scholarly journals Microstructure Evolution in a 6082 Aluminium Alloy during Thermomechanical Treatment

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1319 ◽  
Author(s):  
Cecilia Poletti ◽  
Romain Bureau ◽  
Peter Loidolt ◽  
Peter Simon ◽  
Stefan Mitsche ◽  
...  
Keyword(s):  
Aluminium Alloys ◽  
Dynamic Recovery ◽  
Deformation Model ◽  
Flow Data ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Static Recovery ◽  
Intermetallic Particles ◽  
Dislocation Densities ◽  
Produce Flow

Thermomechanical treatments of age-hardenable wrought aluminium alloys provoke microstructural changes that involve the movement, arrangement, and annihilation of dislocations, the movement of boundaries, and the formation or dissolution of phases. Cold and hot compression tests are carried out using a Gleeble® 3800 machine to produce flow data as well as deformed samples for metallography. Electron backscattered diffraction and light optical microscopy were used to characterise the microstructure after plastic deformation and heat treatments. Models based on dislocation densities are developed to describe strain hardening, dynamic recovery, and static recrystallisation. The models can describe both the flow and the microstructure evolutions at deformations from room temperatures to 450 °C. The static recrystallisation and static recovery phenomena are modelled as a continuation of the deformation model. The recrystallisation model accounts also for the effect of the intermetallic particles in the movements of boundaries.

Solution Strengthening of Various Elements in Aluminium Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 473-478 ◽  
Author(s):  
Zhen Shan Liu ◽  
Volker Mohles
Keyword(s):  
Aluminium Alloys ◽  
Large Temperature ◽  
Strengthening Effect ◽  
Compression Tests ◽  
Dislocation Interaction ◽  
Hardening Mechanism ◽  
Solid Solution Strengthening ◽  
Dislocation Densities ◽  
Solution Strengthening ◽  
Flow Stress Model

In the aluminium wrought alloys, the solid solution strengthening is one of the dominant hardening mechanism. Every solute element shows different strengthening effect. In present work the strengthening effect of different elements in a large temperature range was studied with the microstructure and flow stress model 3IVM+. This model was developed for cell forming metals, in which the work hardening and softening effects due to interaction of dislocation densities are taken into account. Compression tests for various binary aluminium alloys (Al-Mg, Al-Mn, Al-Si) were carried out under various deformation temperatures and strain rates. The contribution of each element to solution strengthening was investigated with 3IVM+. It was found that the dislocation interaction, especially cross slip and climb, is sensitive to the solute type and concentration.

scholarly journals Hot Deformation Of 6xxx Series Aluminium Alloys

2015 ◽  
Vol 60 (2) ◽  
pp. 1079-1084 ◽  
Author(s):  
G. Mrówka-Nowotnik ◽  
J. Sieniawski ◽  
S. Kotowski ◽  
A. Nowotnik ◽  
M. Motyka
Keyword(s):  
Hot Deformation ◽  
Aluminium Alloys ◽  
Dynamic Recovery ◽  
Strain Rate Range ◽  
Compression Tests ◽  
Dynamic Flow ◽  
Hot Deformation Behavior ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
6Xxx Series

Abstract The hot deformation behavior of the 6xxx aluminum alloys was investigated by compression tests in the temperature range 100°C-375°C and strain rate range 10−4s−1 and 4×10−4s−1 using dilatometer DIL 805 BÄHR Thermoanalyse equipped with accessory attachment deformation allows the process to execute thermoplastic in vacuum and inert gas atmosphere. Associated microstructural changes of characteristic states of examined alloys were studied by using the transmission electron microscope (TEM). The results show that the stress level decreases with increasing deformation temperature and deformation rate. And was also found that the activation energy Q strongly depends on both, the temperature and rate of deformation. The results of TEM observation showing that the dynamic flow softening is mainly as the result of dynamic recovery and recrystallization of 6xxx aluminium alloys.

scholarly journals Restoration Mechanisms at Moderate Temperatures for As-Cast ZK40 Magnesium Alloys Modified with Individual Ca and Gd Additions

