Structural changes and thermal expansion behavior of ultrafine titanium powders during compaction and heating

2005 ◽  
Vol 20 (3) ◽  
pp. 580-585 ◽  
Author(s):  
B.B. Panigrahi ◽  
M.M. Godkhindi
Keyword(s):  
Thermal Expansion ◽  
Structural Changes ◽  
Internal Stresses ◽  
Nano Powder ◽  
Expansion Behavior ◽  
Significant Difference ◽  
Nanocrystalline Titanium ◽  
Titanium Powders ◽  
Expansion Coefficients ◽  
Micron Powder

This work represents an attempt to understand the nature of micron and attrition milled nano-sized titanium powders on two different aspects, i.e., pressure-induced phase change and thermal expansion. Contraction in the volume of unit cell in terms of decrease in interplaner spacing (d) has been observed in both powders and tends to restore upon annealing. At a given pressure, nano titanium shows a smaller decrease in d relative to micron titanium. The stress analysis of the compacts indicates higher value of residual stresses and deformations in micron powder than in nano powder. The dilatometric study reveals, first, the release of internal stresses and entrapped gases causes huge expansion in nanopowder compacts during heating. Secondly, there is no significant difference in the expansion coefficients of sintered micro- and nanocrystalline titanium samples.

Structure and Thermal Expansion Behavior of Dy2-xGdxMo4O15 Solid Solution

2008 ◽  
Vol 368-372 ◽  
pp. 1665-1667
Author(s):  
M.M. Wu ◽  
X.L. Xiao ◽  
Y.Z. Cheng ◽  
J. Peng ◽  
D.F. Chen ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Thermal Expansion ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Cell Volumes

A new series of solid solutions Dy2-xGdxMo4O15 (x = 0.0-0.9) were prepared. These compounds all crystallize in monoclinic structure with space group P21/c. The lattice parameters a, b, c and unit cell volumes V increase almost linearly with increasing gadolinium content. The intrinsic thermal expansion coefficients of Dy2-xGdxMo4O15 (x = 0.0 and 0.25) were obtained in the temperature range of 25 to 500°C with high-temperature X-ray diffraction. The correlation between thermal expansion and crystal structure was discussed.

Residual Stresses Distributions within Thin-Walled Ceramic-Metal Seal

2012 ◽  
Vol 503-504 ◽  
pp. 428-431 ◽  
Author(s):  
Guo Liang Zhang ◽  
Lei Shi ◽  
Da Zhi Jin
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Fem Simulation ◽  
Matrix Composites ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Metal Seal ◽  
Significant Difference ◽  
Thin Walled ◽  
Typical Configuration

Due to significant difference of thermal expansion coefficients between ceramic and metal, the residual stresses are deemed to be induced into the interior of matrix composites within the ceramic-metal seal systems. Many investigations of the residual stresses distributions on dissimilar solid materials joints so far have been carried out theoretically and experimentally, whereas ones of the residual stresses distributions within the thin-walled ceramic-metal seal systems are rarely performed. In order to obtain information for improving their seal structures in the future, the residual stresses distributions resulted from the thermal expansion behavior in the typical configuration of the thin-walled ceramic-metal seal are investigated by theoretical formulae, experimental observation and finite element method (FEM) simulation in this paper. The changing trends of the computational results of the residual stresses distributions agree with the experimental results of the measurement with X-ray diffractometer. The overall residual stresses are found to increase drastically near the welding interfaces. The highest tensile stress occurs at the outer surfaces of the ceramic near the welding interfaces.

Thermal expansivities of water + tetrahydrofuran mixtures at 298.15 K

1978 ◽  
Vol 56 (22) ◽  
pp. 2803-2807 ◽  
Author(s):  
Osamu Kiyohara ◽  
Patrick J. D'Arcy ◽  
George C. Benson
Keyword(s):  
Thermal Expansion ◽  
Mole Fraction ◽  
Structural Changes ◽  
Molar Excess ◽  
Thermal Expansion Coefficients ◽  
Thermal Expansivities ◽  
Expansion Coefficients ◽  
Mole Fraction Range

Densities of water + tetrahydrofuran mixtures were measured at 5 K intervals of temperature from 288.15 to 308.15 K. Excess thermal expansion coefficients and partial molar excess thermal expansivities at 298.15 K over the whole mole fraction range were derived from the results. The significance of the expansivities is discussed in terms of the structural changes accompanying the formation of the mixture.

scholarly journals Thermal Expansion of a Multiphase Intermetallic Ti-Al-Nb-Mo Alloy Studied by High-Energy X-ray Diffraction

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 727
Author(s):  
Peter Staron ◽  
Andreas Stark ◽  
Norbert Schell ◽  
Petra Spoerk-Erdely ◽  
Helmut Clemens
Keyword(s):  
Thermal Expansion ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Different Temperatures ◽  
Service Conditions ◽  
Expansion Coefficients ◽  
Alloy Properties

