Crystallization of undercooled liquid spinodals: Part II

1999 ◽  
Vol 14 (9) ◽  
pp. 3663-3667 ◽  
Author(s):  
K. L. Lee ◽  
H. W. Kui
Keyword(s):  
Phase Separation ◽  
Latent Heat ◽  
Spinodal Decomposition ◽  
Liquid State ◽  
Morphological Changes ◽  
Microstructural Analysis ◽  
The Other ◽  
Undercooled Liquid ◽  
Metastable Liquid ◽  
Undercooled Melt

We demonstrated in “Phase separation in undercooled molten Pd80Si20: Part I” that when a molten Pd80Si20 ingot is undercooled into its undercooling regimen with ΔT ≥ 220 K (ΔT = T1 – T, where T1 is the liquidus and T is the temperature of the undercooled melt), liquid-state phase separation by spinodal decomposition occurs. On crystallization, one of the metastable liquid spinodals becomes Pd3Si, whereas the other one turns into Pd9Si2. In both cases, Pd particles precipitate out. Microstructural analysis indicates the Pd3Si subnetwork forms first. It then acts as a seed for the subsequent crystallization of the remaining undercooled melt, which finally forms the Pd9Si2 dendrites. As crystallization proceeds, latent heat and volume contraction bring about morphological changes.

Metastable liquid phase separation in undercooled molten Pd40.5Ni40.5P19

1997 ◽  
Vol 12 (2) ◽  
pp. 314-317 ◽  
Author(s):  
C. W. Yuen ◽  
K. L. Lee ◽  
H. W. Kui
Keyword(s):  
Phase Separation ◽  
Spinodal Decomposition ◽  
Liquid State ◽  
Microstructural Analysis ◽  
Nucleation And Growth ◽  
Transition Regime ◽  
Metastable Liquid ◽  
Temperature Liquid ◽  
Kinetic Crystallization ◽  
Metastable Liquid Phase Separation

It was demonstrated that molten Pd40.5Ni40.5P19 undergoes liquid state phase separation in the undercooling regime δT = T1 − T where T1 is the liquidus of Pd40.5Ni40.5P19 and T is the kinetic crystallization temperature. Liquid state phase separation by nucleation and growth takes place for δT ≤ 60 K while that by spinodal decomposition occurs for δT ≥ 100 K. Microstructural analysis of the undercooled specimen obtained in the undercooling regime of 60 ≤ δT ≤ 100 K indicates that it is the transition regime. Finally, it was found that when undercooled molten Pd40.5Ni40.5P19 undergoes liquid state spinodal decomposition, it first decomposes into two liquid networks, which is finally replaced by a system of three liquid networks.

Formation of Bulk Nanostructured Materials by Rapid Solidification

2000 ◽  
Vol 15 (7) ◽  
pp. 1605-1611 ◽  
Author(s):  
W. H. Guo ◽  
L. F. Chua ◽  
C. C. Leung ◽  
H. W. Kui
Keyword(s):  
Surface Tension ◽  
Rapid Solidification ◽  
Spinodal Decomposition ◽  
Liquid State ◽  
Nanostructured Material ◽  
Synthesis Process ◽  
Undercooled Liquid ◽  
Metastable Liquid ◽  
Characteristic Wavelength ◽  
Eutectic Melt

When a eutectic melt is undercooled below its liquidus T1 by a critical amount, it undergoes metastable liquid-state spinodal decomposition. The resulting morphologies can be described as intermixing undercooled liquid networks of characteristic wavelength λ. At a temperature substantially below T1, λ can be <100 nm. When λ ≤ 100 nm, the undercooled liquid networks break up into nanometer-size droplets/strips driven apparently by surface tension. The morphologies of the tiny droplets/strips can be frozen by subsequent crystallization. The as-crystallized specimen is a nanostructured material. It is microvoid free and the size of the constituent grains is rather uniform. Two systems, Pd40.5Ni40.5P19 and Pd82Si18, were chosen to illustrate the synthesis process.

