scholarly journals Grain Refinement Kinetics in a Low Alloyed Cu-Cr-Zr Alloy Subjected to Large Strain Deformation

2017 ◽  
Author(s):  
Anna Morozova ◽  
Elijah Borodin ◽  
Vladimir Bratov ◽  
Sergey Zherebtsov ◽  
Andrey Belyakov ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Large Strain ◽  
Triple Junctions ◽  
Initial State ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Boundary Triple ◽  
Continuous Dynamic

The microstructure evolution and grain refinement kinetics of a solution treated Cu – 0.1Cr – 0.06Zr alloy during equal channel angular pressing (ECAP) at a temperature of 673 K via route BC were investigated. The microstructure change during plastic deformation was accompanied by the microband formation and an increase in the misorienations of strain-induced subboundaries. The refinement of initial coarse grains was considered as a result of continuous dynamic recrystallization. The dynamic recrystallization kinetics was discussed in terms of grain/subgrain boundary triple junction evolution. The strain dependence of the triple junctions of high-angle boundaries can be expressed by a modified Johnson-Mehl-Avrami-Kolmogorov relationship with a strain exponent of about 1.49. Severe plastic deformation by ECAP led to substantial strengthening of the Cu-0.1Cr-0.06Zr alloy. The yield strength increased from 60 MPa in the initial state to 445 MPa after the total strain of 12.

The Role of Deformation Banding in Grain Refinement under ECAP

2014 ◽  
Vol 783-786 ◽  
pp. 2641-2646 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Sergey Malopheyev ◽  
Vladislav Kulitskiy ◽  
Marat Gazizov
Keyword(s):  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Lamellar Structure ◽  
True Strain ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Deformation Banding ◽  
Continuous Dynamic

The mechanism of grain refinement in an Al-5.4Mg-0.4Mn-0.2Sc-0.09Zr alloy subjected to equal-channel angular pressing (ECAP) at 300°C through route BC is considered. It was shown that the formation of geometrically necessary boundaries (GNB) aligned with a {111} plane at ε≤1 initiates the occurrence of continuous dynamic recrystallization (CDRX). Upon further strain the GNBs transform to low-to-moderate angle planar boundaries that produces lamellar structure. In the strain interval 2-4, 3D arrays of planar boundaries evolve due to inducing the formation of 2nd order and higher orders families of GNBs in new {111} planes. GNBs gradually convert to high-angle boundaries (HAB) with strain. A uniform recrystallized structure is produced at a true strain of ∼8. The role of slip concentration and shearing patterns in the formation of GNBs is discussed.

Role of Strain Gradient and Dynamic Transformation on the Formation of Nanocrystalline Structure Produced by Severe Plastic Deformation

2007 ◽  
Vol 539-543 ◽  
pp. 2787-2792 ◽  
Author(s):  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Jin Guo Li ◽  
Koichi Tsuchiya
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Strain Gradient ◽  
High Pressure Torsion ◽  
Large Strain ◽  
Nanocrystalline Structure ◽  
Angular Pressing ◽  
Dynamic Transformation ◽  
Fine Grained Structure

Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain size larger than 100 nm) had been obtained in many processes such as heavy cold rolling, equal channel angular pressing (ECAP) or accumulative roll bonding (ARB), the formation of nano grained structure (< 100 nm) is limited to processes such as ball milling, shot peening or drilling. In the present study, high pressure torsion (HPT) deformation and drilling were carried out to understand the conditions necessary to obtain nano grained structure in steels. The results of HPT experiments in pure Fe showed that HPT has superior ability of strengthening and grain refinement probably due to a strain gradient but the saturation of grain refinement occurs before reaching nano grained structure. Drilling experiments in high carbon martensitic steel revelaed that nano grained ferrite forms at the drilled hole surface only when the transformation from ferrite to austenite takes place during drilling. Considering various other processes by which nano grained ferrite was produced, it is proposed that heavy strains with large strain gradients together with dynamic transformation are necessary to reach nano grained ferrite structure.

