Effect of Cr content on tensile and Charpy impact behaviors of L12-strengthened Fe-based MPEAs at 298 K and 77 K

L1 2 precipitation-strengthened multi-principal-element alloys (MPEAs) exhibit outstanding quasi-static tensile properties at both ambient (298 K) and cryogenic (77 K) temperatures, highlighting their potential for engineering applications. However, their impact behaviors remain poorly understood. In this work, the tensile and Charpy impact behaviors of (Fe 58.98 Ni 31.7 Al 6 Ti 3 Zr 0.1 C 0.2 B 0.02 ) 100-x Cr x (x = 0, 4, 8, and 13 at.%) at 298 K and 77 K are systematically investigated. The Cr8 alloy achieves the optimal balance of strength, ductility and Charpy impact toughness at both 298 K and 77 K. Notably, the Cr8 alloy delivers exceptional mechanical performance at 77 K, with a yield strength of 927 ± 13 MPa, ultimate tensile strength of 1552 ± 9 MPa, uniform elongation of 48.8 ± 3.0%, and Charpy impact toughness of 87.9 ± 3.4 J/cm 2 . When the Cr content exceeds 8 at.%, the yield strength, ultimate tensile strength, and room-temperature Charpy impact energy of the alloys exhibit a slight decreasing trend. This composition-dependent performance is attributable to Cr-induced modulation of the dominant deformation mechanism. The Cr0 alloy exhibits FCC to BCC transformation; the Cr4 alloy shows co-dominance of deformation twinning and dislocation slip; while the Cr8 and Cr13 alloys are governed by stacking faults and dislocation slip. These results demonstrate that Cr alloying is an effective strategy to tailor the strength, ductility, and impact toughness of L1 2 -precipitate-strengthened Fe-based MPEAs at 298 K and 77 K.