Formation of bulk magnetic nanostructured Fe40Ni40P14B6 alloys by metastable liquid state phase separation

1999 ◽  
Vol 581 ◽  
Author(s):  
Q. Li ◽  
H.W. Kui
Keyword(s):  
Phase Separation ◽  
Spinodal Decomposition ◽  
Eutectic Alloy ◽  
Liquid State ◽  
Decomposition Reaction ◽  
Metastable Liquid ◽  
The One

ABSTRACTMETGLAS alloy #2826 (Fe40Ni40P14B6) is a eutectic alloy. Its melt can undergo metastable liquid state spinodal decomposition deep in the undercooling regime ΔT defined as ΔT = T1 - T where T1 is the liquidus of the alloy and T is the temperature at which the decomposition reaction takes place. Micrographs of undercooled Fe40Ni40P14B6 of ΔT = 209, 260 and 307 K were displayed. All of them exhibit refined microstructures, esp. the one with the largest ΔT.

Growth of InGaN Films by MBE at the Growth Temperature of GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
R. Singh ◽  
T.D. Moustakas
Keyword(s):  
Phase Separation ◽  
Spinodal Decomposition ◽  
Growth Temperature ◽  
Composition Range ◽  
The Other ◽  
Entire Composition Range ◽  
Other Hand ◽  
Ingan Alloys

ABSTRACTWe report the growth of InGaN alloys over practically the entire composition range at the growth temperature of GaN (700–800 °C) by MBE. We found that when the grown films are thick (> 0.3 μm), incorporation of more than about 30% indium results in phase separation of InN, which is consistent with spinodal decomposition. On the other hand we discovered that such phase separation is absent in thin InGaN films ( < 600Å) grown as GaN/InGaN/GaN heterostructures. In such configurations we were able to incorporate up to 81% In, which is the highest yet reported.

Quantitative Microstructural Analysis of a Ni-based Superalloy After Different Heat Treatments

2020 ◽  
Vol 70 (12) ◽  
pp. 4519-4524
Keyword(s):  
Heat Treatment ◽  
Internal Structure ◽  
Microstructural Analysis ◽  
Temperature Treatment ◽  
Heat Treatments ◽  
Metal Melts ◽  
Metallic Inclusions ◽  
Undercooled Melt ◽  
Super Alloy

The efficiency of time-temperature treatment (T-TT) on metal melts can be microstructurally analysed through their degree of purity in non-metallic inclusions. In the case of the Ni-based super alloy under discussion (MSRR 7045) the heat treatment was the undercooling consequences both on the durability of the casting environment (ingots-refractories) and on the internal structure of the metal (porosity, microstructural isotropy). Keywords: time-temperature treatment, undercooled melt, non-metallic inclusions, purity, microstructural isotropy

scholarly journals Hydrometeor and latent heat profiles of tropical cyclones Conson, Ivan and Catarina using PR/TRMM data

2010 ◽  
Vol 25 (2) ◽  
pp. 156-174 ◽  
Author(s):  
Marcelo Barbio Rosa ◽  
Augusto Pereira Filho ◽  
Prakki Satyamurty
Keyword(s):  
Water Content ◽  
Latent Heat ◽  
High Water ◽  
Mean Value ◽  
The Other ◽  
High Water Content ◽  
Hurricane Ivan ◽  
Two Systems ◽  
Low Levels ◽  
Ice Content

ABSTRACT Microphysical and thermodynamical features of two tropical systems, namely Hurricane Ivan and Typhoon Conson, and one sub-tropical, Catarina, have been analyzed based on space-born radar PR measurements available on the TRMM satellite. The procedure to classify the reflectivity profiles followed the Heymsfield et al (2000) and Steiner et al (1995) methodologies. The water and ice content have been calculated using a relationship obtained with data of the surface SPOL radar and PR in Rondonia State in Brazil. The diabatic heating rate due to latent heat release has been estimated using the methodology developed by Tao et al (1990). A more detailed analysis has been performed for Hurricane Catarina, the first of its kind in South Atlantic. High water content mean value has been found in Conson and Ivan at low levels and close to their centers. Results indicate that hurricane Catarina was shallower than the other two systems, with less water and the water was concentrated closer to its center. The mean ice content in Catarina was about 0.05 g kg-1 while in Conson it was 0.06 g kg-1 and in Ivan 0.08 g kg-1. Conson and Ivan had water content up to 0.3 g kg-1 above the 0ºC layer, while Catarina had less than 0.15 g kg-1. The latent heat released by Catarina showed to be very similar to the other two systems, except in the regions closer to the center.

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