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 Effects of Repetitive Upsetting Extrusion on the Microstructure and Texture of GWZK124 Alloy under Different Starting Temperatures

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2437
Author(s):  
Guanshi Zhang ◽  
Zhimin Zhang ◽  
Yingze Meng ◽  
Zhaoming Yan ◽  
Xin Che ◽  
...  
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Volume Fraction ◽  
Bimodal Microstructure ◽  
Continuous Dynamic Recrystallization ◽  
Average Grain Size ◽  
Second Phases ◽  
Continuous Dynamic ◽  
Weak Texture

The effects of repetitive upsetting extrusion under different starting temperatures on the microstructure and texture of GWZK124 alloy were investigated. The results clearly showed that the particles and second phases induced dynamic recrystallization (DRX), which can be explained by the particle-stimulated nucleation (PSN) mechanism. It was shown that grain refinement during repetitive upsetting extrusion (RUE) is dominated by a complicated combination of continuous dynamic recrystallization and discontinuous dynamic recrystallization. The RUEed alloys under different starting temperatures exhibited a bimodal microstructure comprising fine DRXed grains with weak texture and coarse deformed grains with strong texture. The DRXed grains could weaken the texture. As the RUE starting temperature decreased, the average grain size increased and the volume fraction of DRXed grains decreased.

Grain Refinement Mechanisms Oterative during Equal Channel Angular Pressing of Aluminium

2011 ◽  
Vol 702-703 ◽  
pp. 135-138
Author(s):  
Rampada Manna ◽  
N.K. Mukhopadhyay ◽  
G.V.S. Sastry
Keyword(s):  
Grain Refinement ◽  
Equal Channel Angular Pressing ◽  
Room Temperature ◽  
Lattice Rotation ◽  
Recrystallization Process ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Subgrain Formation ◽  
Refinement Process ◽  
Continuous Dynamic

Grain refinement of aluminum deformed by equal channel angular pressing is strongly dependent on the amount of strain. The refinement process at low to high strain level involves elongation of the existing grains by shear deformation, their subdivision into bands and subgrain formation within bands, intersection of the bands during subsequent passes and finally conversion of the subgrains to grains by continuous dynamic recrystallization process. At room temperature the conversion of subgrains to grains takes place by progressive lattice rotation.

Effect of Initial Grain Size on Deformation Behavior and Dynamic Recrystallization of Magnesium Alloy AZ31

2005 ◽  
Vol 488-489 ◽  
pp. 223-226 ◽  
Author(s):  
Xu Yue Yang ◽  
Masayoshi Sanada ◽  
Hiromi Miura ◽  
Taku Sakai
Keyword(s):  
Magnesium Alloy ◽  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Hot Deformation ◽  
Structural Changes ◽  
Kink Bands ◽  
Alloy Az31 ◽  
Continuous Dynamic Recrystallization ◽  
Magnesium Alloy Az31 ◽  
Continuous Dynamic

Hot deformation and associated structural changes were studied in compression of a magnesium alloy AZ31 with initial grain sizes (D0) of 22 µm and 90 µm at a temperature of 573K. D0 influences significantly the flow curve and the kinetics of grain refinement during hot deformation. For D0 = 22 µm, grain fragmentation takes place due to frequent formation of kink bands initially at corrugated grain boundaries and then in grain interiors in low strain, followed by full development of new fine grains in high strain. For D0 = 90 µm, in contrast, twinning takes place in coarser original grains, and then kink bands and new fine grains are formed mainly in finer ones at low strains. Then new grains are formed in necklace along the boundaries of coarse original grains, followed by their development into the grain interiors. Grain refinement in the Mg alloy can be concluded to result from a series of deformation-induced continuous reactions, they are essentially similar to continuous dynamic recrystallization (cDRX).

scholarly journals INTENSE PLASTIC DEFORMATION OF HIGH-PURITY CAST BERYLLIUM

2020 ◽  
pp. 230-235
Author(s):  
A.A. Vasil’ev ◽  
S.P. Stetsenko ◽  
R.L. Vasilenko ◽  
D.G. Malykhin ◽  
P.I. Stoyev ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
High Purity ◽  
Recrystallization Annealing ◽  
Initial State ◽  
Angular Pressing ◽  
Temperature Dependences ◽  
First Time

