Grain boundary evolution during low-strain grain boundary engineering achieved by strain-induced boundary migration in pure copper

In order to get optimal grain boundary character distribution (GBCD) and grain boundary properties, thermomechanical processing (TMP) is usually adopted in grain boundary engineering. However, the mechanism behind the TMP treatments and GBCD optimization is still unclear. The present study has conducted a series experiments involving low-strain TMPs to study the relationship between TMP parameters and the behind microstructural evolution. The experimental results indicate that in the scope of low-strain TMP, strain induced boundary migration (SIBM) is the most effective process for GBCD optimization. Besides, SIBM and grain growth would gradually transfer to recrystallization with the increase of pre-deformation level and annealing temperature. Further quasi in-situ EBSD results infer that SBIM is activated locally in some region with high stored energy, and further gradual initiation of SIBM from one region to another contributes to the gradual increase of special boundaries with annealing time.

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Micromechanisms Involved in Grain Boundary Engineering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.495-497.1225 ◽

2005 ◽

Vol 495-497 ◽

pp. 1225-1230

Author(s):

Andre Luiz Pinto ◽

Carlos Sergio da Costa Viana ◽

Luiz Henrique de Almeida

Keyword(s):

Grain Boundary ◽

Electron Backscatter Diffraction ◽

Boundary Migration ◽

Coincidence Site Lattice ◽

Inconel 625 ◽

Grain Boundary Engineering ◽

Inconel 600 ◽

Special Boundaries ◽

Deformation Step ◽

Backscatter Diffraction

Grain boundary engineering has been applied to different materials in order to increase properties particularly sensitive to intergranular phenomena. This work analyses the micromechanisms that allow the control of the amount of special boundaries which respect coincidence site lattice theory. α-brass, a lead alloy, Inconel 625 and Inconel 600 were submitted to different thermomechanical treatments and were analyzed via electron backscatter diffraction in order to characterize their grain boundaries. The occurrence of thin twins in some crystal directions during the deformation step seems to determine the results obtained as well as strain induced boundary migration.

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Grain Boundary Engineering of Strain-Annealed Hastelloy-X

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.852 ◽

2021 ◽

Vol 1016 ◽

pp. 852-856

Author(s):

Waqas Muhammad ◽

Daniel Wei ◽

Étienne Martin

Keyword(s):

Grain Boundary ◽

Boundary Migration ◽

Applied Strain ◽

Annihilation Rate ◽

Grain Boundary Engineering ◽

Hastelloy X ◽

Dissociation Mechanism ◽

Annealing Conditions ◽

High Annealing ◽

Annealing Twins

The present study investigates the occurrence and effectiveness of the dissociation mechanism of Σ3 CSL boundaries into its variants such as Σ9 and Σ27a-b during strain-annealed grain boundary engineering (GBE) of Hastelloy-X. Multiple cold-rolling strain levels and annealing conditions are studied and it is observed that the density of ∑3 boundaries decreases proportionally to the amount of strain induced boundary migration (SIBM) during the GBE process. The dissociation mechanism of Σ3 annealing twins is activated at the onset of SIBM, causing an increase in the density of the Σ3n variants. It is shown that at high annealing times or temperatures, the rate of generation of CSL boundaries through dissociation mechanism is lower than their annihilation rate. It is further suggested that the dissociation mechanism of ∑3 boundaries during GB migration is more efficient when the amount of applied strain prior to annealing is kept low, thus promoting disruption of the random GB network.

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Formation of Annealing Twins during Recrystallization and Grain Growth in 304L Austenitic Stainless Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.753.113 ◽

2013 ◽

Vol 753 ◽

pp. 113-116 ◽

Cited By ~ 31

Author(s):

Yuan Jin ◽

M. Bernacki ◽

G.S. Rohrer ◽

Anthony D. Rollett ◽

B. Lin ◽

...

