Effect of thermomechanical processing on the microstructure and properties of high-strength Cu-10Ni-6Mn-5Sn alloy

The Cu-Ni-Mn-Sn alloy has emerged as a promising structural material for electromagnetic shielding applications due to its high-density L2 1 -ordered magnetic Heusler phase. To identify the optimum thermomechanical processing route for the Cu-Ni-Mn-Sn alloy, three treatments—cold rolling + solution treatment + aging (P1), cold rolling + aging (P2), and cryogenic rolling + aging (P3)—are designed and comparatively investigated. The P2-processed Cu-10Ni-6Mn-5Sn alloy (80% cold rolled and aged at 350°C for 48 h) exhibits an optimal combination of properties, achieving an exceptional ultimate tensile strength of (1343 ± 10) MPa, an elongation of (4.9 ± 0.01)%, and an electrical conductivity of (9.5 ± 0.02)% IACS. Microstructural analysis reveals that P2 promotes a texture transformation from Brass components to <001>‖ND and <111>‖ND, which reduces plastic anisotropy and improves deformation compatibility. Meanwhile, quantitative calculations confirm that alloy strength originates from well-established strengthening contributions of high-density L2 1 Heusler nanoprecipitates (∼20 nm), dislocations and grain boundaries. Electrical resistivity modeling identifies solute atoms and phase/matrix interfaces as the primary electron scattering sources. Furthermore, although cryogenic rolling (P3) drives more recrystallization nuclei and finer grain structure during subsequent aging, it concurrently accelerates precipitate coarsening (∼30 nm). This competitive trade-off between enhanced matrix strengthening and weakened Orowan bypassing leads no additional macroscopic strength increment. By systematically correlating deformation modes, recrystallization kinetics, and precipitation behaviors, this work demonstrates that direct aging after cold rolling (P2) is a highly effective and industrially viable thermomechanical route to achieve ultra-high-strength Cu-Ni-Mn-Sn alloys.