Full text
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| Author(s): |
Leonardo Pratavieira Déo
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2011-10-20 |
| Examining board members: |
Marcelo Falcão de Oliveira;
Conrado Ramos Moreira Afonso;
Eduardo Bellini Ferreira
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| Advisor: | Marcelo Falcão de Oliveira |
| Abstract | |
In the present work it was verified the accuracy of a proposed criterion to predict compositions of glassy alloys applied in the Zr-Ni-Cu system. This criterion combines the topological instability parameter (\'lâmbda\') and a thermodynamic parameter (\'delta\' h) among the alloying elements. The two parameters correlate quantitatively the chemical composition with the glass forming ability. This criterion is a promising and simple tool to guide and reduce the tedious and intensive work of finding good compositions of glasses in metallic systems. In an attempt to prove the efficiency of such tool, the methodology was to calculate the parameter for the system of interest and prepare alloys in accordance with the compositions provided by the tool. The methodology of preparation of the alloys followed the electric arc- melting and subsequent use of fast cooling techniques, melt-spinning and splat-cooling for the production of metallic ribbons and discs, respectively, and a wedge-shaped chiller mold to produce bulk metallic samples. For samples prepared from the melt-spinning and splat-cooling, it was verified the accuracy of the selection criteria by quantifying the percentage of glassy phases from X-ray diffractograms and their thermal behaviors from thermograms produced by differential scanning calorimetry (DSC). For alloys produced from the wedge-shaped mold, some results were obtained with evidence of vitreous structures that were characterized by X-ray diffraction and metallography. Therefore the conclusion is that the selection criteria applied to the system Zr-Ni-Cu can be used to develop favorable compositions for the formation of glasses before the production of the alloys. It is concluded that the selection criterion is a good tool and can be used as a guide to find the best glass forming alloys, thus reducing the experimental procedures of trial and error. (AU) | |
| FAPESP's process: | 09/13079-9 - Precision evaluation of a new criterion for selection of alloy glass forming compositions |
| Grantee: | Leonardo Pratavieira Deo |
| Support Opportunities: | Scholarships in Brazil - Master |