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.

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.

β Microtexture Analysis in Correlation with HCP Textured Regions Observed in a Forged Near Alpha Titanium Alloy

2005 ◽  
Vol 105 ◽  
pp. 127-132 ◽  
Author(s):  
Philippe Bocher ◽  
Mohammad Jahazi ◽  
Lionel Germain ◽  
Priti Wanjara ◽  
Nathalie Gey ◽  
...  
Keyword(s):  
Grain Size ◽  
Titanium Alloy ◽  
Thermomechanical Processing ◽  
Continuous Dynamic Recrystallization ◽  
Orientation Image Microscopy ◽  
Average Grain Size ◽  
Alpha Titanium ◽  
Imi 834 ◽  
Continuous Dynamic ◽  
The Relationship

The presence of hcp regions with grains having relatively close orientations has been reported in commercial near alpha titanium billets (IMI 834, Ti 6246, etc). The size of these textured regions (called macrozones) is significantly larger than the average grain size of the microstructure observed after thermomechanical processing. The elongated shape of these large hcp regions suggests that they are eventually related to large prior b grains that pancaked during the ingot break down process. In this contribution, Orientation Image Microscopy was used to study the relationship between the hcp local microtexture heterogeneities and the prior b orientations. Specifically, the orientations of the primary (equiaxed) ap grains and the secondary (lamellar) as colonies produced after the transformation of the b phase were discriminated from OIM maps. Furthermore, from the as inherited OIM map, it was possible to reconstruct the corresponding b OIM map over large regions. The analysis showed that the large hcp macrozones observed in the as received material are not related to corresponding bcc macrozones. However, within an hcp macrozone, various clusters of b grains with similar orientations can be found. In such coherent regions, randomly orientated b grains were also observed, which could be related to microstructural changes during deformation (continuous dynamic recrystallization) as suggested by hot deformation results.

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.

Physical and Numerical Simulations of the Microstructure Evolution in AA6082 during Friction Stir Processing by Means of Hot Torsion and FEM

2013 ◽  
Vol 762 ◽  
pp. 590-595 ◽  
Author(s):  
Friedrich Krumphals ◽  
Zeng Gao ◽  
Hassan Zamani ◽  
Stefan Mitsche ◽  
Norbert Enzinger ◽  
...  
Keyword(s):  
Strain Rate ◽  
Microstructure Evolution ◽  
Friction Stir Processing ◽  
Local Strain ◽  
Friction Stir ◽  
Continuous Dynamic Recrystallization ◽  
Fine Grained Structure ◽  
Hot Torsion ◽  
Continuous Dynamic ◽  
Different Strains

A reproduction of the conditions occurring during friction stir processing, where a fine grained structure according to the process parameters rpm, transverse speed and pressure develops is the main focus in the present work. To physically simulate such a friction stir process, hot torsion tests at constant temperatures were carried out in a Gleeble ® 3800 machine at different strains and strain rates. The specimens were immediately water quenched after hot deformation to avoid any static recrystallization. The microstructure was investigated to characterize the grain size evolution and misorientation as a function of the local strain, strain rate and temperature. Dynamic recovery was observed followed by continuous dynamic recrystallization at large deformations. By means of DEFORMTM3D the occurring strain, strain rate and temperature distributions, which are decisive for the observed microstructure evolution, were evaluated.

Kinetics of Grain Refinement by Warm Deformation of 304-Type Stainless Steel

2012 ◽  
Vol 706-709 ◽  
pp. 2326-2331 ◽  
Author(s):  
Marina Tikhonova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Dynamic Recovery ◽  
Large Strains ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Type Stainless Steel ◽  
Power Law Function ◽  
Continuous Dynamic ◽  
Kinetics Of

The dynamic process of grain evolution in an S304H-type austenitic stainless steel was studied in multiple forging tests at temperatures of 500°C, 600°C and 700°C. The deformation microstructure with a grain size of about 100 to 400 nm resulted from continuous dynamic recrystallization. The size of new grains and the recrystallization kinetics decreased with decreasing the deformation temperature. The dynamically equilibrium grain size evolved at large strains followed a power law function of the flow stress with a grain size exponent of about-0.2. The formation of new fine grains was assisted by dynamic recovery, which leads to an apparent steady state flow at large total strains.

