Recrystallization of as-solidified highly-undercooled Fe40Ni40B20 eutectic alloy: In situ formation of duplex structure

•The non-equilibrium microstructures of Fe40Ni40B20 alloy were obtained.•The duplex structure were obtained by futher heat treatment.•The mechanical properties of the samples with duplex structure were largely enhanced.•We provide an effective method to improve the properties of eutectic alloy.

Non-equilibrium effects (e.g. strain energy) are stored upon highly undercooled solidification of Fe40Ni40B20 eutectic alloy. Only for sufficiently high undercooling (e.g. >200 K), recrystallization, with the strain energy as the driving force, can occur upon annealing the as-solidified structure, thus forming a duplex structure consisting of as-recrystallized single-phase layer (outer) and as-solidified two-phase anomalous eutectic bulk (inner). As compared to the samples subjected to lower undercoolings, the mechanical properties of the samples with the duplex structure are improved substantially.