Effect of prestrain on microstructure and mechanical behavior of aged Ti–10V–2Fe–3Al alloy

2009 ◽  
Vol 24 (9) ◽  
pp. 2899-2908 ◽  
Author(s):  
Wei Chen ◽  
Zhenya Song ◽  
Lin Xiao ◽  
Qiaoyan Sun ◽  
Jun Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Grain Boundary ◽  
Mechanical Behavior ◽  
Grain Boundaries ◽  
Aging Time ◽  
Transmission Electron ◽  
Α Particles

The effect of prestrain on microstructure and mechanical behavior of aged Ti–10V–2Fe–3Al alloy was investigated. The results showed that prestrain caused the tensile strength to decrease by 5%, but the elongation to fracture significantly improved by about 200%, in comparison with the unstrained samples, using a much shorter aging time. Transmission electron microscopy investigations showed that nano-sized alpha (α) particles homogeneously precipitated in the beta (β) matrix, and continuous α films formed along grain boundaries in the unstrained and aged samples. However, in the prestrained samples, the coarse stress induced martensite laths decomposed into α- and β-phases in the form of alternately arranged plates, which suppressed formation of the continuous grain boundary α films during aging. The hardness of the prestrained samples was lower than that of the unstrained samples after the same aging treatments. The enhancement of ductility can be mainly attributed to the suppression of grain boundary α films and the reduced hardness in prestrained samples.

Grain-Boundary Segregation and Phase-Separation Mechanism in Yttria-Stabilized Tetragonal Zirconia Polycrystal

2011 ◽  
Vol 484 ◽  
pp. 82-88
Author(s):  
Koji Matsui ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Cubic Phase ◽  
Phase Boundaries ◽  
Transmission Electron ◽  
Sintering Condition

Microstructure development during sintering in 3 mol% Y2O3-stabilized tetragonal ZrO2 polycrystal (Y-TZP) was systematically investigated in two sintering conditions: (a) 1100-1650°C for 2 h and (b) 1300°C for 0-50 h. In the sintering condition (a), the density and grain size in Y-TZP increased with the increasing sintering temperature. Scanning transmission electron microscopy (STEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that the Y3+ ion distribution was nearly homogeneous up to 1300°C, i.e., most of grains were the tetragonal phase, but cubic-phase regions with high Y3+ ion concentration were clearly formed in grain interiors adjacent to the grain boundaries at 1500°C. High-resolution transmission electron microscopy (HRTEM) and nanoprobe EDS measurements revealed that no amorphous or second phase is present along the grain-boundary faces, and Y3+ ions segregated not only along the tetragonal-tetragonal phase boundaries but also along tetragonal-cubic phase boundaries over a width below about 10 nm, respectively. These results indicate that the cubic-phase regions are formed from the grain boundaries and/or the multiple junctions in which Y3+ ions segregated. We termed this process a “grain boundary segregation-induced phase transformation (GBSIPT)” mechanism. In the sintering condition (b), the density was low and the grain-growth rate was much slow. In the specimen sintered at 1300°C for 50 h, the cubic-phase regions were clearly formed in the grain interiors adjacent to the grain boundaries. This behavior shows that the cubic-phase regions were formed without grain growth, which can be explained by the GBSIPT model.

Grain Boundary Transformations in Bi-Doped Copper

1991 ◽  
Vol 238 ◽  
Author(s):  
Elsie C. Urdaneta ◽  
David E. Luzzi ◽  
Charles J. McMahon
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Treatment Time ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTBismuth-induced grain boundary faceting in Cu-12 at ppm Bi polycrystals was studied using transmission electron microscopy (TEM). The population of faceted grain boundaries in samples aged at 600°C was observed to increase with heat treatment time from 15min to 24h; aging for 72h resulted in de-faceting, presumably due to loss of Bi from the specimen. The majority of completely faceted boundaries were found between grains with misorientation Σ=3. About 65% of the facets of these boundaries were found to lie parallel to crystal plane pairs of the type {111}1/{111]2- The significance of these findings in light of recent high resolution electron microscopy experiments is discussed.

