scholarly journals Nucleation and Growth of Crystalline Grains in RF-Sputtered TiO2Films

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
J. C. Johnson ◽  
S. P. Ahrenkiel ◽  
P. Dutta ◽  
V. R. Bommisetty
Keyword(s):  
Volume Fraction ◽  
Classical Model ◽  
Grain Morphology ◽  
Carbon Support ◽  
Number Density ◽  
Crystalline Volume Fraction ◽  
Grain Number ◽  
Transmission Electron ◽  
Average Grain Size

AmorphousTiO2thin films were radio frequency sputtered onto siliconmonoxide and carbon support films on molybdenum transmission electron microscope (TEM) grids and observed during in situ annealing in a TEM heating stage at250∘C. The evolution of crystallization is consistent with a classical model of homogeneous nucleation and isotropic grain growth. The two-dimensional grain morphology of the TEM foil allowed straightforward recognition of amorphous and crystallized regions of the films, for measurement of crystalline volume fraction and grain number density. By assuming that the kinetic parameters remain constant beyond the onset of crystallization, the final average grain size was computed, using an analytical extrapolation to the fully crystallized state. Electron diffraction reveals a predominance of the anatase crystallographic phase.

scholarly journals New Approach to Produce a Nanocrystalline Layer on Surface of a Large Size Pure Titanium Plate

Coatings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 430
Author(s):  
Yuzhu Fu ◽  
Ge Wang ◽  
Jing Gao ◽  
Quantong Yao ◽  
Weiping Tong
Keyword(s):  
Pure Titanium ◽  
Grain Morphology ◽  
Optical Microscope ◽  
Surface Mechanical Attrition Treatment ◽  
Titanium Plate ◽  
Hardness Tester ◽  
Large Size ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Nanocrystalline Layer

It was demonstrated that the mechanical shot peening (MSP) technique was a viable way to obtain a nanocrystalline layer on a large size pure titanium plate due to the MSP provided for severe plastic deformation (SPD) of surface high velocity balls impacting. The MSP effects of various durations in producing the surface nanocrystalline layer was characterized by optical microscope (OM), X-ray diffraction (XRD), transmission electron microscope (TEM), and Vickers micro-hardness tester. The results showed that the thickness of the SPD layer gradually increased with the MSP processing time increase, but saturated at 230 μm after 30 min. The average grain size was refined to about 18.48 nm in the nanocrystalline layer. There was equiaxed grain morphology with random crystallographic orientation in the topmost surface. By comparing with the nanocrystalline layer, acquired by surface mechanical attrition treatment (SMAT), the microstructure and properties of the nanocrystalline layer acquired by MSP was evidently superior to that of the SMAT, but the production time was cut to about a quarter of the time used for the SMAT method.

Using Recycled Materials for Semi- Solid Processing of Al-Si-Mg Based Alloys

2022 ◽  
Vol 327 ◽  
pp. 207-222
Author(s):  
Jiehua Li ◽  
Xun Zhang ◽  
Johannes Winklhofer ◽  
Stefan Griesebner ◽  
Bernd Oberdorfer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Shape Factor ◽  
Volume Fraction ◽  
Solidification Microstructure ◽  
Number Density ◽  
Foundry Industry ◽  
Transmission Electron ◽  
Eutectic Si ◽  
Semi Solid ◽  
Secondary Materials

In order to reduce CO2 emission and energy consumption, more recycled secondary materials have to be used in foundry industry, especially for Al-Si-Mg based alloys for semi-solid processing. In this paper, Al-Si-Mg based alloys with the addition of recycled secondary materials up to 30 % (10, 20, 30 %, respectively) have been produced by semi-solid processing. The solidification microstructure was investigated using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, computed tomography (CT) was also used to elucidate the size, size distribution, number density, volume fraction of porosities. It was found that with the addition of the recycled secondary materials up to 30 %, there is no significant effect on the solidification microstructure in terms of the grain size and the shape factor of primary α-Al and the second α-Al. More importantly, the morphology of eutectic Si can be well modified and that of the Fe-containing phase (π-AlSiMgFe) can be tailored. Furthermore, with increasing recycled secondary materials, at least another two important issues should also be highlighted. Firstly, more TiB2 particles were observed, which can be due to the addition of Al-Ti-B grain refiners for the grain refinement of recycled secondary materials. Secondly, a significant interaction between Sr and P was also observed in the recycled secondary materials. The present investigation clearly demonstrates that Al-Si-Mg based alloys with the addition of recycled secondary materials at least up to 30% can be used for semi-solid processing, which may facilitate better sustainability.

