Effects of Dendrite Spacing of Ingot and Cold Deformation Amount on Microstructure and Hardness of Cu-15Ni-8Sn Alloy

Cu-15Ni-8Sn alloy ingots with dendrite spacing of 11, 18, 23, 50 mm, respectively, were prepared by intermediate frequency induction furnace and high frequency induction furnace, and then treated in the order of homogenization annealing, solid solution, cold deformation and aging. The effects of dendrite spacing of the ingot and cold deformation amount on the microstructure and hardness of the alloy were studied. The results show that the microstructures of the tested alloy ingots were obvious dendritic structures. After homogenization annealing and solid solution, the microstructure of the alloy with relatively small ingot dendrite spacing was relatively uniform. The deformation of grains in the alloy was relatively large with a relatively large cold deformation amount, furthermore the black discontinuous precipitates and the aging hardness peak appeared earlier after aging at 400℃. With the same cold deformation amount, the black discontinuous precipitates and the aging hardness peak appeared later in the alloy with relatively small ingot dendrite spacing.