scholarly journals Formation of Interfacial Reaction Layers in Al2O3/SS 430 Brazed Joints Using Cu-7Al-3.5Zr Alloys

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 990 ◽  
Author(s):  
Hoejun Heo ◽  
Hyeonim Joung ◽  
Keeyoung Jung ◽  
Chung-Yun Kang
Keyword(s):  
Liquid Phase ◽  
Interfacial Reaction ◽  
Eutectic Temperature ◽  
Liquid Phases ◽  
430 Stainless Steel ◽  
Brazed Joints ◽  
Solid Phases ◽  
Α Al2o3 ◽  
Kinetics Of ◽  
Liquid And Solid Phases

The formation of interfacial reaction layers was investigated in an α-Al2O3/430 stainless steel (SS430) joint brazed using a Cu-7Al-3.5Zr active brazing alloy. Brazing was conducted at above its eutectic temperature of 945 °C and below liquidus 1045 °C, where liquid and solid phases of the brazing alloys coexists. At 1000 °C, the liquid phase of the brazing alloy was wet onto the α-Al2O3 surface. Zr in the liquid phase reduced α-Al2O3 to form a continuous ZrO2 layer. As the dwell time increased, Zr in the liquid phases near α-Al2O3 interface was used up to thicken the reaction layers. The growth kinetics of the layer obeys the parabolic rate law with a rate constant of 9.25 × 10−6 cm·s−1/2. It was observed that a number of low yield strength Cu-rich particles were dispersed over the reaction layer, which can release the residual stress of the joint resulting in reduction of crack occurrence.

scholarly journals Application of equilibrium phase diagrams for calculation of segregation kinetics during two-component melt cooling

2020 ◽  
Vol 63 (2) ◽  
pp. 129-134
Author(s):  
A. D. Drozin ◽  
E. Yu. Kurkina
Keyword(s):  
Liquid Phase ◽  
Equilibrium State ◽  
Cross Section ◽  
Diffusion Coefficients ◽  
Solid Phase ◽  
Equilibrium Phase ◽  
Minimum Size ◽  
Two Component ◽  
Solid Phases ◽  
Liquid And Solid Phases

According to the equilibrium state diagrams, when the melt is cooled to a certain temperature below liquidus, compositions of liquid and solid phases are uniquely determined by corresponding curves in the diagram. However, it does not happen in reality. For equilibrium (which the diagram describes), it is necessary that the melt is maintained indefinitely at each temperature, or thermal conductivity of liquid and solid phases, and the diffusion coefficients of their components, are infinitely large. We made an attempt to find out how these processes occur in reality. In this work, we consider the growth of individual crystal during cooling of a two-component melt. Mathematical model is constructed based on the following. 1. The melt area with volume corresponding to one grain, the periphery of which is cooled according to a certain law, is considered. 2. At the initial instant of time, a crystal nucleus of a certain minimum size is in the liquid. 3. At the surface of crystal, compositions of liquid and solid phases correspond to equilibrium state diagram at a given temperature on its surface. 4. Changes in temperature and composition in liquid and solid phases occur according to the laws of heat conduction and diffusion, respectively. As the melt gets cold and the crystal grows, the liquid phase is enriched in one component and depleted in another, the solid phase – on the contrary. Since the diffusion coefficients of the components in the solid phase are small, the composition of the crystal does not have time to completely equalize its cross section. The model proposed in the work allows us to study this phenomenon, to calculate for each cooling mode how the composition of the crystal will vary over its cross section. The calculations have shown that the temperature equalization occurs almost instantly, and composition of the liquid phase equalizes much slower. Equalization of the solid phase composition does not occur in the foreseeable time. The results of the work will help to improve technology of generation of alloys with an optimal structure.

scholarly journals Solid-liquid phase equilibria in the ternary systems H2O+ZnCl2+NaCl at temperatures of 298, 313 and 333 K

2021 ◽  
pp. 53-53
Author(s):  
Sevilay Demirci ◽  
Vedat Adiguze ◽  
Omer Sahin
Keyword(s):  
Liquid Phase ◽  
Phase Equilibria ◽  
Solid Phase ◽  
Ternary Systems ◽  
Viscosity Data ◽  
Isothermal Method ◽  
Chloride Water ◽  
Solid Phases ◽  
Solid Liquid ◽  
Liquid And Solid Phases

