Effects of ageing treatment on microstructure and mechanical properties of cast Cu-15Ni-8Sn alloy were investigated. It is found that with ageing at 400 癈
the supersaturated solid solution a is firstly decomposed spinodally
then the metastable ?’ precipitated phase appears after spi-nodal decomposition
and thereafter discontinuous precipitation ? phase occurs in grain boundary. The microstructure transformation process affects the mechanical properties of the alloy with ageing treatment. Tensile strength
yield strength and hardness of the alloy are gradually increased to a peak value (formation of meatstable ?’precipitated phase ) earlier
then is decreased with increasing the ageing time or temperature. Fracture toughness of the alloy is severely impaired due to the grain boundary precipitates.