Inhibition of discontinuous precipitation and enhanced properties of Cu–15Ni–8Sn alloy with Fe addition

The mechanical properties and microstructure transformation of Cu–15Ni–8Sn-xFe (x = 0, 0.1, 0.3, 0.5, wt. %) alloys prepared by vacuum induction melting were investigated by using optical microscopy (OM), atom-probe tomography (APT) and scanning transmission electron microscopy (STEM). The results showed that the addition of Fe in Cu–15Ni–8Sn alloy could improve the anti-aging resistance, hardness and tensile properties. Further, when the Fe content is 0.1%, the maximum hardness, ultimate tensile strength and yield strength of the alloy were 30 HV, 123 MPa and 58 MPa higher than that of the Fe-free alloy, respectively. Through APT analysis, it is found that Fe was mainly enriched at the core of the DO22 ordered phase, which probably the key factor to improve the performance. Moreover, the inhibition of the discontinuous precipitation (DP) was related to the increases in the interlamellar spacing of DP, the decrease in the solute diffusivity along the advancing boundary, and increase in the stability of the DO22 ordered phase.