scholarly journals INFLUENCE OF PURITY ON MICROSTRUCTURE AND STRENGTH CHARACTERISTICS OF REFRIGABLE MICROCOMPOSITES

2020 ◽  
pp. 38-43
Author(s):  
N.A. Azarenkov ◽  
V.Е. Semenenko ◽  
S.V. Lytovchenko ◽  
N.G. Styervoyedov
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
High Temperature ◽  
Dimensional Stability ◽  
Structural Materials ◽  
Strength Characteristics ◽  
Crystallization Heat ◽  
Source Materials

The influence of the purity of the source materials on the structural and dimensional stability of micro-composites obtained in the process of controlled invariant phase transformation is investigated. The influence of high-temperature post-crystallization heat treatment on the processes of cleaning and increasing the technological ductility of structural materials is considered. The possibility of their practical use is discussed.

Phase Transformation of Coal at High Temperature

2014 ◽  
Vol 809-810 ◽  
pp. 815-821
Author(s):  
Xiao Hu Hua ◽  
Xiao Gang Wang ◽  
Jia Qing Yang ◽  
Shu He Lu ◽  
Li Rong Deng ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Phase Composition ◽  
High Temperature ◽  
Internal Migration ◽  
Heat Treatment Temperature ◽  
Functional Group ◽  
Treatment Temperature ◽  
Conductive Phase ◽  
Higher Temperature

Anthracite and bitumite were processed respectively at 1400°C,1700°C, 2000°C, 2200°C, 2400°C and 2600°C,and their chemical composition,resistivity,microstructure, phase composition,and the internal migration of molecular functional group were tested and characterized. The results indicate that moisture, ash and volatile in coal have gradually shifted and lost with the elevation of heat treatment temperature, while the higher temperature, the quicker and completer phase change. Heat treatment can make the coal transform from approximately insulative phase to conductive phase,. Furthermore, as the temperature increases, the conductive phase transformation effect is better. The higher the heat treatment temperature of coal, the more amorphous carbon transforming into crystalline carbon completely, but the less types of phases .

Effect of High Temperature on the Change in Color, Dimensional Stability and Mechanical Properties of Spruce Wood

Holzforschung ◽  
2003 ◽  
Vol 57 (5) ◽  
pp. 539-546 ◽  
Author(s):  
P. Bekhta ◽  
P. Niemz
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
High Temperature ◽  
Dimensional Stability ◽  
Modulus Of Elasticity ◽  
Bending Strength ◽  
Treatment Time ◽  
Color Difference ◽  
Treatment Temperature ◽  
Color Changes

Summary In this study the effect of high temperature on mechanical properties, dimensional stability and color of spruce was investigated. Wood specimens conditioned at different relative humidities (50, 65, 80 and 95%) were subjected to heat treatment at 200°C for 2, 4, 8, 10 and 24 h and at 100, 150 and 200°C for 24 h. Color changes were measured in the Minolta Croma-Meter CR-300 color system. Bending strength and modulus of elasticity were determined according to DIN 52186. The results show that heat treatment mainly resulted in a darkening of wood tissues, improvement of the dimensional stability of wood and reduction of its mechanical properties. The darkening accelerated generally when treatment temperature exceeded approximately 200°C. Most of the darkening occurred within the first 4 h of exposure. For the specimens heated to high temperatures, the average decrease in bending strength was about 44–50%, while modulus of elasticity was reduced by only 4–9%. We found that treatment time and temperature were more important than relative humidity regarding the color responses. Strong correlations between total color difference and both modulus of elasticity and bending strength were found. Thus, the color parameters can be estimated quantitatively and used as a prediction of wood strength.

Effects of Different Heat Treatment Temperatures on the Properties of Quartz Fibers

2010 ◽  
Vol 105-106 ◽  
pp. 115-118 ◽  
Author(s):  
Qi Hong Wei ◽  
Chong Hai Wang ◽  
Zhi Qiang Cheng ◽  
Ling Li ◽  
Hong Sheng Wang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Phase Transformation ◽  
Fiber Strength ◽  
Single Fiber ◽  
Significant Phase ◽  
Surface Micromorphology ◽  
Heat Treated ◽  
Different Temperatures ◽  
Crystallization Heat

In this paper, XRD was engaged in studying phase transformation of quartz fibers, SEM was engaged in studying the surface micromorphology of quartz fibers heat treated at different temperatures, and the tensile strength was measured by a single fiber strength electronics instrument. The results indicate that surface infiltration agent have been iliminated after heat treatment at 500°C, and the tensile strength decreaced significantly. The higher the temperature was, the more the tensile strength decreaced. There were no significant phase transformation and no crystallization heat treatmented at 500~800°C. But there were some round and strip bulges, and scap defects on the surface. With temperature increasing,some scab defects and bulges began to flake off, and some new rifts and cracks were formed. This was one of the important factors that decreaced tensile strength markedly.

