Evolution of Microstructure in Pure Nickel during Processing for Grain Boundary Engineering

2013 ◽  
Vol 753 ◽  
pp. 97-100 ◽  
Author(s):  
Brian Lin ◽  
Gregory S. Rohrer ◽  
Anthony D. Rollett ◽  
Yuan Jin ◽  
Nathalie Bozzolo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Thermomechanical Processing ◽  
Electron Backscatter Diffraction ◽  
Experimental Studies ◽  
Recrystallization Process ◽  
Grain Boundary Engineering ◽  
Triple Junctions ◽  
Special Boundaries ◽  
Before And After ◽  
Over Time

Grain boundary engineered (GBE) materials have improved properties that are associated with the high fraction special Σ3n boundaries in the microstructure, where n = 1,2,3. Previous experimental studies with high purity nickel before and after thermomechanical processing have shown that the fraction of Σ3 boundaries increased by at least factor of two [1]. Electron backscatter diffraction (EBSD) is used to characterize the evolution of these special boundaries throughout the recrystallization process of a 25% cold rolled sample annealed at 490°C. The fractions of the Σ3 boundaries and coherent twins have been measured over time revealing a steadily increasing behavior over the entire microstructure. However partitioning to only include recrystallized regions reveals a different behavior in the Σ3 boundaries as fractions, which increase rapidly at first and then stagnate over time. Additional triple junction characterization was performed to monitor the evolution of triple junctions containing special boundaries.

Micromechanisms Involved in Grain Boundary Engineering

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.

Grain Boundary Engineering: Progress and Challenges

2007 ◽  
Vol 539-543 ◽  
pp. 3389-3394 ◽  
Author(s):  
Wei Guo Wang
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Engineering ◽  
Special Boundaries ◽  
Grain Boundary Character ◽  
Proposed Model ◽  
Backscatter Diffraction

The progress of grain boundary engineering (GBE) is overviewed and the challenges for further investigations emphasized. It points out that, the electron backscatter diffraction (EBSD) reconstruction of grain boundaries, which gives the information of connectivity interruption of general high angle boundaries (HABs), is more significant than purely pursuing high frequency of so-called special boundaries. The criterion for the optimization of grain boundary character distribution (GBCD) needs to be established. The energy spectrum and the degradation susceptibility of grain boundaries of various characters including HABs and low Σ（Σ≤29） coincidence site lattice (CSL) needs to be studied and ascertained. And finally, the newly proposed model of non-coherent Σ3 interactions for GBCD optimization are discussed.

A Grain Boundary Engineering Approach to Promote Special Boundaries in a Pb-base Alloy

2002 ◽  
Vol 730 ◽  
Author(s):  
D.S. Lee ◽  
H.S. Ryoo ◽  
S.K. Hwang
Keyword(s):  
Grain Boundary ◽  
Thermomechanical Processing ◽  
Base Alloy ◽  
Coincidence Site Lattice ◽  
Grain Boundary Engineering ◽  
Site Lattice ◽  
Special Boundaries ◽  
Engineering Approach ◽  
Electrochemical Evaluation ◽  
Battery Application

AbstractA grain boundary engineering approach was employed to improve the microstructure of a commercial Pb-base alloy for better performance in automobile battery application. Through a combination of cold working, recrystallization and subsequent thermomechanical-processing, it was possible to increase the fraction of the low ∑ coincidence site lattice boundaries up to 91% in addition to the substantial grain refinement. A preliminary electrochemical evaluation indicated a better corrosion resistance in the experimental material laden with the special boundaries. The high frequency of the coincidence site lattice boundaries in the specimens was interpreted in terms of the '∑3 regeneration' model proposed in previous works.

scholarly journals Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies

2000 ◽  
Vol 6 (S2) ◽  
pp. 940-941
Author(s):  
A.J. Schwartz ◽  
M. Kumar ◽  
P.J. Bedrossian ◽  
W.E. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Thermomechanical Processing ◽  
Electron Backscatter Diffraction ◽  
Grain Boundary Character Distribution ◽  
Atomic Force ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Network Engineering ◽  
Backscatter Diffraction

Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of “special” and “random” grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM)5 and atomic force microscopy (AFM) to elucidate these fundamental mechanisms.An example of the coupling of TEM and EBSD is given in Figures 1-3. The EBSD image in Figure 1 reveals “segmentation” of boundaries from special to random and random to special and low angle grain boundaries in some grains, but not others, resulting from the 15% compression of an Inconel 600 polycrystal.