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.

scholarly journals Microstructure and Texture Evolution of AZ31 Alloy Prepared by Cyclic Expansion Extrusion with Asymmetrical Extrusion Cavity at Different Temperatures

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3757
Author(s):  
Jie Zheng ◽  
Zhaoming Yan ◽  
Qiang Wang ◽  
Zhimin Zhang ◽  
Yong Xue
Keyword(s):  
Dynamic Recrystallization ◽  
Texture Evolution ◽  
Az31 Alloy ◽  
Continuous Dynamic Recrystallization ◽  
Initial Stage ◽  
Cumulative Strain ◽  
Coarse Grains ◽  
Different Temperatures ◽  
Continuous Dynamic ◽  
Equiaxed Grains

This work is to study the microstructure and texture evolution of AZ31 alloy prepared by cyclic expansion extrusion with an asymmetrical extrusion cavity (CEE-AEC) at different deformation temperatures. The result shows AZ31 alloy undergoes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) during CEE-AEC processing. At the initial stage of deformation, AZ31 alloys exhibit similar bimodal microstructure of coarse deformed grains surrounded by fine DRXed grains. As the passes increase, the cumulative strain increases, and the coarse grains of all samples are almost replaced by fine equiaxed grains. The average grain sizes and the basal texture intensities of the deformed samples increase as the deformation temperature increases. In addition, due to the existence of an asymmetrical cavity, as the passes increase, the basal textures of all samples are deflected with maximum intensities increase, and even an unusual bimodal texture is formed, resulting in a soft orientation that is easy to basal slip.

Continuous Dynamic Recrystallization during Warm Deformation of Tempered Lath Martensite in a Medium Carbon Steel

2012 ◽  
Vol 508 ◽  
pp. 124-127 ◽  
Author(s):  
Un Hae Lee ◽  
Naoya Kamikawa ◽  
Goro Miyamoto ◽  
Tadashi Furuhara
Keyword(s):  
Dynamic Recrystallization ◽  
Microstructural Evolution ◽  
Boundary Migration ◽  
Lath Martensite ◽  
Medium Carbon Steel ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Dynamic Recrystallization Behavior ◽  
Fine Grained Structure ◽  
Continuous Dynamic

To Understand the Mechanisms of Accelerated Dynamic Recrystallization Behavior during the Warm Deformation of Martensites, the Tempered Lath Martensite of 0.4C Steel (Fe-0.399%C-1.96%Mn in Mass %) Was Deformed at 650 °C in Compression to Different Reductions, and Microstructural Evolution Was Investigated. During the Deformation, an Initial Lath Martensite Structure with a Complicated Morphology Was Gradually Changed into More Equiaxed Structure. After 50% Reduction and above, an Equiaxed, Fine Grained Structure Mainly Surrounded by High-Angle Boundaries Was Uniformly Formed with Dislocation Substructures, where the Dislocation Density in the Grains Is Relatively Low. Since there Was No Significant Boundary Migration during this Process, this Microstructural Evolution Can Be Termed as Continuous Dynamic Recrystallization.

scholarly journals Mechanical Behaviour and Microstructure of Aluminum-Steel Sheets Joined by FSSW

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
S. Bozzi ◽  
A. L. Etter ◽  
T. Baudin ◽  
A. Robineau ◽  
J. C. Goussain
Keyword(s):  
Dwell Time ◽  
Mechanical Tests ◽  
Welding Parameters ◽  
Friction Stir ◽  
Continuous Dynamic Recrystallization ◽  
Steel Sheets ◽  
High Microhardness ◽  
Welding Spot ◽  
Continuous Dynamic ◽  
Electron Back Scattered Diffraction

At the prospect of a lightening of the automobile structures, welded spots have been realized on a stacking of two sheets (a 6008 aluminum alloy on steel) Friction Stir Spot welding (FSSW). Different process parameters have been tested, but only the influence of the dwell time will be described in the present paper. The dwell time corresponds to the time during which the probe stays in rotation at its bottom location before extracting. A study of the microstructures and textures associated to mechanical tests (tensile shear tests) allowed determining the best set of welding parameters. The recrystallized area around the welding spot has been characterized by electron back-scattered diffraction (EBSD). A mechanism of continuous dynamic recrystallization has been identified since the misorientation of subboundaries increases close to the weld, and this is for all the dwell times tested. Elsewhere, the increase of the dwell time induced a larger recrystallized zone. It has also been found that a long dwell time induced a larger welded area but also a higher quantity of intermetallic compounds (especially FeAl, Fe2Al7, and FeAl2) with high-microhardness values (up to 800 Hv). Thus, the dwell time must not exceed a certain value, otherwise it can weaken the weld.

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.

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