Activation Volume for Inelastic Deformation in Polycrystalline Ag Films at Low Temperatures

1999 ◽  
Vol 594 ◽  
Author(s):  
Mauro J. Kobrinsky ◽  
Carl V. Thompson
Keyword(s):  
Thin Films ◽  
Inelastic Deformation ◽  
Activation Volume ◽  
Metallic Thin Films ◽  
Thermally Activated ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Relaxation Experiments ◽  
The Mean

AbstractThe low temperature (T < 100 °C) inelasticity of polycrystalline Ag thin films on thick substrates has been studied. In-situ Transmission Electron Microscopy and stress-relaxation experiments indicate that thermally-activated glide of dislocations through forest-dislocation obstacles is the dominant inelastic mechanism. Values of the activation volume for inelastic deformation obtained with both experiments are reported. The mean distance between obstacles along the length of moving dislocations was found to be significantly smaller than the thickness of the film and the average grain size, which explains why current models for dislocationmediated plasticity underestimate the strength of thin films. Results from these experiments on Ag are expected to be representative of other metallic thin films (e.g. Cu and Au) on substrates.

Cluster Dynamics Study of Neutron Irradiation Induced Defects in Fe-12.5at%Cr Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 449-457 ◽  
Author(s):  
Aleksandr R. Gokhman ◽  
Andreas Ulbricht ◽  
Uwe Birkenheuer ◽  
Frank Bergner
Keyword(s):  
Interstitial Atom ◽  
Volume Fraction ◽  
Size Distributions ◽  
Number Density ◽  
Vacancy Clusters ◽  
Transmission Electron ◽  
Induced Defects ◽  
Irradiation Induced Defects ◽  
Best Fit

Cluster dynamics (CD) is used to study the evolution of the size distributions of vacancy clusters (VC), self-interstitial atom (SIA) clusters(SIAC) and Cr precipitates in neutron irradiated Fe-12.5at%Cr alloys at T = 573 K with irradiation doses up to 12 dpa and a flux of 140 ndpa/s. Transmission electron microscopy (TEM) and small angle neutron scattering (SANS) data on the defect structure of this material irradiated at doses of 0.6 and 1.5 dpa are used to calibrate the model. A saturation behavior was found by CD for the free vacancy and free SIA concentrations as well as for the number density of the SIAC and the volume fraction of the Cr precipitates for neutron exposures above 0.006 dpa. The CD simulations also indicate the presence of VC with radii less than 0.5 nm and a strong SIAC peak with a mean diameter of about 0.5 nm, both invisible in SANS and TEM experiments. A specific surface tension of about 0.028 J/m2 between the a matrix and the Cr-rich a' precipitate was found as best fit value for reproducing the long-term Cr evolution in the irradiated Fe-12.5%Cr alloys observed by SANS.

