Ultrahigh strength in a ductile complex concentrated copper alloy enabled by immiscibility-driven nanocluster networks

Achieving yield strengths above 1000 MPa in copper alloys usually causes severe embrittlement, with elongation typically below 8%. Here, repulsive Cu-Cr immiscibility is exploited to redirect the phase separation pathway of a complex concentrated Cu-Ni-Mn-Al alloy. Adding 5 at.% Cr drives the formation of 3.4 nm Cr-rich nanoclusters and raises the L12-(Ni,Cu,Mn)3Al volume fraction from 25.2% to 32.9%, generating a three-dimensional interpenetrating nanocluster network. Both nanoclusters remain coherent and shearable. The alloy achieves a yield strength of 1020 ± 19 MPa with 12.7 ± 1.3% elongation, and first-principles calculations give an antiphase-boundary energy of 189 mJ·m−2, underpinning a ∼570 MPa order-strengthening contribution.