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Special Issue "Dynamic Recrystallization and Microstructural Evolution in Alloys"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 15 September 2018

Special Issue Editor

Guest Editor
Prof. Sergey Zherebtsov

Department of Materials Science and Nanotechnology, Belgorod State University, 85 Pobeda street, Belgorod, 308015, Russia
Website | E-Mail
Interests: deformation; grain refinement; phase transformation; titanium alloys; high-entropy alloys; interphase boundaries; grain boundaries; twinning, mechanical properties

Special Issue Information

Dear Colleagues,

The control of the microstructure of metallic materials through thermomechanical processing is one of the main targets of materials science. Microstructure refinement during hot or warm working by the process of dynamic recrystallization is a commonly-employed approach. That is why recrystallization and related annealing phenomena have long been recognized as being both of technological importance and scientific interest. However, although considerable advances have been made recently in the techniques available to the researcher and therefore in the understanding of the processes during deformation, many aspects in the field of deformation-induced microstructure evolution are not well understood.

Lack of understanding is obviously attributed to high complexities of the phenomenon, which consists of a combination of the deformed state of metals and alloys and the processes of local nucleation and grain growth. Qualitative and quantitative characterization of the deformed state and careful description of grain or interphase boundary structure and properties constitute the areas of fundamental importance for the understanding of recrystallization.

Over the past two decades one of the most rapidly developed methods of microstructure refinement was associated with severe plastic deformation. In this case ultrafine grained structures are formed during deformation at relatively low temperatures. This is one of the most promising topics in material science because it could lead to the production of submicron to nanometer sized crystallites in a wide variety of structural metals and alloys. Developments in this area have highlighted the necessary to subdivide recovery, recrystallization and grain growth phenomena into traditional high-temperature ‘discontinuous’ and low-temperature ‘continuous’ variants.

One of the main advantage of a new look at these fields can be associated with the use of modern techniques, such as TEM, EBSD, spectrometers and modeling capabilities which are providing us with far better images and analysis than ever previously possible. These new techniques can be used for investigation not only “traditional” metals and alloys but also for such novel objects as high-entropy alloys or metal-matrix composites.

The purpose of this Special Issue is to collect works related to various manifestations of dynamic recrystallization during hot, warm or cold deformation. It is my pleasure to invite you to submit manuscripts for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Sergey Zherebtsov
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Dynamic  recrystallization
  • Metals,Alloys
  • Deformation
  • Microstructure evolution
  • Grain boundaries, interphases
  • Phase transformation
  • Mechanical behavior

Published Papers (10 papers)