The Influence of the SPD Temperature on Superplasticity of Aluminium Alloys

2006 ◽  
Vol 503-504 ◽  
pp. 585-590 ◽  
Author(s):  
Rinat K. Islamgaliev ◽  
N.F. Yunusova ◽  
Ruslan Valiev
Keyword(s):  
Aluminium Alloys ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Strain Rates ◽  
Angular Pressing ◽  
Thin Foils ◽  
Transmission Electron ◽  
In Situ Heating

Recent studies have demonstrated that ultrafinе-grainеd (UFG) alloys processed by equal channel angular pressing (ECAP) and high pressure torsion (HPT) can exhibit enhanced supеrplacticity at relatively low temperature and/or high strain rates. At the same time severe plastic deformation (SPD) of aluminium alloys is often carried out at elevated temperatures leading to various grain size and volume fraction of precipitates. The significance of the SPD temperature for commercial 1420 and 1421 aluminium alloys has been evaluated in this paper using in-situ heating of thin foils in the column of a transmission electron microscope. Superplastic characteristics of alloys processed at various ECAP temperatures are discussed.

scholarly journals In Situ Development and High Temperature Features of CoCrFeNi-M6Cp High Entropy-Alloy Based Hardmetal

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 408
Author(s):  
Huizhong Li ◽  
He Lin ◽  
Xiaopeng Liang ◽  
Weiwei He ◽  
Bin Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Volume Fraction ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Average Grain Size ◽  
Carbide Particles

In this work, an in-situ CoCrFeNi-M6Cp high entropy-alloy (HEA) based hardmetal with a composition of Co25Cr21Fe18Ni23Mo7Nb3WC2 was fabricated by the powder metallurgy (PM) method. Microstructures and mechanical properties of this HEA were characterized and analyzed. The results exhibit that this HEA possesses a two-phase microstructure consisting of the face-centered cubic (FCC) matrix phase and the carbide M6C phase. This HEA has an average grain size of 2.2 μm, and the mean size and volume fraction of carbide particles are 1.2 μm and 20%. The tensile tests show that the alloy has a yield strength of 573 MPa, ultimate tensile strength of 895 MPa and elongation of 5.5% at room temperature. The contributions from different strengthening mechanisms in this HEA were calculated. The grain boundary strengthening is the dominant strengthening mechanism, and the carbide particles are significant for the further enhancement of yield strength by the dislocation strengthening and Orowan strengthening. In addition, with increasing temperatures from 600 °C to 900 °C, the HEA shows a reduced yield strength (YS) from 473 MPa to 142 MPa, a decreased ultimate tensile strength (UTS) from 741 MPa to 165 MPa and an enhanced elongation from 10.5% to 31%.

The Electron-Beam Sensitivity of Binary Metal Azides

1992 ◽  
Vol 296 ◽  
Author(s):  
Patrick J. Herley ◽  
William Jones
Keyword(s):  
Electron Beam ◽  
Rapid Evolution ◽  
Carbon Support ◽  
Range Data ◽  
Mechanical Shock ◽  
Rapid Decomposition ◽  
Transmission Electron ◽  
Product Gas ◽  
Induced Decomposition

AbstractThe metal azides (or azido complexes) of La, Ce, Ti, Fe(III), Co, Ni, Pd, Ag, Tl, Cd, Sn, Sb and Bi have been synthesised and subjected in situ within a high resolution transmission electron microscope, to electron-beam fluxes (ca 0.1–1.0 A/cm2) to induce rapid decomposition. The materials, which are highly energetic and some are reportedly explosively sensitive, were carefully handled during synthesis to avoid mechanical shock, and only microgram quantities were decomposed whilst on holey carbon support films. In all cases beam-induced decomposition was very rapid. The exothermicity of the reaction induced in the beam promotes vigorous melting which either precedes or is accompanied by radiolysis. The net result is a rapid evolution of nitrogen (product) gas, which causes atomisation and spallation of the metal products. These molten metal particles are hard landed on a 300–500 μm 2 area of the support film with diameters in the nanometre size range. Data is presented on the synthesis of the azides, the nature of the beam-induced process as well as representative electron micrographs of some of the pristine starting materials and the nanoparticulate products.

