Microstructures and properties of Cu-10Sn oil bearings reinforced by Al2O3 nanoparticles

Using Sn and Cu-Al powders as raw materials, three oxide dispersion-strengthened (ODS) Cu-10Sn alloy powders with different Al₂O₃ mass content (0.42%, 0.85% and 1.68%, respectively) were prepared by mechanochemical synthesis combined with diffusion alloying method. The oil bearings were then fabricated by pressing and sintering. The effects of Al₂O₃ on microstructures and properties of the powders and the oil bearings were investigated. The results show that Al₂O₃ nanoparticles with sizes of about 5 nm are uniformly distributed in the ODS Cu powders. The content of Al₂O₃ nanoparticles has no effect on the distribution uniformity of tin during the diffusion process. And three ODS Cu-10Sn alloy powders with homogeneous tin distribution are prepared. However, the temperatures of forming liquid phases in the ODS Cu-10Sn alloys decrease with increasing Al₂O₃ content. This affects the sintering behaviors and mechanical properties of oil bearings. Increasing Al₂O₃ content also has a significant promoting effect on the precipitation of Sn-rich particles. In order to synergize the solid solution strengthening of tin and the dispersion strengthening of Al₂O₃ nanoparticles, the content of Al₂O₃ in the ODS Cu-10Sn alloys will not exceed 0.85%. The ODS Cu-10Sn oil bearings with 0.42% Al₂O₃ sintered at 900 °C have the best comprehensive properties, with uniform radial and axial shrinkage, oil content of 19.1%, radial crushing strength of 284 MPa and micro-hardness of 142 HV.