On the discontinuous precipitation reaction and solute redistribution in a Cu-15%Ni-8%Sn alloy

Optical and transmission electron microscopy studies have been undertaken in order to clarify some morphological aspects of the discontinuous precipitation (DP) reaction in a Cu-15Ni-8Sn (wt.%) alloy in the temperature range 800–950 K. The DP reaction proceeds in the ternary Cu–Ni–Sn system relatively fast (in binary Cu–Ni alloy is not present) with typical morphological features like change of growth direction, appearance and disappearance of solute-rich γ lamellae. A fine continuous precipitation of single Ni and Sn-rich phase was also evidenced within the solute-depleted α lamellae. An energy-dispersive X-ray analysis showed the level of partitioning of the alloying elements. Most of the Ni and Sn is located in the γ lamellae. However, the formula of the γ lamellae is still close to (Cu3Sn), which indicates that some Cu atoms are replaced by Ni.