Interface design of lead-free free-cutting titanium reinforced graphite brass composites and its effect on mechanical properties and cutting performance

Abstract

Graphite (Gr) is used as a substitute element for lead to avoid environmental pollution and human hazards due to its solid lubrication and chip breaking similar to lead in brass. However, the mechanical properties of brass would be reduced due to non-wetting and weak interfacial bonding between Gr and brass matrix. Based on the preparation of graphite brass composites by powder metallurgy (P/M), the strength of the matrix is expected to be enhanced by solution and precipitation strengthening of titanium (Ti), and the interface bonding between Gr and brass matrix is improved by interfacial reaction of Ti with Cu and Gr to form intermetallic compounds. The results show that the addition of Gr can significantly improve the cutting performance of brass, but it is at the expense of mechanical properties. With the introduction of Ti, the formation of submicron Cu2Ti4O particles and nano Ti clusters effectively improves the mechanical properties of brass matrix. Meanwhile, TiC reaction layer formed on the interface significantly strengthens the interfacial bonding between graphite and the matrix, which is the basis of ensuring the good cutting performance of brass. The original graphite/brass non-reactive interface is transformed into graphite/reaction layer/brass and brass/precipitates/brass dual-interface structure. This study lays a research foundation for the development of lead-free free-cutting brass composites.