Intermetallic γ-TiAl-based alloys are lightweight materials for high-temperature applications, e.g., in the aerospace and automotive industries. They can replace much heavier Ni-based alloys at operating temperatures up to 750 °C. Advanced variants of this alloy class enable processing routes that include hot forming. These alloys consist of three relevant crystallographic phases (γ-TiAl, α2-Ti3Al, βo-TiAl) that transform into each other at different temperatures. For thermo-mechanical treatments as well as for adjusting alloy properties required under service conditions, the knowledge of the thermal expansion behavior of these phases is important. Therefore, thermal expansion coefficients were determined for the relevant phases in a Ti-Al-Nb-Mo alloy for temperatures up to 1100 °C using high-energy X-ray diffraction.

scholarly journals The irreversible thermal expansion of an energetic material

2021 ◽  
Author(s):  
Hervé Trumel ◽  
François Willot ◽  
Thomas Peyres ◽  
Maxime Biessy ◽  
François Rabette
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Volume Fraction ◽  
Energetic Material ◽  
Internal Stresses ◽  
Plastic Yielding ◽  
Initial State ◽  
Expansion Behavior ◽  
Small Volume Fraction

The works deals with a macroscopically isotropic energetic material based on triamino-trinitrobenzene (TATB) crystals bonded with a small volume fraction of a thermoplastic polymer. This material is shown experimentally to display an irreversible thermal expansion behavior characterized by dilatancy and variations of its thermal expansion coefficient when heated or cooled outside a narrow reversibility temperature range. The analysis of cooling results suggests the existence of residual stresses in the initial state, attributed to the manufacturing process. Microstructure-level FFT computations including the very strong anisotropic thermoelastic TATB crystal response and temperature-dependent binder plasticity, show that strong internal stresses develop in the disoriented crystals under thermal load, either heating or cooling. Upon cooling, binder plastic yielding in hindered, thus promoting essentially brittle microcracking, while it is favored upon heating. Despite its low volume fraction, the role of the binder is essential, its plastic yielding causing stress redistribution and residual stresses upon cooling back to ambient.

Regularities of the thermal expansion of cladding tubes and rods from E110opt alloy in the temperature range 273-1473 K (20-1200°C)

2020 ◽  
Vol 4 ◽  
pp. 51-64
Author(s):  
M.G. Isaenkova ◽  
◽  
A.V. Tenishev ◽  
Yu.A. Perlovich ◽  
S.D. Stolbov ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Phase Transformations ◽  
Orientation Dependence ◽  
Internal Stresses ◽  
Layer By Layer ◽  
Temperature Range ◽  
Heating And Cooling ◽  
Expansion Coefficients ◽  
Analytical Expressions ◽  
Tangential Directions

The regularities of the thermal expansion of cladding tubes and rods from the E110opt alloy, as well as the anisotropy of their thermal properties in the case of layer-by-layer texture inhomogeneity are studied. The thermal linear expansion coefficients (TLEC) of rods and cladding tubes were measured in the axial, radial and tangential directions during heating and cooling in the temperature range of 293-1473 K (20-1200°C). It is shown that as a result of a→b→a phase transformations in the samples, a stable texture of phase transformations is formed which is preserved during subsequent heating and cooling cycles. Analytical expressions are obtained that describe the temperature dependence of the thermal expansion coefficient in the first cycle of heating products from the E110opt alloy, taking into account possible a→b phase transformations and the resulting a-Zr crystal lattice deformation along the a and c axes. It was established that the presence of layer-by-layer inhomogeneity in the samples leads to the appearance of stresses between layers with different crystallographic textures and, as a result, affects the orientation dependence of phase transformations that are sensitive to the stress state in the material. The results obtained indicate the need to take into account the internal stresses arising in textured anisotropic materials during heating and cooling, and to separate the contributions of thermal expansion and plastic deformation when analyzing data from dilatometric measurements of sample sizes.

The Influences of Cu-Coated SiCp on the Porosity and Thermal Expansion Behavior of Cu-SiCp Composites

2013 ◽  
Vol 795 ◽  
pp. 241-244
Author(s):  
K. Azmi ◽  
M.I.M. Tajuddin ◽  
A. Azida
Keyword(s):  
Thermal Expansion ◽  
Thermal Management ◽  
Metal Matrix ◽  
Coefficient Of Thermal Expansion ◽  
Copper Matrix ◽  
Matrix Composites ◽  
Electroless Coating ◽  
Expansion Behavior ◽  
Significant Difference ◽  
Powder Metallurgy Methods

The widespread use of metal matrix composites as the packaging materials is due to their tailorable thermal conductivity and coefficient of thermal expansion (CTE). For the same reason, silicon carbide reinforced copper matrix (Cu-SiCp) composites are highly rated as thermal management materials in the electronic packaging applications. However, the Cu-SiCp composites fabricated via the conventional powder metallurgy methods have inferior thermophysical properties due to the presence of porosity in the interface of copper matrix and the SiCp reinforcement. In order to improve the bonding between the two constituents, the SiCp were coated with copper via electroless coating process. Based on the experimental results, the CTE values of the copper coated Cu-SiCp composites were found significantly lower than those of the non-Coated Cu-SiCp composites. The CTEs of the composites tend to decrease as the porosity increases. The significant difference in the CTE values was related to the presence of sub-micron gap between the copper matrix and the SiCp reinforcement.

