Columnar to Equiaxed Transition in Al-Cu-Ag

2010 ◽  
Vol 649 ◽  
pp. 379-384 ◽  
Author(s):  
Els Nagels ◽  
Ludo Froyen
Keyword(s):  
Temperature Gradient ◽  
Ternary System ◽  
Cooling Rate ◽  
Binary Systems ◽  
Temperature Gradients ◽  
Alloying Element ◽  
The Third ◽  
Columnar To Equiaxed Transition ◽  
Lower Temperature

In this work the transition from columnar to equiaxed growth is studied during the solidification of the univariant eutectic L=> α(Al) + θ-Al2Cu in the ternary Al-Cu-Ag system. The columnar to equiaxed transition (CET) in a ternary system behaves very similar to the CET observed in binary systems [1]. It is observed that the CET occurs at lower temperature gradients when the amount of the third alloying element, in this case Ag, is increased. Another important solidification parameter is the cooling rate of the furnace. When the cooling rate is increased, the CET will occur at lower positions in the sample where the temperature gradient is lower.

Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys

2016 ◽  
Vol 35 (1) ◽  
pp. 37-45
Author(s):  
Maryana Zagula-Yavorska ◽  
Jolanta Romanowska ◽  
Sławomir Kotowski ◽  
Jan Sieniawski
Keyword(s):  
Thermodynamic Properties ◽  
Ternary System ◽  
Boundary Conditions ◽  
Mole Fraction ◽  
Thermodynamic Functions ◽  
Binary Systems ◽  
Interaction Parameters ◽  
Ternary Interaction ◽  
The Third ◽  
Gibbs Triangle

AbstractThermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd),µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich–Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich–Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.

scholarly journals The Effects of Molecular Packing Behavior of Small-Molecule Acceptors in Ternary Organic Solar Cells

2021 ◽  
Vol 11 (2) ◽  
pp. 755
Author(s):  
Eunhee Lim
Keyword(s):  
Solar Cells ◽  
Energy Level ◽  
Ternary System ◽  
Small Molecule ◽  
Organic Solar Cells ◽  
Orbital Energy ◽  
Working Mechanism ◽  
Energy Level Structure ◽  
The Third ◽  
Molecular Backbone

Herein, two diketopyrrolopyrrole (DPP)-based, small-molecule isomers, o- and p-DPP-PhCN, were introduced as acceptors in ternary organic solar cells (OSCs). The isomers have the same molecular backbone but differ in the positions of the cyanide (CN) substituents (ortho and para), which greatly affects their packing behavior. Ternary solar cells composed of poly(3-hexylthiophene) (P3HT):DPP-PhCN:phenyl-C61-butyric acid methyl ester (PCBM) were fabricated, and the effects of the different packing behaviors of the third component on the device performance and the working mechanism of the ternary cells were investigated. The addition of o-DPP-PhCN with a relatively high-lying lowest unoccupied molecular orbital energy level resulted in an increase in the open-circuit voltage (VOC) in the ternary devices, demonstrating the alloy-like structure of the two acceptors (o-DPP-PhCN and PCBM) in the ternary system. However, the p-DPP-PhCN-based ternary cells exhibited VOC values similar to that of a P3HT:PCBM binary cell, irrespective of the addition of p-DPP-PhCN, indicating a cascade energy-level structure in the ternary system and an effective charge transfer from the P3HT to the PCBM. Importantly, by increasing the addition of p-DPP-PhCN, the short-circuit current density increased substantially, resulting in pronounced shoulder peaks in the external quantum efficiency responses in the long-wavelength region, corresponding to the contribution of the photocurrent generated by the light absorption of p-DPP-PhCN. Despite sharing the same molecular backbone, the two DPP-PhCNs exhibited substantially different packing behaviors according to the position of their CN substituents, which also greatly affected the working mechanism of the ternary devices fabricated using the DPP-PhCNs as the third component.

scholarly journals The principle of minimum entropy production and snow structure

2004 ◽  
Vol 50 (170) ◽  
pp. 342-352 ◽  
Author(s):  
Perry Bartelt ◽  
Othmar Buser
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Entropy Production ◽  
Surface Curvature ◽  
The State ◽  
Temperature Gradients ◽  
Curvature Radius ◽  
Minimum Entropy ◽  
Snow Layer ◽  
Minimum Entropy Production

