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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 30 for “"undercooling"”.
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Undercooling and rapid solidification of Fe-Cr-Ni ternary alloys
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.
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Rapid Solidification and Undercooling of Aluminum-Germanium Alloys: Characterization and Control of Microstructure (Metastability, Metallic Glass, Electron Microscopy)
A determination of the importances of undercooling and cooling rate in the microstructural development of Al-Ge alloys during rapid solidification has been carried out. A new technique has been developed which allows for such determinations to be performed directly in a transmission electron …
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On the Melting and Crystallization of Linear Polyethylene, Poly(ethylene oxide) and Metallocene Linear Low-Density Polyethylene
… the initial lamellar thickness vs. reciprocal of undercooling plot were similar within the limits of experimental error to those obtained here through the non-linear Hoffman-Weeks method. In the next step, the Lauritzen-Hoffman (LH) secondary nucleation theory was modified to account for the …
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Microstructure and mechanical properties of biomedical alloys produced by Rapid Manufacturing techniques
… characteristic of RM techniques is the large undercooling the parts undergo during the process. This undercooling results in peculiar, very fine, metastable microstructures, associated to peculiar mechanical behaviour. Metastable microstructures can change on post-melting operations, making …
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Effects of an electric current applied to metals during solidification
… that there might be a trend of increased undercooling in a metallic sample as more current was applied. An expansion of those experiments was commenced to A) confirm this trend and B) explore its potential causes, with the ultimate goal of being able to reliably change undercooling in a …
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Molecular dynamics modeling of orientation-induced nucleation in short alkanes : toward molecular modeling of flow-induced crystallization in polymers
… has been found to increase with the level of undercooling Tm - T decrease, consistent with the classical nucleation theory. Our atomnistic molecular dynamics simulation model is even tractable at the small levels of undercooling, thus clearly demonstrating the effects of orientation (melt …
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The influence of thermal history on the hot ductility of Ti containing C Mn Al and C Mn Nb Al steels
… s '. The influence of the addition of a 100°C undercooling step into the test cycle with a subsequent re-heat to the test temperature (at 500°C/min) was investigated. It has been shown that Ti additions, both to C-Mn-Al and C-Mn-Nb-Al steels impair hot ductility. Also, Nb containing steels give …
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Containerless processing of stainless steel
… ferritic phase, defining a value of the critical undercooling for metastable bee nucleation significantly lower than previously reported. Phase selection during recalescence was successfully performed by use of different trigger materials: at temperatures below the bee To , a bee Fe trigger …
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Strain-induced crystallization of crosslinked polyethylene
… mechanism regardless of draw ratio and degree of undercooling. The crystal growth rate exhibited a normal exponential decay with the degree of undercooling as predicted by theories. The size of the critical growth nucleus is found to increase exponentially with the concentration of chemical …
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Microstructure and Microchemistry of Rapidly Solidified Nickel-Base Powders
… chemical segregation on a very fine scale. Bulk undercooling experiments were also conducted and the microstructures of these samples were compared to those of the rapidly solidified powders. Computer calculations were performed to simulate the solidification of individual powder particles using …
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The kinetics of growth competition during rapid solidification of ternary steel alloys
… (Vss ) was confirmed to be independent of undercooling and was determined to be a function of solute concentration. Because the build-up of solute ahead of the dendrite acts to slown down the growing tip, growth velocity decreases as solute concentation increases. It has been shown …
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Non-equilibrium energy transfer and phase change during intense picosecond laser-metal interactions
… produces a large degree of superheating and undercooling during melting and solidification. First, this work investigates experimentally non-equilibrium heating processes during intense picosecond laser heating of metal films. Results show excellent agreement with predictions of the two-step …
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Development of (Re)BaCuO Coated Conductors by Liquid Phase Epitaxy
… carefully controlled growth temperature and undercooling. The film growth mode (c- or a,b-oriented) is determined by the growth rate, which is directly related to the level of RE supersaturation that could be controlled by the undercooling used along with the amount of total RE solubility in …
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Crystallization and melting behavior of (ε-caprolactone)-based homopolymer and triblock copolymer
… growth rates and the inverse relation between undercooling and the lamellar thickness. Claims have appeared in the literature that analysis of growth rate data using the LH theory does not yield physically meaningful parameters. This work will show that the lateral and fold interfacial free …
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Pattern formation in systems far from equilibrium
… in the way growth velocity scales with undercooling. Scaling behaviour in the evolution of interfacial instability is found, in a planar geometry, indicating a non-linear selection of a unique length-scale, insensitive to short length-scale fluctuations.
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Rapid Solidification Processing of High Temperature and Reactive Alloys
… thermal treatments to determine the extent of undercooling and microstructural modifications.
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Mathematical modelling of the onset of transformation from austenite to pearlite under non-continuous cooling conditions
… which are based on the cooling rate or degree of undercooling. To develop a method that is capable of predicting the onset of transformation in the steel, applicable to industrial processing conditions, a theoretical study has been conducted to critically examine the consequences and implications …
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Crystallization and Melting Studies of Poly(ε-caprolactone) and Poly(ethylene oxide) using Flash™ Differential Scanning Calorimetry and Preparation and Characterization of Poly(δ-valerolactone) Fractions
… equation that included a non-linear undercooling dependence for the kinetic fold surface free energy upon crystallization and permitted accurate modeling of the observed melting behavior. The isothermal crystallization rates of four narrow molecular weight poly(ethylene oxide) …
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Electrochemically driven phase transformation in energy storage compounds
… which are the electrical analogs to undercooling and superheating. So far, overpotential effects on phase stability and transformation mechanisms have not been studied in detail. Here we use synchrotron X-ray diffraction performed in-situ during potentiostatic and galvanostatic …
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Numerical simulation of dendritic growth of binary alloys
… under a variety of conditions show that the undercooling and surface tension are the main factors that determine the final dendritic structures. In simulations of alloy solidification, where both the energy and solutal concentration equations are solved, the results for the onset of interface …
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