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Cu-30Ni-xRE (x = 0-0.213) alloys were prepared by a metal mould casting method. The effect of RE on the microstructure and mechanical properties of the alloys was investigated using optical microscope, scanning electronic microscope with energy-dispersive spectrometer, X-ray diffraction, and mechanical test. The results show that RE has obvious effect on refining dendrite structure and grain size, as well as on purifying the melting of Cu-30Ni alloy. With the increase of RE content, the ultimate tensile strength, yield strength, and elongation increase at first and then decrease after adding RE more than 0.095 wt.%. Cu-30Ni-0.095RE alloy possesses preferable mechanical properties, i.e., the ultimate tensile strength, yield strength, and elongation are 308 MPa, 125 MPa, and 51.2%, respectively. The microstructure and mechanical properties are worsened with increasing RE content more than 0.095 wt.%. The improvement of mechanical properties of Cu-30Ni-0.095RE alloy is attributed to RE refining microstructure and purifying the matrix.

Many studies suggest that severe plastic deformation (SPD) can produce nanocrystalline metallic structures. Based on structural characterization using transmission electron microscopy, dislocation cellular structures are indeed produced by SPD. However, should we regard such nanocellular structures as nanocrystalline? In other words, can SPD alone produce a well-defined nanocrystalline structure? In this study, we applied SPD to surfaces of Cu-30Ni alloy specimens by repeated punching and divided them into two groups; one of which was subjected to subsequent annealing (recovery treatment) and the other was not. Both groups showed similar nanocrystalline morphologies under an atomic force microscope. However, their surface and electrochemical properties are quite different, evidenced by differences in the electron work function, electrochemical polarization behavior, and other properties. This indicates that simply categorizing the SPD-produced structures with cellular domains as nanocrystalline structures is questionable.