The Mechanism of Grain Boundary Serration and Fan-Type Structure Formation in Ni-Based Superalloys

2020 ◽  
Vol 51 (7) ◽  
pp. 3648-3657 ◽  
Author(s):  
V. V. Atrazhev ◽  
S. F. Burlatsky ◽  
D. V. Dmitriev ◽  
D. Furrer ◽  
N. Y. Kuzminyh ◽  
...  
2018 ◽  
Vol 9 (1) ◽  
pp. 61-71
Author(s):  
Agung Sedayu

Foundation is a part of building construction having function continuously to support entire or all the building burden to ground. One of the factor of buildingcon truction should be supported by the sturdy foundation, and sturdy foundation depend on his compiler composition and dimension of foundation. Therefore it is needed tire calculations of foundation so that we get well guaranted of his stability. Besides that, ground factor also have stability of structure, because the ground sustain the foundation and place where burden given by foundation. Power factor support the ground against the foundation action is highly varied, it is _depend on composition and nature of ground, information concerning energy number support of this ground can be shown passing investigation _of ground. To guarantee security in a building one of the among others is to looking for comparison between foundations and well-balanced ground. The dimension of foundation must be enough and fit with the power of ground. Detennination of building foundation is very influenced by energy support the ground. And energy support the ground depict strength of ground to accepted burden. Energy support the ground is very influenced by character, nature, type, structure, formation, and component compiler of ground, besides also usage of foundation type is also influenced by contour, ground water face and topography. Energy support  the ground explained by some concept or theories, among others is Terzaghi theory and accepted encumbering principle or apply at the foundation structure. From both this concept determinable of enough and stable dimension of strength sustain a building. The foundation dimension is reckoned by the minimum or smallest measure or dimension, but have ever been optimal to sustain the burden befall it.


2021 ◽  
Vol 2103 (1) ◽  
pp. 012193
Author(s):  
D A Rogova ◽  
O Yu Sinel’shchikova ◽  
N V Besprozvannykh ◽  
N A Morozov

Abstract In this work, titanate Cs2Fe2Ti6O16 with a hollandite-type structure was synthesized by solid-phase synthesis. The electrical conductivity of the obtained ceramics was investigated in the temperature range from 25 to 800 °C in air and in the presence of an argon-hydrogen mixture (3% H2). It was found that the electrical conductivity of the compound under consideration depends on the composition of the atmosphere — the activation energy of conduction changes (0.57 eV in air and 0.91 eV in the presence of hydrogen). The volumetric and grain-boundary contributions to the total resistance of the sample in the gases under consideration are separated by impedance spectroscopy at a temperature of 800 °C.


Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.


Author(s):  
P. Humble

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.


Author(s):  
L.E. Murr

Ledges in grain boundaries can be identified by their characteristic contrast features (straight, black-white lines) distinct from those of lattice dislocations, for example1,2 [see Fig. 1(a) and (b)]. Simple contrast rules as pointed out by Murr and Venkatesh2, can be established so that ledges may be recognized with come confidence, and the number of ledges per unit length of grain boundary (referred to as the ledge density, m) measured by direct observations in the transmission electron microscope. Such measurements can then give rise to quantitative data which can be used to provide evidence for the influence of ledges on the physical and mechanical properties of materials.It has been shown that ledge density can be systematically altered in some metals by thermo-mechanical treatment3,4.


Author(s):  
J. W. Matthews ◽  
W. M. Stobbs

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.


Author(s):  
Shiro Fujishiro

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.


Author(s):  
H.C. Eaton ◽  
B.N. Ranganathan ◽  
T.W. Burwinkle ◽  
R. J. Bayuzick ◽  
J.J. Hren

The shape of the emitter is of cardinal importance to field-ion microscopy. First, the field evaporation process itself is closely related to the initial tip shape. Secondly, the imaging stress, which is near the theoretical strength of the material and intrinsic to the imaging process, cannot be characterized without knowledge of the emitter shape. Finally, the problem of obtaining quantitative geometric information from the micrograph cannot be solved without knowing the shape. Previously published grain-boundary topographies were obtained employing an assumption of a spherical shape (1). The present investigation shows that the true shape deviates as much as 100 Å from sphericity and boundary reconstructions contain considerable error as a result.Our present procedures for obtaining tip shape may be summarized as follows. An empirical projection, D=f(θ), is obtained by digitizing the positions of poles on a field-ion micrograph.


Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.


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