Laves-controlled microstructure evolution and tensile behavior of an aged FeCrAl alloy

The microstructural evolutions and tensile behaviors of a 1.0Wt.% Nb-containing FeCrAl alloy aged at 600 °C for 1–1000 h were systematically investigated by means of a combination of SEM/EDS, XRD, EBSD and TEM, and tensile testing at room temperature and 350–450 °C. The process of aging induced the formation of Nb–Mo-rich Fe 2 Nb-type Laves precipitates, whose fraction and dimensions increased over time in a prolonged aging environment. Despite long-term thermal exposure, the grain size remained relatively stable, indicating that Laves precipitates have exerted an apparent Zener pinning effect on grainboundary migration. The results of the electron backscatter diffraction (EBSD) analysis revealed aging-related the presence of changes in the substructure and local orientation gradients. Tensile tests showed that aging enhanced the strength at both ambient and elevated temperatures. The maximum ultimate tensile strength reached approximately 780 MPa after aging for 1000 h and testing at 350 °C. Among the microstructural factors directly evaluated in the present work, the dominant strengthening contribution is associated with Laves precipitation, while grain/subgrain-boundary stabilization and increased local orientation heterogeneity provide additional support. However, the ductility exhibited a variation in response to the aging time and the testing temperature, thereby indicating a competition between precipitation strengthening, precipitate coarsening, and plastic deformation capacity. This work clarifies the role of Nb-rich Laves precipitates in regulating the microstructural stability and strength–ductility balance of aged FeCrAl alloys.