High-entropy alloys have exhibited unusual materials properties. The stability of equimolar single-phase solid solution of five or more elements is supposedly rare and identifying the existence of such alloys has been challenging because of the vast chemical space of possible combinations. Herein, based on high-throughput density-functional theory calculations, we construct a chemical map of single-phase equimolar high-entropy alloys by investigating over 658,000 equimolar quinary alloys through a binary regular solid-solution model. We identify 30,201 potential single-phase equimolar alloys (5% of the possible combinations) forming mainly in body-centered cubic structures. We unveil the chemistries that are likely to form high-entropy alloys, and identify the complex interplay among mixing enthalpy, intermetallics formation, and melting point that drives the formation of these solid solutions. We demonstrate the power of our method by predicting the existence of two new high-entropy alloys, i.e. the body-centered cubic AlCoMnNiV and the face-centered cubic CoFeMnNiZn, which are successfully synthesized.
The concept of high entropy alloys (HEAs) has already provided specific alloys presenting improved structural and functional properties. However, the discovery and development of new HEAs still represent a big challenge due to their chemical complexity. Diffusion multiples can be used as an experimental approach to screen large composition ranges. The method consists in heat-treating intimately bonded metallic blocks to activate diffusion, thus creating gradients of compositions. Local chemical and physical properties can be directly probed using advanced characterization techniques. The measured characteristics and properties can be further analysed to estimate diffusion properties or mechanical properties. In the present study, four different diffusion multiples related to the Cantor alloy system, Cr-Fe-Mn-Co-Ni, were investigated. Resulting microstructures were investigated after several heat treatments to assess the claimed entropy-based stabilization of a single phase. Crystallographic characterization by EBSD coupled to EDX mapping were compared to Calphad predictions. Local nano-indentation mapping was carried out and compared to the prediction of the yield strength model proposed by Walbru ¨hl et al.
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