Ligas metálicas amorfas: um novo método de predição de composição com capacidade de formação de amorfos

Detalhes bibliográficos
Ano de defesa: 2014
Autor(a) principal: Nascimento, Carlos Ociran Silva
Orientador(a): Ishikawa, Tomaz Toshimi lattes
Banca de defesa: Não Informado pela instituição
Tipo de documento: Tese
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Federal de São Carlos
Programa de Pós-Graduação: Programa de Pós-Graduação em Ciência e Engenharia de Materiais - PPGCEM
Departamento: Não Informado pela instituição
País: BR
Palavras-chave em Português:
Palavras-chave em Inglês:
Área do conhecimento CNPq:
Link de acesso: https://repositorio.ufscar.br/handle/20.500.14289/735
Resumo: This thesis presents the development of a new criterion which can indicate new compositions for amorphous metallic alloys. This new criterion was based on dense packing of spheres combined with the lambda criterion through the coordination number. The mathematical development is presented and a software was developed with the purpose of indicating alloys with best glass forming ability (GFA). This software includes and concatenates several other criteria. For this purpose, we performed a mathematical analysis of the criteria, which included: (i) (λmin) criterion which uses the minimum topological instability parameter and it is used as an indication of phase competition during the solidification. (ii) the γ parameter, which reflects the relative GFA between bulky metallic glasses (BMG) and it is based on characteristic temperatures, such as: the glass transition temperature - Tg, the crystallization onset temperature - Tx and the liquidus temperature - Tl. (iii) the parameter Zc that is the critical thickness for bulky glass formation, which corresponds to the maximum dimension in which the molten can be formed without any crystals precipitation and (iv) the parameter Rc that is the critical cooling rate for glass formation, which decreases inversely to the Zc values. Through a mathematical formalism combining all the parameters, the software can decide the most suitable composition range to produce a new alloy. The results are presented and compared with the ones available on the literature. Also, for comparison, new alloys were developed by using the new criterion. These results indicate good agreement with the literature and with the experimental data since it is not a general theory, but intends to meet some specific cases with a reasonable convergence and which still need to be better studied.