scholarly journals Densification of wood veneers combined with oil-heat treatment. Part 1: Dimensional stability

BioResources ◽  
2010 ◽  
Vol 6 (1) ◽  
pp. 373-385
Author(s):  
Chang-Hua Fang ◽  
Alain Cloutier ◽  
Pierre Blanchet ◽  
Ahmed Koubaa ◽  
Nicolas Mariotti
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Populus Tremuloides ◽  
Dimensional Stability ◽  
Large Wood ◽  
Wood Veneer ◽  
Compression Set ◽  
Compression Direction ◽  
Long Duration ◽  
Biological Attack

is often a problem due to compression recovery. Alternatively, oil-heat treatment (OHT) improves wood dimensional stability and enhances resistance to biological attack. This study examined combined wood densification and OHT. Large wood veneer 700 700 mm specimens prepared with aspen (Populus tremuloides) were densified using heat, steam, and pressure at 160ºC, 180ºC, and 200°C, respectively. OHT at 180, 200ºC, and 220ºC for 1, 2, and 3h was then applied to the densified veneers. Results show that OHT efficiently improved dimensional stability and reduced compression set recovery. OHT temperature and duration markedly influenced the reduction of compression set recovery: the higher the OHT temperature and duration, the lower the recovery. Less than 5% recovery was obtained under various OHT conditions, and almost 0% recovery under some OHT conditions. Radial and tangential swellings of densified veneers were reduced dramatically. Compared to OHT duration, OHT temperature had a pronounced higher impact on radial and tangential swelling. Irreversible swelling (IS) in the compression direction of densified veneers decreased after OHT, particularly with high temperature and long duration, and anti-swelling efficiency (ASE) in the compression direction improved significantly.

scholarly journals Property Improvement of Additively Manufactured Ti64 by Heat Treatment Characterized by In Situ High Temperature EBSD and Neutron Diffraction

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1661
Author(s):  
Shigehiro Takajo ◽  
Toshiro Tomida ◽  
El’ad N. Caspi ◽  
Asaf Pesach ◽  
Eitan Tiferet ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
High Temperature ◽  
Grain Boundaries ◽  
Beta Phase ◽  
Powder Materials ◽  
Layer By Layer ◽  
Slow Cooling ◽  
Α Phase

Among various off-equilibrium microstructures of additively manufactured Ti-6Al-4V alloy, electron beam powder bed fusion, in which three dimensional metallic objects are fabricated by melting the ingredient powder materials layer by layer on a pre-heated bed, results in a specimen that is nearly free of the preferred orientation of the α-Ti phase as well as a low beta phase fraction of ∼1 wt%. However, when further heat treatment of up to 1050 ∘C was applied to the material in our previous study, a strong texture aligning the hexagonal basal plane of α phase with the build direction and about 6% β phase appeared at room temperature. In this study, to understand the mechanism of this heat treatment, the grain level microstructure of the additively manufactured Ti-6Al-4V was investigated using in situ high temperature EBSD up to 1000 ∘C, which allows the tracking of individual grains during a heat cycle. As a result, we found a random texture originating from the fine grains in the initial material and observed a significant suppression of α phase nucleation in the slow cooling after heating to 950 ∘C within the α and β dual phase regime but close to the the β-transus temperature at ∼980 ∘C, which led to a coarse microstructure. Furthermore, the texture resulting from phase transformation of the additively manufactured Ti-6Al-4V assuming nucleation at the grain boundaries was modeled, using the double Burgers orientation relationship for the first time. The model successfully reproduced the measured texture, suggesting that the texture enhancement of the α phase by the additional heat treatment derives also from the variant selection during the phase transformation and nucleation on grain boundaries.

AEM of reaction-bonded SiC

1992 ◽  
Vol 50 (1) ◽  
pp. 344-345
Author(s):  
K Das Chowdhury ◽  
R. W. Carpenter ◽  
W. Braue
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
High Temperature ◽  
Epitaxial Growth ◽  
Liquid Silicon ◽  
Structural Ceramic ◽  
Few Data

Research on reaction-bonded SiC (RBSiC) is aimed at developing a reliable structural ceramic with improved mechanical properties. The starting materials for RBSiC were Si,C and α-SiC powder. The formation of the complex microstructure of RBSiC involves (i) solution of carbon in liquid silicon, (ii) nucleation and epitaxial growth of secondary β-SiC on the original α-SiC grains followed by (iii) β>α-SiC phase transformation of newly formed SiC. Due to their coherent nature, epitaxial SiC/SiC interfaces are considered to be segregation-free and “strong” with respect to their effect on the mechanical properties of RBSiC. But the “weak” Si/SiC interface limits its use in high temperature situations. However, few data exist on the structure and chemistry of these interfaces. Microanalytical results obtained by parallel EELS and HREM imaging are reported here.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

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