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Searching for new metallic glasses


The main barrier to expand the use of metallic glasses in engineering projects is the development of chemical compositions able to form glassy parts with dimensions of several millimeters or even centimeters, which is known as Glass Forming Ability (GFA). The GFA depends on the critical cooling rate for glass formation, and this, in turn, on the proper combination and amount of metallic elements in the alloy. Such chemical composition setting, however, is not trivial, given the complexity of the phenomena involved during the vitrification process. Recently a new criterion was proposed for the formulation of these alloys which presents good correlation with critical cooling rates of several metallic glasses in different systems. This new criterion combines a minimal topological instability parameter (lmin), used as an indication of the competition of phases during solidification, and a thermodynamic parameter (Dh), which depends on the average difference of work function (Df) and the average difference of electronic density (Dnws1 / 3) among the elements in the alloys. It is a promising and easy to use criterion. The main objective of this project is to test the effectiveness of this criterion in the selection of new glassy alloys in several metallic systems, starting with the optimization of the best known and studied alloys. The methodology for the production of the metallic glass parts consists in the appropriate calculation of compositions and their synthesis by arc melting in an ultra-pure environment immediately followed by suction chill casting. The produced samples will be characterized by microscopy (optical and electronic), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) to verify the amorphous volume fraction and correlate it with the selection criterion adopted. (AU)

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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DE OLIVEIRA, M. F.; ALMYRAS, G. A.; EVANGELAKIS, G. A.. Structural differences of amorphous Cu65Zr35 between rapidly quenched and topologically destabilized crystalline Cu and Zr metals by molecular dynamics simulations. COMPUTATIONAL MATERIALS SCIENCE, v. 104, p. 92-97, . (11/17117-2, 12/20888-3)

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