Strengthening and Toughening of the Co₃₄Cr₃₂Ni₂₇Al_3.5Ti_3.5 Alloy Through Coherent L1₂ Nanoprecipitates

Herein, the L1₂‐strengthened Co₃₄Cr₃₂Ni₂₇Al_3.5Ti_3.5 medium‐entropy alloy (MEA) with outstanding strength and ductility is developed through cold rolling and annealing (CRA). The CRA promotes the formation of coherent L1₂ nanoprecipitates in the matrix and precipitates inside the grains (Ti‐rich phases), resulting in dislocation sliding and multiplication during deformation. The as‐cast sample exhibits low yield strength (YS) of ≈498.5 MPa, ultimate tensile strength (UTS) of ≈820.5 MPa, and uniform elongation (UE) of ≈29.8%. After cold rolling and annealing, the YS, UTS, and UE are significantly increased to ≈678.4, ≈1109.3 MPa, and ≈44.5%, respectively. The excellent mechanical performance results from dislocation strengthening and precipitation strengthening of the L1₂ phase. The trade‐off of strength‐ductility is resolved by achieving an appropriate balance between the hard phase rich in L1₂/Ti and the soft face‐centered cubic phase. This finding demonstrates that the CRA method can be used to create coherent L1₂ nanoprecipitates that are beneficial for strong and ductile MEA. This work provides a broader perspective for CoCrNi‐based MEAs with high performance in the future.