The feasibility of preparing high entropy alloys in the Al-Sc-Ti-V-Cr system has been evaluated taking into account the different criteria reported in the literature. Based on such criteria, three Al-Sc-Ti-V-Cr alloys were chosen with contents of each element varying from 10 to 35 at. %, and prepared by arc melting. All alloys exhibit a two-phase dendritic microstructure, with the major dendritic phase being a bcc solid solution enriched in Ti, V, or Cr. Scandium is strongly rejected from the dendrites towards the interdendritic regions to form Al 2 Sc in the three alloys. The bcc solid solution dendrites become harder with high Ti content and lower with high Cr content. The toughness of the alloys depends on the hardness of the dendrites, with alloys with harder dendrites becoming more brittle. The results indicate that neither empirical criteria used nor THERMOCALC calculus tool can predict properly the formation of a single solid solution nor the nature of the existing phases respectively. Citation/Citar como: Pérez, P.; Garcés, G.; Fruto-Myro, E.; Antoranz, J.M.; Tsipas, S.; Adeva, P. (2019). "Design and characterization of three light-weight multi-principal-element alloys potentially candidates as high-entropy alloys". Rev. Metal. 55(3): e147. https://doi.org/10.3989/revmetalm.147
TIMETAL® 575, developed by Titanium Metals Corporation (TIMET), is a high strength forgeable α+β titanium alloy with comparable density, beta transus temperature and processing characteristics to Ti-6Al-4V but with enhanced static and fatigue strength primarily aimed at aero-engine disc or blade applications. Recent research on this alloy has focussed on microstructure evolution as a means to optimise mechanical behaviour and it has been concluded that a solution heat treatment followed by an ageing step yields a resulting “tri-modal” microstructure, consisting of equiaxed primary α and bi-lamellar transformation product containing nano-scale “tertiary alpha” laths, which appear to provide an excellent balance of strength and ductility. The key objective of the work presented here is to characterise this complex nanoscale microstructure in detail at various stages of alloy processing. For that purpose various advanced and recently developed transmission electron microscopy (TEM) techniques have been used. These include alpha and beta phase mapping Precession Electron Diffraction (PED), overall microstructure imaging with conventional BF and DF TEM, distinction of fine phase detail with high angle annular dark field (HAADF) scanning TEM (STEM), and correlation of the nanostructure to the elemental distribution using scanned Electron Energy Loss Spectroscopy (EELS).
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