2009 Volume 50 Issue 4 Pages 776-781
Microstructure, tensile properties and Vickers hardness of the copper sulfide (Cu2S)-dispersed bronze produced by adding MoS2 to molten bronze consisting of Cu and Sn were examined. The amount of Cu2S and the number of casting defects increase with the amount of added MoS2. The Vickers hardness of Cu2S-dispersed bronze increases with the amount of added MoS2. This is because the solid-solution hardening owing to Mo and the hardening due to the dispersion of Cu2S are superior to the softening due to casting defects. The tensile strength of Cu2S-dispersed bronze decreases with increasing amount of added MoS2. This is because the softening due to casting defects outweights the solid-solution hardening due to Mo and the strengthening due to the dispersion of Cu2S. The fracture elongation of Cu2S-dispersed bronze decreases with the amount of added MoS2. This is because the number of casting defects increases and Cu2S acts as a nucleus of voids. To produce Pb-free bronze having excellent machinability and mechanical properties equivalent to those of CAC406 containing Pb and CAC902 containing Bi, adequate control of the amount and size of Cu2S and the number of casting defects is of great importance.