AbstractAn essential problem in snow science is to predict the changing form of ice grains within a snow layer. Present theories are based on the idea that form changes are driven by mass diffusion induced by temperature gradients within the snow cover. This leads to the well-established theory of isothermal- and temperature-gradient metamorphism. Although diffusion theory treats mass transfer, it does not treat the influence of this mass transfer on the form — the curvature radius of the grains and bonds — directly. Empirical relations, based on observations, are additionally required to predict flat or rounded surfaces. In the following, we postulate that metamorphism, the change of ice surface curvature and size, is a process of thermodynamic optimization in which entropy production is minimized. That is, there exists an optimal surface curvature of the ice grains for a given thermodynamic state at which entropy production is stationary. This state is defined by differences in ice and air temperature and vapor pressure across the interfacial boundary layer. The optimal form corresponds to the state of least wasted work, the state of minimum entropy production. We show that temperature gradients produce a thermal non-equilibrium between the ice and air such that, depending on the temperature, flat surfaces are required to mimimize entropy production. When the temperatures of the ice and air are equal, larger curvature radii are found at low temperatures than at high temperatures. Thus, what is known as isothermal metamorphism corresponds to minimum entropy production at equilibrium temperatures, and so-called temperature-gradient metamorphism corresponds to minimum entropy production at none-quilibrium temperatures. The theory is in good agreement with general observations of crystal form development in dry seasonal alpine snow.

Microstructure Development in Copper Welded by the FSW-Process

2003 ◽  
Vol 807 ◽  
Author(s):  
Therese Källgren ◽  
Rolf Sandström
Keyword(s):  
Welding Process ◽  
Mechanical Deformation ◽  
Microstructure Development ◽  
Friction Stir ◽  
Friction Heat ◽  
The Third ◽  
Lower Temperature ◽  
Weld Root ◽  
Nuclear Fuel Waste ◽  
Joining Process

ABSTRACTTo ensure safe storage of nuclear fuel waste, copper canisters are proposed as corrosion barrier. One alternative for sealing the copper canisters is Friction Stir Welding (FSW). During the joining process friction heat and mechanical deformation appear between the rotating tool and the material being welded. Liquid metal will not form, since this is a solid state welding process. Three distinct microstructural zones are developed namely the nugget, the thermo-mechanically affected zone (TMAZ) and heat-affected zone (HAZ). The nugget is in the centre of the weld, where the pin is located and where severe plastic deformation occurs that leads to recrystallisation. Surrounding the nugget, the TMAZ is only partially recrystallised, due to lower temperature increase and deformation compared to the nugget. The third zone, HAZ, surrounds the TMAZ. The initial nugget can have a classic round aluminium nugget image, when the welding conditions are cold, but the steady state nugget, is wider near the shoulder and shorter in the weld root.

scholarly journals The columnar to equiaxed transition in the directional solidification of aluminum based multicomponent alloys

2015 ◽  
Vol 68 (1) ◽  
pp. 85-90 ◽  
Author(s):  
Otávio Lima Rocha ◽  
Laércio Gouvea Gomes ◽  
Daniel Joaquim Conceição Moutinho ◽  
Ivaldo Leão Ferreira ◽  
Amauri Garcia
Keyword(s):  
Cooling Rate ◽  
Tip Growth ◽  
Solute Concentration ◽  
Unidirectional Solidification ◽  
Unsteady State ◽  
Flow Conditions ◽  
Multicomponent Alloys ◽  
Vertical Solidification ◽  
Columnar To Equiaxed Transition ◽  
Si Content

In this work the columnar to equiaxed transition (CET) was experimentally investigated in the unidirectional solidification of three aluminum based multicomponent alloys (Al-nSi-3Cu), with "n" equal to 5.5, 7.5 and 9 wt.%. The main parameters analyzed include the tip temperature gradient (GL), tip growth rate (VL), tip cooling rate (TR) and Si content. A water-cooled solidification experimental setup was developed, and specimens were solidified under unsteady state heat flow conditions. It is shown that for the alloys examined, the solute concentration influences the position of the CET, which occurs for an average cooling rate of about 1.17 0C/s. A comparative analysis between the results of this work and those from literature proposed to analyze the CET during upward vertical solidification of Al-Si alloys is reported and the results show that the end of the columnar region is abbreviated as a result of seven times higher critical cooling rate than that verified for Al-Si alloys.

scholarly journals Two-phase equilibrium in binary and ternary systems II. The system methane-ethylene III. The system methane-ethane-ethylene

1940 ◽  
Vol 176 (964) ◽  
pp. 140-152 ◽  
Keyword(s):  
Phase Equilibrium ◽  
Ternary System ◽  
Binary Systems ◽  
Ternary Systems ◽  
Two Phase ◽  
Composition Diagram ◽  
Wide Range ◽  
Binary And Ternary Systems

The liquid-vapour equilibrium of the system methane-ethylene has been determined at 0, -42 , -78, -88 and -104° C over a wide range of pressures and the results are shown on a pressure-composition-temperature diagram and by a series of pressure-composition curves. The liquid-vapour equilibrium of the ternary system methane-ethane-ethylene has been determined at -104, -78 and 0° C. Values for the two binary systems methane-ethane and methane-ethylene and for the ternary system methane-ethane-ethylene are shown on a composite pressure-composition diagram.

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