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Type: Artigo de periódico
Title: Growth and characterization of the NiAl-NiAlNb eutectic structure
Author: Ferrandini, PL
Araujo, FLGU
Batista, WW
Caram, R
Abstract: Despite presenting potential as high-temperature structural material, the NiAl intermetallic compound cannot be easily employed due to its low room temperature fracture toughness and poor creep strength. A solution for such a problem is combining such a compound with other phase using a eutectic transformation, as in the case of the NiAl NiAlNb eutectic structure. In this study, several samples containing Ni, Al and Nb were arc melted in order to evaluate the eutectic composition of this transformation, as well as the temperature at which it occurs. The resulting phases were the B2 NiAl and the Laves phase NiAlNb. It was found that the eutectic alloy occurs close to 16.0 at% Nb and the eutectic transformation temperature is 1487 degrees C. The amount of NiAl phase clearly decreases when the Nb content is raised. Thus, hypoeutectic alloys present NiAl dendrites with NiAlNb precipitated at the grain boundaries while hypereutectic alloys present primary dendrites of NiAlNb. The eutectic alloy was directionally solidified at growth rates varying from 5.0 to 50.0 mm/h. As expected, the lamellar spacing was found to decrease as the growth rate was increased. (C) 2004 Elsevier B. V. All rights reserved.
Subject: Directional solidification
Phase diagrams
Bridgman technique
Country: Holanda
Editor: Elsevier Science Bv
Citation: Journal Of Crystal Growth. Elsevier Science Bv, v. 275, n. 41671, n. E147, n. E152, 2005.
Rights: fechado
Identifier DOI: 10.1016/j.jcrysgro.2004.10.101
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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