Studies were made into the effect of severe plastic deformation on the mechanical properties, structure, and texture of high-purity cast beryllium. For the first time, angular pressing of high-purity cast beryllium was carried out at temperatures of 600 and 500 °C. It is shown that the degree of grain refinement during angular pressing into a strip reaches a significant value. In a single deformation cycle, the grain is crushed from 3 mm down to 10 μm. Temperature dependences of the mechanical properties of the material of extruded billets in the initial state and after recrystallization annealing at a temperature of 650 °C for one hour were studied. It has been established that the best mechanical properties are shown by the samples of material deformed at 600 °C with subsequent annealing at 650 °C for an hour.

scholarly journals Continuous dynamic recrystallization during severe plastic deformation

2015 ◽  
Vol 90 ◽  
pp. 148-156 ◽  
Author(s):  
Mattia Bacca ◽  
David R. Hayhurst ◽  
Robert M. McMeeking
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Dynamic Recrystallization ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic

Microstructure Evolution in an Al-Cu-Mg-Ag Alloy during ECAP at 300°C

2011 ◽  
Vol 409 ◽  
pp. 41-46
Author(s):  
Marat Gazizov ◽  
Rustam Kaibyshev
Keyword(s):  
Dynamic Recrystallization ◽  
Equal Channel Angular Pressing ◽  
Microstructure Evolution ◽  
Solution Treatment ◽  
Total Strain ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Continuous Dynamic ◽  
Average Size

A novel Al-Cu-Mg-Ag alloy with small additions of zirconium and scandium was subjected to equal channel angular pressing (ECAP) by using route BC at 300°C to strains ranging from ~1 to ~12. Initially, the alloy was subjected to solution treatment followed by water quenching; subsequent overageing was carried out at 380°C for 3 h. It was shown that continuous dynamic recrystallization (CDRX) occurs during ECAP resulting in partially recrystallized structure; at a total strain of ~12, the portion of high-angle boundaries (HAB) attains 50 pct., average misorientation is ~25°. Crystallites having elongated shape and an average size of ~1 μm are evolved after a total strain of ~12.

Geometric Dynamic Recrystallization in α-Zirconium at Elevated Temperatures

2004 ◽  
Vol 467-470 ◽  
pp. 1145-1150 ◽  
Author(s):  
S.R. Barrabes ◽  
M.E. Kassner ◽  
Maria Teresa Pérez-Prado ◽  
E. Evangelista
Keyword(s):  
Dynamic Recrystallization ◽  
Grain Refinement ◽  
Elevated Temperatures ◽  
Tensile Deformation ◽  
Bimodal Distribution ◽  
High Angle ◽  
Misorientation Distribution ◽  
Continuous Dynamic Recrystallization ◽  
Micron Size ◽  
Continuous Dynamic

The micron-size grain refinement of pure a-zirconium obtained with elevated temperature tensile deformation was investigated. The development of low-misorientation subboundaries caused the serration of the original grain boundaries at low strains. The final microstructure (e.g. strains > 3) was predominantly composed of fine, equiaxed “crystallites” with ⅔ of the boundaries being of very low misorientations (< 3°) and the remaining ⅓ being high angle boundaries (θ > 8°, and typically 25-35°). Discontinuous dynamic recrystallization was excluded as a possible mechanism due to the absence of newly formed grain nuclei. The bimodal distribution of the crystallite or (sub)grain boundary misorientations is inconsistent with the occurrence of continuous dynamic recrystallization and rotational recrystallization. The continual thinning of the original grains, the serration of the high angle boundaries, the bimodal misorientation distribution of misorientations, ⅔ of boundaries of very low misorientations at high strains all strongly suggest geometric dynamic recrystallization and dynamic recovery as the grain refinement and restoration mechanisms.

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