Design of a twinning-induced plasticity high entropy alloy

We introduce a liquid metallurgy synthesized, non-equiatomic Fe40Mn40Co10Cr10 high entropy alloy that is designed to undergo mechanically-induced twinning upon deformation at room temperature. Microstructure characterization, carried out using SEM, TEM and APT shows a homogeneous fcc structured single phase solid solution in the as-cast, hot-rolled and homogenized states.

Deformation twins at ∼45% true strain in Fe40Mn40Co10Cr10 revealed by TEM: (a) dark field micrograph with beam direction [0 0 2]T; (b) selected-area diffraction pattern; (c) orientation and phase mapping of the same area by the ASTAR software.

Investigations of the deformation substructures at specific strain levels with electron channeling contrast imaging (ECCI) combined with EBSD reveal a clear change in the deformation mechanisms of the designed alloy starting from dislocation slip to twinning as a function of strain. Such twinning induced plasticity has only been observed under cryogenic conditions in the equiatomic FeMnNiCoCr high entropy alloy. Thus, despite the decreased contribution of solid solution strengthening, the tensile properties of the introduced lean alloy at room temperature are found to be comparable to that of the well-studied five component FeMnNiCoCr system.

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