Tailoring the solidification microstructure and properties of Cu–12Sn-xBi-2Ni alloys by varying Bi content

Abstract

A novel self-lubricating Cu–12Sn-xBi-2Ni alloy was developed and the effect of Bi on microstructure and properties of Cu–12Sn-xBi-2Ni was investigated. The formation reason of the solidification microstructure was analyzed by CALPHAD method and verified by water quenching experiment. The mechanical properties and the friction properties of alloys were tested by the pin-on-disc wear tester and electronic universal material tester. The tensile property deteriorates with the increase in Bi content, while the Brinell hardness and anti-friction properties of the alloy are enhanced, and Cu–12Sn–6Bi–2Ni alloy is identified to be the alloy with the best self-lubricating property. The addition of Bi increases the number of Sn-rich phase and changes the morphology of Sn-rich phase, resulting in fine Bi-rich phase and lamellar microstructure precipitate around the Sn-rich phase. Liquid Bi as nucleating particles promotes the precipitation of δ phase, resulting in the formation of lamellar δ phase and the Sn-poor α-Cu phase.