In this study, an economic separation method was suggested with the use of phase equilibria in order to ensure the recycling of ZnCl2 whose industrial waste amount is very high and to prevent it to form an environmental pollution. Sodium chloride-zinc chloride-water systems were examined with the isothermal method at temperatures of 298, 313 and 333 K. The analyses of the liquid and solid phases were used to determine the composition of the solid phase using the Schreinemakers graphic method. The solid-liquid phase equilibrium and viscosity data belonging to all ternary systems were identified and the solubility and viscosity changes with temperature were compared. The viscosity values were inversely proportional to the temperature as the amount of ZnCl2 in the solution increased. NaCl, 2NaCl ZnCl2 nH2O (n: 2, 0), ZnCl2 salts were observed at 298, 313, 333 K in the solid phases which are at equilibrium with the liquid phase at the invariant point.

THE DISTRIBUTION OF CHLOROPHYLL IN RUMEN CONTENTS AND THE ONSET OF BLOAT IN CATTLE

1986 ◽  
Vol 66 (1) ◽  
pp. 97-102 ◽  
Author(s):  
W. MAJAK ◽  
J. W. HALL ◽  
R. E. HOWARTH
Keyword(s):  
Particulate Matter ◽  
Liquid Phase ◽  
Key Words ◽  
Rumen Fluid ◽  
Gas Production ◽  
Solid Phases ◽  
Relationship Of ◽  
The Relationship ◽  
Liquid And Solid Phases ◽  
Chlorophyll Concentrations

Chlorophyll levels in rumen contents from the dorsal and ventral sac were examined before alfalfa ingestion to determine the relationship of chloroplast particles to the onset of pasture bloat in cattle. Chlorophyll concentrations were significantly higher in cattle that subsequently bloated than in those that did not. The higher levels were observed in both the liquid and solid phases of rumen contents from cattle predisposed to bloat but the liquid phase showed a greater increase. Chlorophyll levels were uniformly distributed in the rumen with little or no difference between samples obtained from the ventral and dorsal sacs. In agreement with previous results, animals predisposed to bloat showed higher rates of gas production and greater buoyancy of particulate matter in prefeeding rumen fluid. The results suggest that chloroplast particles in the rumen have a slower rate of clearance in bloating animals than in nonbloating ones. Key words: Bloat, alfalfa, cattle, rumen, chlorophyll, chloroplast particles

Computational Model of Phase Transformations in Thermo-Chemical Cathodes Using Kinetic Approach

2012 ◽  
Vol 510-511 ◽  
pp. 9-14
Author(s):  
A.A. Kavokin ◽  
I.H. Kazmi ◽  
B. Munir
Keyword(s):  
Heat Equation ◽  
Solid Phase ◽  
State Diagram ◽  
Two Phase ◽  
One Dimensional ◽  
Self Similar Solution ◽  
Self Similar ◽  
Solid Phases ◽  
Kinetics Of ◽  
Liquid And Solid Phases

The paper presents the results of modeling of the processes of phases transformations occurring in cathode of plasmatron with zirconium insertion. Model describes temperature and liquid-solid phase transformation in cathode considering kinetics of transformation in accordance with a state diagram. The comparison between one-dimensional mathematical models was exploited for estimation of the kinetics coefficient. First model is based on well-known heat equation with Stefans condition on the free boundary between liquid and solid phases [. The standard analytical self-similar solution for two-phase case is applied. In the second model, for heat equation instead of Stefans conditions, differential equations of kinetics are used.

scholarly journals Phases and Phase Transitions in the First Few Layers of Methane, Argon and Krypton Adsorbed on Graphite

1992 ◽  
Vol 280 ◽  
Author(s):  
David Goodstein ◽  
P. Day ◽  
M. LaMadrid ◽  
M. Lysek
Keyword(s):  
Phase Transitions ◽  
Phase Diagrams ◽  
Capillary Condensation ◽  
Equilibrium Phase ◽  
Scanning Calorimetry ◽  
Liquid Phases ◽  
Thermodynamic Measurements ◽  
Solid Phases ◽  
Liquid And Solid Phases