Application of Electron Backscatter Diffraction to Grain Boundaries

2010 ◽  
Vol 160 ◽  
pp. 39-46 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Experimental Methodology ◽  
Polycrystalline Materials ◽  
Grain Boundary Engineering ◽  
Network Characteristics ◽  
Grain Boundary Plane ◽  
Electron Backscatter ◽  
Measurement Strategies ◽  
Backscatter Diffraction

The technique of electron backscatter diffraction (EBSD) is ideal for the characterisation of grain boundary networks in polycrystalline materials. In recent years the experimental methodology has evolved to meet the needs of the research community. For example, the capabilities of EBSD have been instrumental in driving forward the topic of ‘grain boundary engineering’. In this paper the current capabilities of EBSD for grain boundary characterisation will be reviewed and illustrated by examples. Topics are measurement strategies based on misorientation statistics, determination of grain boundary plane distributions and grain boundary network characteristics.

scholarly journals Effects of Unidirection/Bidirection Torsional Thermomechanical Processes on Grain Boundary Characteristics and Plasticity of Pure Nickel

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 236
Author(s):  
Yao Lin ◽  
Shan Liu ◽  
Tao Wu ◽  
Guangchun Wang
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Pure Nickel ◽  
Random Boundary ◽  
Special Boundaries ◽  
Grain Boundary Characteristics ◽  
Thermomechanical Processes ◽  
Boundary Characteristics ◽  
Boundary Modification ◽  
Boundary Characteristic

The “torsion and annealing” grain boundary modification of pure nickel wires with different diameters was carried out in this paper. The effects of torsional cycles as well as unidirectional/bidirectional torsion methods on grain boundary characteristic distribution and plasticity were investigated. The fraction of special boundaries, grain boundary characteristic distributions and grain orientations of samples with different torsion parameters were detected by electron backscatter diffraction. Hardness measurement was conducted to characterize the plasticity. Then, the relationship between micro grain boundary characteristics and macro plasticity was explored. It was found that the special boundaries, especially Σ3 boundaries, are increased after torsion and annealing and effectively broke the random boundary network. The bidirectional torsion with small torsional circulation unit was the most conducive way to improve the fraction of special boundaries. The experiments also showed that there was a good linear correlation between the fraction of special boundaries and hardness. The plasticization mechanism was that plenty of grains with Σ3 boundaries, [001] orientations and small Taylor factor were generated in the thermomechanical processes. Meanwhile, the special boundaries broke the random boundary network. Therefore, the material was able to achieve greater plastic deformation. Moreover, the mechanism of torsion and annealing on the plasticity of pure nickel was illustrated, which provides theoretical guidance for the pre-plasticization of nickel workpieces.

The Use of Rodrigues-Frank Space for Representing Discrete Misorientation Distributions

2005 ◽  
Vol 495-497 ◽  
pp. 157-166 ◽  
Author(s):  
Leo Kestens ◽  
Kim Verbeken ◽  
R. Decocker ◽  
Roumen H. Petrov ◽  
Patricia Gobernado ◽  
...  
Keyword(s):  
Single Point ◽  
Carbon Steels ◽  
Recrystallization Process ◽  
Large Set ◽  
Low Carbon ◽  
Triple Junctions ◽  
Misorientation Distribution ◽  
Orientation Relations ◽  
Before And After ◽  
The Given

It is often assumed that the texture formation during solid state transformations in low carbon steels critically depends on the local crystallographic misorientation at the interface between transformed and not yet transformed material volume. In some cases, a theoretical crystallographic orientation relation can be presumed as a necessary prerequisite for the transformation to occur. Classical examples of such misorientation conditions in steel metallurgy are the orientation relations between parent and product grains of the allotropic phase transformation from austenite to ferrite (or martensite) or the hypothetical <110>26.5º misorientation between growing nuclei and disappearing grains in a recrystallization process. One way to verify the validity of such misorientation conditions is to carry out an experiment in which the transformation is partially completed and then observe locally, at the transformation interface, whether or not the presumed crystallographic condition is complied with. Such an experiment will produce a large set of misorientation data. As each observed misorientation Dg is represented by a single point in the Rodrigues-Frank (RF) space, a distribution of discrete misorientation points is obtained. This distribution is compared with the reference misorientation Dgr, corresponding to a specific physical condition, by determining the number fraction dn of misorientations that are confined within a narrow misorientation volume element dw around the given reference misorientation Dgr. In order to evaluate whether or not the proposed misorientation condition is obeyed, the number fraction dn of the experimentally measured distribution must be compared with the number fractions dr obtained for a random misorientation distribution. The ratio dn/dr can be interpreted as the number intensity fi of the given reference misorientation Dgr. This method was applied on the observed local misorientations between the recrystallizing grains growing into the single crystal matrix of a Fe-2.8%Si alloy. It was found that the number intensity of the <110>26.5º misorientation increased with a factor 10 when the misorientation distribution was evaluated before and after the growth stage. In another example the method was applied to the misorientations measured at the local interface between parent austenite and product martensite grains of a partially transformed Fe-28%Ni alloy. It could be established that the Nishiyama- Wasserman relations ({111}g//{110}a <112>g//<110>a) prevail over the Kurdjumov-Sachs relations ({111}g//{110}a and <110>g//<111>a) although a considerable scatter was observed around either of the theoretical correspondences. A full parametric misorientation description was also applied to evaluate the relative grain boundary energies associated with a set of crystallographic misorientations observed near triple junctions in Fe-2%Si. In this instance it was found that the boundaries carrying a misorientation of the type <110>w carry a lower interfacial energy than the <100> or <111> type boundaries.

