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.