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1140
Author(s):  
Ricardo Henrique Buzolin ◽  
Leandro Henrique Moreno Guimaraes ◽  
Julián Arnaldo Ávila Díaz ◽  
Erenilton Pereira da Silva ◽  
Domonkos Tolnai ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Dynamic Recovery ◽  
Deformation Behaviour ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Ca Addition ◽  
Synchrotron Radiation Diffraction ◽  
Dynamic Recrystallisation ◽  
Restoration Mechanism ◽  
Continuous Dynamic

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 °C and 300 °C. Compression tests were carried out at 0.0001 s−1 and 0.001 s−1 using a modified Gleeble system during in-situ synchrotron radiation diffraction experiments. The deformation mechanisms are corroborated by post-mortem investigations using scanning electron microscopy combined with electron backscattered diffraction measurements. The restoration mechanisms in α-Mg are listed as follows: the formation of misorientation spread within α-Mg, the formation of low angle grain boundaries via dynamic recovery, twinning, as well as dynamic recrystallisation. The Gd and Ca additions increase the flow stress of the ZK40, which is more evident at 0.001 s−1 and 300 °C. Dynamic recovery is the predominant restoration mechanism in all alloys. Continuous dynamic recrystallisation only occurs in the ZK40 at 250 °C, competing with discontinuous dynamic recrystallisation. Discontinuous dynamic recrystallisation occurs for the ZK40 and ZK40-Gd. The Ca addition hinders discontinuous dynamic recrystallisation for the investigated temperatures and up to the local achieved strain. Gd addition forms a semi-continuous network of intermetallic compounds along the grain boundaries that withstand the load until their fragmentation, retarding discontinuous dynamic recrystallisation.

scholarly journals Dynamic Softening Mechanisms and Microstructure Evolution of TB18 Titanium Alloy during Uniaxial Hot Deformation

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 789
Author(s):  
Qiang Fu ◽  
Wuhua Yuan ◽  
Wei Xiang
Keyword(s):  
Titanium Alloy ◽  
Dynamic Recovery ◽  
True Strain ◽  
Hot Workability ◽  
Compression Tests ◽  
Phase Zone ◽  
Β Phase ◽  
Stability And Instability ◽  
Dynamic Softening ◽  
Transus Temperature

In this study, isothermal compression tests of TB18 titanium alloy were conducted using a Gleeble 3800 thermomechanical simulator for temperatures ranging from 650 to 880 °C and strain rates ranging from 0.001 to 10 s−1, with a constant height reduction of 60%, to investigate the dynamic softening mechanisms and hot workability of TB18 alloy. The results showed that the flow stress significantly decreased with an increasing deformation temperature and decreasing strain rate, which was affected by the competition between work hardening and dynamic softening. The hyperbolic sine Arrhenius-type constitutive equation was established, and the deformation activation energy was calculated to be 303.91 kJ·mol−1 in the (α + β) phase zone and 212.813 kJ·mol−1 in the β phase zone. The processing map constructed at a true strain of 0.9 exhibited stability and instability regions under the tested deformation conditions. The microstructure characteristics demonstrated that in the stability region, the dominant restoration and flow-softening mechanisms were the dynamic recovery of β phase and dynamic globularization of α grains below transus temperature, as well as the dynamic recovery and continuous dynamic recrystallization of β grains above transus temperature. In the instability region, the dynamic softening mechanism was flow localization in the form of a shear band and a deformation band caused by adiabatic heating.

scholarly journals Effect of Trace Magnesium Additions on the Dynamic Recrystallization in Cast Alloy 825 after One-Hit Hot-Deformation

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 36
Author(s):  
Munir Al-Saadi ◽  
Wangzhong Mu ◽  
Christopher N. Hulme-Smith ◽  
Fredrik Sandberg ◽  
Pär G. Jönsson
Keyword(s):  
Service Life ◽  
Dynamic Recrystallization ◽  
Hot Deformation ◽  
Cast Alloy ◽  
True Strain ◽  
Peak Strain ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Hollomon Parameter ◽  
Test Conditions

