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Precipitation in a Cu-20%Ni-8%Sn Alloy and the Phase Diagram of the Cu–Ni Rich Cu–Ni–Sn System

1984; Japan Institute of Metals and Materials; Volume: 25; Issue: 9 Linguagem: Inglês

10.2320/matertrans1960.25.593

2432-4701

Masamichi Miki, Yoshikiyo Ogino,

Microstructure and mechanical properties

The precipitation sequence in a Cu-20 mass%Ni-8 mass%Sn alloy at 623–773 K and the equilibrium phase diagram at 823 K of Cu–Ni–Sn system were investigated by optical and electron microscopic observations, X-ray analysis, and hardness measurements.The equilibrium precipitate phase in a Cu-20%Ni-8%Sn alloy was δ phase (β-Cu3Ti type) with the lattice parameters of a=0.451, b=0.538 and c=0.427 nm. The precipitation sequence of this alloy is as follows; (1) α-supersatulated solid solution, (2) the formation of the modulated structure in a matrix and (3) the growth of the cell consisted of equilibrium α and δ phases. The ordered phases in the modulated structure at 723 K and 673 K were DO22 and L12 type, respectively. The values of apparent activation energies for intragranular and cellular precipitation of this alloy are 170 and 180 kJ/mol, respectively.The phase boundaries among (α+γ(DO3)), (α+γ+δ), (α+δ), (α+δ+θ(DO19)) and (α+θ) regions at 823 K in the Cu–Ni rich Cu–Ni–Sn system were determined.