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Research

Open AccessArticle Experimental and Numerical Studies on Recrystallization Behavior of Single-Crystal Ni-Base Superalloy
Materials 2018, 11(7), 1242; https://doi.org/10.3390/ma11071242
Received: 27 June 2018 / Revised: 10 July 2018 / Accepted: 16 July 2018 / Published: 19 July 2018
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Abstract
The recrystallization (RX) behavior of superalloy during standard solution heat treatment (SSHT) varies significantly with deformation temperature. Single-crystal (SX) samples of Ni-base superalloy were compressed to 5% plastic deformation at room temperature (RT) and 980 °C, and the deformed samples were then subjected
[...] Read more.
The recrystallization (RX) behavior of superalloy during standard solution heat treatment (SSHT) varies significantly with deformation temperature. Single-crystal (SX) samples of Ni-base superalloy were compressed to 5% plastic deformation at room temperature (RT) and 980 °C, and the deformed samples were then subjected to SSHT process which consists of 1290 °C/1 h, 1300 °C/2 h, and 1315 °C/4 h, air cooling. RT-deformed samples showed almost no RX grains until the annealing temperature was elevated to 1315 °C, while 980 °C-deformed samples showed a large number of RX grains in the initial stage of SSHT. It is inferred that the strengthening effect of γ’ phases and the stacking faults in them increase the driving force of RX for 980 °C-deformed samples. The RX grains nucleate and grow in dendritic arms preferentially when the microstructural inhomogeneity is not completely eliminated by SSHT. A model coupling crystal plasticity finite element method (CPFEM) and cellular automaton (CA) method was proposed to simulate the RX evolution during SSHT. One ({111} <110>) and three ({111} <110>, {100} <110>, {111} <112>) slip modes were assumed to be activated at RT and 980 °C in CPFEM calculations, respectively. The simulation takes the inhomogeneous as-cast dendritic microstructure into consideration. The simulated RX morphology and density conform well to experimental results. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle The Effect of Dynamic Recrystallization on Monotonic and Cyclic Behaviour of Al-Cu-Mg Alloy
Materials 2018, 11(6), 874; https://doi.org/10.3390/ma11060874
Received: 30 April 2018 / Revised: 20 May 2018 / Accepted: 21 May 2018 / Published: 23 May 2018
Cited by 1 | PDF Full-text (6048 KB) | HTML Full-text | XML Full-text
Abstract
The paper presents an investigation that was conducted to determine the possibility of the occurrence of the process of dynamic recrystallization in 2024 alloy during monotonic tensile and creep tests at the elevated temperatures of 100 °C, 200 °C, and 300 °C. As-extruded
[...] Read more.
The paper presents an investigation that was conducted to determine the possibility of the occurrence of the process of dynamic recrystallization in 2024 alloy during monotonic tensile and creep tests at the elevated temperatures of 100 °C, 200 °C, and 300 °C. As-extruded material was subjected to creep process with constant force at elevated temperatures, until two varying degrees of deformation were reached. After cooling at ambient temperature, the pre-deformed material was subjected to monotonic and fatigue tests as well as metallographic analysis. The process of dynamic recrystallization was determined in monotonic tests to occur at low strain rate (0.0015/s) only at the temperature of 300 °C. However, in the creep tests, this process occurred with varying efficiency, both during creep at 200 °C and 300 °C. Dynamic recrystallization was indicated to have a significant influence on the monotonic and cyclic properties of the material. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle A Continuum Model for the Effect of Dynamic Recrystallization on the Stress–Strain Response
Materials 2018, 11(5), 867; https://doi.org/10.3390/ma11050867
Received: 3 May 2018 / Revised: 18 May 2018 / Accepted: 18 May 2018 / Published: 22 May 2018
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Abstract
Austenitic Stainless Steels and High-Strength Low-Alloy (HSLA) steels show significant dynamic recovery and dynamic recrystallization (DRX) during hot forming. In order to design optimal and safe hot-formed products, a good understanding and constitutive description of the material behavior is vital. A new continuum
[...] Read more.
Austenitic Stainless Steels and High-Strength Low-Alloy (HSLA) steels show significant dynamic recovery and dynamic recrystallization (DRX) during hot forming. In order to design optimal and safe hot-formed products, a good understanding and constitutive description of the material behavior is vital. A new continuum model is presented and validated on a wide range of deformation conditions including high strain rate deformation. The model is presented in rate form to allow for the prediction of material behavior in transient process conditions. The proposed model is capable of accurately describing the stress–strain behavior of AISI 316LN in hot forming conditions, also the high strain rate DRX-induced softening observed during hot torsion of HSLA is accurately predicted. It is shown that the increase in recrystallization rate at high strain rates observed in experiments can be captured by including the elastic energy due to the dynamic stress in the driving pressure for recrystallization. Furthermore, the predicted resulting grain sizes follow the power-law dependence with steady state stress that is often reported in literature and the evolution during hot deformation shows the expected trend. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Evolution of Grain Interfaces in Annealed Duplex Stainless Steel after Parallel Cross Rolling and Direct Rolling
