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.

Microstructure and Texture Evolution during Continuous Dynamic Recrystallization at Warm Deformation of Titanium

2004 ◽  
Vol 467-470 ◽  
pp. 1211-1216 ◽  
Author(s):  
S.Yu. Mironov ◽  
Gennady A. Salishchev ◽  
Sergey V. Zherebtsov
Keyword(s):  
Texture Evolution ◽  
Pure Titanium ◽  
Internal Stresses ◽  
High Angle ◽  
Warm Deformation ◽  
Misorientation Distribution ◽  
Continuous Dynamic Recrystallization ◽  
12 Steps ◽  
Continuous Dynamic ◽  
High Level

The microstructure and texture evolutions in pure titanium during severe plastic deformation at T=400°C were investigated. Compressive deformation of prismatic samples was sequentially applied in three orthogonal directions up to 12 steps and a strain at each step of 40%. A radical microstructure refinement (from 20 to 0.2 µm) during strain has been found. The features of the deformation structure are a high level of internal stresses, high density of dislocations, a large number of deformation induced boundaries and the presence of twins. It is shown that during strain there is a significant change in disorientation angles and axes of individual high angle grain boundaries. At the same time the total set of high angle boundaries - Misorientation Distribution Function (MDF) and texture - does not change significantly with strain. The reasons for the change in disorientation angles and axes at new deformation-induced boundaries during plastic flow are discussed.

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.

Microstructure Evolution of Martensitic Ti-6Al-4V Alloy during Warm Deformation

2014 ◽  
Vol 783-786 ◽  
pp. 679-684 ◽  
Author(s):  
Qi Chao ◽  
Peter Hodgson ◽  
Hossein Beladi
Keyword(s):  
Microstructure Evolution ◽  
Thermomechanical Processing ◽  
Microscopy Observation ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Novel Approach ◽  
Resolution Electron ◽  
Continuous Dynamic ◽  
Equiaxed Grains ◽  
Electron Back Scattered Diffraction

The microstructure evolution of martensitic Ti-6Al-4V alloy was investigated through uniaxial hot compression at 700°C and a strain rate of 10-3s-1. A combination of scanning electron microscopy observation in conjunction with high resolution electron back scattered diffraction (EBSD) was used to characterize the microstructure in detail. The development of the microstructure displayed continuous fragmentation of martensitic laths with increasing strain (i.e. continuous dynamic recrystallization), concurrently with decomposition of supersaturated martensite resulting in the formation of equiaxed grains. At a strain of 0.8, an ultrafine equiaxed grained structure with mostly high angle grain boundaries was successfully obtained. The current work proposes a novel approach to produce equiaxed ultrafine grains in a Ti-6Al-4V alloy through thermomechanical processing of a martensitic starting microstructure.

The EBSD Investigation on Microstructure Evolution in Fe-32%Ni Alloy during Multi-Axial Forging

2010 ◽  
Vol 26-28 ◽  
pp. 260-264
Author(s):  
Bao Jun Han
Keyword(s):  
Microstructure Evolution ◽  
Strain Path ◽  
High Angle ◽  
Deformation Bands ◽  
Electron Backscattered Diffraction ◽  
Continuous Dynamic Recrystallization ◽  
Loading Direction ◽  
Ni Alloy ◽  
Coarse Grains ◽  
Continuous Dynamic

The microstructure evolution taking place in Fe-32%Ni alloy during multi-axial forging was investigated by electron backscattered diffraction (EBSD). The samples were compressed with loading direction changed through 90º from pass to pass at temperature of 650°C and a strain rate of 10-1/s. The results show the microstructure evolution is characterized by continuous grain subdivision process, i.e. the multi-axial forging promotes the development of deformation bands in various direction followed by their frequent intersection in grain interiors with changing of strain path, which results in continuous fragmentation of coarse grains into subgrains. Concurrently the misorientations of subgrain boundaries rise gradually with repetitive deformation followed by their progressive transformation into high angle boundaries. The ultra-fine grains are concluded to evolve by continuous dynamic recrystallization (CDRX).

Mechanisms of Microstructure Refinement in Titanium during “abc” Deformation at 400°C

2010 ◽  
Vol 667-669 ◽  
pp. 439-444
Author(s):  
Sergey V. Zherebtsov ◽  
Egor A. Kudryavtsev ◽  
Gennady A. Salishchev
Keyword(s):  
Microstructure Evolution ◽  
Coincidence Site Lattice ◽  
Pure Titanium ◽  
High Angle ◽  
Microstructure Refinement ◽  
Continuous Dynamic Recrystallization ◽  
Commercial Pure Titanium ◽  
S Curve ◽  
Continuous Dynamic ◽  
Flow Stage

Mechanical behavior and microstructure evolution of commercial pure titanium during successive compressions of samples along three orthogonal directions (or so-called “abc” deformation) at 400°C and strain rate 10-3s-1 were studied. The cumulative S- curve demonstrates a steady state flow stage following the intensive strengthening. The microstructure evolution of titanium during first increments of “abc” deformation is associated with twinning and shear deformation. Further deformation results in microstructure refinement due to transformation of coincidence site lattice twin boundaries to high-angle arbitrary ones and formation of high-angle deformation induced boundaries. Another mechanism of new grains formation is continuous dynamic recrystallization.

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.

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.

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