Deformation mechanisms of the Cu-15Ni-8Sn-0.18Nb alloy in as-quenched and aged conditions

The Cu-15Ni-8Sn (wt%) based alloys exhibit an excellent combination of strength, stress-relaxation resistance and corrosion-resistance properties, and have become an important material widely used in aerospace, ocean and mining industries. So far, the mechanical behaviors of the alloys have not been understood, which limits the effective regulation of the mechanical properties of the alloys. To improve understanding of deformation mechanisms responsible for its mechanical properties, tensile tests were performed at room temperature and interrupted at the special strains to acquire deformation microstructures, and the deformation microstructures are characterized by electron backscattered diffraction and transmission electron microscopy. In contrast to pure copper in which dislocation slipping dominates the plastic deformation, the results indicate that the mainly deformation mechanism of the as-quenched Cu-15Ni-8Sn-0.18Nb alloy includes deformation twinning, dislocations slipping and generation of stacking faults (SFs), while deformation twins are inhibited in the aged sample, and dislocations and SFs dominate the deformation microstructure. The reasons for the change of deformation mechanism are due to the different stacking fault energy in the as-quenched and aged samples and the hindering effect of nanoscale precipitates to twinning in the aged sample.