Microstructure evolution of a Cu-15Ni-8Sn-0.8Nb alloy during prior deformation and aging treatment

The microstructure evolution of Cu-15Ni-8Sn-0.8Nb alloy during prior cold deformation by rotary swaging (RS) and subsequent aging treatment was investigated. Electron back scattered diffraction (EBSD) results indicated that the deformed microstructure mainly consisted of refined and elongated grains. Discontinuous precipitates appeared at previous grain boundaries (PGBs) and shear bands after deformation of 45 pct reduction. Transmission electron microscope (TEM) studies revealed that the transformation kinetics of both DO22 ordered phases and discontinuous precipitates were significantly accelerated by prior deformation, and the transformation from DO22 to L12 ordering was suppressed to a certain degree. The maximum yield strength of the specimens with 45 pct reduction reached to about 1230 MPa after aging treatment, but the corresponding ductility was poor due to the rapid growth of discontinuous precipitates.