Regarding fracture plane with minimum toughness and fracture anisotropy associated with elongated grain boundaries in ultra-fine-grained Cu

2021 ◽  
pp. 107654
Author(s):  
Shoudao Qu ◽  
Zesheng You ◽  
Ruicong Gu ◽  
Yao Jiang ◽  
Jing Tao Wang
Keyword(s):  
Grain Boundaries ◽  
Fracture Plane ◽  
Fine Grained ◽  
Fracture Anisotropy

Influence of cooling media in achieving grain refinement of AA2014 alloy using friction stir processing

2020 ◽  
Vol 234 (22) ◽  
pp. 4520-4534
Author(s):  
MVNV Satyanarayana ◽  
Adepu Kumar
Keyword(s):  
Grain Boundaries ◽  
Friction Stir Processing ◽  
Heat Dissipation ◽  
Electron Backscattered Diffraction ◽  
Friction Stir ◽  
Fine Grained ◽  
Fine Grained Structure ◽  
Cooling Media ◽  
Processing Zone ◽  
Friction Stir Processing Sample

The present paper studies the influence of different cooling media (water and cryogenic media) on microstructure, mechanical, and corrosion behavior of friction stir processing of AA2014. From the electron backscattered diffraction results, it was observed that the grain size in stir zone of air-cooled friction stir processing, dry ice-cooled friction stir processing, and underwater friction stir processing are 4.9 µm, 3.5 µm, and 0.9 µm respectively, and the fraction of high angle grain boundaries are more in underwater friction stir processing sample compared to other conditions. The ultra-fine grained structure (0.9 µm) was achieved in underwater friction stir processing due to uniform heat dissipation from the processing zone to the water. Mechanical properties such as hardness and strength were improved in underwater friction stir processing compared to other conditions. The fine precipitates formed in the underwater friction stir processing sample were distributed randomly at grain boundaries, and hence corrosion resistance was improved in underwater friction stir processing sample compared to other conditions.

scholarly journals Further Observations on Stress-generated Ice in the Blue Glacier, Washington, U.S.A.

1970 ◽  
Vol 9 (55) ◽  
pp. 87-101 ◽  
Author(s):  
Charles A. Knight ◽  
E. LaChapelle
Keyword(s):  
Grain Boundaries ◽  
Thin Section ◽  
Liquid Water ◽  
Detailed Examination ◽  
Crystal Formation ◽  
Fine Grained ◽  
Water Filling ◽  
Flow Effects ◽  
Ice Crystallization

AbstractA more detailed examination is made of the stress-generated ice crystallization features already discussed by LaChapelle (1968), using mainly thin-section techniques. The crystallization features on the walls of a tunnel within the Blue Glacier are localized at fine-grained layers and are led by liquid water traveling along grain boundaries within the wall and within the deposits themselves. The water filling the crevasse encountered at the end of the tunnel was freezing uniformly to the crevasse walls as well as forming Thomson crystals within the water, and the evidence points to an important role for constitutional super-cooling in the Thomson crystal formation. The forms of most of the Thomson crystals are explainable qualitatively by beat flow effects.

Mössbauer Spectroscopy of Grain Boundaries in Ultrafine-Grained Metal Materials

2014 ◽  
Vol 783-786 ◽  
pp. 2671-2676 ◽  
Author(s):  
Vladimir V. Popov
Keyword(s):  
Grain Boundaries ◽  
The State ◽  
Coarse Grained ◽  
Resonance Spectroscopy ◽  
Fine Grained ◽  
Nuclear Gamma Resonance ◽  
Ultrafine Grained ◽  
Emission Mode ◽  
Metal Materials

Capabilities of the Mössbauer (nuclear gamma-resonance) spectroscopy for investigation of the state of grain boundaries in ultra-fine grained materials are analyzed, and the main problems of such studies are discussed. The emission and absorption NGR spectroscopy are compared, and it is demonstrated that the emission mode of the Mössbauer spectroscopy is preferential for GB studies. These studies enable to reveal differences in the state of GBs in ultra-fine grained materials and coarse-grained polycrystals with GBs of recrystallization origin.