The Role of Transmission Electron Microscopy in Characterizing the Nature and Behavior of Grain Boundaries

1971 ◽  
Vol 29 ◽  
pp. 102-103
Author(s):  
L. E. Murr
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Degrees Of Freedom ◽  
Effective Means ◽  
Average Energy ◽  
Interfacial Free Energy ◽  
Transmission Electron ◽  
And Behavior

Grain boundaries represent the single, most dominant imperfection in structural materials of engineering and industrial importance, and are a controlling factor in the strength of materials. Transmission electron microscopy, combined with the ability to gain direct crystallographic information from associated selected-area electron diffraction patterns, represents perhaps the most effective means for the investigation of the nature and behavior of grain boundaries in solids.Any segment of a grain boundary has associated with it five degrees of freedom. The electron microscope has the capability to characterize these degrees of freedom and to uniquely define the geometrical and crystallographic nature of a grain boundary. In addition, once the true geometry of intersecting grain boundaries or grain boundaries intersecting with other interfaces is determined, interfacial free energy ratios can be calculated from which the average energy associated with particular types of interfaces can be determined.

In-Plane Grain Boundary Effects on the Transport Properties of La0.7Sr0.3MnO3-δ Thin Films

1997 ◽  
Vol 494 ◽  
Author(s):  
J. Y. Gu ◽  
S. B. Ogale ◽  
K. Ghosh ◽  
T. Venkatesan ◽  
R. Ramesh ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Effects ◽  
Epitaxial Relationship ◽  
X Ray ◽  
Low Field ◽  
Grain Structures ◽  
Transmission Electron

ABSTRACTC-axis oriented La0.7Sr0.3MnO3.δ (LSMO) films were fabricated on the top of SrTiO3/YBa2Cu3O7 grown on MgO(001) substrates. From x-ray φ-scan and planar transmission electron microscopy measurements, the LSMO layer in the LSMO/SrTiO3/YBa2Cu3O7/MgO heterostructure is found to have coherent in-plane grain boundaries with a predominance of 45° rotations (between [100] and [110] grains) in addition to the cube-on-cube epitaxial relationship. Also, epitaxial LSMO/Bi4Ti3O12/LaAl03 (001) and c-axis textured LSMO/Bi4Ti3O12/SiO2/Si(001) with random in-plane grain boundaries are introduced as the counterparts for comparison. The resistivity and magnetoresistance (MR) of LSMO layer were measured and compared in these three different heterostructures. The low field MR at low temperature shows a dramatic dependence on the nature of the grain boundary. An attempt is made to interpret these results on the basis of correlation between the magnetic properties and grain structures.

Structure of the ∑=3 (111) Grain Boundary in Cu-1.5%Sb

1992 ◽  
Vol 295 ◽  
Author(s):  
Richard W. Fonda ◽  
David E. Luzzi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Auger Electron ◽  
Preliminary Investigation ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

AbstractGrain boundaries in quenched and aged Cu-i.5%Sb were examined with Auger electron microscopy, transmission electron microscopy, and high resolution electron microscopy. The ∑=3 grain boundaries are strongly faceted, with the facets lying primarily along the coincident (111) planes of the two grains. The grain boundaries are enriched in antimony, as demonstrated by both AES and HREM. HREM images of the ∑=3 (111) ║ (111) grain boundary differ from those of the Cu-Bi ∑ =3 (111) ║ (111) grain boundary in the lack of a significant grain boundary expansion to accommodate the excess solute at the boundary. A preliminary investigation of the atomic structure of the ∑=3 (111) ║ (111) facet by HREM and multislice calculations is presented.

Grain boundary character information via individual imaging or statistical analyses: complexion transitions and grain boundary segregation

2021 ◽  
Author(s):  
Katharina Marquardt ◽  
David Dobson ◽  
Simon Hunt ◽  
Ulrich Faul
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Bulk Viscosity ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Boundary Character ◽  
Grain Boundary Character ◽  
Transmission Electron

<p>Grain boundaries affect bulk properties of polycrystalline materials, such as electrical conductivity, melting or bulk viscosity. In the past two decades, observations of marked bulk material property changes have been associated with changes in the structure and composition of grain boundaries. This led to the term “grain boundary complexions” to mark the phase-like behaviour of grain boundaries while differing from phases in the sense of Gibbs (Cantwell 2014).</p><p>Here we introduce the principles of grain boundary structure to property relations and potent methods to study these. The focus is on the combination of structural, chemical and statistical analysis as obtainable using transmission electron microscopy and electron backscatter diffraction. Data from these complementary methods will be discussed on two systems; garnet and olivine polycrystals.</p><p>Past elasticity measurements showed that the Youngs modulus of garnet polycrystals changes as a function of sintering pressure (Hunt et al. 2016). Here we used high resolution transmission electron microscopy to study the structure of grain boundaries from polycrystals synthesized at low (4-8 GPa) and high (8-15) GPa sintering pressure. The HRTEM data were acquired using an image-corrected JEOL ARM 300 to achieve the highest resolution at low electron doses using a OneView camera. Our data indicate a grain boundary structural change occurs from “low-pressure” to “high pressure” grain boundaries, where the grain boundary facets change from >100 nm – 20 nm to 3-7 nm length scale, respectively. We conclude that sintering pressure affects grain-boundary strength and we will evaluate how this may influence anelastic energy loss of seismic waves through elastic or diffusional accommodation of grain-boundary sliding.</p><p>Polycrystalline olivine samples show different viscosity related to grain boundary segregation of impurities. To investigate if the distribution of grain boundaries is affected by grain boundary chemistry, we analysed grain orientation data from over 4x10<sup>4</sup> grains, corresponding to more than 6000 mm grain boundary length per sample. Using stereology, we extract the geometry of the interfacial network. The thus obtained grain boundary character distribution (GBCD) is discussed in relation to bulk viscosity.</p>

