BMG’s containing great majority Al element are missing in the literature. Only traditional amorphous ribbon could be prepared so far with thicknesses well below 1 mm. Surveying the data from the literature and more then 30 home made compositions, it turned out that  in order to obtain ductile Al-based metallic glasses (MG’s) containing more then 75-80 at% Al, one have to select alloying elements for which the heats of formation (ΔH) are between -5 and -25 kJ/mole. In addition, we have to exclude those alloying elements which form compounds with high Al content, above 80 at%. We have calculated also the atomic mismatch (Λ parameter of Egami) for these alloys and using the ΔH versus Λ map we tried to assess the GFA.  We have found new amorphous Al -based compositions basing on the assumption that the higher the number of stable and meta-stable phases in the surroundings of the selected composition the higher the GFA.

Instead of BMG’s the one phase crystalline solid solution of high entropy alloys (HEA) would be a good candidate for a light metal structural material combining the high strength and ductility. In order to obtain a crystalline solid solution both the atomic mismatch (Λ) and the free energy (ΔG) should be small enough to not drive out the solute element in compound like precipitates. The free energy can be diminished by increasing the configurational entropy composing a multi-component alloy with equal atomic concentrations of at least 5 constituents: ΔG = ΔH-TΣc_ilnc_i,  This idea proved to be valid for the mixing of the late transition elements (Cu, Ni, Co, Fe, Cr) and their derivatives [1]. In the case of Al and Ti based multi-component alloys however, extended solid solution was observed only for components which forms no compound phases.

Electric discharge assisted compaction was applied to obtain BMG and HEA samples as disks of 2 mm thick and 10 mm diameter.

References

1. J-W. Yeh, et al. Adv. Eng. Mat. 6 (2004) 299-303

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