scholarly journals Thermal Kinetics of SiCp Reinforced Al-Zn-Mg-Cu Alloy Composite

2021 ◽  
Author(s):  
Saikat Das ◽  
R. Govinda Rao ◽  
Prasanta Kumar Rout
Keyword(s):  
Base Alloy ◽  
Accelerated Aging ◽  
Stir Casting ◽  
Hardness Profile ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
The Matrix ◽  
Aging Kinetics ◽  
Aging Phenomena ◽  
Kinetics Of

Abstract In the present work, the artificial aging kinetics of SiCp particles reinforced AA7075-SiCp composite fabricated by stir casting method was investigated. The aging behavior of AA7075-SiCp composite was investigated by Rockwell hardness tests and differential scanning calorimetry (DSC). Results show there are no changes in the sequences of formation and dissolution of precipitate. Reinforced particles are uniformly distributed throughout the matrix. The hardness profile shows increase in hardness with the comparison of AA7075 base alloy. In addition to SiCp in the matrix, precipitation kinetics has changed compared with base alloy since higher dislocations present in composite, hence requires lower activation energy to form ή precipitate and takes less time to reach the maximum hardness. In contrast, the addition of SiCp at low volume percent also showing accelerated aging phenomena in the composite during the aging process. High-resolution transmission electron microscope (HRTEM) micrograph of peak age (T6) condition divulges that enormous fine and plate-like ή (MgZn2) precipitates are uniformly distributed in the composite.

The effect of composition and cooling rate on the structure of rapidly solidified (Fe, Ni)3Al–C alloys

1989 ◽  
Vol 4 (1) ◽  
pp. 44-49 ◽  
Author(s):  
S. A. Myers ◽  
C. C. Koch
Keyword(s):  
Cooling Rate ◽  
Base Alloy ◽  
Weight Percent ◽  
Quench Rate ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Metastable Structure ◽  
The Matrix ◽  
Rapidly Solidified ◽  
Kinetics Of

There is controversy in the literature regarding the existence of the metastable γ′ phase with an ordered Ll2 structure in rapidly solidified Fe–Ni–Al–C alloys. In this study, the quench rate–metastable structure dependence was examined in the Fe–20Ni–8Al–2C (weight percent) alloy. The effect of silicon on the kinetics of phase formation was studied by adding two weight percent silicon to a base alloy of Fe–20Ni–8Al–2C. Samples were rapidly solidified in an arc hammer apparatus and examined by transmission electron microscopy. In the Fe–20Ni–8Al–2C alloy, the nonequilibrium γ′ and γ phases were found in foils 65 to 100 μm thick. At higher quench rates, i.e., thinner samples, the matrix was observed to be disordered fcc γ with K-carbide precipitates. Samples containing silicon were found to have a matrix composed of γ′ and γ structures when the foils were thicker than 40 μm. At higher quench rates, the matrix was disordered fcc γ with K-carbide precipitates. The nonequilibrium γ′ and γ structures are present in samples with or without silicon, but are observed at higher cooling rates with the addition of silicon. This sensitivity to cooling rate and composition in resulting metastable structures may explain the differences reported in the literature for these rapidly solidified materials.

Temporal Evolution of Bimodal Distribution of γ’ Precipitates in Ni-Al-Mo Alloys under the Influence of Coherency Strains

1995 ◽  
Vol 398 ◽  
Author(s):  
A.D. Sequeira ◽  
H.A. Calderon ◽  
G. Kostorz
Keyword(s):  
Lattice Mismatch ◽  
Bimodal Distribution ◽  
X Ray Diffraction ◽  
Double Step ◽  
Bimodal Size Distribution ◽  
Elastic Fields ◽  
Transmission Electron ◽  
The Matrix ◽  
Kinetics Of ◽  
Coherency Strains

ABSTRACTThe influence of coherency strains produced by the γ-γ’ lattice mismatch, δ, on the decomposition process of Ni-Al-Mo alloys with a bimodal size distribution is presented. Samples with δ ranging from positive to negative, were investigated in a double-step aging procedure. The evolution of the microstructure and the kinetics of coarsening were studied using transmission electron microscopy (TEM). The lattice mismatch between the matrix and the different classes of precipitates was determined by high-resolution high-temperature x-ray diffraction. It is shown that the strain fields produced by the lattice mismatch can influence dramatically the decomposition of metallic alloys. It is suggested that the reduction of the coarsening rate of the large precipitates, the fast coarsening rate of the small precipitates and the distortions detected in the matrix are all direct consequences of the elastic fields produced by the γ-γ’ lattice mismatch.

