Segregation Effects and Phase Developments during Solidification of Alloy 625

The solidification behaviour of pure Alloy 625, and Alloy 625 enriched respectively in iron and carbon, was investigated in situ by hot-stage light optical microscopy. Using this technique planar front solidification for distances of several hundred microns was facilitated. After solidification, the material that experienced planar front solidification corresponded accurately to that of dendrites tens of microns in width adopting an equivalent dendrite arm width approach. Eventually, the planar solidification front broke down, where after the residual liquid solidified eutectic-like. This material contained γ-phase, Laves phase and, if carbon was dissolved in the liquid, niobium rich carbides formed. Molybdenum and niobium showed strong tendencies to segregate. Their segregation was balanced by inverse segregation of nickel and iron. The chromium concentration remained almost constant in γ in the entire matrix material. Addition of carbon did not cause detectable alterations of the material that experienced planar front solidification. However, it promoted the formation of niobium rich carbides in the material that solidified eutectic-like. Thus, this material differed from that of the pure sample in constitution, and consequently in γ-phase composition. Niobium rich carbides formed prior to Laves phase; in carbon rich volumes only the carbides form. As compared to the pure sample, the sample enriched in iron had decreased global minimal solute concentration in the material that experienced planar front solidification. However, once the concentrations were corrected with respect to the dilution simply caused by the presence of iron, the solidification behaviour in this material was identical to that of the pure sample. The constitution in the material that solidified eutectic-like was γ and Laves phase. As compared to the pure sample, the Laves phase was enriched in iron.

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Alignment of small He-Bubbles during in situ deformation of Al-foils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109124 ◽

1978 ◽

Vol 36 (1) ◽

pp. 396-397

Author(s):

E. Ruedl ◽

P. Schiller

Keyword(s):

Fusion Reactor ◽

Matrix Material ◽

Fusion Reactors ◽

First Wall ◽

Potential Matrix ◽

In Situ Deformation ◽

Α Particles ◽

Metal Aluminium

The low Z metal aluminium is a potential matrix material for the first wall in fusion reactors. A drawback in the application of A1 is the rel= atively high amount of He produced in it under fusion reactor conditions. Knowledge about the behaviour of He during irradiation and deformation in Al, especially near the surface, is therefore important.Using the TEM we have studied Al disks of 3 mm diameter and 0.2 mm thickness, which were perforated at the centre by double jet polishing. These disks were bombarded at∽200°C to various doses with α-particles, impinging at any angle and energy up to 1.5 MeV at both surfaces. The details of the irradiations are described in Ref.1. Subsequent observation indicated that in such specimens uniformly distributed He-bubbles are formed near the surface in a layer several μm thick (Fig.1).After bombardment the disks were deformed at 20°C during observation by means of a tensile device in a Philips EM 300 microscope.

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Initial Stages of InAs Quantum Dots Evolution in GaAs/AlAs Matrixes

MRS Proceedings ◽

10.1557/proc-749-w13.8 ◽

2002 ◽

Vol 749 ◽

Author(s):

Michael Yakimov ◽

Vadim Tokranov ◽

Alex Katnelson ◽

Serge Oktyabrsky

Keyword(s):

Quantum Dots ◽

Direct Evidence ◽

Matrix Material ◽

Single Layer ◽

High Energy ◽

Inas Quantum Dots ◽

Auger Signal ◽

The Matrix ◽

Growth Evolution

ABSTRACTWe have studied the first phases of post-growth evolution of InAs quantum dots (QDs) using in-situ Auger electron spectroscopy in conjunction with Reflection High Energy Electron Diffraction (RHEED). Direct evidence for InAs intermixing with about 6ML (monolayers) of the matrix material is found from Auger signal behavior during MBE overgrowth of InAs nanostructures. Re-establishment of 2D growth mode by overgrowth with GaAs or AlAs was monitored in single-layer and multi-layer QD structures using RHEED. Decay process of InAs QDs on the surface is found to have activation energy of about 1.1 eV that corresponds to In intermixing with the matrix rather than evaporation from the surface.

