Arborescent polymers: Designed macromolecules with a dendritic structure

Three unusual Ru-rich phases have been identified in a multicomponent Ni-base single crystal superalloy, including a L21 Ru2AlTa Heusler phase, a B2 RuAl phase and a hcp Re(Ru)-rich δ phase. These phases have their own preferential precipitation location within the dendritic structure. No conventional topologically-close-packed (TCP) phases have been observed with thermal exposure at 950oC for 1500 hours.

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Development of Al–Mg–Si alloy performance by addition of grain refiner Al–5Ti–1B alloy

Science Progress ◽

10.1177/00368504211029469 ◽

2021 ◽

Vol 104 (2) ◽

pp. 003685042110294

Author(s):

Khaled Abd El-Aziz ◽

Emad M Ahmed ◽

Abdulaziz H Alghtani ◽

Bassem F Felemban ◽

Hafiz T Ali ◽

...

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Corrosion Resistance ◽

Testing Machine ◽

Dendritic Structure ◽

Grain Refiner ◽

Corrosion Properties ◽

Average Grain Size ◽

Structural Applications ◽

Alloy Addition

Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al–5Ti–1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al–Mg–Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al–Mg–Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al–Mg–Si alloy were improved by GR alloy addition. GR alloy addition to Al–Mg–Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al–Mg–Si alloy.

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Impact of Solidification on Inclusion Morphology in ESR and PESR Remelted Martensitic Stainless Steel Ingots

Metals ◽

10.3390/met11030408 ◽

2021 ◽

Vol 11 (3) ◽

pp. 408

Author(s):

Ewa Sjöqvist Persson ◽

Sofia Brorson ◽

Alec Mitchell ◽

Pär G. Jönsson

Keyword(s):

Stainless Steel ◽

Martensitic Stainless Steel ◽

Dendritic Structure ◽

Steel Grade ◽

Solidification Structure ◽

Production Scale ◽

Steel Grades ◽

Steel Ingots ◽

Columnar Dendritic Structure ◽

The Impact

This study focuses on the impact of solidification on the inclusion morphologies in different sizes of production-scale electro-slag remelting (ESR) and electro-slag remelting under a protected pressure-controlled atmosphere, (PESR), ingots, in a common martensitic stainless steel grade. The investigation has been carried out to increase the knowledge of the solidification and change in inclusion morphologies during ESR and PESR remelting. In order to optimize process routes for different steel grades, it is important to define the advantages of different processes. A comparison is made between an electrode, ESR, and PESR ingots with different production-scale ingot sizes, from 400 mm square to 1050 mm in diameter. The electrode and two of the smallest ingots are from the same electrode charge. The samples are taken from both the electrode, ingots, and rolled/forged material. The solidification structure, dendrite arm spacing, chemical analyzes, and inclusion number on ingots and/or forged/rolled material are studied. The results show that the larger the ingot and the further towards the center of the ingot, the larger inclusions are found. As long as an ingot solidifies with a columnar dendritic structure (DS), the increase in inclusion number and size with ingot diameter is approximately linear. However, at the ingot size (1050 mm in diameter in this study) when the center of the ingot converts to solidification in the equiaxial mode (EQ), the increase in number and size of the inclusions is much higher. The transition between a dendritic and an equiaxial solidification in the center of the ingots in this steel grade takes place in the region between the ingot diameters of 800 and 1050 mm.

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Topology Selectivity in On-Surface Dehydrogenative Coupling Reaction: Dendritic Structure versus Porous Graphene Nanoribbon

ACS Nano ◽

10.1021/acsnano.0c08920 ◽

2021 ◽

Vol 15 (3) ◽

pp. 4617-4626

Author(s):

Jianmin Huang ◽

Yu Pan ◽

Tao Wang ◽

Shengsheng Cui ◽

Lin Feng ◽

...

