Abstract: Heterogeneous microlaminated BCC/FCC structures are desirable to achieve the excellent strength-ductility synergy in medium entropy alloys (MEAs). However, traditional BCC alloys have long borne intrinsic brittleness at cryogenic temperatures due to the severe restriction of dislocation multiplication and motion. Here, we demonstrate a strategy that introducing dual-scale multicomponent ordered BCC (B2) nanoprecipitates in BCC grains of a Fe-based BCC/FCC duplex microlaminated MEA. Both large B2 nanoprecipitates acting as sustainable dislocation sources at low stress levels, and small B2 nanoprecipitates promoting the dislocation nucleation and multiplication at high stress levels, together with the microbands in FCC grains, render a good combination of yield strength and uniform elongation. This dual-scale precipitates strategy offers a paradigm to develop high-performance cryogenic alloys for structural applications.

Key words: Medium-entropy alloy, Nanoprecipitates, Mechanical properties, Deformation mechanisms