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Toward a theory of the evolution of drop morphology and splintering by freezing

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-20-0029.1 ◽

2021 ◽

Author(s):

Alexander Staroselsky ◽

Ranadip Acharya ◽

Alexander Khain

Keyword(s):

Drop Size ◽

Phase Field Model ◽

Surface Fluxes ◽

Freezing Process ◽

Drop Surface ◽

Surface Nucleation ◽

Planar Front ◽

Bulk Nucleation ◽

Ice Shell

AbstractThe drop freezing process is described by a phase-field model. Two cases are considered: when the freezing is triggered by central nucleation and when nucleation occurs on the drop surface. Depending on the environmental temperature and drop size, different morphological structures develop. Detailed dendritic growth was simulated at the first stage of drop freezing. Independent of the nucleation location, a decrease in temperature within the range from ~ −5 to −25°C led to an increase in the number of dendrites and a decrease in their width and the interdendritic space. At temperatures lower than about −25°C, a planar front developed following surface nucleation, while dendrites formed a granular-like structure with small interdendritic distances following bulk nucleation. An ice shell grew in at the same time (but slower) as dendrites following surface nucleation, while it started forming once the dendrites have reached the drop surface in the case of central nucleation. The formed ice morphology at the first freezing stage predefined the splintering probability. We assume that stresses needed to break the ice shell arose from freezing of the water in the interdendritic spaces. Under this assumption, the number of possible splinters/fragments was proportional to the number of dendrites, and the maximum rate of splintering/fragmentation occurred within a temperature range of about −10 °C to −20°C, in agreement with available laboratory and in situ measurements. At temperatures < −25°C, freezing did not lead to the formation of significant stresses, making splintering unlikely. The number of dendrites increased with drop size, causing a corresponding increase in the number of splinters. Examples of morphology that favors drop cracking are presented, and the duration of the freezing stages is evaluated. Sensitivity of the freezing process to the surface fluxes is discussed.

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In-situ synthesis via laser metal deposition of a lean Cu–3.4Cr–0.6Nb (at%) conductive alloy hardened by Cr nano-scale precipitates and by Laves phase micro-particles

Acta Materialia ◽

10.1016/j.actamat.2020.07.035 ◽

2020 ◽

Vol 197 ◽

pp. 330-340 ◽

Cited By ~ 1

Author(s):

Anoop R Kini ◽

Dora Maischner ◽

Andreas Weisheit ◽

Dirk Ponge ◽

Baptiste Gault ◽

...

Keyword(s):

In Situ Synthesis ◽

Metal Deposition ◽

Laves Phase ◽

Laser Metal Deposition ◽

Nano Scale ◽

Micro Particles

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On diffusion and interfacial enrichment of boron in the Laves phase: an in situ TEM-heat-treatment study on newly developed 3Co–3W–9Cr steel

Philosophical Magazine Letters ◽

10.1080/09500839.2019.1670880 ◽

2019 ◽

Vol 99 (8) ◽

pp. 284-291

Author(s):

P. S. M. Jena ◽

S. Tripathy ◽

B. Mahato ◽

J. K. Sahu

Keyword(s):

Heat Treatment ◽

Laves Phase ◽

In Situ Tem ◽

9Cr Steel

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Fabrication and characterization of TiB2-reinforced functionally graded aluminum matrix material

Industrial Lubrication and Tribology ◽

10.1108/ilt-12-2019-0538 ◽

2020 ◽

Vol 72 (10) ◽

pp. 1147-1152

Author(s):

Ömer Savaş

Keyword(s):

