Microstructure Evolution of Hot-Extruded Cu-15Ni-8Sn Alloy with Different Extrusion Ratios

Cu-15Ni-8Sn alloy is a spinodal hardened alloy which possesses excellent combination of strength, elastic modulus, corrosion resistance and wear resistance. Much concern focuses on the microstructures and properties of this wrought alloys after heat treatment, however, the microstructure feature of the alloy during hot plastic deformation processing is rarely declared. The microstructure evolution of the hot-extruded Cu-15Ni-8Sn alloy with different extrusion ratio were investigated by optical microscope, scanning electronic microscope, electron backscattered diffraction. The results showed that dynamic recrystallization occured during hot extrusion at extrusion ratio ranging from 6 to 17. With the increase of extrusion ratio, the fraction of recrystallized grain increased. However, the amount of discontinuous γ precipitates reduced. The cellular structure was observed to grow not only on grain boundaries but also in the coarsening annealing grains when the extrusion ratio was below 13. When extrusion ratio was 17, the discontinuous γ precipitates and the residual annealing grains were suppressed and some recrystallized grains grew up.