Alloy 825 is widely used in several industries, but its useful service life is limited by both mechanical properties and corrosion resistance. The current work explores the effect of the addition of magnesium on the recrystallization and mechanical behavior of alloy 825 under hot compression. Compression tests were performed under conditions representative of typical forming processes: temperatures between 1100 and 1250 °C and at strain rates of 0.1–10 s−1 to a true strain of 0.7. Microstructural evolution was characterized by electron backscattered diffraction. Dynamic recrystallization was found to be more prevalent under all test conditions in samples containing magnesium, but not in all cases of conventional alloy 825. The texture direction ⟨101⟩ was the dominant orientation parallel to the longitudinal direction of casting (also the direction in which the samples were compressed) in samples that contained magnesium under all test conditions, but not in any sample that did not contain magnesium. For all deformation conditions, the peak stress was approximately 10% lower in material with the addition of magnesium. Furthermore, the differences in the peak strain between different temperatures are approximately 85% smaller if magnesium is present. The average activation energy for hot deformation was calculated to be 430 kJ mol−1 with the addition of magnesium and 450 kJ mol−1 without magnesium. The average size of dynamically recrystallized grains in both alloys showed a power law relation with the Zener–Hollomon parameter, DD~Z−n, and the exponent of value, n, is found to be 0.12. These results can be used to design optimized compositions and thermomechanical treatments of alloy 825 to maximize the useful service life under current service conditions. No experiments were conducted to investigate the effects of such changes on the service life and such experiments should now be performed.

The Work Hardening of Single Phase and Multi-Phase Aluminium Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 71-78 ◽  
Author(s):  
J. David Embury ◽  
Warren J. Poole ◽  
David J. Lloyd
Keyword(s):  
Work Hardening ◽  
Aluminium Alloys ◽  
Single Phase ◽  
Dynamic Recovery ◽  
Uniform Elongation ◽  
Strengthening Mechanisms ◽  
Plastic Response ◽  
Spring Back ◽  
Hardening Process ◽  
Multi Phase

The process of work hardening in aluminum alloys is important from the viewpoint of formability and the prediction of the properties of highly deformed products. However the complexity of the strengthening mechanisms in these materials means that one must carefully consider the interaction of dislocations with the detailed elements of the microstructure and the related influence of the elements on dislocation accumulation and dynamic recovery. In addition, it is necessary to consider the influence of the work hardening process at various levels of plastic strain. This permits the possibility of designing microstructure for tailored plastic response, e.g. not simply designed for yield strength but also considering uniform elongation, spring-back, ductility etc. This presentation will explore the concept of identifying the various interactions which govern the evolution of the work hardening and their possible role in alloy design.

scholarly journals Effect of Supra-Transus Deformation Conditions on Recrystallization of Beta Ti Alloy

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1278
Author(s):  
Chao Voon Samuel Lim ◽  
Yang Liu ◽  
Chen Ding ◽  
Aijun Huang
Keyword(s):  
Hot Deformation ◽  
Static Recrystallization ◽  
Dynamic Recovery ◽  
Texture Evolution ◽  
High Strength ◽  
Ex Situ ◽  
Mechanical Processing ◽  
Ti Alloy ◽  
Electron Backscattered Diffraction ◽  
Beta Ti Alloy

There is increasing usage of high strength Beta Ti alloy in aerospace components. However, one of the major challenges is to obtain homogeneous refined microstructures via the thermo-mechanical processing. To overcome this issue, an understanding of the hot deformation conditions effect on the microstructure, prior to and after annealing, is needed. In this work, the effect of strain levels, which is more precise than percentage of reduction, and strain rate under supra-transus deformation temperature on beta annealing are studied using a double cone sample. The Electron Backscattered Diffraction (EBSD) is used to determine the deformed microstructure and texture evolution, as well as the static recrystallized grains evolution using the ex situ annealing approach. This work provides evidence that the mechanisms of dynamic recovery and recrystallization, along with texture evolution, are affected by the deformation conditions, which in turn affected the subsequent static recrystallization during annealing. It will also be shown that high levels of strain do not necessarily lead to an increase in the rate of recrystallization. Finally, the results obtained provided several examples of guidance in designing the TMP processes for obtaining not only a refine microstructure, but a more homogeneous beta microstructure during the beta processing of Beta Ti alloy.

