Microstructure characterization and thermal stability of TC11/Ti2AlNb joints during thermal exposure

2018 ◽  
Vol 145 ◽  
pp. 461-472 ◽  
Author(s):  
B.C. Xie ◽  
C. Qin ◽  
Y.Q. Ning ◽  
C. Zhou ◽  
Z.K. Yao
Keyword(s):  
Thermal Stability ◽  
Thermal Exposure ◽  
Microstructure Characterization ◽  
Thermal Stability Of

Thermal stability of nanocrystalline WC–Co powder synthesized by using mechanical milling at low temperature

2001 ◽  
Vol 16 (2) ◽  
pp. 478-488 ◽  
Author(s):  
Jianhong He ◽  
Leoanardo Ajdelsztajn ◽  
Enrique J. Lavernia
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Mechanical Milling ◽  
Gradual Increase ◽  
Thermal Exposure ◽  
X Ray Diffraction ◽  
Cryomilled Powder ◽  
X Ray ◽  
Increasing Temperature ◽  
Thermal Stability Of

Nanostructured WC–18% Co powder was synthesized by using cryogenic mechanical milling, and the thermal stability of the nanostructured powder was investigated in detail. The results indicated that the as-synthesized WC–18% Co powder had an average WC particle size of 25 nm. Growth of WC particles occurred above 873 K; however, the average WC particle size remained smaller than 100 nm in the powder isothermally heated for 4 h at 1273 K. Thermal exposure in air at T < 623 K did not result in significant oxidation of the cryomilled powder. The thermal exposure did promote the formation of WO2 and WO3 oxides. The Co6W6C phase was detected by x-ray diffraction in the powder heated in nitrogen at 1273 K, and the phases associated with decarburization of WC, such as W2C, W3C phases, were not observed. With increasing temperature, the dissolution of W and C elements in the Co matrix led to a gradual increase in {111} crystallographic plane spacing, eventually leading to the formation of an amorphous phase.

scholarly journals Study of the thermal stability of foam of different expansion ratio

2020 ◽  
Vol 29 (3) ◽  
pp. 103-110
Author(s):  
A. V. Koksharov ◽  
S. I. Osipenko ◽  
E. V. Gaynullina
Keyword(s):  
Thermal Stability ◽  
Thermal Exposure ◽  
Expansion Ratio ◽  
Heat Fluxes ◽  
Foam Layer ◽  
Destructive Effect ◽  
Foam Expansion ◽  
Destruction Rate ◽  
Wide Range ◽  
Thermal Stability Of

Introduction. Currently, the industry produces a wide range of foam generators to produce fire-extinguishing foams, and the foams they produce differ significantly in their expansion ratio and, consequently, fire resistance. Since heat fluxes have the main destructive effect on the foam, the purpose of this paper is to establish the patterns of destruction of foam of different expansion ratio when heated.Methods of research. The foam with expansion ratio from 7.5 to 80 was used for the tests. It was obtained by mechanical beating of 6 % solution of foaming agent PO-6RZ. The thermal stability of the foam was studied when the heat flow from the gas burner flame affects the foam layer. During the experiment, the change in the height of the foam column in time was recorded.Results and Discussion. The results of measurements, presented in the form of dependence of foam layer destruction rate on time, quantity of released liquid phase on 1 m2·s, dependence of foam layer destruction rate on its density allowed revealing a number of patterns. The destruction rate of foam with an expansion ratio of up to 30 remains constant throughout the entire duration of thermal exposure. As the foam expansion ratio increases, the rate of destruction at the initial stage of heat flux exposure increases. With a foam expansion ratio of more than 50, there is initially a sharp increase in the rate of destruction, which subsequently decreases as the foam column decreases. In the conditions of the experiment, the best characteristics were shown by the foam with an expansion ratio of 50, because in the foam with a smaller expansion ratio the syneresis makes a significant contribution to its destruction, and the foams with a larger expansion ratio are destroyed by the mechanical effect of convective flame flows.Conclusion. The study of the foam destruction patterns under thermal impact allowed establishing the fact that its destruction is limited by the rate of impoverishment of the upper layers with liquid.

scholarly journals Microstructure, Mechanical Properties, and Thermal Stability of Carbon-Free High Speed Tool Steel Strengthened by Intermetallics Compared to Vanadis 60 Steel Strengthened by Carbides

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1901
Author(s):  
Alena Michalcová ◽  
Vojtěch Pečinka ◽  
Zdeněk Kačenka ◽  
Jan Šerák ◽  
Jiří Kubásek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Tool Steel ◽  
High Speed ◽  
Intermetallic Phase ◽  
High Hardness ◽  
Thermal Exposure ◽  
Machining Process ◽  
Material Utilization ◽  
Thermal Stability Of

High speed tool steels are materials that exhibit superior mechanical properties (e.g., high hardness). They should also be resistant to thermal exposure to maintain high hardness during the machining process. In this paper, a C-free tool steel formed of Fe matrix and a Mo6Co7 intermetallic phase was studied. This steel was compared to the well-known Vanadis 60 steel containing Fe matrix and carbides. Microstructures were investigated by scanning (SEM) and transmission (TEM) electron microscopy, and the mechanical properties and thermal stability of both materials were compared. It was proven that the strengthening in the Vanadis 60 steel was mainly caused by the carbides, while the C-free steel was strengthened by the Mo6Co7 phase. The hardness values of both materials were comparable in the utilization state (approx. 950 HV). The hardness of Vanadis 60 steel decreased after several minutes of annealing at 650 °C under the value that enables material utilization. The hardness value of the steel strengthened by the intermetallics also decreased but significantly slower. Based on these results, the main finding of this study is that the C-free steel exhibited much better thermal stability and may be utilized at higher temperatures for longer periods of time than Vanadis 60.