Materials 2018, 11(5), 816; https://doi.org/10.3390/ma11050816
Received: 14 April 2018 / Revised: 7 May 2018 / Accepted: 14 May 2018 / Published: 16 May 2018
Cited by 1 | PDF Full-text (3923 KB) | HTML Full-text | XML Full-text
Abstract
Changes in various grain interfaces, including the grain boundary and phase boundary, are a strong indication of microstructural changes, particularly ultra-fined grains achieved by large strain deformation and subsequent annealing. After direct rolling and cross rolling with the same strain of ε =
[...] Read more.
Changes in various grain interfaces, including the grain boundary and phase boundary, are a strong indication of microstructural changes, particularly ultra-fined grains achieved by large strain deformation and subsequent annealing. After direct rolling and cross rolling with the same strain of ε = 2, the distributions of the interfaces in annealed UNS S32304 duplex stainless steel were investigated using electron backscatter diffraction (EBSD) in this study. The ferrite experienced continued recovery, and a high density of low-angle grain boundaries (LAGBs) was produced. The percentage and number of twin boundaries (TBs) and LAGBs varied within the austenite. TBs were frequently found within austenite, showing a deviation from the Kurdjumov-Sachs (K-S) orientation relationship (OR) with ferrite matrix. However, LAGBs usually occur in austenite, with the K-S OR in the ferrite matrix. LAGBs were prevalent in the precipitated austenite grains, and therefore a strong texture was introduced in the cross-rolled and annealed samples, in which the precipitated austenite readily maintained the K-S OR in the ferrite matrix. By contrast, more TBs and a less robust texture were found in the precipitated austenite in direct-rolled and annealed samples, deviating from the K-S OR. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle The Effect of Ultrafine-Grained Microstructure on Creep Behaviour of 9% Cr Steel
Materials 2018, 11(5), 787; https://doi.org/10.3390/ma11050787
Received: 16 April 2018 / Revised: 4 May 2018 / Accepted: 8 May 2018 / Published: 12 May 2018
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Abstract
The effect of ultrafine-grained size on creep behaviour was investigated in P92 steel. Ultrafine-grained steel was prepared by one revolution of high-pressure torsion at room temperature. Creep tensile tests were performed at 873 K under the initially-applied stress range between 50 and 160
[...] Read more.
The effect of ultrafine-grained size on creep behaviour was investigated in P92 steel. Ultrafine-grained steel was prepared by one revolution of high-pressure torsion at room temperature. Creep tensile tests were performed at 873 K under the initially-applied stress range between 50 and 160 MPa. The microstructure was investigated using transmission electron microscopy and scanning electron microscopy equipped with an electron-back scatter detector. It was found that ultrafine-grained steel exhibits significantly faster minimum creep rates, and there was a decrease in the value of the stress exponent in comparison with coarse-grained P92 steel. Creep results also showed an abrupt decrease in the creep rate over time during the primary stage. The abrupt deceleration of the creep rate during the primary stage was shifted, with decreasing applied stress with longer creep times. The change in the decline of the creep rate during the primary stage was probably related to the enhanced precipitation of the Laves phase in the ultrafine-grained microstructure. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Effects of the Tempering and High-Pressure Torsion Temperatures on Microstructure of Ferritic/Martensitic Steel Grade 91
Materials 2018, 11(4), 627; https://doi.org/10.3390/ma11040627
Received: 22 March 2018 / Revised: 16 April 2018 / Accepted: 16 April 2018 / Published: 19 April 2018
Cited by 1 | PDF Full-text (6271 KB) | HTML Full-text | XML Full-text
Abstract
Grade 91 (9Cr-1Mo) steel was subjected to various heat treatments and then to high-pressure torsion (HPT) at different temperatures. Its microstructure was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Effects of the tempering temperature and the HPT temperature on the
[...] Read more.
Grade 91 (9Cr-1Mo) steel was subjected to various heat treatments and then to high-pressure torsion (HPT) at different temperatures. Its microstructure was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Effects of the tempering temperature and the HPT temperature on the microstructural features and microhardness in the ultrafine-grained (UFG) Grade 91 steel were researched. The study of the UFG structure formation takes into account two different microstructures observed: before HPT in both samples containing martensite and in fully ferritic samples. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Comparisons of Different Models on Dynamic Recrystallization of Plate during Asymmetrical Shear Rolling
Materials 2018, 11(1), 151; https://doi.org/10.3390/ma11010151
Received: 30 November 2017 / Revised: 4 January 2018 / Accepted: 8 January 2018 / Published: 17 January 2018
Cited by 1 | PDF Full-text (3546 KB) | HTML Full-text | XML Full-text
Abstract
Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation.
[...] Read more.