Disordered Spheres with Extensive Overlap in Projection: Image Simulation and Analysis

2011 ◽  
Vol 17 (6) ◽  
pp. 872-878 ◽  
Author(s):  
Christopher D. Chan ◽  
Michelle E. Seitz ◽  
Karen I. Winey
Keyword(s):  
Particle Size ◽  
Critical Thickness ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Spherical Particles ◽  
Specimen Thickness ◽  
Number Density ◽  
Particle Volume ◽  
Transmission Electron ◽  
Projection Image

AbstractThis article simulates highly overlapped projections of spherical particles that are distributed randomly in space. The size and number of the features in the projections are examined as well as how these features change with particle size and concentration. First, there are discernable features in projection even when particles overlap extensively, and the size of these discernable features is the expected size of an individual particle. Second, the number of features increases with specimen thickness at a rate of t0.543 when the specimen thickness is below a critical value and becomes independent of specimen thickness at higher thicknesses. A criterion is established for the critical thickness based on particle size and particle volume fraction. When the specimen thickness is known and smaller than the critical thickness, a single representative transmission electron microscopy (TEM) (or scanning TEM) image exhibiting extensive particle overlap can be used to determine the size and number density of the spherical particles.

scholarly journals Influence of Fe and Mn on the Microstructure Formation in 5xxx Alloys—Part II: Evolution of Grain Size and Texture

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3312
Author(s):  
Jakob Grasserbauer ◽  
Irmgard Weißensteiner ◽  
Georg Falkinger ◽  
Peter J. Uggowitzer ◽  
Stefan Pogatscher
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Number Density ◽  
Secondary Phases ◽  
Zener Pinning ◽  
Average Grain Size ◽  
Fe And Mn ◽  
Fe Alloys ◽  
Size And Morphology ◽  
Grain Size And Orientation

In recent decades, microstructure and texture engineering has become an indispensable factor in meeting the rising demands in mechanical properties and forming behavior of aluminum alloys. Alloying elements, such as Fe and Mn in AlMg(Mn) alloys, affect the number density, size and morphology of both the primary and secondary phases, thus altering the grain size and orientation of the final annealed sheet by Zener pinning and particle stimulated nucleation (PSN). The present study investigates the grain size and texture of four laboratory processed AlMg(Mn) alloys with various Fe and Mn levels (see Part I). Common models for deriving the Zener-limit grain size are discussed in the light of the experimental data. The results underline the significant grain refinement by dispersoids in high Mn alloys and show a good correlation with the Smith–Zener equation, when weighting the volume fraction of the dispersoids with an exponent of 0.33. Moreover, for high Fe alloys a certain reduction in the average grain size is obtained due to pinning effects and PSN of coarse primary phases. The texture analysis focuses on characteristic texture transformations occurring with pinning effects and PSN. However, the discussion of the texture and typical PSN components is only possible in terms of trends, as all alloys exhibit an almost random distribution of orientations.

In Situ Tem Study of Reactions in Iron/amorphous Carbon Layered Thin Films

1995 ◽  
Vol 382 ◽  
Author(s):  
Toshio Itoh ◽  
Robert Sinclair
Keyword(s):  
Grain Size ◽  
Amorphous Carbon ◽  
Layered Structure ◽  
Annealing Temperature ◽  
In Situ Tem ◽  
Dc Sputtering ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Deposited Films

ABSTRACTReactions between Fe and amorphous carbon (a-C) below 600ºC have been investigated. In situ annealing in a transmission electron microscopy (TEM) was performed on a-C/Fe/a-C trilayer films deposited by DC sputtering. As-deposited films showed a well defined tri-layered structure and an average Fe grain size of about 50Å. Cementite (Fe3C) grains appeared in the Fe layer by annealing around 300ºC. As the annealing temperature was raised, the number and size of the cementite grains increased. When the annealing temperature reached 500ºC, the Fe layer completely turned into cementite with an average grain size of 1000Å. At this point the film still kept a well defined tri-layered structure even though some parts of the cementitelayer agglomerated. Above 500ºC, the cementite layer started to “move” into the a-C leaving graphite behind. Graphite formed in this process is strongly textured with the (0002) graphite basal planes parallel to the surface of the moving cementite. This process is concluded to be carbide mediated crystallization of a-C, similar to silicide mediated crystallization of silicon in Ni-Si and Pd-Si systems.

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