Effect of Zr addition on microstructure, mechanical and tribological properties of Cu-Ni-Sn alloy fabricated by spark plasma sintering

Synergistic improvement between the mechanical properties and wear resistance of Cu-Ni-Sn alloys is critical for extending the service life of materials in practical applications. In this study, Cu-12.5Ni-5Sn-xZr alloys (x = 0, 0.5, 1.0, and 1.5 wt%) were prepared by spark plasma sintering (SPS). Subsequently, the effects of Zr addition on the microstructure, mechanical, and high temperature tribological properties were systematically investigated. We found that Zr addition significantly refined the alloy grains and allowed the gamma-phase to more easily precipitate with needle-like or particulate-like shapes. When 1.0 wt% Zr was added, the formation of nano-scale Ni4SnZr phase inhibited discontinuous precipitation (DP) nucleation and reduced the growth rate. Meanwhile, the hardness and yield strength reached aging peaks of 326.8 HB and 669.5 MPa, respectively, which were approximately 30 % and 43 % higher than without Zr. This improvement was mainly attributed to grain refinement, nano-precipitation strengthening and the inhibition of DP. Furthermore, the addition of 1.0 wt% Zr could improve the tribological properties of the matrix alloy, especially the wear rate reached an order of magnitude of 9.28 x 10_6 mm3/N & sdot;m at room temperature. From room temperature to 500 degrees C, the decrease in friction coefficient of the alloys was mainly due to the formation of metal oxides, whereas the increase in wear rate was mainly the decrease in mechanical properties and severe oxidation at high temperature.