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.

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.

Effect of ECAP on Microstructure and Mechanical Properties of an Al-Mg-Sc Alloy

2010 ◽  
Vol 667-669 ◽  
pp. 949-954 ◽  
Author(s):  
Anna Mogucheva ◽  
Rustam Kaibyshev
Keyword(s):  
Mechanical Properties ◽  
Dynamic Recrystallization ◽  
Yield Stress ◽  
Three Dimensional ◽  
Subgrain Structure ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Angular Pressing ◽  
Continuous Dynamic ◽  
Strain Mechanisms

An Al-4.57%Mg–0.2%Sc was subjected to equal channel angular pressing up to fixed true strains of 1, 2, 4, 8 and 12 at a temperature of 300oC. It was shown that extensive grain refinement occurs in this alloy through continuous dynamic recrystallization. As a result, ECAP can provide the formation of subgrain structure, partially recrystallized structure and fully recrystallized structure. The type of structure evolved is dependent on strain imposed. At ε2, the formation of three-dimensional arrays of low-angle boundaries takes place. Next, in the strain interval from 4 to 8 these low-angle boundaries gradually convert into high-angle boundaries. At ε12, fully recrystallized structure is evolved. Yield stress and ultimate strength gradually increases with increasing strain. Mechanisms of strengthening are discussed.

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.

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.

Investigation on Dynamic Recrystallization Behavior in Hot Deformed Superalloy Inconel 718

2007 ◽  
Vol 546-549 ◽  
pp. 1297-1300 ◽  
Author(s):  
Y. Wang ◽  
Wen Zhu Shao ◽  
Liang Zhen ◽  
L. Lin ◽  
Y.X. Cui
Keyword(s):  
Dynamic Recrystallization ◽  
Inconel 718 ◽  
High Angle ◽  
Twin Boundaries ◽  
Continuous Dynamic Recrystallization ◽  
Subgrain Rotation ◽  
Dynamic Recrystallization Behavior ◽  
Ebsd Technique ◽  
Continuous Dynamic ◽  
The Individual

The nucleation and development of dynamic recrystallization (DRX) in hot deformed superalloy Inconel 718 during uniaxial compression were investigated by optical microscopy and electron back-scattered diffraction (EBSD) technique. The results showed that the discontinuous dynamic recrystallization was the predominant DRX mechanism in this alloy. The variations of partial crystallographic orientations led to the individual nucleation inside the deformed grains, which implied the occurrence of local continuous dynamic recrystallization. The progressive subgrain rotation can be confirmed neither near the prior high angle grain boundaries nor within the original grains. It was found that, as the strain increased, the initial twin boundaries were gradually transformed to ordinary mobile high angle boundaries. Meanwhile, the new twin boundaries were formed inside the recrystallized grain necklaces. It was suggested that the characteristics of the twin boundaries evolution with increasing strain were associated with the transformation of initial twin boundaries as well as the generation of new ones, which resulted in the development of DRX.

Continuous Dynamic Recrystallization of AISI 430 Ferritic Stainless Steel by Hot Torsion Deformation

2005 ◽  
Vol 475-479 ◽  
pp. 145-148 ◽  
Author(s):  
Jae-Young An ◽  
Suk Min Han ◽  
Young Jae Kwon ◽  
Yeon Chul Yoo
Keyword(s):  
Stainless Steel ◽  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Ferritic Stainless Steel ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
High Angle ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic ◽  
Aisi 430

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㎛.

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.

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.

Structure and Properties of Cu Alloys Alloying with Cr and Hf after Equal Channel Angular Pressing

2014 ◽  
Vol 922 ◽  
pp. 651-656 ◽  
Author(s):  
Daria Shangina ◽  
Yulia Maksimenkova ◽  
Natalia Bochvar ◽  
Vladimir Serebryany ◽  
Georgy Raab ◽  
...  
Keyword(s):  
Structure Formation ◽  
Equal Channel Angular Pressing ◽  
Temperature Interval ◽  
Subgrain Structure ◽  
Structure And Properties ◽  
High Angle ◽  
Angular Pressing ◽  
Cu Alloys ◽  
Tension Tests ◽  
Average Size

Equal channel angular pressing (ECAP) results in grain-subgrain structure formation in Cu0.75 %Cr alloy with the average size of structure elements of 320 ± 73 nm Addition of hafnium into the Cu-Cr alloy leads to decrease of average size down to 225±82 nm and to increase of the high angle boundaries fraction from 40% to 53%. Microhardness of the Cu-0.7 %Cr-0.9 %Hf alloy is higher, than of the Cu-0.75 %Cr alloy, as after ECAP, so after heating when the aging processes occur in the temperature interval 400–550 °С. The strength in the tension tests of the Cu-0.7 %Cr-0.9 %Hf alloy after ECAP rises in 2.2 times compared with the quenched state. The aging leads to additional strength growth by 19%.

Superplastic Behavior of an AA2139 Subjected to ECAP

2016 ◽  
Vol 838-839 ◽  
pp. 373-378
Author(s):  
Marat Gazizov ◽  
Rustam Kaibyshev
Keyword(s):  
Thermomechanical Processing ◽  
Solution Treatment ◽  
Initial Strain Rate ◽  
Sensitivity Coefficient ◽  
Initial Strain ◽  
Strain Rates ◽  
High Angle ◽  
Superplastic Behavior ◽  
Angular Pressing ◽  
Average Size

An AA2139 alloy belonging to Al-Cu-Mg-Ag system was subjected to thermomechanical processing (TMP) included solution treatment at 525°C for 1 h, quenching in water, over-aging at 380°C for 3 h followed by equal-channel angular pressing (ECAP) at 250°C to a total strain of ~12 via route BC. This TMP produced a partially recrystallized structure with fine crystallites having an average size of ~0.9 μm and a fraction of high-angle boundaries of ~56%. Tensile test was performed in the temperature interval 300-500°C at initial strain rates ranging from ~1.8×10-4 to ~1.7×10-1 s-1. It was shown that the highest elongation-to-fracture of ~660% appears at a temperature of 400°C and an initial strain rate of 1.4×10-3 corresponding with the coefficient of sensitivity coefficient, m, of 0.34.

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