Keyword(s):

Dendritic Structure ◽

Coupling Reaction ◽

Graphene Nanoribbon ◽

Porous Graphene ◽

Dehydrogenative Coupling ◽

Structure Versus

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Microstructural Changes of Welded Zn-AI Alloy

MRS Proceedings ◽

10.1557/proc-367-391 ◽

1994 ◽

Vol 367 ◽

Author(s):

Yao Hua Zhu

Keyword(s):

Phase Transformation ◽

Early Stage ◽

Dendritic Structure ◽

Metastable Phases ◽

Grain Structure ◽

Al Alloy ◽

Cast State ◽

Microstructural Changes ◽

Fine Grain ◽

Ageing Processes

AbstractExtruded eutectoid Zn-Al alloy was welded by a melt of the same eutectoid alloy. Two different microstructures were observed in the joint part and the bulk of the welded alloy. Typical dendritic structure of as cast Zn-Al alloy was observed in the joint part of the welded alloy. The bulk ofthe welded Zn-Al alloy appeared as fine grain structure. Two different metastable phases η'T decomposed from η's of chilled as cast state and η'E of extruded state were found to be unstable during early stage of ageing. A four phase transformation occurred after the decompositions of these two metastable phases of η'T. Microstructures of both joint part and bulk of the welded alloy were investigated parallely during ageing processes.

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Morphological perceptrons with dendritic structure

The 12th IEEE International Conference on Fuzzy Systems, 2003. FUZZ '03. ◽

10.1109/fuzz.2003.1206618 ◽

2004 ◽

Cited By ~ 19

Author(s):

G.X. Ritter ◽

L. Iancu ◽

G. Urcid

Keyword(s):

Dendritic Structure

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A Model for Silicon Dendrite Growth During Laser/Plasma Deposition from a Silane Discharge

MRS Proceedings ◽

10.1557/proc-75-755 ◽

1986 ◽

Vol 75 ◽

Author(s):

Harold M. Anderson ◽

Philip J. Hargis

Keyword(s):

Laser Plasma ◽

Plasma Deposition ◽

Dendritic Structure ◽

Negative Temperature ◽

Supercooled Liquid ◽

Interface Temperature ◽

Laser Fluences ◽

Krf Laser ◽

Si Films ◽

Tip Radius

AbstractA model for dendrite growths in polycrystalline Si films formed during laser/plasma deposition with a silane discharge and a pulsed KrF laser has been developed. The model assumes a thin (less than 10 nm) amorphous silicon (a-Si) film is deposited on a substrate prior to phase transformation due to laser heating. The observed dendritic structure of the overall polycrystalline Si films is attributed to Si crystals shooting from an excessively supercooled Si liquid bath. Supercooled liquid forms since the melting point for a-Si can be reached at relatively low KrF laser fluences. Latent heat evolved at the solid-liquid interface induces an interface temperature higher than that of the melt and the requisite negative temperature gradient for absolute bath supercooling. Since the formation of an undercooled liquid by fast melting a-Si is also an important first step in explosive crystal regrowth studies, these results may have important implications for crystal growth and transient annealing. A conical approximation model is used in this study to characterize the stability of the dendrite tip in terms of local temperature gradients, i.e., the degree of undercooling at the tip of the parabolic dendrite. The degree of undercooling and hence the tip radius appears to be significantly affected by small changes in the laser fluence. Stability criteria lead to a relationship between regrowth velocity, V, and the tip radius, R, of the form VR2= constant. The size and stability of the dendrite tip is determined from a balance between the destabilizing force due to thermal diffusion and the stabilizing capillary force. Based on the observed tip radii formed at laser fluences from 0.13 to 0.25 J/cm2, the model predicts regrowth velocities in a range between 2.0 and 20 m/s – values consistent with transient annealing studies of a-Si

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Dependence of Microstructures and Mechanical Properties on the Growth Rate and Composition in Directionally Solidified Mg-Gd Alloys

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.327.82 ◽

2022 ◽

Vol 327 ◽

pp. 82-97

Author(s):

He Qin ◽

Guang Yu Yang ◽

Shi Feng Luo ◽

Tong Bai ◽

Wan Qi Jie

Keyword(s):

