Fabrication and properties of lead-free machinable brass with Ti additive by powder metallurgy

The aim of this paper was to investigate the properties of Cu40Zn2.2Bi + Ti for the development of a new lead-free, high-strength and machinable brass by powder metallurgy. The effect of Ti addition on the mechanical properties and machinability of BS40-2.2Bi (Cu40Zn2.2Bi) brass was studied with respect to different contents of Ti addition. BS40 (Cu40Zn) and BS40-2.2Bi brass powders were prepared by water atomization process, and the β phase was retained in the raw powders predominately. The BS40-2.2Bi powder and Ti powder were elementally mixed to prepare BS40-2.2Bi + xTi (x = 0.3, 0.5 and 1.0 wt.%) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that intermetallic compounds (IMCs) such as Ti 2Bi were formed via the reaction between additive Ti and Bi alloying elements, and improved the ductility of BS40-2.2Bi significantly. The yield strength (YS) and ultimate tensile strength (UTS) were increased by increasing the contents of Ti addition, however, the elongation showed a decrease trend and the machinability became worse. The optimal content of Ti addition was 0.3 wt.%, which served excellent mechanical properties and machinability comparing with BS40-2.2Bi. For example, it had a YS of 235 MPa, a UTS of 459 MPa and an elongation of 39%, which showed 4.9%, 4.1% and 18% higher than that of extruded BS40-2.2Bi brass, respectively. The water atomized BS40-2.2Bi powder was prepared to retain super-saturation of Bi in brass powder. Ti powder was elementally mixed to prepare BS40-2.2Bi + xTi (x = 0.3, 0.5 and 1.0 wt.%) premixed powders. The premixed powders were solidified by spark plasma sintering (SPS) and extruded subsequently, to prepare lead-free machinable brass. [Display omitted]