Thermal stability, phase transformations and mechanical properties of a Fe64B24Y4Nb6 metallic glass
Résumé
Fe64B24Y4Nb6 metallic glass ribbon and its bulk counterpart were characterized by conventional and high rate differential scanning calorimetry, electron probe microanalysis, in-situ X-ray diffractometry, high resolution transmission electron microscopy and instrumented microhardness. The metallic glass possesses a high glass forming ability. It is thermally stable up to 585 °C while primary crystallization of Fe2B and FeB occurs at 677 °C. Estimated by the Kissinger and Moynihan’s methods, the activation energy of glass transition was shown to be lower than that of primary crystallization. After total crystallization, the bulk alloy contains a terminal Fe solid solution, Fe2B, FeB, Fe3B8Nb7 and BFe14Y2 phases while the ribbon contains additional yttria as well. The loading and unloading curves as well as the indentation features are very suitable in order to evidence the effect of the various crystallization events on the mechanical behavior of the bulk alloy. The hardness of the amorphous and fully crystallized bulk alloys amount to 1198 ± 21 and 461 ± 65 HV0.5, respectively and their reduced Young modulus are close to 174 ± 5 GPa. The deformation ability of the fully crystallized alloy is twice that of the glassy alloy.
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