Microstructural Evolution in Reduced TiO2

Since point defects have a limited solubility in the rutile (TiO2) lattice, small deviations from stoichiometry are known to produce crystallographic shear (CS) planes which accomodate local variations in composition. The material used in this study was porous polycrystalline TiO2 (60% dense), in the form of 3mm. diameter disks, 1mm thick. Samples were mechanically polished, ion-milled by conventional techniques, and initially examined with the use of a Siemens EM102. The electron transparent thin foils were then heat-treated under controlled atmospheres of CO/CO2 and H2 and reexamined in the same manner.The “as-received” material contained mostly TiO2 grains (∼5μm diameter) which had no extended defects. Several grains however, aid exhibit a structure similar to micro-twinned grains observed in reduced rutile. Lattice fringe images (Fig. 1) of these grains reveal that the adjoining layers are not simply twin related variants of a single TinO2n-1 compound. Rather these layers (100 - 250 Å wide) are alternately comprised of stoichiometric TiO2 (rutile) and reduced TiO2 in the form of Ti8O15, with the Ti8O15 layers on either side of the TiO2 being twin related.

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Influence of ion-milling on the T2 phase in Al-2.5%Li-2.5%Cu alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153415 ◽

1989 ◽

Vol 47 ◽

pp. 288-289

Author(s):

J. R. Reed ◽

D. J. Michel ◽

P. R. Howell

Keyword(s):

Thin Foil ◽

Icosahedral Symmetry ◽

Ion Milling ◽

Cu Alloy ◽

Thin Foils ◽

Heat Treated ◽

Aluminum Solid Solution ◽

In Situ Heating ◽

The Stability

The Al6Li3Cu (T2) phase, which exhibits five-fold or icosahedral symmetry, forms through solid state precipitation in dilute Al-Li-Cu alloys. Recent studies have reported that the T2 phase transforms either during TEM examination of thin foils or following ion-milling of thin foil specimens. Related studies have shown that T2 phase transforms to a microcrystalline array of the TB phase and a dilute aluminum solid solution during in-situ heating in the TEM. The purpose of this paper is to report results from an investigation of the influence of ion-milling on the stability of the T2 phase in dilute Al-Li-Cu alloy.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimens were solution heat treated 1 h at 550°C and aged 1000 h at 190°C in air to develop the microstructure. The disc specimens were electropolished to achieve electron transparency using a 20:80 (vol. percent) nitric acid: methanol solution at -60°C.

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Multiscale Green’s-function method for modeling point defects and extended defects in anisotropic solids: Application to a vacancy and free surface in copper

Physical Review B ◽

10.1103/physrevb.69.094109 ◽

2004 ◽

Vol 69 (9) ◽

Cited By ~ 22

Author(s):

V. K. Tewary

Keyword(s):

Free Surface ◽

Green’S Function ◽

Green's Function ◽

Point Defects ◽

Function Method ◽

Extended Defects ◽

Green’S Function Method

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Microstructural Characterization Of Laser Heat Treated AISI 4140 Steel With Improved Fatigue Behavior

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0125 ◽

2015 ◽

Vol 60 (2) ◽

pp. 1331-1334 ◽

Cited By ~ 5

Author(s):

M.C. Oh ◽

H. Yeom ◽

Y. Jeon ◽

B. Ahn

Keyword(s):

Fatigue Strength ◽

Alloy Steel ◽

Microstructural Evolution ◽

Fatigue Behavior ◽

Microstructural Characterization ◽

Optical Microscope ◽

Heat Treated ◽

Aisi 4140 ◽

Ultrasonic Fatigue

Abstract The influence of surface heat treatment using laser radiation on the fatigue strength and corresponding microstructural evolution of AISI 4140 alloy steel was investigated in this research. The AISI 4140 alloy steel was radiated by a diode laser to give surface temperatures in the range between 600 and 800°C, and subsequently underwent vibration peening. The fatigue behavior of surface-treated specimens was examined using a giga-cycle ultrasonic fatigue test, and it was compared with that of non-treated and only-peened specimens. Fatigue fractured surfaces and microstructural evolution with respect to the laser treatment temperatures were investigated using an optical microscope. Hardness distribution was measured using Vickers micro-hardness. Higher laser temperature resulted in higher fatigue strength, attributed to the phase transformation.

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Influence of Growth Rate and C/Si-Ratio on the Formation of Point and Extended Defects in 4H-SiC Homoepitaxial Layers Investigated by DLTS

Materials Science Forum ◽

10.4028/www.scientific.net/msf.615-617.393 ◽

2009 ◽

Vol 615-617 ◽

pp. 393-396 ◽

Cited By ~ 2

Author(s):

Bernd Zippelius ◽

Michael Krieger ◽

Heiko B. Weber ◽

Gerhard Pensl ◽

Birgit Kallinger ◽

...

Keyword(s):

Point Defects ◽

Vapour Deposition ◽

Electronic Devices ◽

Pulse Length ◽

Chemical Vapour ◽

Extended Defects ◽

Deposition Method ◽

Active Point ◽

Homoepitaxial Layers ◽

Chemical Vapour Deposition Method

4H-SiC epilayers are homoepitaxially grown on 4H-SiC substrates with different C/Si-ratios and different growth rates by the chemical vapour deposition method. DLTS investigations are applied in order to trace energetically deep states of electrically active point defects and extended defects, which may act as the source for the degradation of electronic devices. In addition, the dependence of the DLTS signal heights on the filling pulse length is studied.