Thermal Stability of High k Layers

2002 ◽  
Vol 745 ◽  
Author(s):  
C. Zhao ◽  
V. Cosnier ◽  
P. J. Chen ◽  
O. Richard ◽  
G. Roebben ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Phase Transformation ◽  
Surface Preparation ◽  
Thermal Exposure ◽  
Amorphous Phases ◽  
High K ◽  
M Phase ◽  
Crystallization Onset Temperatures ◽  
Spike Annealing ◽  
Thermal Stability Of

ABSTRACTThermal stability of amorphous phases in various high-k layers (Al2O3, ZrO2, HfO2, ZrAlOx, HfAlOx and HfSiOx) and the phase transformation of crystalline ZrO2 and HfO2 were studied experimentally, as functions of surface preparation, deposition conditions, material composition and post deposition thermal treatment. It is found that pure ZrO2 and HfO2 show relatively low crystallization onset temperatures. The crystalline ZrO2 or HfO2 phases are tetragonal or monoclinic, depending on the layer thickness. The phase transformation of metastable t-phase into stable m-phase has been observed in ZrO2 and HfO2. Crystallization behavior of Al2O3 depends on the surface preparation of the substrate. ALCVD grown Al2O3 layers on an oxide-based surface remain amorphous after 1100°C spike annealing, while those on HF-last surface crystallize at temperatures around 800°C. Alloying Al2O3 into ZrO2 and HfO2 can improve their resistance to crystallization under thermal exposure. The kinetics of the crystallization in the alloys can be described by linear TTT curves. Hf-aluminates show better thermal stability than Zr-aluminates. A defect model relative to the phase transformation is discussed, based on the above observations.

scholarly journals Corrosion and Thermal Stability of CrMnFeNi High Entropy Alloy in Molten FLiBe Salt

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohamed Elbakhshwan ◽  
William Doniger ◽  
Cody Falconer ◽  
Michael Moorehead ◽  
Calvin Parkin ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Stainless Steel ◽  
Molten Salt ◽  
Thermal Exposure ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Molten Fluoride ◽  
Fluoride Salts ◽  
Bcc Phase ◽  
Thermal Stability Of

AbstractThe corrosion behavior of the FCC Cr18Mn27Fe27.5Ni27.5 high entropy alloy (HEA) after exposure to molten FLiBe salt at 700 °C for 1000 hours, has been investigated. Results show that the HEA lost a higher mass compared to the reference 316 H stainless steel due to the dissolution of Mn into the molten salt. The loss of Mn from the alloy appeared to discourage the dissolution of Cr in the molten fluoride salts which is widely recognized as the mechanism of corrosion degradation. Thermal exposure at 700 °C for 1000 hours also led to the precipitation of an additional BCC phase Cr67Fe13Mn18.5Ni1.5, which was confirmed by CALPHAD predictions.

Thermal Stability of Lubricants for Application in Heat-Assisted Magnetic Recording

2013 ◽  
Author(s):  
Bala Krishna Pathem ◽  
Xing-Cai Guo ◽  
Yoko Saito ◽  
Robert Waltman ◽  
John Burns ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Magnetic Recording ◽  
Experimental Studies ◽  
Thermal Exposure ◽  
Areal Density ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Film Evaporation ◽  
Thermal Stability Of

In order to meet the demand to increase the areal density of magnetic recording, promising technologies such as heat-assisted magnetic recording (HAMR) are being extensively pursued [1–3]. However, the high transient disk temperature (400–500 °C, nanosecond time scale) required by this recording scheme might dramatically affect the reliability of the head-disk interface. Possible issues include overcoat oxidation and graphitization, both on head and disk, as well as lubricant evaporation, thermodiffusion, and decomposition. Although modeling and experimental studies have been published describing the lubricant film evaporation under thermal exposure, very few studies have been directed toward understanding the mechanisms of lubricant decomposition [4–7].

The Thermal Stability of a TiAl Based Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
C. Jin ◽  
W. Chen ◽  
J. Wang ◽  
X. Wan
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Significant Variation ◽  
Thermal Exposure ◽  
Thermally Stable ◽  
Bending Tests ◽  
Exposure Temperature ◽  
Alloy Microstructure ◽  
Thermal Stability Of

AbstractThe thermal stability of a TiAl based alloy was investigated through a series of high temperature exposures in air and vacuum. The microstructures were found to be thermally stable. The bending tests showed that both ductility and strength of air-exposed specimens decreased, but no significant variation was observed in those exposed in vacuum. The influence of alloy microstructure, thermal exposure temperature and time was also taken into account here.

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