Dislocation - Grain Boundary Interaction in Nickel Bicrystals Evolution of the Resulting Defects under Thermal Treatment

2000 ◽  
Vol 652 ◽  
Author(s):  
Louisette Priester ◽  
Sophie Poulat ◽  
Brigitte Décamps ◽  
Jany Thibault
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Thermal Treatment ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Dislocation Network ◽  
Boundary Interaction ◽  
Transmission Electron

ABSTRACTThe interactions between lattice dislocations and grain boundaries were studied in nickel bicrystals. Three types of grain boundaries, according to their energy, were investigated : singular σ3 {111}, vicinal near σ11 {311} and general near σ11 {332} grain boundaries. The experiments were performed by transmission electron microscopy using a set of techniques : conventional, weak beam, in situ and high resolution transmission electron microscopy. Dislocation transmission from one crystal to the other was only observed for σ3 {111} GB. It consists in a decomposition within the grain boundary of the trapped lattice dislocation followed by the emission of one partial in the neighbouring crystal. A high resolved shear stress is required to promote the emission process. Most often, the absorbed lattice dislocations or extrinsic grain boundary dislocations react with the intrinsic dislocation network giving rise to complex configurations. The evolutions with time and upon thermal treatment of these configurations were followed by in situ transmission electron microscopy. The evolution processes, which differ with the type of grain boundaries, were analyzed by comparison with the existing models for extrinsic grain boundary dislocation accommodation. They were tentatively interpretated on the basis of the grain boundary atomic structures and defects obtained by high resolution transmission electron microscopy studies.

Atomic and Electronic Structure of High Purity SiC Grain Boundary

2000 ◽  
Vol 652 ◽  
Author(s):  
Eriko Takuma ◽  
Hideki Ichinose
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Rotation Angle ◽  
Rotation Axis ◽  
Atomic Resolution ◽  
Crystallization Method ◽  
Transmission Electron ◽  
Atomic And Electronic Structure

ABSTRACTFully relaxed SiC grain boundaries were produced by the sublimation re-crystallization method. Several kinds of grain boundaries of bi- and tri-crystals were investigated applying an atomic resolution high-voltage transmission electron microscopy (ARHVTEM). The rotation axis and the rotation angle were common tofrequently observed grain boundaries, which were, respectively, 70.5 degrees and <1120>. But boundary planes differed from each other. It was shown that the atomic bonding direction was continuous across the stable grain boundary.

scholarly journals Transmission Electron Microscopy Studies of Grain Boundary Precipitation in Spinodally Decomposed Cu-Ni-Fe Alloys

1974 ◽  
Vol 32 ◽  
pp. 498-499
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Miscibility Gap ◽  
Phase Identification ◽  
Transmission Electron ◽  
Boundary Precipitation ◽  
Binary Section ◽  
Grain Boundary Precipitation

In many alloy systems the grain boundaries play an important role in controlling properties but little is known about the mechanism of grain boundary precipitation reactions. Transmission electron microscopy and diffraction are necessary to distinguish reactions such as discontinuous precipitation and preferential coarsening. The present paper describes current progress on the Cu-Ni-Fe system which is known to be embrittled at the grain boundaries. Two alloys are considered, having their compositions on a binary section through the Cu-Ni-Fe ternary with terminal values at the Cu corner and the point Ni0.7Fe0.3. Alloy A(51.5 at % Cu-33.5 at % Ni-15 at % Fe) lies very near to the center of the miscibility gap. Phase identification in the electron micrographs is facilitated by comparison with alloy B (69.3 at % Cu-19.4 at X Ni-11.1 at % Fe) of asymmetrical composition. The microstructure shown in Fig. 1 results from aging alloy B within the spinodal (650°C) for 10 hrs.

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