Precipitation driven nano-twinning: Simultaneous enhancement of mechanical and electrical properties in Cu-Ni-Sn alloys

After homogenization, hot forging and solid-solution treatment at 800 °C, the Cu-15Ni-9Sn alloy was cold-rolled to a 60 % thickness reduction and aged at 400 °C. After 1 h aging, spinodal decomposition produced the Sn and Ni enriched DO₂₂ phase coherent with the matrix, while abundant nanotwins emerged in the vicinity of (Cu, Ni)₃Sn precipitates in the recrystallized matrix. Compared to the as-rolled state, the alloy exhibited enhanced hardness (316 HV), ultimate tensile strength (1131 MPa), and electrical conductivity (9.7 % IACS). Extending aging to 4 h led to extensive (Cu, Ni)₃Sn secondary phase formation and pronounced recrystallization, reducing strength to 855 MPa but increasing electrical conductivity to 11.7 % IACS and total elongation to 12.9 %. The synergistic interplay of spinodal decomposition, local recrystallization, precipitation and nano-twinning underpinned the superior mechanical and electrical properties of the 1 h aged Cu-15Ni-9Sn alloy.