Characteristics and machinability of lead-free P/M Cu60–Zn40 brass alloys dispersed with graphite

The aim of this paper was to produce a lead-free machinable brass dispersed with graphite particles by powder metallurgy process.The weight of brass powder decreased with increasing the heat treatment temperature over 873 K by vaporized zinc. The voids were also observed according to Kirkendall effect by the difference of diffusion velocity between Cu and Zn at the brass powder surface. In the case of spark plasma sintering, however, zinc vaporization has not occurred because of sealing pressurization and pressure forming. A specimen of brass without graphite particle, sintered at 1053 K by SPS, had a large elongation similar to that of the cast brass alloy.Using the blended brass powder with graphite particles, graphite particles were dispersed in extruded material by applying the SPSed billet. P/M extruded brass alloys with 1 mass% graphite particle was significantly effective to improve their machinability as well as the conventional brass alloys with lead.

The uniform distribution process of graphite particles into brass alloy by powder metallurgy (P/M), and machinable lead-free P/M brass with graphite additives were described. In extruded material using the sintered compact produced by spark plasma sintering (SPS), graphite particles are kept separated during extrusion through the effect of combined primary particle boundary.Figure optionsDownload as PowerPoint slide