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The Stability of γ ’-Co3(Al,W) Phase in Co-Al-W Ternary System

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.448 ◽

2010 ◽

Vol 654-656 ◽

pp. 448-451 ◽

Cited By ~ 37

Author(s):

Yuki Tsukamoto ◽

Satoru Kobayashi ◽

Takayuki Takasugi

Keyword(s):

Heat Treatment ◽

Ternary System ◽

Microstructural Evolution ◽

Treatment Time ◽

Bulk Alloy ◽

Epma Analysis ◽

Heat Treated ◽

Cold Rolled ◽

The Stability ◽

Couple Method

The thermodynamic stability ’- Co3(Al,W) phase (L12) in the Co-Al-W ternary system at 900 °C was investigated through microstructure and EPMA analysis on a heat-treated bulk alloy. To promote microstructural evolution, the bulk alloy was cold rolled before heat treatment. By heating at 900 °C, the ’ phase was formed discontinuously in contact with the -Co (A1) phase. With increasing heat treatment time, however, the fraction of ’ phase decreased while that of , CoAl (B2) and Co3W (D019) phases increased. These results are consistent with our previous work with a diffusion-couple method, indicating that the ’ phase is metastable, and the three phases of, CoAl and Co3W are thermodynamically stable at 900 °C.

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Application of Stress Relaxation Testing in Metallurgical Life Assessment Evaluations of GTD111 Alloy Turbine Buckets

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education ◽

10.1115/98-gt-370 ◽

1998 ◽

Cited By ~ 1

Author(s):

Joseph A. Daleo ◽

Keith A. Ellison ◽

David A. Woodford

Keyword(s):

Creep Rate ◽

Stress Relaxation ◽

Microstructural Evolution ◽

Creep Rupture ◽

Life Assessment ◽

Standard Heat ◽

Treated Condition ◽

Heat Treated ◽

Temperature Capability ◽

Heat Treated Condition

Stress relaxation and constant displacement rate tensile tests were performed on poly-crystalline GTD111 alloy material removed from General Electric MS6001B first stage combustion turbine buckets. Samples were examined in the standard heat treated condition, thermally exposed at 900°C for 5000 hours and from service run buckets. Creep rates of the material were measured and evaluated directly in terms of temperature capability at 850°C and 900°C. Stress relaxation tests done at 0.8% total strain indicated that the creep rate properties in the service exposed airfoil were an order of magnitude higher than the material properties in the standard heat treated condition measured in the root form. In terms of temperature capability, the creep rate properties of the service run airfoil material had decreased by the equivalent of almost 40°C. The stress relaxation test method was demonstrated to be a very useful tool in quantifying the degradation of creep properties in service run components. Creep data that would require years to gather using conventional creep tests was generated in a few days. This now makes realistic life assessment and repair / replace decisions possible during turbine overhauls. The test method’s unique ability to measure changes in creep rate over a large stress range, enabled the technique to distinguish between changes in creep strength due to (normal) microstructural evolution from the combined effects of microstructural evolution and strain related creep damage. A method for estimating standard constant load creep rupture life from the stress relaxation creep rate data is also presented along with time-temperature parameter correlations. The data sets examined in this study indicate that creep rupture lives can be estimated within a factor of three from the stress relaxation data. The information and analysis techniques described in this paper are directly applicable to metallurgical life assessment evaluations and the re-qualification of repaired General Electric buckets in Frame 3, 5, 6, 7 and 9 engine models.

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From extended defects and interfaces to point defects in three dimensions—The case of InxGa1−xN

Physica B Condensed Matter ◽

10.1016/j.physb.2007.09.041 ◽

2007 ◽

Vol 401-402 ◽

pp. 639-645 ◽

Cited By ~ 5

Author(s):

C. Kisielowski ◽

T.P. Bartel ◽

P. Specht ◽

F.-R. Chen ◽

T.V. Shubina

Keyword(s):

Point Defects ◽

Three Dimensions ◽

Extended Defects

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Microstructural evolution and strain hardening behavior of heat-treated 17-4 PH stainless steel

Materials Today Communications ◽

10.1016/j.mtcomm.2020.101416 ◽

2020 ◽

Vol 25 ◽

pp. 101416

Author(s):

Athul Sathyanath ◽

Anil Meena

Keyword(s):

Stainless Steel ◽

Strain Hardening ◽

Microstructural Evolution ◽

Hardening Behavior ◽

Heat Treated ◽

Strain Hardening Behavior

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Hydrogen Interaction with Point Defects in the Si-SiO2 Structures and its Influence on the Interface Properties

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.131-133.345 ◽

2007 ◽

Vol 131-133 ◽

pp. 345-350 ◽

Cited By ~ 2

Author(s):

Daniel Kropman ◽

E. Mellikov ◽

Tiit Kärner ◽

Ü. Ugaste ◽

Tony Laas ◽

...

Keyword(s):

Point Defects ◽

Hydrogen Adsorption ◽

Impurity Content ◽

Magnetic Interaction ◽

Interface Properties ◽

Extended Defects ◽

Oxidation Condition ◽

Paramagnetic Impurities ◽

Defects And Impurities ◽

P Type

The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects with extended defects and impurities affects the SiO2 structure and Si-SiO2 interface properties. Hydrogen adsorption on n- and p- type wafers is different. One possible reason for that can be the strength of the magnetic interaction between the hydrogen and paramagnetic impurities of the adsorbent. The influence of point defects and impurities may be diminished and the interface properties improved by an appropriate choice of the oxidation conditions and postoxidation laser irradiation.

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