Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

2020 ◽  
Vol 2020 (11) ◽  
pp. 1292-1299
Author(s):  
I. M. Razumovskii ◽  
V. I. Razumovskiy ◽  
I. A. Logachev ◽  
A. O. Rodin ◽  
M. I. Razumovsky
Keyword(s):  
High Temperature ◽  
Grain Boundaries ◽  
Refractory Metals ◽  
High Temperature Alloys

The Refractory Metals

1966 ◽  
Vol 70 (668) ◽  
pp. 787-794
Author(s):  
G. Llewelyn
Keyword(s):  
High Temperature ◽  
Refractory Metals ◽  
Atomic Energy ◽  
Melting Points ◽  
Ferrous Alloys ◽  
Energy Field ◽  
New Family ◽  
High Temperature Alloys ◽  
Aero Engines ◽  
Nickel Base

The refractory metals are usually referred to as metals which have melting points equal to, or higher than, chromium. A number of these metals, such as chromium, molybdenum, niobium, and tungsten are already being used quite extensively as alloying elements in both ferrous and non-ferrous alloys. Tungsten has been used in the lamp industry for many years, while molybdenum has been used for heating elements and niobium has been of interest in the atomic energy field.The advancements in design and efficiency of aero engines has been associated with an increase in engine temperature. If this advancement is to continue, it will be necessary for a new family of alloys to be made available to the engineer. The current nickel-base high temperature alloys are now approaching their limit. It is difficult to be precise about these temperatures because the applications in terms of stress vary widely.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

1996 ◽  
Vol 54 ◽  
pp. 522-523
Author(s):  
G.A. Botton ◽  
C.J. Humphreys
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Industrial Applications ◽  
Edge Structure ◽  
Structural Applications ◽  
Yield Behaviour ◽  
Late Transition ◽  
Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

Radiation-enhanced high-temperature cobalt diffusion at grain boundaries of nanostructured hardmetal

2021 ◽  
pp. 129746
Author(s):  
A.A. Zaitsev ◽  
I. Konyashin ◽  
P.A. Loginov ◽  
E.A. Levashov ◽  
A.S. Orekhov
Keyword(s):  
High Temperature ◽  
Grain Boundaries

Roles definition of TiN particles in enhancing the creep properties of IN718C high temperature alloys

2021 ◽  
pp. 161441
Author(s):  
Yuantao Zhao ◽  
Rui Wang ◽  
Yanle Sun ◽  
Lianbo Wang ◽  
Xinfeng Wu ◽  
...  
Keyword(s):  
High Temperature ◽  
Creep Properties ◽  
High Temperature Alloys ◽  
Definition Of

Heat Resistance of Ferritic Stainless Steels with 15% Chromium for Automobile Exhaust System

2011 ◽  
Vol 239-242 ◽  
pp. 1799-1803
Author(s):  
Hua Bing Li ◽  
Zhou Hua Jiang ◽  
Qi Feng Ma ◽  
Dong Ping Zhan
Keyword(s):  
High Temperature ◽  
Grain Boundaries ◽  
Thermal Fatigue ◽  
Fatigue Cracks ◽  
Exhaust System ◽  
High Temperature Strength ◽  
Temperature Oxidation ◽  
Ferritic Stainless Steels ◽  
Automobile Exhaust ◽  
Thermal Fatigue Cracks

The high-temperature strength and thermal fatigue properties of Fe-Cr-Nb-Mo ferritic stainless steel (FSSNEW) developed for automobile exhaust system were investigated. The results show that the high-temperature tensile strength and yield strength of FSSNEW are better than or equal to those of the presently applied ferritic stainless steels. The thermal fatigue cracks nucleate at the V-notch. The inclusions along grain boundaries become prior regions for initiation of the cracks. The inclusions distributed at the defects make the formation of cracks in the materials easily through the effects of cycle thermal stress and thermal strain. The length and propagated rate of thermal fatigue cracks increase with the maximum tested temperature increasing. When the maximum temperature arrives at 900°C, the high-temperature oxidation is serious along the grain boundaries, which aggravates the cracks propagating along the grain boundaries. The principle mechanism of stress assisted grain boundary oxygen (SAGBO) embrittlement can be applied to illustrate the effects of external stress on aggravating the damage caused by environmental factors. Therefore, the high-temperature oxidation is the main reason for the propagation of thermal fatigue cracks. The FSSNEW is satisfied for the applied requirement of high-temperature strength in the hot side of the automobile exhaust system.

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