Mechanical Properties of an Accumulative Roll Bonded Aluminium Alloy Composite

2009 ◽  
Vol 618-619 ◽  
pp. 551-554 ◽  
Author(s):  
O. Al-Buhamad ◽  
M. Zakaria Quadir ◽  
Michael Ferry
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Annealing Temperature ◽  
Sheet Material ◽  
Commercial Purity ◽  
Alloy Composite ◽  
High Angle ◽  
Roll Bonding ◽  
Fine Grained ◽  
Strength And Ductility

A multilayered sheet composite of commercial purity Al and Al-0.3%Sc alloys was produced by accumulative roll bonding. The final sheet material consisted of 64 ultra fine grained layers, each of ~7.8mm in thickness. The as-deformed material was annealed at temperatures ranging from 250 to 350°C to study the changes in microstructure and their associated influence on mechanical properties. The as-deformed structures largely comprised of high angle grain boundaries in the Al layers and low angle grain boundaries in the Al(Sc) layers. During annealing, the structures in the Al(Sc) layers remained unaltered, whereas the Al layers recrystallized rapidly to the full layer thickness. The mechanical properties of the Al-Al(Sc) composite were measured and found to be unique in strength and ductility with annealing temperature having a significant influence on these properties.

Effect of Sintering Process on Microstructure of Al2O3/LiTaO3 Composite Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 2363-2365
Author(s):  
You Feng Zhang ◽  
Yu Zhou ◽  
De Chang Jia ◽  
Qing Chang Meng
Keyword(s):  
Grain Boundaries ◽  
Relative Density ◽  
Theoretical Density ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Hot Press ◽  
Composite Ceramics ◽  
Fine Grained ◽  
N2 Atmosphere ◽  
Hot Press Sintering

Effects of different sintering methods such as pressureless sintering and hot press sintering on relative density and microstructure of the Al2O3p/LiTaO3 (ALT) composite ceramics were investigated to obtain a preferable sintering process. Relative densities of all ALT composites are below 90% when sintered with the cold isostatical pressing followed by pressureless sintering at temperatures of 1250 to 1350°C. The relative densities and microstructure of ALT composite ceramics with the hot press sintering process in a N2 atmosphere at 1150 and 1300°C were investigated. The relative density of ALT composite hot pressed at 1150°C is only 77%, and almost theoretical density at 1300°C. This indicates that sintering pressure plays an important role in the densification of ALT composite ceramics in temperature range of 1150 to 1350°C. Investigation on morphologies of the composites shows that the Al2O3 particles distributed along grain boundaries of LiTaO3, which leads to a fine-grained microstructure in the ALT composite ceramics

Molecular Dynamics Based Observations of Grain Boundaries and Lattice Defects Functions in Fine Grained Metal

2010 ◽  
Vol 654-656 ◽  
pp. 1582-1585 ◽  
Author(s):  
Toshihiro Kameda ◽  
Bao Rong Zhang
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundaries ◽  
Deformation Process ◽  
Crystal Defects ◽  
View Point ◽  
Dislocation Source ◽  
Fine Grained ◽  
Grain Sizes ◽  
Polycrystalline Metals ◽  
Source And Sink

In order to study the characteristics of fine grained polycrystalline metals, it is important to recognize the function of grain boundaries (GB), crystal defects such as dislocation and/or nanoscale voids, since the fraction of GB increases as grain sizes decreases, the deformation process of these metals could be different from those in larger size grains. In this study, we first evaluate the hypothesis that GB behaves as dislocation source and sink during the deformation of fine grained metal, then compare the behavior between GB and a tiny defect from the view point of dislocation source and sink phenomena. Since continuous dislocation supplies could be considered as the key issue to improve the toughness of fine grained metals, this concept could be helpful to design next generation polycrystalline metals.

