Additive manufacturing of a new non-equiatomic high-entropy alloy with exceptional strength-ductility synergy via in-situ alloying

Equiatomic high -entropy alloys (HEAs) fabricated by additive manufacturing (AM) have gained increasing attention since they present superior mechanical properties over their counterparts made by traditional synthesis routes. However, few studies have investigated AM of non-equiatomic HEAs, although this type of HEAs showing excellent mechanical properties. In this paper, we additively manufactured a novel non-equiatomic FeCoCrNi HEA via in -situ alloying 316L stainless steel and CrCoNi medium -entropy alloy. Besides the fine grain size (9 mu m) and high dislocation density (3.8 x 1014 m-2), we observed unexpected high -intensity of hybrid crystalamorphous precipitates, which have never been reported in NiCoCr-based alloys made by AM. These unique microstructures led to exceptional combination of strength (561 MPa) and elongation (41 %) exceeding those of additively manufactured equiatomic FeCoCrNi HEAs. Our observation from EBSD, TEM and atomistic simulations reveals a group of deformation mechanisms of stacking faults, deformation twins, TB -dislocation and dislocation -precipitates interactions. Our findings not only provide new insights into AM of non-equiatomic HEAs via in situ alloying, also shed lights on understanding the microstructure -properties relationship of nonequiatomic HEAs fabricated by AM.