Mechanisms of Dynamic Recrystallization in Aluminum Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 784-789 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Sergey Malopheyev

Mechanisms of dynamic recrystallization operating at severe plastic deformation in a wide temperature range are reviewed for aluminum alloys. The main mechanism of grain refinement in all aluminum alloys is continuous dynamic recrystallization (CDRX). Temperature, deformation process and distribution of secondary phases strongly affect the CDRX mechanism. Initial formation of geometrically necessary boundaries (GNBs) and a dispersion of nanoscale particles accelerate CDRX facilitating the formation of a 3D network of low-angle boundaries (LAB) followed by their gradual transformation to high-angle boundaries (HAB). At high and intermediate temperatures, 3D networks of LABs may evolve due to rearrangement of lattice dislocations by climb, and mutual intersection of GNB, respectively. At high temperatures, in aluminum alloys containing no nanoscale dispersoids the CDRX occurs through the impingement of initial boundaries forced by deformation-induced LABs. This recrystallization process is termed as geometric dynamic recrystallization (GDRX). At low temperatures, the extensive grain refinement occurs through a continuous reaction which is distinguished from CDRX by restricted rearrangement of lattice dislocation. Introduction of large misorientation may occur through the formation of 3D networks of GNBs, only.

2014 ◽  
Vol 783-786 ◽  
pp. 2641-2646 ◽  
Author(s):  
Rustam Kaibyshev ◽  
Sergey Malopheyev ◽  
Vladislav Kulitskiy ◽  
Marat Gazizov

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.


Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2437
Author(s):  
Guanshi Zhang ◽  
Zhimin Zhang ◽  
Yingze Meng ◽  
Zhaoming Yan ◽  
Xin Che ◽  
...  

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.


2017 ◽  
Vol 53 (6) ◽  
pp. 4563-4573 ◽  
Author(s):  
Giovanni Maizza ◽  
Renato Pero ◽  
Maria Richetta ◽  
Roberto Montanari

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 923 ◽  
Author(s):  
Morteza Azarbarmas ◽  
Seyed Mirjavadi ◽  
Ali Ghasemi ◽  
Abdel Hamouda

Titanium alloys with high stacking-fault energy show continuous dynamic recrystallization (CDRX) instead of discontinuous dynamic recrystallization (DDRX) during high-temperature deformation. During the CDRX mechanism, new recrystallized grains are generated by the progressive increasing of the low-angle boundary misorientations. In the present work, the CDRX phenomenon was modeled by using a cellular automaton (CA)-based method. The size of seeds was determined based on a phenomenological approach, and then the number and distribution of recrystallized grains as well as the topological changes were applied by utilizing the CA approach. In order to verify the capacity of the proposed model for predicting the microstructural characteristics, the experimental data of the hot-compressed TiNiFe alloy were used. Results showed that the presented model can accurately estimate the fraction of the recrystallized area. Moreover, the macroscopic flow curves of the alloy were well predicted by the present model.


2008 ◽  
Vol 58 (8) ◽  
pp. 368-374 ◽  
Author(s):  
Hiroki ADACHI ◽  
Yusuke YAMAMOTO ◽  
Hidetaka NAKANISHI ◽  
Tetsuo AIDA ◽  
Manabu IMAOKA ◽  
...  

2005 ◽  
Vol 475-479 ◽  
pp. 145-148 ◽  
Author(s):  
Jae-Young An ◽  
Suk Min Han ◽  
Young Jae Kwon ◽  
Yeon Chul Yoo

The high temperature deformation behavior of AISI 430 ferritic stainless steel has been studied over a temperature range of 800 to 1000°C and strain rate of 0.05-5.0/sec. The evolution of flow stress and microstructures showed the characteristics of continuous dynamic recrystallization (CDRX). The flow stress curves gradually decreased with increasing strain over the peak stress until 500% of strain without any steady state shown in typical austenitic stainless steel. Sub-grains of low angle firstly formed along the original high angle grain boundary were propagated into the inside of original grain and transformed to high angle. The CDRX grain sizes of AISI 430 deformed at 1000 °C and 0.5/sec was about 30-35㎛.


2011 ◽  
Vol 702-703 ◽  
pp. 135-138
Author(s):  
Rampada Manna ◽  
N.K. Mukhopadhyay ◽  
G.V.S. Sastry

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.


2005 ◽  
Vol 488-489 ◽  
pp. 223-226 ◽  
Author(s):  
Xu Yue Yang ◽  
Masayoshi Sanada ◽  
Hiromi Miura ◽  
Taku Sakai

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).


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