ABSTRACTThe equilibrium phase diagrams of monolayers of many substances adsorbed on graphite have long been studied as examples of 2-dimensional (2D) matter. One typically observes 2D gas and liquid phases, and solid phases that may be commensurate or incommensurate with the substrate lattice. Many experimental techniques have been used, but thermodynamic measurements are generally the most useful for tracing out phase boundaries.Recent advances in technique have made it possible to use thermodynamic measurements to study the phase diagrams of the second and higher layers, up to the fifth or sixth. These advances include ultra high resolution scanning calorimetry, and a detailed understanding of the role of capillary condensation in corners and pores of the graphite foam substrate. We find a rich array of phases and phase transitions in multilayer methane, argon and krypton. The second and third layers typically have distinct 2D gas, liquid and solid phases evidenced by 2D triple points and critical points. We observe phase transitions between solid phases that are commensurate and incommensurate with the layer below. We also observe melting of the first layer at higher temperatures, even when one to five additional layers are adsorbed on top of it.In argon and krypton, but not in methane, a strange new phenomenon is observed at temperatures above the gas-liquid critical point of the nth layer for n> 3. Below that temperature, nthlayer gas coexists with a condensed nth layer. At some temperature above it, a new coexistence region is observed in which a partial nth layer coexists with a partial n + 1st layer. This behavior is thought to be evidence for a theoretically predicted phase transition of the bulk interface, called the preroughening transition.

The Vibrational Spectra of Methyl Cyanoacetate and Methyl Cyanoacetate-d3

1974 ◽  
Vol 52 (17) ◽  
pp. 3057-3062 ◽  
Author(s):  
Deepali Sinha ◽  
J. E. Katon
Keyword(s):  
Liquid Phase ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Vibrational Assignment ◽  
Conformational Isomers ◽  
Solid Phases ◽  
Liquid And Solid Phases

The i.r. spectra of methyl cyanoacetate in both liquid and solid phases and of methyl cyanoacetate-d3 in the liquid phase have been recorded in the region 4000–250 cm−1. The Raman spectra of both the compounds in the liquid phase have also been recorded. A tentative vibrational assignment has been made both for the light and the heavy ester. Evidence is presented for the existence of conformational isomers in the liquid phase.

Numerical Study of the Influence of Diffusion-Governed Growth Kinetics of Ternary Alloy on Macrosegregation

2014 ◽  
Vol 790-791 ◽  
pp. 85-90 ◽  
Author(s):  
Meng Huai Wu ◽  
Abdellah Kharicha ◽  
Andreas Ludwig
Keyword(s):  
Ternary Alloy ◽  
Growth Kinetics ◽  
Growth Kinetic ◽  
Numerical Study ◽  
Diffusion Kinetics ◽  
Initial Stage ◽  
Solid Phases ◽  
Kinetics Of ◽  
Liquid And Solid Phases

This article is to assess the modeling treatment of the growth kinetics (finite or infinite diffusion in liquid and solid phases) during solidification and its influence on the calculation of macrosegregation. A model of diffusion-governed growth kinetic for ternary alloy is developed and used for this assessment. Solidification of a 2D casting (50 x 50 mm2) of a ternary alloy (Fe-0.45 wt.% C-1.06 wt.%Mn) is considered. The result shows that finite diffusion in liquid, important for the initial stage of solidification, plays very important role in the formation of macrosegregation. Moreover, the role of the finite diffusion kinetics in the formation of macrosegregation shows differently in the two extreme cases of solidification structures (columnar or equiaxed).

Computation of Microsegregation and Microstructure in Solidification with Fluid Convection

1998 ◽  
Vol 538 ◽  
Author(s):  
D. Juric
Keyword(s):  
Fluid Flow ◽  
Dendritic Solidification ◽  
Liquid Phases ◽  
Fluid Convection ◽  
Solidification Morphology ◽  
Full Coupling ◽  
Solid Phases ◽  
Single Field ◽  
Quiescent Liquid ◽  
Liquid And Solid Phases

AbstractThe effects of fluid flow on the dendritic solidification morphology of pure materials is studied using a computational methodology based on a two-dimensional front tracking/finite difference method. A general single-field formulation is presented for the full coupling of phase change, fluid flow, and heat transport in both the solid and liquid phases. This formulation accounts for interfacial rejection/absorption of latent heat, interfacial anisotropies, discontinuities in material properties between the liquid and solid phases, shrinkage/expansion upon solidification and motion and deformation of the solid. Numerical results are presented for the dendritic solidification of pure succinonitrile in a shear flow. Comparison with solidification into a quiescent liquid indicates that fluid convection increases the overall rate of solidification while the growth rate of the leading dendrite tip is unchanged.

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