In SituHigh-Resolution Electron Spectroscopic Imaging and Real-Time Image Simulation of Precipitate Growth Mechanisms

1997 ◽  
Vol 3 (S2) ◽  
pp. 627-628
Author(s):  
J. M. Howe ◽  
M. M. Tsai ◽  
A. A. Csontos
Keyword(s):  
Atomic Level ◽  
Interface Motion ◽  
Bonding Structure ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Precipitate Growth ◽  
The Matrix ◽  
Interphase Boundaries ◽  
Transformation Mechanisms ◽  
Kinetics Of

Precipitate interfaces are ideal for studying the relationship between atomic bonding, structure and composition at internal interfaces and the mechanisms and kinetics of their motion as a function of temperature or driving force for reaction. The crystallography between coherent and semicoherent precipitates and the matrix is well-defined and the precipitate interfaces are often planar and grow by a terrace-ledge-kink mechanism, making them well-suited for study by conventional and high-resolution transmission electron microscopy (HRTEM).Motion of precipitate interfaces, or more generally, interphase boundaries, involves a change in lattice, composition or both. In order to understand the mechansims of interfacial motion, it is necessary to determine the structural and compositional changes that occur at the highest possible resolution, i.e., as close to the atomic level as possible, and also, to determine the corresponding kinetics of interface motion. HRTEM is an excellent technique for determining the atomic structure of transformation interfaces and in situhot-stage HRTEM is deal for determining interface dynamics at the atomic level, provided the transformation mechanisms are not altered by the thinness of the TEM foil.

Characterization of Nanocrystalline γ–Fe2O3Prepared by Wet Chemical Method

1999 ◽  
Vol 14 (4) ◽  
pp. 1570-1575 ◽  
Author(s):  
G. Ennas ◽  
G. Marongiu ◽  
A. Musinu ◽  
A. Falqui ◽  
P. Ballirano ◽  
...  
Keyword(s):  
Isothermal Treatment ◽  
X Ray Diffraction ◽  
Ferrous Chloride ◽  
Scanning Calorimetry ◽  
Direct Transformation ◽  
X Ray ◽  
Transmission Electron ◽  
Xrd Techniques ◽  
Kinetics Of

Homogeneous maghemite (γ–Fe2O3) nanoparticles with an average crystal size around 5 nm were synthesized by successive hydrolysis, oxidation, and dehydration of tetrapyridino-ferrous chloride. Morphological, thermal, and structural properties were investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) techniques. Rietveld refinement indicated a cubic cell. The superstructure reflections, related to the ordering of cation lattice vacancies, were not detected in the diffraction pattern. Kinetics of the solid-state phase transition of nanocrystalline maghemite to hematite (α–Fe2O3), investigated by energy dispersive x-ray diffraction (EDXRD), indicates that direct transformation from nanocrystalline maghemite to microcrystalline hematite takes place during isothermal treatment at 385 °C. This temperature is lower than that observed both for microcrystalline maghemite and for nanocrystalline maghemite supported on silica.

Crystallization of Al-Gd-La-Ni Metallic Glasses

1999 ◽  
Vol 580 ◽  
Author(s):  
T.K. Croat ◽  
A.K. Gangopadhyay ◽  
K.F. Kelton
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Metallic Glasses ◽  
Low Temperatures ◽  
Alloy Composition ◽  
Composition Range ◽  
Scanning Calorimetry ◽  
Crystallization Sequence ◽  
Transmission Electron ◽  
Kinetics Of

AbstractThe crystallization kinetics of Al-Gd-La-Ni metallic glasses to nanostructured phases are analyzed using differential scanning calorimetry and transmission electron microscopy. In a narrow alloy composition range near Al88Gd6La2Ni4, TEM reveals an amorphous phase separation that occurs upon annealing at low temperatures prior to crystallization. Al-enriched regions, typically 40 nm in diameter, bounded by rare-earth rich regions, are visible. Upon crystallization, α-Al forms preferentially at the interface between these phase separated regions. The relevance of this crystallization sequence to previous work in Al-RE-TM glasses and to the evolution of nanoscale microstructures common in the crystallization of other metallic glasses are discussed.

The Study of Epoxy Resins Modified By PPESK

2012 ◽  
Vol 463-464 ◽  
pp. 181-184
Author(s):  
Ya Juan Xu ◽  
Qin Cun Cao ◽  
Xi Gao Jian
Keyword(s):  
Fracture Toughness ◽  
Critical Stress Intensity Factor ◽  
Diglycidyl Ether ◽  
Fracture Mechanisms ◽  
Moderate Increase ◽  
Scanning Calorimetry ◽  
Curing Reaction ◽  
Accelerated Curing ◽  
The Matrix ◽  
Kinetics Of

A series of blends have been prepared by adding a novel thermoplastic poly (phthalazinone ether sulfone ketone) (PPESK) in varying proportions to diglycidyl ether of bisphenol A epoxy resin (DGEBA) cured with p-diaminodiphenylsulfone. The kinetics of curing reaction and glass transition temperature (Tg) of PPESK/DGEBA blends were performed using differential scanning calorimetry (DSC) technique. It is proved that the addition of PPESK accelerated curing reaction and resulted in great enhancement of thermal properties of the blends. There was moderate increase in the fracture toughness as estimated by the critical stress intensity factor (KIc). Compared to that of unmodified epoxy, the maximum toughness of the modified blends had increased 32% by addition of 15 phr PPESK. Fracture mechanisms such as crack deflection and branches, ductile microcracks, ductile tearing of the thermoplastic of the matrix were responsible for the increase in the fracture toughness of the blends

scholarly journals Precipitation Process in a Cu-Ni-Be Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 432-436 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen
Keyword(s):  
Electron Microscopy ◽  
Precipitation Process ◽  
Average Thickness ◽  
Precipitation Sequence ◽  
Transmission Electron ◽  
The Matrix ◽  
Precipitated Phases ◽  
Kinetics Of ◽  
Ledge Mechanism ◽  
Habit Planes

