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Master's Dissertation
DOI
Document
Author
Full name
Cecilio Alvares da Cunha
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1986
Supervisor
Committee
Ramanathan, Lalgudi Venkataraman (President)
Ambrozio Filho, Francisco
Goldenstein, Helio
Title in Portuguese
Estudo da cinética da transformação de fase no estado sólido UAl3 + Al → UAl4
Keywords in Portuguese
cinética
ligas de alumínio
transformações de fase
Abstract in Portuguese
A cinética da transformação de fase UAl3 + Al → UAl4 foi estudada em duas ligas Al-U, com 31,4 % e 33,4 % U em peso respectivamente, através de metalografia quantitativa. Os resultados mostraram que esta transformação é um processo de nucleação e crescimento termicamente ativado, com a nucleação ocorrendo heterogeneamente nas interfaces UAl3/AI(∞) e o crescimento sendo controlado por difusão em volume. A energia de ativação empírica do processo foi determinada, cujo valor médio é da ordem de 54,8 kcal/mol. Foi verificado que a cinética de crescimento da fase UAl4 obedece uma lei parabólica. As interfaces UAl4/ UAl3 e UAl4/Al(∞) migram em direções opostas, sendo que a velocidade da interface UAl4/ UAl3 é aproximadamente cinco vezes maior que aquela da interface UAl4/Al(∞). O coeficiente de difusão química do Al e do U na fase UAl4 foi avaliado ser da ordem de 10-9 cm 2/s a 600°C.
Title in English
Kinetics of solid state phase transformation UAl3 + Al → UAl4
Keywords in English
aluminium alloys
kinetics
phase transformations
Abstract in English
The kinetics of phase transformation UAl3 + Al → UAl4 of two Al-U alloys, with 31.4 and 33.4 wt % U respectively, was studied by quantitative microscopy. The results have shown that this transformation is a nucleation and thermally activated growth process. The nucleation occurs heterogeneously at the UAl3/AI(∞) interfaces and growth is controlled by volume diffusion. The empirical activation energy of the process was determined, whose mean value is of about 54.8 kcal/mol. It was verified that a parabolic growth law is obeyed. The UAl4/ UAl3 and UAl4/Al(∞) interfaces migrates in opposite directions, with the UAl4/ UAl3 interface velocity was approximately 5 times greater than that of UAl4/Al(∞) interface. The chemical diffusion coefficient of Al and U in the UAl4 phase were evaluated to be of the order of 10-9 cm 2/s at 600°C.
 
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1986CunhaEstudo.pdf (3.46 Mbytes)
Publishing Date
2012-11-09
 
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