Abstract
High entropy alloys (HEAs) in the hexagonal close-packed (hcp) phase usually show poor mechanical properties. We demonstrate here, by use of ab initio simulations and detailed experimental investigations, that the mechanical properties can be improved by optimizing the microstructure. In particular we design a dual-phase HEA consisting of a body-centered cubic (bcc) matrix and hcp laths, with nanoprecipitates of the ω phase in the Sc-Ti-Zr-Hf-Re system, by controlling the Re content. This dedicated microstructure reveals, already in the as-cast state, high compressive strength and good ductility of 1910 MPa and 8%, respectively. Our study lifts the hcp-based HEAs onto a competitive, technological level.
Highlights
Al20Li20Mg10Sc20Ti30 hcp High entropy alloys (HEAs) using heat-treated mechanically-alloyed powders
In order to quantitatively assess the bcc-hcp-ω phase stabilities for the selected compositions, we resort to ab initio calculations
It is found that adding Re energetically stabilizes the bcc and the ω phases compared to hcp phase
Summary
Al20Li20Mg10Sc20Ti30 hcp HEA using heat-treated mechanically-alloyed powders. Single-phase hcp structures were found in cast YGdTbDyLu, GdTbDyTmLu [12] and HoDyYGdTb [13] alloys. Mo-Ru-Rh-Pd and Mo-Tc-Ru-Rh-Pd alloys show the hcp phase [16,17], which was investigated using ab initio calculations [18]. Despite these works, the hcp HEA field is still in its infancy, and it is desirable to further enhance their microstructural and mechanical properties. It is known that a mixture of bcc and hcp phases leads to an optimal combination of strength and ductility for the conventional Ti-6Al-4 V wt% alloy [19]
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