Microstructural Peculiarities of Al-Rich Al-La-Ni-Fe Alloys
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INTRODUCTION
SINCE the seeding studies of Inoue et al.[1,2] and G. [3]
Shiflet et al. in 1988, Al-based metal glasses containing rare-earth elements (RE) together with transition metals (TM) have been under intensive study due to their high metallic glass formation ability and excellent mechanical properties, such as high strength and corrosion resistance. Two groups of ternary Al-based alloys containing La, namely, Al-La-Ni and Al-La-Fe, were already considered in those pioneering research works. In subsequent studies, it was shown that the reported high
A.L. VASILIEV is with the National Research Center ‘‘Kurchatov Institute’’, Ak. Kurchatov sq. 1, 123182 Moscow, Russia, with the Shubnikov Institute of Crystallography of FSRC ‘‘Crystallography and Photonics’’, RAS, Leninsky pr, 59, 119333 Moscow, Russia, and also with Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, 141701 Moscow Region, Russia. Contact e-mail: [email protected] N.D. BAKHTEEVA and E.V. TODOROVA are with the Baikov Institute of Metallurgy and Materials Science, RAS, Leninsky pr, 39, 119334 Moscow, Russia. M.YU. PRESNIAKOV and N.N. KOLOBYLINA are with the National Research Center ‘‘Kurchatov Institute’’. S. LOPATIN is with the King Abdullah University of Science and Technology (KAUST), Core Labs, Thuwal, 23955-6900, Saudi Arabia. A.G. IVANOVA is with the Shubnikov Institute of Crystallography of FSRC ‘‘Crystallography and Photonics’’. Manuscript submitted May 23, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
glass-forming ability and mechanical properties could be substantially improved by the addition of a second transition element.[4–6] The quaternary alloys with two transition elements, in particular Fe and Ni, are characterized by a higher thermal stability and better mechanical properties. Studies of the microstructure and phase formation processes in ternary and quaternary alloys during annealing have been carried out mainly by X-ray and electron diffraction (XRD and ED, respectively) since these materials were discovered, but in most cases, they were limited to ascertaining the presence of fcc-Al and one or more binary phases. Quaternary intermetallic compounds, to the best of our knowledge, were not found and were not considered. To some extent, this might be due to issues related to the completeness of their identification by XRD or ED for a number of reasons. On the one hand, XRD spectra from low-symmetry binary phases exhibit a significant number of maxima, which could conceal the presence of ternary and quaternary phases. Studies of the microstructure of amorphous alloys after thermal treatment or intense plastic deformation were carried out mostly in samples with extremely high mechanical characteristics in which the grain sizes often did not exceed 100 nm.[4,7,8] Such grain sizes precluded investigations by ED; however, these alloys are most interesting. In addition, during annealing or intensive plastic deformation, along with stable phases, metastable intermetallic phases could appear. If so, fo
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