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Grain Boundary ◽

Grain Growth ◽

Boundary Migration ◽

Annealing Twin ◽

Strain Level ◽

Grain Boundary Engineering ◽

Twin Density ◽

Annealing Twins

Understanding of the mechanisms of annealing twin formation is fundamental for grain boundary engineering. In this work, the formation of annealing twins in a 304L austenitic stainless steel is examined in relation to the thermo-mechanical history. The behaviour of annealing twins of various morphologies is analysed using an in-situ annealing device and EBSD. The results confirm that there is a synergistic effect of prior strain level on annealing twin density generated during recrystallization. The higher the prior strain level, the higher the velocity of grain boundary migration and the higher the annealing twin density in the recrystallized grains. This effect decreases as the recrystallization fraction increases. The existing mathematical models (Pande's model and Gleiter's model), which were established to predict annealing twin density in the grain growth regime, can not predict this phenomenon.

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Optimization of the grain boundary character distribution of pure copper by low-strain thermomechanical processing

International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) ◽

10.1515/ijmr-2020-1110808 ◽

2020 ◽

Vol 111 (8) ◽

pp. 668-675

Author(s):

Ming Huang ◽

Kunpeng Zhao ◽

Ziyun Chen ◽

Yuan Qin ◽

Xinye Yang ◽

...

Keyword(s):

Grain Boundary ◽

Grain Growth ◽

Boundary Migration ◽

Pure Copper ◽

Grain Boundary Character Distribution ◽

Grain Boundary Migration ◽

Boundary Character ◽

Grain Boundary Character ◽

Character Distribution ◽

Boundary Character Distribution

Abstract Although thermomechanical processing has been widely used in grain boundary engineering, the relationship between thermomechanical parameters and grain boundary character distribution is still not well understood. In the present study, electron backscatter diffraction was used to study the grain boundary character distribution in pure copper after lowstrain thermomechanical treatments. It was found that the low-R coincidence site lattice frequency and grain size decreases in the following sequence, 10% compression > 15% compression > 5% compression, except for 700 0C. During thermomechanical treatments of copper, strain-induced grain boundary migration and grain growth may occur during annealing of 5% compressed copper, and recrystallization dominates during annealing of 15% compressed copper, while the annealing mechanism of 10% compressed copper changes from strain-induced grain boundary migration and grain growth to recrystallization when the annealing temperature exceeds 600 0C. The results indicated that during single-step low-strain thermomechanical treatments, straininduced grain boundary migration and grain growth would gradually change to recrystallization with the increase of pre-deformation level and annealing temperature. Among the three mechanisms, strain-induced grain boundary migration seems to be more effective than recrystallization and grain growth in the optimization of grain boundary character distribution, and it is suggested that this is due to the high boundary migration rate of strain-induced grain boundary migration.

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Measurement of solute segregation to grain boundaries in the AEM: A review

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105096 ◽

1988 ◽

Vol 46 ◽

pp. 606-607

Author(s):

D. B. Williams ◽

A. D. Romig

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Boundary Migration ◽

Grain Boundary Migration ◽

Boundary Misorientation ◽

Collector Plate ◽

Segregation Process ◽

Grain Boundary Misorientation ◽

Structure Boundary ◽

Equilibrium Segregation

The segregation of solute or imparity elements to grain boundaries can occur by three well-defined processes. The first is Gibbsian segregation in which an element of minimal matrix solubility confines itself to a monolayer at the grain boundary. Classical examples include Bi in Cu and S or P in Fe. The second process involves the depletion of excess matrix solute by volume diffusion to the boundary. In the boundary, the solute atoms diffuse rapidly to precipitates, causing them to grow by the ‘collector-plate mechanism.’ Such grain boundary diffusion is thought to initiate “Diffusion-Induced Grain Boundary Migration,” (DIGM). This process has been proposed as the origin of eutectoid transformations or discontinuous grain boundary reactions. The third segregation process is non-equilibrium segregation which result in a solute build-up around the boundary because of solute-vacancy interactions.All of these segregation phenomena usually occur on a sub-micron scale and are often affected by the nature of the grain boundary (misorientation, defect structure, boundary plane).

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Domain coarsening by grain boundary migration in ordered Ni4Mo

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144279 ◽

1986 ◽

Vol 44 ◽

pp. 560-561

Author(s):

K. Vasudevan ◽

H. P. Kao ◽

C. R. Brooks ◽

E. E. Stansbury

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Short Range ◽

Boundary Migration ◽

Grain Boundary Migration ◽

Rapid Cooling ◽

Temperature Range ◽

Fee Structure ◽

Domain Coarsening ◽

Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

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