Effect of the Time between Last Deformation Pass and Accelerated Cooling on the Mechanical Properties in Nb and Nb-Mo Microalloyed Steels

2016 ◽  
Vol 716 ◽  
pp. 281-290
Author(s):  
Gorka Larzabal ◽  
Nerea Isasti ◽  
J.M. Rodriguez-Ibabe ◽  
Isabel Gutiérrez ◽  
P. Uranga
Keyword(s):  
Mechanical Properties ◽  
Charpy Impact ◽  
Holding Time ◽  
Microalloyed Steels ◽  
Accelerated Cooling ◽  
Low Carbon ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Microstructural Refinement ◽  
Deformation Pass

The microstructural refinement induced when the holding time between last deformation pass and accelerated cooling is reduced, affects the mechanical properties in low carbon Nb and Nb-Mo microalloyed steels. Plane strain compression tests were performed and mechanical property samples machined in order to quantify this effect using tensile and Charpy impact tests. A complete microstructural characterization was carried out using electron backscattered diffraction (EBSD) measuring unit size distributions and homogeneity of complex microstructures. The synergetic combination of Nb and Mo elements modifies the final microstructures and, therefore, affects the contribution of different strengthening mechanisms, such as substructure, precipitation hardening and dislocation density. Even though strength is not clearly affected by the reduction of the holding time after the last deformation pass, Charpy properties are considerably improved in the case of the Nb steel. The presence of MA islands in the Nb-Mo steel limits the beneficial effect of the microstructural refinement and toughness remains unmodified.

scholarly journals Morphological and Crystallographic Characteristics of α Structure in a Low-Carbon Iron–Nickel Alloy

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 468 ◽  
Author(s):  
Gaojun Mao ◽  
Cyril Cayron ◽  
Xiuli Mao ◽  
Rui Cao ◽  
Roland Logé ◽  
...  
Keyword(s):  
Lath Martensite ◽  
Granular Bainite ◽  
Body Centered Cubic ◽  
Low Carbon ◽  
Electron Backscattered Diffraction ◽  
Dislocation Densities ◽  
Lath Bainite ◽  
Crystallographic Characteristics ◽  
Iron Nickel ◽  
Relationship Of

The features of α (body-centered cubic) structures were investigated in a low-carbon multicomponent alloy from morphological and crystallographic perspectives. In addition to apparent features of granular bainite and lamellar martensite, a morphological similarity can be found between lath martensite and lath bainite. Therefore, it is of interest to explore possible discrepancies between lath martensite and lath bainite from a crystallographic perspective. These microstructures were obtained by various cooling rates (i.e., water quenching, 5 °C/s, and 0.05 °C/s) and then were characterized by a combination of scanning electron microscopy and electron backscattered diffraction techniques. It is shown that: (1) Lath martensite (LM) formed in the samples that were water-quenched, and a mixture of LM and lath bainite (LB) and granular bainite (GB) formed in the samples cooled at rates of 5 °C/s and 0.05 °C/s, respectively; (2) A Kurdjumov-Sachs relationship was mostly found in as-quenched martensite, while a Greninger-Troiano relationship represented the orientation relationship of LB and GB; (3) As the cooling rate decreased, the dislocation densities in corresponding microstructures were reduced, while the tendency of variant grouping was enhanced.

Hot Deformation and Dynamic Recrystallization in Titanium Aluminide

2018 ◽  
Vol 941 ◽  
pp. 1391-1396 ◽  
Author(s):  
Nitish Bibhanshu ◽  
Satyam Suwas
Keyword(s):  
Shear Band ◽  
Dynamic Recrystallization ◽  
Titanium Aluminide ◽  
Volume Fraction ◽  
Shear Bands ◽  
Hot Workability ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Gamma Titanium Aluminide ◽  
Z Contrast

The hot workability of gamma titanium aluminide alloy, Ti-48Al-2V-2Nb, was assessed in the cast condition through a series of compression tests conducted over a range of temperatures (1000 to 1175 °C) and at the strain rate of 10 S-1. The mechanism of dynamics recrystallization has been investigated from SEM Z-contrast images and from the Electron backscattered diffraction EBSD as well. It has been observed that volume fraction of the recrystallized grains increases with increasing the deformation temperature. The major volume fraction of the recrystallized grains was observed in the shear band which was forming at an angle 45 ̊ with respect to the compression direction. The mechanism of breaking of the laths and the region of the dynamic recrystallization were also investigated from the SEM Z-contrast image and EBSD. The dynamic recrystallization occurred in the region of the broken laths and shear bands. The breaking of the laths was because of the kinking of the lamellae. The shear band, kinked lamellae and dynamic recrystallized region where all investigated simultaneously.

Sign in / Sign up

Export Citation Format

Share Document