrystallization grain size will also be larger.

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.

Effect of Warm Deformation on Ferrite Microstructure Evolution in a Ti-Microalloyed Steel

2007 ◽  
Vol 558-559 ◽  
pp. 497-504
Author(s):  
Beitallah Eghbali
Keyword(s):  
Microstructure Evolution ◽  
Microalloyed Steel ◽  
Early Stage ◽  
Microstructural Analysis ◽  
Optical Microscope ◽  
Low Carbon ◽  
High Angle ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic

Warm deformation is one of the promising hot rolling strategies for producing thin hot rolled steel strips. A better understanding of the microstructure evolution during warm deformation is important for a successful introduction of such processing into the industrial production. In the present research, the effect of deformation strain on the ferrite microstructure development in a low carbon Ti-microalloyed steel was investigated through warm torsion testing. Microstructural analysis with optical microscope and electron back-scattering diffraction was carried out on the warm deformed ferrite microstructures. The results show that at the early stage of deformation an unstable subboundaries network forms and low angle boundaries are introduced in the original grains. Then, with further straining, low angle boundaries transform into high angle boundaries and stable fine equiaxed ferrite grains form. It was considered that dynamic softening and dynamically formation of new fine ferrite grains, with high angle boundaries, were caused by continuous dynamic recrystallization of ferrite.

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

scholarly journals Investigation on Sub-Solvus Recrystallization Mechanisms in an Advanced γ-γ’ Nickel-Based Superalloy GH4151

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4553
Author(s):  
Shaomin Lv ◽  
Jinbin Chen ◽  
Xinbo He ◽  
Chonglin Jia ◽  
Kang Wei ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Energy Surface ◽  
Electron Backscatter Diffraction ◽  
True Strain ◽  
Continuous Dynamic Recrystallization ◽  
Nickel Based Superalloy ◽  
Transmission Electron ◽  
Continuous Dynamic ◽  
Backscatter Diffraction

Sub-solvus dynamic recrystallization (DRX) mechanisms in an advanced γ-γ’ nickel-based superalloy GH4151 were investigated by isothermal compression experiments at 1040 °C with a strain rate of 0.1 s−1 and various true strain of 0.1, 0.3, 0.5, and 0.7, respectively. This has not been reported in literature before. The electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) technology were used for the observation of microstructure evolution and the confirmation of DRX mechanisms. The results indicate that a new dynamic recrystallization mechanism occurs during hot deformation of the hot-extruded GH4151 alloy. The nucleation mechanism can be described as such a feature, that is a primary γ’ (Ni3(Al, Ti, Nb)) precipitate embedded in a recrystallized grain existed the same crystallographic orientation, which is defined as heteroepitaxial dynamic recrystallization (HDRX). Meanwhile, the conventional DRX mechanisms, such as the discontinuous dynamic recrystallization (DDRX) characterized by bulging grain boundary and continuous dynamic recrystallization (CDRX) operated through progressive sub-grain merging and rotation, also take place during the hot deformation of the hot-extruded GH4151 alloy. In addition, the step-shaped structures can be observed at grain boundaries, which ensure the low-energy surface state during the DRX process.

Microstructural Evolution and Deformation Mechanisms for Superplasticity of NiAl Intermetallic

2005 ◽  
Vol 475-479 ◽  
pp. 2995-2998
Author(s):  
Jian Ting Guo ◽  
Rong Shi Chen ◽  
Xing Hao Du ◽  
Gu Song Li ◽  
Lan Zhang Zhou
Keyword(s):  
Electron Microscopy ◽  
Microstructural Evolution ◽  
Superplastic Deformation ◽  
Tensile Elongation ◽  
Deformation Mechanisms ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Transmission Electron ◽  
Continuous Dynamic ◽  
Temperature Strain

The microstructural evolution during superplastic deformation of the extruded stoichiometric NiAl polycrystals were systemically investigated in various conditions of temperature, strain rate and strain by means of optical microscopy (OM) and transmission electron microscopy (TEM). Consequently, The deformation microstructures corresponding to the large tensile elongation consisted of subgrains, low angle grains as well as high angle grains, which indicated that continuous dynamic recrystallization (CDRX) process was operating during superplastic deformation.

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.

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