Evolution of Local Two‐Dimensional Ordered Composite Defects: A Novel Strategy for Strength Breakthrough in FeMnCrCo High‐Entropy Alloys

FeMnCrCo metastable high‐entropy alloys (HEAs) have gained significant attention for their excellent plastic deformation capacity; however, traditional processing methods cannot overcome the strength enhancement bottleneck. Therefore, this study designed an Fe 49 Mn 33.2 Cr 9.6 Co 8.2 HEA (stacking fault energy = 13.3mJ/m 2 ) through thermodynamic calculations and precisely tailored its microstructure via rolling combined with short‐time heat treatment. Microstructural analysis shows that after annealing at 800°C, the alloy displays a single‐phase face‐centered cubic(FCC) structure; generated stacking faults(SFs) interact with retained partial deformation twins to form local two‐dimensional ordered composite defects. During deformation, these defects give the alloy a tensile strength of 1115 MPa (240 MPa higher than traditional FeMnCrCo HEAs) and 17% room‐temperature elongation, with a strength‐ductility product surpassing that of cold‐rolled counterparts. Notably, it maintains stable mechanical properties under short‐time heat treatment at 800–1000°C, demonstrating good process window stability. This study elucidates the defect mechanism and provides an innovative pathway for the strengthening and toughening design of FeMnCrCo metastable HEAs.)