TiC nanoparticles tune phase stability and deformation mechanisms in directed energy deposition processed Fe60Co15Ni15Cr10 medium-entropy alloy composites

Ahn, S. Y.*; Kim, E. S.*; Jeong, S. G.*; Harjo, S.   ; 川崎 卓郎   ; Gong, W.   ; Kim, H.-J.*; Hong, S.-J.*; Hong, S. I.*; Kwon, H.*; Kim, J. G.*; Kim, H. S.*

Ahn, S. Y.*; Kim, E. S.*; Jeong, S. G.*; Harjo, S.; Kawasaki, Takuro; Gong, W.; Kim, H.-J.*; Hong, S.-J.*; Hong, S. I.*; Kwon, H.*; Kim, J. G.*; Kim, H. S.*

Additive manufacturing (AM) of particle-reinforced metal matrix composites (MMCs) enables control of both strength and deformation behavior. In this study, TiC (2 wt%) nanoparticles were added to FeCoNiCr medium-entropy alloy (MEA) using directed energy deposition (DED). Although part of the TiC decomposed during processing, the released C and Ti stabilized the -austenite phase and suppressed deformation-induced martensitic transformation (DIMT), shifting deformation toward slip-dominated behavior. Microstructural observations revealed dispersed TiC particles and modified grain boundary morphology that promoted distributed plastic flow. In-situ neutron diffraction during tensile testing confirmed enhanced early-stage dislocation activity. These findings demonstrate that nanoparticle-induced phase stability changes strongly influence deformation mechanisms in AM-processed MMCs.