Special Issue "Recrystallization of Metallic Materials"

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: 1 January 2019

Special Issue Editors

Guest Editor
Prof. Matti Ristinmaa

Division of Solid Mechanics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden
Website | E-Mail
Interests: material mechanics; modeling of coupled fields; mixture theory; smart materials; structural optimization; experimental mechanics
Guest Editor
Assoc. Prof. Håkan Hallberg

Division of Solid Mechanics, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden
Website | E-Mail
Interests: material mechanics; recrystallization; grain growth; phase transformations; texture evolution

Special Issue Information

Dear Colleagues,

Recrystallization (RX) is a key driver behind microstructure evolution in crystalline materials.  The phenomenon is commonly observed in a range of different materials, comprising geo-materials, such as rocks and ice, as well as engineering materials, such as metals and alloys. The latter category of materials is in focus for this Special Issue of Crystals.

In general terms, RX can be defined as the formation of a new grain structure in a cold worked material and occurs through the formation and migration of mobile grain boundaries. A distinction is frequently made between RX that progresses by distinct nucleation-and-growth processes (discontinuous RX, DRX) or that occurring by a continuous grain structure evolution (CDRX). Such differences are closely linked to which material and which processing conditions are presently under consideration.

On a macroscopic scale, RX can take place during materials processing under static conditions (SRX), or under dynamic conditions (DRX) in conjunction with concurrent deformation of the material. Important processing parameters include the temperature, deformation and deformation rate. On the micro-/mesoscopic scale, RX is intimately linked to the properties of grain boundaries, crystallographic texture, grain morphologies, development of dislocation structures and a range of other processes and features of the crystal aggregate. At even finer length scales, detailed aspects of, for example, grain boundary structure, interface energies/mobilities and dislocation mechanics become relevant. Observations as these highlight the inherent multiscale nature of RX, which is a challenge—not least—in numerical modelling of RX.

Recognizing the multitude of highly relevant research topics that are linked to RX, the present Special Issue of Crystals welcomes, but is not limited to, studies on:

  • Thermo-mechanical materials processing during which RX is active
  • The exploitation of RX in materials design
  • Observation and characterization of the processing-microstructure-property links and their dependence on RX
  • Nucleation mechanisms in RX
  • Influence of grain boundary structure on RX
  • Grain boundary properties and their relation to RX
  • Texture influence and evolution in RX
  • Numerical models of RX
  • Multiscale approaches in modelling and simulation of RX

The adopted methods can be based either on experimental characterization and observation or on numerical modelling. In particular, submissions that combine experimental observations with numerical simulation models are encouraged. In addition, studies that aim to develop suitable experimental methods or to establish new numerical methods for describing and observing RX are welcome.

Prof. Matti Ristinmaa
Dr. Håkan Hallberg
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Crystals 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 1200 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

  • Recrystallization
  • Grain boundaries
  • Nucleation
  • Texture
  • Metals and alloys
  • Experiment
  • Modeling
  • Simulation

Published Papers (3 papers)

