L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties rema...L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties remain untapped,as alloy design has historically focused on systems with specific CrCoNi-or FeCoCrNi-based FCC matrix and Ni_(3)Al L1_(2)phase compositions.This study introduces novel Co-Ni-Mo-Al alloys with L1_(2)precipitates by systematically altering Al content,aiming to bridge this research gap by revealing the strengthening mechanisms.The(CoNi)_(81)Mo_(12)Al_(7)alloy achieves yield strength of 1086 MPa,tensile strength of 1520 MPa,and ductility of 35%,demonstrating an impressive synergy of strength,ductility,and strain-hardening capacity.Dislocation analysis via transmission electron microscopy,supported by generalized stacking fault energy(GSFE)calculations using density functional theory(DFT),demonstrates that Mo substitution for Al in the L1_(2)phase alters dislocation behavior,promoting the formation of multiple deformation modes,including stacking faults,super-dislocation pairs,Lomer-Cottrell locks,and unusual nano-twin formation even at low strains.These behaviors are facilitated by the low stacking fault energy(SFE)of the FCC matrix,overlapping of SFs,and dislocation dissociation across anti-phase boundaries(APBs).The increased energy barrier for superlattice intrinsic stacking fault(SISF)formation compared to APBs,due to Mo substitution,further influences dislocation activity.This work demonstrates a novel strategy for designing high-performance M/HEAs by expanding the range of FCC matrix and L1_(2)compositions through precipitation hardening.展开更多
基金financially supported by the National Research Foundation of Korea grant funded by the Korea government(MSIT)(Nos.NRF-2022R1A5A1030054,NRF-RS-2024-00345498,and NRFRS-2023-00281508)by Korea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(HRD Program for Industrial Innovation-No P0023676)+1 种基金funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-No 519607530funding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Grant Agreement No 865855).
文摘L1_(2)precipitates are known to significantly enhance the strength and ductility of single-phase face-centered cubic(FCC)medium-or high-entropy alloys(M/HEAs).However,further improvements in mechanical properties remain untapped,as alloy design has historically focused on systems with specific CrCoNi-or FeCoCrNi-based FCC matrix and Ni_(3)Al L1_(2)phase compositions.This study introduces novel Co-Ni-Mo-Al alloys with L1_(2)precipitates by systematically altering Al content,aiming to bridge this research gap by revealing the strengthening mechanisms.The(CoNi)_(81)Mo_(12)Al_(7)alloy achieves yield strength of 1086 MPa,tensile strength of 1520 MPa,and ductility of 35%,demonstrating an impressive synergy of strength,ductility,and strain-hardening capacity.Dislocation analysis via transmission electron microscopy,supported by generalized stacking fault energy(GSFE)calculations using density functional theory(DFT),demonstrates that Mo substitution for Al in the L1_(2)phase alters dislocation behavior,promoting the formation of multiple deformation modes,including stacking faults,super-dislocation pairs,Lomer-Cottrell locks,and unusual nano-twin formation even at low strains.These behaviors are facilitated by the low stacking fault energy(SFE)of the FCC matrix,overlapping of SFs,and dislocation dissociation across anti-phase boundaries(APBs).The increased energy barrier for superlattice intrinsic stacking fault(SISF)formation compared to APBs,due to Mo substitution,further influences dislocation activity.This work demonstrates a novel strategy for designing high-performance M/HEAs by expanding the range of FCC matrix and L1_(2)compositions through precipitation hardening.
