Characteristics of Lead-free Machinable Brass of Powder Metallurgycu-40 MassZn/1.0 Mass mg with Graphite Particles

摘要

In this paper, highstrength and lead-free machinable brass alloy with magnesium (Mg)and graphite (Gr) particles was fabricated via powder technology process. Mg particles were added 1.0 mass% for strengthening of brass matrix. Gr particles as machinable elements were added to the Cu-40 mass%Zn/1.0 mass% Mg(Cu-40Zn/1.0Mg) premixed powder by conventional mixing process. Spark plasma sintering process was used to consolidate the above mixed powder at 973 K. The SPSed Cu-40Zn/1.0Mg + X%Gr specimens were pre-heated at the solid solutecondition of Cu-Zn-Mg IMC, and immediately extruded. The machinability was evaluated by a drilling test using a drill tool under dry conditions. The extruded materialsexhibited fine α-β duplex phases, containing very fine precipitates of CuMgZn IMCs with 1-2μm in diameter regardless of Graddition. There was no reaction phase of reducing the machinability between brass matrix and Gr particles. Tensile properties of the extruded Cu-40Zn/1.0Mg +0.75 mass% Grmaterialwereyield strength (YS): 351 MPa, ultimate tensile strength (UTS): 539 MPa, and 18% elongation. Average of drilling speed of Cu-40Zn/1.0Mg +0.75 Gr (N=10 times) was 0.15 mm/sthough the extruded Cu-40Zn/1.0Mg could not be drilled over 5 times.