Microstructure and properties of Cu-Cr-Nb/graphite composites with high softening temperature

Abstract

In the study high-energy ball milling was employed to fabricate Cu-Cr-Nb /graphite composites through the powder metallurgy method. Cu-Cr-Nb powders mixed with flake graphite were milled together and combined with various concentrations of Cu–10Sn by continuous high-energy ball milling. Rapid hot press sintering was applied to create Cu-Cr-Nb/graphite/Sn composites. In situ carbide production and alloying elements in Cu-Cr-Nb alloys were employed to enhance the material's characteristics. The composites' mechanical properties and softening temperature were characterized. Results indicated a speckled C solid solution in the composite Cu-Cr-Nb/graphite powders. The Cu-Cr-Nb/graphite composites produced in this experiment had a density of >99 %, a hardness of 94 HV, a friction coefficient of 0.12 (the load of 10 N), a compressive yield strength of 185.4 MPa, and a high-temperature softening resistance of 900 °C. To generate carbide, the composites were significantly enriched in Cr and C toward the boundary. The Cr precipitates and the trace of Cr-carbides not only increased mechanical properties but also hindered recrystallization and grain growth, enhancing the softening temperature.