The effects of Nb additions on the microstructure evolution in Cu–9Ni–6Sn alloy.

Cu–9Ni–6Sn specimens with different Nb contents ranging from 0 to 0.22 wt% were prepared by a vacuum induction furnace, and needle-like NbNi 3 particles were found at the grain boundaries and interior after solution treatment. The results indicated that these NbNi 3 particles suppressed the discontinuous precipitation (DP) growth during aging treatment. By using Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and Arrhenius equation, the kinetics of DP is also figured out and the activation energy (Q) of the DP in Cu–9Ni–6Sn- x Nb (x = 0, 0.05, 0.22 wt%) alloys are 75.8 kJ/mol, 80.9 kJ/mol and 88.5 kJ/mol, respectively, indicating that the atom diffusion for producing DP is more difficult in Nb-bearing alloys, and the formation of DP is inhibited correspondingly. What's more, the lamellar spacing (S) of DP increased and the growth rate of DP decreased in the with the Nb-bearing Cu–9Ni–6Sn alloy. • Fine grain sizes are appeared in Nb-addition alloy. • The NbNi 3 particles are observed in Nb-addition alloy. • The DP in Cu–9Ni–6Sn alloy can be suppressed by addition of Nb. • Interlamellar spacing of DP increases with increasing Nb content. [ABSTRACT FROM AUTHOR]