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

Abstract

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-Cu+Ni₃Si. The third and fourth phase transformation could be described to the precipitation of the δ-Ni₂Si phase in the region close to the grain boundary phase and the internal of the primary α-Cu grains respectively.