Wear Rate ◽

Abrasive Wear ◽

Peer Review ◽

Centrifugal Force ◽

Matrix Material ◽

Aluminum Matrix ◽

Functionally Graded ◽

Aluminum Matrix Composites ◽

Content Type

Purpose This study aims to investigate the production and abrasive wear rate of functionally graded TiB2/Al composites. TiB2 particles have been spontaneously formed in liquid matrix using in situ technique. The properties of composites such as hardness, abrasive wear rate and microstructure have been examined. Design/methodology/approach In situ TiB2 reinforcement phase was synthesized by using a liquid Al–Ti–B system. A semi-solid composite (Al(l)-TiB2(s)) prepared at 900°C was solidified under a centrifugal force to both grade functionally and give the final shape to materials. Abrasive wear test of materials was conducted using the pin-on-disk method at room temperature. The wear tests were carried out with two different loads of 1 Newton (N) and 2 N, a sliding velocity of 3.5 m s−1 and a sliding distance of 75 m. Findings This research provided the following findings; TiB2 particles can be successfully synthesized with in situ reaction technique in molten aluminum. It was determined that abrasive wear rate increases with increasing load and decreases with increasing TiB2 reinforcement content within matrix. Originality/value In previous studies, there have been many trials on the in situ production of TiB2-reinforced aluminum matrix composites. However, there are few studies on production of in situ TiB2-reinforced aluminum matrix functionally graded materials. At the same time, there is no study that the properties of composite, such as hardness and abrasive wear rate, are examined together according to centrifugal force. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2019-0538/

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From the Laves Phase CaRh2 to the Perovskite CaRhH3–in Situ Investigation of Hydrogenation Intermediates CaRh2Hx

Inorganic Chemistry ◽

10.1021/acs.inorgchem.8b01547 ◽

2018 ◽

Vol 57 (17) ◽

pp. 10925-10934 ◽

Cited By ~ 1

Author(s):

André Götze ◽

Jens Möllmer ◽

Holger Kohlmann

Keyword(s):

Laves Phase ◽

In Situ Investigation

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Coherency Strain Energy in any Crystal System: Applications to in Situ Observations of Cigm in Calcite

MRS Proceedings ◽

10.1557/proc-205-245 ◽

1990 ◽

Vol 205 ◽

Author(s):

R.S. May ◽

B. Evans

Keyword(s):

Driving Force ◽

Migration Rate ◽

Strain Energy ◽

Solute Concentration ◽

Coherency Strain ◽

Solute Diffusion ◽

Boundary Orientation ◽

In Situ Observations ◽

And Migration

AbstractIn situ observations of CIGM in CaCO3 bicrystals with a SrCO3 solute source were made. The change in boundary orientation and migration rate were compared with solute concentration. The liquid film model for coherency strain Induced migration was generalized to any non-cubic system and applied to CaCO3-SrCO3. The coherent layer was modeled as a thin film on an infinite half-space. The strain energy was found from solution of the Hooke's law expressions transformed to the appropriate coordinate system. For triclinic or monoclinic films the strain tensor was found by an eigenvector decomposition of the transformation matrix that defined the lattice parameter change with composition. High anisotropy of Vegard's law constants for CaCO3-SrCO3 caused (111) to have the lowest coherency strain per unit solute. Surfaces perpendicular to (111) in coherent equilibria were predicted to have half the solute concentration and three times the migration driving force of those perpendicular to (111). However, no correlation between solute concentration and boundary orientation was observed. Ambiguous and contradictory evidence for a relationship between solute concentration, boundary orientation, and migration rate was found. The self-stress state of a grain boundary in a solute diffusion field may be better modelled as hydrostatic rather than plane stress. Hydrostatic compression may interact with the boundary excess volume and cause a PV driving force for migration. Predictions based on coherent equilibrium at a surface have not been tested for that geometry in calcite; they should be tested before they are applied to grain boundaries.

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Investigation on Mechanism of Faceted Cellular Array Growth in International Space Station

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.323-325.533 ◽

2012 ◽

Vol 323-325 ◽

pp. 533-537 ◽

Cited By ~ 2

Author(s):

Y. Inatomi ◽

I. Yoshizaki ◽

K. Sakata ◽

T. Shimaoka ◽

T. Sone ◽

...

Keyword(s):

International Space Station ◽

Space Station ◽

Solute Concentration ◽

Butyl Alcohol ◽

Cellular Growth ◽

International Space ◽

Cellular Array ◽

Microgravity Conditions ◽

Solid Liquid

Anin situobservation experiment of faceted cellular growth was carried out using transparent organic alloy, salol -t-butyl alcohol, in microgravity conditions on the International Space Station. The temperature and solute concentration fields in the vicinity of the solid-liquid and the growth rate were simultaneously measured by microscopic interferometers.

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