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Ductile and Strong Non-Equiatomic High-Entropy Alloys: Design, Processing, Microstructure, and Mechanical Properties

In a set of projects we study the field of strong and ductile non-equiatomic high-entropy alloys (HEAs).

The materials reviewed are mainly based on massive transition-metal solute solutions and exhibit a broad spectrum of microstructures and mechanical properties. Three relevant aspects of such non-equiatomic HEAs with excellent strength–ductility combination are studied in detail in our group, namely phase stability-guided design, controlled and inexpensive bulk metallurgical processing routes for appropriate microstructure and compositional homogeneity, and the resultant microstructure–property relations. In addition to the multiple principal substitutional elements used in these alloys, minor interstitial alloying elements are also considered. We show that various groups of strong and ductile HEAs can be obtained by shifting the alloy design strategy from single-phase equiatomic to dual- or multiphase non-equiatomic compositional configurations with carefully designed phase instability. This design direction provides ample possibilities for joint activation of a number of strengthening and toughening mechanisms. Some potential research efforts which can be conducted in the future are also proposed.

Fig.:Variations in FCC grain size and HCP phase fraction in dual-phase Fe50Mn30Co10Cr10 alloy with increasing annealing time at 900°C. Annealing time of 0 min refers to the cold-rolled state of the samples without annealing.

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