Asymmetrical shear rolling with velocity asymmetry and geometry asymmetry is beneficial to enlarge deformation and refine grain size at the center of the thick plate compared to conventional symmetrical rolling. Dynamic recrystallization (DRX) plays a vital role in grain refinement during hot deformation. Finite element models (FEM) coupled with microstructure evolution models and cellular automata models (CA) are established to study the microstructure evolution of plate during asymmetrical shear rolling. The results show that a larger DRX fraction and a smaller average grain size can be obtained at the lower layer of the plate. The DRX fraction at the lower part increases with the ascending speed ratio, while that at upper part decreases. With the increase of the offset distance, the DRX fraction slightly decreases for the whole thickness of the plate. The differences in the DRX fraction and average grain size between the upper and lower surfaces increase with the ascending speed ratio; however, it varies little with the change of the speed ratio. Experiments are conducted and the CA models have a higher accuracy than FEM models as the grain morphology, DRX nuclei, and grain growth are taken into consideration in CA models, which are more similar to the actual DRX process during hot deformation. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling
Materials 2018, 11(1), 53; https://doi.org/10.3390/ma11010053
Received: 11 December 2017 / Revised: 27 December 2017 / Accepted: 28 December 2017 / Published: 29 December 2017
Cited by 4 | PDF Full-text (7774 KB) | HTML Full-text | XML Full-text
Abstract
The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20–23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C
[...] Read more.
The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20–23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (<40%), while grain (twin) boundary strengthening prevailed at higher strains. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Grain Refinement Kinetics in a Low Alloyed Cu–Cr–Zr Alloy Subjected to Large Strain Deformation
Materials 2017, 10(12), 1394; https://doi.org/10.3390/ma10121394
Received: 14 November 2017 / Revised: 29 November 2017 / Accepted: 4 December 2017 / Published: 6 December 2017
Cited by 4 | PDF Full-text (5384 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates the microstructural evolution and grain refinement kinetics of a solution-treated Cu–0.1Cr–0.06Zr alloy during equal channel angular pressing (ECAP) at a temperature of 673 K via route BC. The microstructural change during plastic deformation was accompanied by the formation
[...] Read more.
This paper investigates the microstructural evolution and grain refinement kinetics of a solution-treated Cu–0.1Cr–0.06Zr alloy during equal channel angular pressing (ECAP) at a temperature of 673 K via route BC. The microstructural change during plastic deformation was accompanied by the formation of the microband and an increase in the misorientations of strain-induced subboundaries. We argue that continuous dynamic recrystallization refined the initially coarse grains, and discuss the dynamic recrystallization kinetics in terms of grain/subgrain boundary triple junction evolution. A modified Johnson–Mehl–Avrami–Kolmogorov relationship with a strain exponent of about 1.49 is used to express the strain dependence of the triple junctions of high-angle boundaries. Severe plastic deformation by ECAP led to substantial strengthening of the Cu–0.1Cr–0.06Zr alloy. The yield strength increased from 60 MPa in the initial state to 445 MPa after a total strain level of 12. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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Open AccessArticle Development of a Model for Dynamic Recrystallization Consistent with the Second Derivative Criterion
Materials 2017, 10(11), 1259; https://doi.org/10.3390/ma10111259
Received: 4 October 2017 / Revised: 26 October 2017 / Accepted: 27 October 2017 / Published: 2 November 2017
Cited by 1 | PDF Full-text (14441 KB) | HTML Full-text | XML Full-text
Abstract
Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas,
[...] Read more.
Dynamic recrystallization (DRX) processes are widely used in industrial hot working operations, not only to keep the forming forces low but also to control the microstructure and final properties of the workpiece. According to the second derivative criterion (SDC) by Poliak and Jonas, the onset of DRX can be detected from an inflection point in the strain-hardening rate as a function of flow stress. Various models are available that can predict the evolution of flow stress from incipient plastic flow up to steady-state deformation in the presence of DRX. Some of these models have been implemented into finite element codes and are widely used for the design of metal forming processes, but their consistency with the SDC has not been investigated. This work identifies three sources of inconsistencies that models for DRX may exhibit. For a consistent modeling of the DRX kinetics, a new strain-hardening model for the hardening stages III to IV is proposed and combined with consistent recrystallization kinetics. The model is devised in the Kocks-Mecking space based on characteristic transition in the strain-hardening rate. A linear variation of the transition and inflection points is observed for alloy 800H at all tested temperatures and strain rates. The comparison of experimental and model results shows that the model is able to follow the course of the strain-hardening rate very precisely, such that highly accurate flow stress predictions are obtained. Full article
(This article belongs to the Special Issue Dynamic Recrystallization and Microstructural Evolution in Alloys)
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