A novel strategy for developing fine-grained FeCrAl alloys with high strength and ductility

Grain boundary hardening is an important mechanism for improving the strength and ductility of metal materials. However, the industrial fabrication of fine-grained FeCrAl alloys was limited by the interaction between the recrystallization and precipitation. Here, we report the facile mass production of fine-grained FeCrAl alloys by Si alloying and manipulation of the recrystallization process through introducing heterogeneous Si-rich Laves precipitates. The pre-precipitation of heterogeneous Laves phase not only promotes subsequent recrystallization grain nucleation by the PSN (Particles simultaneous nucleation) and SIBM (Strain-induced grain boundary migration) mechanisms, but also provides resistance to grain growth by the Zener pinning mechanism. Moreover, continuous grain refinement can be achieved by intensifying the heterogeneous Laves precipitates through decreasing their formation energy. This approach enables the preparation of a fully recrystallized fine-grain structure with a grain size of 4.6 µm without the introduction of segregated boundaries. Consequently, an unprecedented synergy enhancement of strength (σ_y = 625 MPa, σ_uts = 867 MPa,) and ductility (ε_u = 13.8%) is achieved in the fine-grain structured FeCrAl alloys compared with the coarse grain counterpart. The experimental results prove that the proposed strategy is appropriate for developing high strength and ductility FeCrAl alloys, and further boosting its potential applications as accident-tolerant-fuel cladding in nuclear reactors. In addition, this grain-refinement strategy should be extendable to other alloy systems, where there is a significant difference between precipitation and recrystallization temperatures.