The softening behavior of a 60 % cold‐drawn Cu‐0.48Cr‐0.16Sn alloy during annealing at temperatures between 450 °C and 750 °C was investigated. The mechanical properties and microstructures evolution of the alloy in both as‐drawn and annealed conditions were analyzed using hardness measurement, transmission electron microscopy (TEM) and electron back‐scatter diffraction (EBSD) technique. The results showed that the softening behavior of the alloy was strongly affected by precipitate coarsening, recovery and recrystallization, and was predominant by recrystallization when the temperature higher than 500 °C. The recrystallization kinetics was characterized by measurements of hardness. The obtained experimental data were evaluated in terms of the Johnson‐Mehl‐Avrami‐Kolmogorov model. The values of the Avrami exponent were ranged from 0.87 to 1.36, and the activation energy of recrystallization was about 117.9 kJ mol‐1 for 60 % cold‐drawn Cu−0.48Cr−0.16Sn alloy, which suggested that recrystallization process of the Cu−Cr−Sn alloy was mainly controlled by grain boundary migration. The softening resistance of the Cu−Cr−Sn alloy is stronger than that of the pure copper due to the addition of Chromium (Cr) and Tin (Sn). In addition, the reduction in strain had a positive effect on the improvement of softening resistance.

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The microstructure evolution and mechanical property of Cu-25Ni-25Mn alloy after solution treatment and aging treatment are investigated via TEM observation, XRD analysis and Vickers hardness test. The effect of the NiMn precipitates on hardness and its strengthening mechanism in the Cu-25Ni-25Mn alloy is quantitatively analyzed. The results show that in 450 °C aging process, Ni and Mn precipitate from the copper matrix and form nanoscale NiMn phase particle with a face-centered tetragonal (FCT) structure. The XRD analysis indicates that the NiMn precipitates have a lattice constant of a = b = 0.3693 ± 0.0004 nm, c = 0.3570 ± 0.0006 nm, which is fully coherent with the copper matrix. The precipitation of NiMn phase lead to a precipitation strengthening, which provides significant increase in hardness in the peak-aged Cu-25Ni-25Mn alloy. Compared to the solution treated sample, the hardness of peak-aged sample has been increased by 367 HV. The coherency strengthening and modulus strengthening are the dominant strengthening mechanisms. The hardness increment predicted by coherence strengthening and modulus strengthening mechanism has good consistency with the experiment results.