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Research

Open AccessArticle Aging Behavior of Aluminum Alloy 6082 Subjected to Friction Stir Processing
Crystals 2018, 8(9), 337; https://doi.org/10.3390/cryst8090337
Received: 27 July 2018 / Revised: 14 August 2018 / Accepted: 16 August 2018 / Published: 22 August 2018
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Abstract
The present work examined the effect of artificial aging on the microstructure, texture, and hardness homogeneity in aluminum alloy AA6082 subjected to friction stir processing (FSP). Aging was applied to FSP samples at three different temperatures (150 °C, 175 °C, and 200 °C)
[...] Read more.
The present work examined the effect of artificial aging on the microstructure, texture, and hardness homogeneity in aluminum alloy AA6082 subjected to friction stir processing (FSP). Aging was applied to FSP samples at three different temperatures (150 °C, 175 °C, and 200 °C) for a period of 1 h, 6 h, and 12 h. Microstructure analysis using optical Microscopy (OM) and Electron Back-Scattered Diffraction (EBSD) indicated that FSP produced fine equiaxed grains, with an average grain size of 6.5 μm, in the stir zone (SZ) due to dynamic recrystallization. Aging was shown to result in additional grain refinement in the SZ due to the occurrence of recovery and recrystallization with either increasing aging temperature and/or aging time. An optimum average grain size of 3–4 μm was obtained in the SZ by applying aging at 175 °C. This was accompanied by an increase in the fraction of high-angle grain boundaries. FSP provided a simple shear texture with a major component of B fiber. Increasing aging temperature and/or time resulted in the formation of recrystallization texture of a Cube orientation. In addition, Vickers microhardness was evaluated for the FSP sample, indicating a softening in the SZ due to the dissolution of the hardening precipitates. Compared to other aging temperatures, aging at 175 °C resulted in maximum hardness recovery (90 Hv) to the initial value of base metal (92.5 Hv). The hardness recovery is most likely attributed to the uniform distribution of fine hardening precipitates in the SZ when increasing the aging time to 12 h. Full article
(This article belongs to the Special Issue Recrystallization of Metallic Materials)
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Open AccessArticle Stress Relaxation Properties and Microscopic Deformation Structure in Bending of the C7025 and C7035 Alloy
Crystals 2018, 8(8), 324; https://doi.org/10.3390/cryst8080324
Received: 27 June 2018 / Revised: 8 August 2018 / Accepted: 9 August 2018 / Published: 14 August 2018
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Abstract
Stress relaxation tests in cantilever bending were performed on the C7025 and C7035 alloys at 298 K and 393 K, respectively. The effect of stress-relief treatments on stress relaxation properties was investigated. The structural changes associated with the stress relaxation process were examined
[...] Read more.
Stress relaxation tests in cantilever bending were performed on the C7025 and C7035 alloys at 298 K and 393 K, respectively. The effect of stress-relief treatments on stress relaxation properties was investigated. The structural changes associated with the stress relaxation process were examined using transmission electron microscopy. The stress relaxation curve fits well to empirical formula σ* = [K’ln(t + α0) + C]−n for stress relaxation. The curves can be split into two stages. The stress drops fast at first and then it gets slower in the second stage, and tends towards a certain limited value after a long time. The curve and microstructure reveal that the C7035 alloy has a lower rate of stress relaxation and a higher anti-stress relaxation capacity than the C7025. The first reason is that the movement of vacancies required by spinodal decomposition is inhibited, and the quantity of cobalt-containing vacancies decreases dramatically in the C7035 alloy. The other reason is that the precipitated phases became uniformly diffused in the C7035 alloy. The precipitate phase is uniformly distributed in the grain boundaries and the matrix, during the relaxed condition, and thus the dislocation movement is blocked by the precipitate. Full article
(This article belongs to the Special Issue Recrystallization of Metallic Materials)
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Open AccessArticle Constitutive Modelling and Hot Workability Analysis by Microstructure Examination of GH4169 Alloy
Crystals 2018, 8(7), 282; https://doi.org/10.3390/cryst8070282
Received: 26 May 2018 / Revised: 5 July 2018 / Accepted: 6 July 2018 / Published: 9 July 2018
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Abstract
The relationships between hot deformation parameters and flow behaviour have attracted many researchers’ attention for the past few decades, whilst precise constitutive modelling of GH4169 remained a problem, which seriously affected the process and microstructure control of alloys. In this work, a modified
[...] Read more.
The relationships between hot deformation parameters and flow behaviour have attracted many researchers’ attention for the past few decades, whilst precise constitutive modelling of GH4169 remained a problem, which seriously affected the process and microstructure control of alloys. In this work, a modified Arrhenius type model was introduced to describe the flow stresses of various compression conditions. The model showed high precision in flow stress prediction. In order to facilitate workability evaluation for engineering applications, the hot processing maps were established at the strain of 0.4~0.6. The processing maps revealed an instability domain at 900~950 °C and 0.1~1 s−1, a high dissipation efficiency domain at 1060~1100 °C and 0.001~0.01 s−1, and a stable deformation domain for the rest of processing parameters. Microstructures of each domain were observed via optical microscope (OM) and electron backscattered diffraction (EBSD). The intriguing finding was that the microstructures morphology agreed well with the descriptions in “discontinuous mechanism”, and incompletely recrystallized microstructures were found in the instability domain. Fully recrystallized microstructures were found in the stable deformation domain, and grain coarsen in the high dissipation efficiency domain. Optimal hot working conditions were suggested based on the microstructure analysis. This investigation contributed to a comprehensive understanding of the workability of GH4169. Full article
(This article belongs to the Special Issue Recrystallization of Metallic Materials)
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