Mechanical Properties ◽

Growth Rate ◽

Tensile Strength ◽

Ultimate Tensile Strength ◽

Dendritic Structure ◽

Directionally Solidified ◽

Dendrite Morphology ◽

Microstructural Parameters ◽

Wide Range ◽

Microstructures And Mechanical Properties

Microstructures and mechanical properties of directionally solidified Mg-xGd (5.21, 7.96 and 9.58 wt.%) alloys were investigated at a wide range of growth rates (V = 10-200 μm/s) under the constant temperature gradient (G = 30 K/mm). The results showed that when the growth rate was 10 μm/s, different interface morphologies were observed in three tested alloys: cellular morphology for Mg-5.21Gd alloy, a mixed morphology of cellular structure and dendritic structure for Mg-7.96Gd alloy and dendrite morphology for Mg-9.58Gd alloy, respectively. Upon further increasing the growth rate, only dendrite morphology was exhibited in all experimental alloys. The microstructural parameters (λ1, λ2) decreased with increasing the growth rate for all the experimental alloy, and the measured λ1 and λ2 values were in good agreement with Trivedi model and Kattamis-Flemings model, respectively. Vickers hardness and the ultimate tensile strength increased with the increase of the growth rate and Gd content, while the elongation decreased gradually. Furthermore, the relationships between the hardness, ultimate tensile strength, the growth rate and the microstructural parameters were discussed and compared with the previous experimental results.

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Voltage behavior along the irregular dendritic structure of morphologically and physiologically characterized vagal motoneurons in the guinea pig

Journal of Neurophysiology ◽

10.1152/jn.1990.63.2.333 ◽

1990 ◽

Vol 63 (2) ◽

pp. 333-346 ◽

Cited By ~ 27

Author(s):

R. Nitzan ◽

I. Segev ◽

Y. Yarom

Keyword(s):

Steady State ◽

Guinea Pig ◽

Time Constant ◽

Dendritic Structure ◽

Input Resistance ◽

Membrane Properties ◽

Small Cells ◽

Physiological Data ◽

Motor Nucleus ◽

Cable Length

1. Intracellular recordings from neurons in the dorsal motor nucleus of the vagus (vagal motoneurons, VMs) obtained in the guinea pig brain stem slice preparation were used for both horseradish peroxidase (HRP) labeling of the neurons and for measurements of their input resistance (RN) and time constant (tau 0). Based on the physiological data and on the morphological reconstruction of the labeled cells, detailed steady-state and compartmental models of VM were built and utilized to estimate the range of membrane resistivity, membrane capacitance, and cytoplasm resistivity values (Rm, Cm, and Ri, respectively) and to explore the integrative properties of these cells. 2. VMs are relatively small cells with a simple dendritic structure. Each cell has an average of 5.3 smooth (nonspiny), short (251 microns) dendrites with a low order (2) of branching. The average soma-dendritic surface area of VMs is 9,876 microns 2. 3. Electrically, VMs show remarkably linear membrane properties in the hyperpolarizing direction; they have an average RN of 67 +/- 23 (SD) M omega and a tau 0 of 9.4 +/- 4.1 ms. Several unfavorable experimental conditions precluded the possibility of faithfully recovering ("peeling") the first equalizing time constant (tau 1) and, thereby, of estimating the electrotonic length (Lpeel) of VMs. 4. Reconciling VM morphology with the measured RN and tau 0 through the models, assuming an Ri of 70 omega.cm and a spatially uniform Rm, yielded an Rm estimate of 5,250 omega.cm2 and a Cm of 1.8 microF/cm2. Peeling theoretical transients produced by these models result in an Lpeel of 1.35. Because of marked differences in the length of dendrites within a single cell, this value is larger than the maximal cable length of the dendrites and is twice as long as their average cable length. 5. The morphological and physiological data could be matched indistinguishably well if a possible soma shunt (i.e., Rm, soma less than Rm, dend) was included in the model. Although there is no unique solution for the exact model Rm, a general conclusion regarding the integrative capabilities of VM could be drawn. As long as the model is consistent with the experimental data, the average input resistance at the dendritic terminals (RT) and the steady-state central (AFT----S) and peripheral (AFS----T) attenuation factors are essentially the same in the different models. With Ri = 70 omega.cm, we calculated RT, AFS----T, and AFT----S to be, on the average, 580 M omega, 1.1, and 13, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

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