Critical role of L2 and L1 phase in deformation behaviors of additively manufactured FeCrNiAlTi alloy

Wang, X.*; Wang, Y.*; Gong, W.   ; Wu, W.*; Zhang, Y.*; Harjo, S.   ; Yang, Z.*; Chen, H.*

Wang, X.*; Wang, Y.*; Gong, W.; Wu, W.*; Zhang, Y.*; Harjo, S.; Yang, Z.*; Chen, H.*

Precipitation hardening strengthens FCC alloys but often reduces ductility. This study shows that precipitates can also modify deformation behavior to mitigate this trade-off. An FeCrNiAlTi FCC alloy fabricated by laser additive manufacturing contains incoherent L2 precipitates at cell walls and coherent L1 precipitates within cells. By controlling precipitation, an excellent strength-ductility balance was achieved at both ambient and cryogenic temperatures. High-density precipitates provide strengthening while promoting deformation-induced stacking faults and twinning, thereby enhancing work hardening via strain heterogeneity. In situ neutron diffraction indicates that post-yield lattice strain governs stacking fault and twin formation. Simulations show that interfacial misfit of the L2 phase and the size and spacing of the L1 phase amplify local strain.