Thermal Expansion and Viscoelasticity of Rubber in Relation to Crosslinking and Molecular Packing

1966 ◽  
Vol 39 (2) ◽  
pp. 408-417
Author(s):  
P. Mason
Keyword(s):  
Thermal Expansion ◽  
Free Volume ◽  
Specific Volume ◽  
Crosslink Density ◽  
Qualitative Change ◽  
Linear Increase ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Packing Effects

Abstract Effects of crosslinking on specific volume, thermal expansion coefficient, glass transition temperature (Tg) and viscoelasticity of rubber have been studied. Materials were prepared by heating purified natural rubber with varying amounts of cumyl peroxide. This procedure formed networks by intermolecular carbon-to-carbon bonding, and an approximately sixty-fold range of crosslink density was obtained. Crosslink density could be estimated with reasonable confidence up to about 1020/g. At this level the effects observed were, approximately, a one per cent decrease in specific volume; 23 per cent and 6 per cent decreases in the thermal expansion coefficients respectively below and above Tg; 5° C increase in Tg; and a displacement of the viscoelastic response by +5° C. These changes are accounted for in terms of the reduction in free volume consequent on crosslinking. There was also a qualitative change in behavior, the thermal expansion and viscoelastic transitional regions widening as crosslinking increased. The thermal expansion behavior is explained in terms of a linear increase in the variance of monomeric free volume with crosslinking up to 1020/g. At higher densities crosslinks are so close that their packing effects interact and the nature of the phenomenon changes.

Thermal Expansion of Anti-Perovskite Mn3Zn1-xSnxN Compounds

2012 ◽  
Vol 512-515 ◽  
pp. 890-893 ◽  
Author(s):  
Xue Hua Yan ◽  
Jia Qi Liu ◽  
Zhu Yuan Hua ◽  
Bing Yun Li ◽  
Xiao Nong Cheng
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Cubic Crystal ◽  
Thermal Expansion Behavior ◽  
Sn Doping ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Curve ◽  
Wide Perspective ◽  
Expansion Coefficients

The anti-perovskite structured Mn3XN(X=Cu,Al,Ag,Zn,Ga,Sn,In) have wide perspective and practicability with unique advantages compared with other materials as a new negative thermal expansion (NTE) material. Because of its simple preparation and unique properties of NTE, this kind of compounds aroused scientists’ attention. The metallic nitrides Mn3Zn1-xSnxN (x=0.1, 0.2, 0.3, 0.4, 0.5) were prepared by solid-state sintering. The anti-perovskite compound Mn3Zn1-xSnxN has a cubic crystal structure with space group Pm3m. It shows that Zn element is partial replaced by Sn element. The Sn doping in Mn3Zn1-xSnxN compound can cause the thermal expansion behavior of the compound to change between positive and negative by analyzing the curve of thermal expansivity with the temperature. Mn3Zn0.7Sn0.3N shows a very strong NTE. Its negative thermal expansion coefficients were -4.39×10-4/K from 345.4 °C to 476.2 °C. In addition, the variation of the thermal expansion curve for Mn3Zn0.8Sn0.2N is almost negligible with the increasing of temperature to 600 °C, exhibiting nearly zero thermal expansion behavior. Therefore, the thermal expansion of Mn3Zn1-xSnxN could be tuned via different contents of Sn in Mn3ZnN.

Thermal Expansion Behavior of ZnSe and ZnS0.03Se0.97 Epilayers on GaAs at Temperatures in the Range, 25°C - 250°C

1994 ◽  
Vol 340 ◽  
Author(s):  
J. R. Kim ◽  
R. M. Park ◽  
K. S. Jones
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Thermal Expansion Behavior ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Lattice Matched

ABSTRACTThe thermal expansion behavior of ZnSe and ZnS0.03Se0.97 epilayers grown on GaAs has been investigated using high resolution X-ray diffraction at temperatures between room temperature and the growth temperature. The lattice parameters perpendicular and parallel to the surface were measured with the Bond's method. The lattice mismatch for a partially relaxed ZnSe layer was Δa(⊥)/a =2300 ppm and Δa(‖)/a = 2600 ppm at room temperature(R.T.) and Δa (⊥)/a =3600 ppm and Δa(‖)/a =2400 ppm at 250°C. For ZnS0.03Se0.97 which is almost lattice matched at R.T. to GaAs, Δa(⊥)/a =200 ppm, Δa(⊥)/a =20ppmatR.T. and Δa(⊥)/a =1400ppm, Δa(⊥)/a =50ppm at 250°C. The relaxed lattice constants were evaluated and the thermal expansion coefficients of relaxed ZnSe layers were found to vary from 7.8*10−6/°C at room temperature to 12.2*10−6/°C at 250°C and for ZnS0.03Se0.97 layers the variation was from 7.5*10−6/°C at R.T. to 11.7*10−6/°C at 250°C.

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