Crystal orientation of β-Sn grain in Ni(P)/Sn–0.5Cu/Cu and Ni(P)/Sn–1.8Ag/Cu joints

2010 ◽  
Vol 25 (10) ◽  
pp. 1950-1957 ◽  
Author(s):  
Sun-Kyoung Seo ◽  
Moon Gi Cho ◽  
Hyuck Mo Lee
Keyword(s):  
Grain Boundary ◽  
Crystal Orientation ◽  
Electron Backscatter Diffraction ◽  
Boundary Crossing ◽  
High Angle ◽  
Before And After ◽  
Columnar Grains ◽  
Sn Grain Orientation ◽  
Backscatter Diffraction ◽  
Solder Composition

Electron backscatter diffraction analysis was used to compare the crystal orientation of β-Sn grains in Ni(P)/Sn–0.5Cu/Cu and Ni(P)/Sn–1.8Ag/Cu joints before and after aging. In Ni(P)/solder/Cu joints, the solder composition (Cu versus Ag) significantly affects β-Sn grain orientation. In Ni(P)/Sn–0.5Cu/Cu, there are two types of small columnar grains grown from Ni(P) and Cu under bump metallurgy with a high-angle grain boundary crossing the joint closer to the Ni side; in contrast, Ni(P)/Sn–1.8Ag/Cu has large grains with low-angle boundaries. During thermal aging at 150 °C for 250 h, the Ni(P)/Sn–0.5Cu/Cu joints undergo a more significant microstructural change than the Ni(P)/Sn–1.8Ag/Cu joint. Additionally, obvious ledges developed along the high-angle grain boundary between the upper and lower areas in the Sn–0.5Cu joint.

scholarly journals Effects of Trace Amounts of Mn, Zr and Sc on the Recrystallization and Corrosion Resistance of Al-5Mg Alloys

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 926
Author(s):  
Sheng-Long Lee ◽  
Yang-Chun Chiu ◽  
Tse-An Pan ◽  
Mien-Chung Chen
Keyword(s):  
Corrosion Resistance ◽  
Grain Boundary ◽  
Grain Growth ◽  
Intergranular Corrosion ◽  
Electron Backscatter Diffraction ◽  
Recrystallization Process ◽  
Corrosion Morphology ◽  
Electron Microscopes ◽  
Backscatter Diffraction ◽  
Better Than

This study aimed to explore the effects of trace amounts of Mn, Zr, and Sc on the recrystallization behavior and corrosion resistance of Al-5Mg alloys after process annealing by means of alloy design and microstructure analysis of electron backscatter diffraction (EBSD), electron microprobe (EPMA), and electron microscopes (TEM and SEM). The main objective was to obtain alloys with better corrosion resistance. The results show that the fine Al3Zr and Al3Sc precipitated particles were both superior to the MnAl6 particles in inhibiting grain and sub-grain boundary migrations. Therefore, the Zr-containing and Sc-containing alloys were better than the Mn-containing alloy in inhibiting recrystallization. For further comparison, the thermal stability of the Al3Sc particles was better than that of the Al3Zr particles, so the Sc-containing alloy at the high temperature above 350 °C inhibited grain growth better than the Zr-containing alloy. During the recovery stage of the alloy in the recrystallization process, the β-Mg2Al3 phase precipitated on the sub-grain boundary, thus reducing the occurrence of intergranular corrosion. However, in the initial stage of recrystallization, the β-Mg2Al3 phase continuously precipitated on the grain boundary, causing obvious intergranular corrosion. For the Sc-containing alloy, because there was no obvious grain growth stage, the β-Mg2Al3 phase continuously precipitated on the grain boundary, and thereby intergranular corrosion occurred. Therefore, its corrosion resistance was greatly reduced. By contrast, for the alloy containing Mn or Zr, because of obvious grain growth, magnesium atoms aggregated. As a result, the β-Mg2Al3 phase discontinuously precipitated on the grain boundary. The corrosion morphology was local pitting corrosion rather than intergranular corrosion, and thus the corrosion resistance of the alloy was enhanced. As a novelty, this study clearly observed the sensitized precipitation and corrosion morphology of the β-Mg2Al3 phase of Al-5Mg alloy under different recrystallization methods. This will be of benefit to the design of anti-corrosion measures for the future manufacturing and application of Al-5Mg alloy.

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