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Master's Dissertation
DOI
10.11606/D.88.2003.tde-25092014-143240
Document
Author
Full name
Terlize Cristina Niemeyer
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2003
Supervisor
Committee
Grandini, Carlos Roberto (President)
Adorno, Antônio Tallarico Vicente
Florêncio, Odila
Title in Portuguese
Estudo da interação do oxigênio intersticial com a matriz metálica em ligas de Nb-0,3%pTi
Keywords in Portuguese
Atrito interno
Elementos intersticiais
Ligas de nióbio
Relaxações anelásticas
Abstract in Portuguese
As propriedades mecânicas de metais com estrutura cristalina cúbica de corpo centrado (CCC), tais como nióbio e suas ligas, são alteradas de forma bastante significativa com a adição de elementos intersticiais pesados. Estes elementos intersticiais (oxigênio, nitrogênio e carbono) presentes na matriz metálica ocupam sítios octaedrais e constituem um dipolo elástico de simetria tetragonal, podendo produzir relaxações anelásticas. As amostras utilizadas foram policristais da liga Nb-Ti, contendo 0,3% em peso de Ti. As medidas de espectroscopia anelástica foram efetuadas usando um pêndulo de torção invertido, operando com freqüência da ordem de hertz, em um intervalo de temperatura entre 300 e 700 K, com taxa de aquecimento de 1 K/min. Esta dissertação apresenta estruturas de relaxação termicamente ativadas observadas em amostras da liga Nb - 0,3%pTi, contendo diferentes concentrações de oxigênio em solução sólida. Estas estruturas de relaxação foram atribuídas à reorientação induzida por tensão de átomos intersticiais em tomo de átomos da matriz metálica. Tais estruturas foram analisadas e foram encontrados os seguintes processos de relaxação: Nb-O, Ti-O, Nb-N e Nb-C. Os resultados mostraram também uma relação direta entre as intensidades das estruturas de relaxação e a concentração dos elementos intersticiais presentes nas amostras.
Title in English
Study of the interaction of interstitial oxygen with the metallic matrix in Nb - 0.3%wt.Ti alloys
Keywords in English
Anelastic relaxation
Internal friction
Interstitial elements
Niobium alloys
Abstract in English
The mechanical properties of metals with body centered cubic (BCC) crystalline structure such as Nb and its alloys are modified of sufficiently significant form with the addition of heavy interstitial elements. These interstitial elements (oxygen, for example) present in the metallic matrix occupy octahedral sites and constitute an elastic dipole of tetragonal symmetry, being able to produce an elastic relaxation. The used samples were polycrystals of the Nb-Ti alloy, having 0.3 % in weight of Ti. The an elastic spectroscopy measurements were taken using an inverted torsion pendulum, operating with frequency of the order of hertz, in a temperature range between 300 and 700 K, with heating rate of 1 K/min. This dissertation shows thermally activated relaxation structures observed in samples of the Nb - 0.3wt.%Ti alloy, having different concentrations of oxygen in solid solution. These relaxation structures were attributed to stress induced ordering of interstitial atoms around the metallic matrix atoms. Such structures were analyzed and were found the following relaxation processes: Nb-O, Ti-O, Nb-N and Nb-C. The results had also shown a direct relation between the intensities of the relaxation structures and the concentration of interstitial elements in the samples.
 
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Publishing Date
2014-10-09
 
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