The precipitation process in an aged Cu-1.9wt%Ni-0.3wt%Be alloy has been examined by high-resolution transmission electron microscopy. The precipitation sequence found is: Guinier- Preston (G.P.) zones → γ'' → γ' → stable γ. The disk-shaped G.P. zones and the disk-shaped γ'', γ' and γ precipitated phases are composed of monolayers of Be atoms on {100}αof the Cu matrix and alternative Be and Ni matrix layers parallel to {100}α. The γ'' phases consisting of two to eight Be-layers has a body-centered tetragonal (bct) lattice witha=b=0.24 nm andc=0.28 nm. The γ' or γ phase is bct witha=b=0.24 nm andc=0.26 nm ora=b=0.26 nm andc=0.27 nm. The γ'', γ' or γ phase aligns with the matrix according to the Bain orientation relationship. The growth kinetics of disk-shaped γ precipitates on aging at 500°C has been also investigated. The {001}αhabit planes of the γ precipitates migrate by a ledge mechanism. The average thickness of the γ disks increases with aging timetast1/2. An analysis of experimental data using a kinetic model yields the diffusivity of solute in the Cu matrix, which is in agreement with the reported diffusivity of Ni in Cu.

Novel Collagen Based Material for Local Drug Delivery Systems

2007 ◽  
Vol 1008 ◽  
Author(s):  
Luciano Castaneda ◽  
Suzanne Pluskat ◽  
Darline Ky ◽  
Earry Te ◽  
Katarzyna Slowinska
Keyword(s):  
Drug Delivery ◽  
Drug Delivery Systems ◽  
Crosslinking Agent ◽  
Collagen Matrix ◽  
Gold Clusters ◽  
Local Drug Delivery ◽  
Scanning Calorimetry ◽  
Cytotoxicity Assays ◽  
Transmission Electron ◽  
The Matrix

AbstractIn a search for new drug delivery matrix, the synthesis of a novel collagen material based on tiopronin protected gold clusters (MPC) as a crosslinking agent is proposed. The structure of collagen matrix modified with MPC is studied using transmission electron microscope. The thermal properties are examined with differential scanning calorimetry. To assess the biocompatibility of the matrix, the cytotoxicity assays are conducted.

Melting And Solidification Behaviour Of Lead Particles Embedded In Quasicrystalline Matrices

1998 ◽  
Vol 553 ◽  
Author(s):  
Alok Singh ◽  
A. P. Tsai
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Matrix Interface ◽  
Orientation Relationships ◽  
Scanning Calorimetry ◽  
Decagonal Phase ◽  
Solidification Behaviour ◽  
Transmission Electron ◽  
The Matrix ◽  
Melting And Solidification

AbstractComposites of nanoparticles of lead were prepared by embedding into Al-Cu-V and Al- Cu-Fe icosahedral, and Al-Cu-Co decagonal phase alloys by means of rapid solidification. The microstructure of these composites, the orientation relationships and the interfaces formed between the particles and the matrix has been studied by transmission electron microscopy. The melting and solidification behaviour of the lead particles in these matrices has been studied by differential scanning calorimetry. The microstructure and the nature of the particle-matrix interface has been related to the melting/solidification behaviour of the particles in the matrix.

Effect of Mg Content on the Precipitation in Al-Mg-Ge Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 2049-2052 ◽  
Author(s):  
Kenji Matsuda ◽  
Teruyoshi Munekata ◽  
Susumu Ikeno
Keyword(s):  
Cross Sections ◽  
Base Alloy ◽  
Lattice Parameter ◽  
Chemical Compositions ◽  
Crystal Lattices ◽  
Β Phase ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
The Matrix ◽  
Mg Content

Rod-shaped precipitates in Al -1.1 mass% Mg2Ge (balanced) and Al -1.0 mass% Mg2Ge – 0.5 mass% Mg (excess Mg) alloys aged at 523 K were observed by high-resolution transmission electron microscope (HRTEM) to understand their crystal lattices and chemical compositions. Rod-shaped precipitates were parallel to <100> directions of the matrix. There were 2 groups for rod-shaped precipitates in the base alloy, namely, small cross sections about 10 nm and large ones over 20nm in diameter. Small precipitates showed a hexagonal network of bright dots in their HRTEM images, and its crystal lattice was estimated as a hexagonal having a= 0.72 and c= 0.405 nm based on analysis of HRTEM images and selected area electron diffraction (SAED) patterns. This lattice parameter was slight larger than that of the β’-phase in Al-Mg-Si alloy.

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