The Creep Behaviors of Two Fine-grained XD TiAl Alloys Produced by Similar Heat Treatments

2004 ◽  
Vol 842 ◽  
Author(s):  
Hanliang Zhu ◽  
Dongyi Seo ◽  
Kouichi Maruyama ◽  
Peter Au
Keyword(s):  
Grain Boundaries ◽  
Creep Resistance ◽  
Lamellar Spacing ◽  
Heat Treatments ◽  
Tensile Creep ◽  
Microstructural Stability ◽  
Creep Tests ◽  
Tial Alloys ◽  
Fine Grained ◽  
Interlocked Grain

ABSTRACTThe microstructural characteristics and creep behavior of two fine-grained XD TiAl alloys, Ti-45Al and 47Al–2Nb–2Mn+0.8vol%TiB2 (at%), were investigated. A nearly lamellar structure (NL) and two kinds of fully lamellar (FL) structures in both alloys were prepared by selected heat treatments. The results of microstructural examination and tensile creep tests indicate that the 45XD alloy with a NL structure possesses an inferior creep resistance due to its coarse lamellar spacing and larger amount of equiaxed γ grains at the grain boundaries, whereas the same alloy in a FL condition with fine lamellar spacing lowers the minimum creep rates. Contrary to 45XD, the 47XD alloy with a NL structure exhibits the best creep resistance. However, 47XD with a FL structure with finer lamellar spacing shows inferior creep resistance. On the basis of microstructural deformation characteristics, it is suggested that the well-interlocked grain boundary and relatively coarse colony size in FL and NL 47XD inhibit sliding and microstructural degradation at the grain boundaries during creep deformation, resulting in better creep resistance. Therefore, good microstructural stability is essential for improving the creep resistance of these alloys.

Paleomagnetic and isotopic evidence for the diagenesis and alteration of evaporites in the Paleozoic Elk Point Basin, Saskatchewan, Canada

1997 ◽  
Vol 34 (12) ◽  
pp. 1619-1629 ◽  
Author(s):  
G. Koehler ◽  
T. K. Kyser ◽  
R. Enkin ◽  
E. Irving
Keyword(s):  
Low Temperature ◽  
Grain Boundaries ◽  
Fluid Inclusions ◽  
Low Temperatures ◽  
Late Paleozoic ◽  
Isotopic Data ◽  
Fine Grained ◽  
Tectonic Events ◽  
Stable Isotopic ◽  
Reversed Polarity

In the Paleozoic Elk Point Basin, Saskatchewan, Canada, hematite in evaporite rocks of the Middle Devonian Prairie Formation records two magnetizations that are very different from those expected when the evaporites were originally deposited. The first (X magnetization) corresponds to Cretaceous or Cenozoic paleofield directions and contains both normal and reversed polarities. The second (Y magnetization) appears to be a composite of Cretaceous–Cenozoic and late Paleozoic (Kiaman) reversed polarity directions. The X magnetization occurs in anomalous ores and is associated with fine-grained hematite occurring predominantly along grain boundaries. The Y magnetization occurs in normal ore and is associated with sylvite that has hematite both along grain boundaries and within sylvite crystals, the latter inferred to be of Kiaman age. K–Ar ages of the host sylvites are also composite, and are consistent with those inferred from paleomagnetic directions. Stable isotopic compositions of fluid inclusions in halite and the associated hematite in the Prairie Formation indicate that the hematite carrying the X magnetization formed at low temperature (about 60 °C) by fluids similar to those currently resident in overlying formations. The hematite carrying the inferred late Paleozoic magnetization was also formed at low temperatures by fluids having δD and δ18O values significantly lower than Paleozoic seawater. Paleomagnetic, petrographic, and isotopic data, and K–Ar ages indicate that evaporites in the Elk Point Basin have been affected by major fluid events that occurred during the late Paleozoic and Cretaceous–Cenozoic. These fluids are most probably related to brines mat have their origins within the basin, which were mobilized by major tectonic events.

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