Experimental investigation on phase transformation of Cu-Ni-Si alloy melts during cooling

Rapid water quenching experiments were first carried out according to differential scanning calorimetry results, and then the microstructure and phase composition of such water quenching Cu-8·33Ni-1·67Si (wt-%) samples were investigated. Subsequently, calculation on the competition nucleation of the primary phase was also carried out. Based on the experimental and calculational results, the phase transformation behaviour of Cu-8·33Ni-1·67Si melts during the cooling process was discussed, and the results can be summarised as follows. First, the α-Cu phase formed as a primary phase due to the shorter incubation time and higher time dependent nucleation rate. Subsequently, a eutectic reaction occurred in the interdendritic residual liquid phase of the primary α-Cu grains, and its product was α-CuzNi₃Si. The third and fourth phase transformation could be described to the precipitation of the δ-Ni ₂Si phase in the region close to the grain boundary phase and the internal of the primary α-Cu grains respectively.