Microstructure and solidification behavior of Cu-Ni-Si alloys

摘要

The microstructure and solidification behavior of Cu-Ni-Si alloys with four different Cu contents was studied systematically under near-equilibrium solidification conditions. The microstructures of these Cu-Ni-Si alloys were characterized/by SEM and the phase composition was identified by XRD analysis. The phase transition during the solidification process was studied by DTA under an Ar atmosphere. The results show that the microstructure and solidification behavior is closely related to the composition of Cu-Ni-Si alloys. The microstructure of Cu-Ni-Si alloys with higher than 40 percent Cu content consists of primary phase alpha-Cu(Ni, Si) and eutectic phase (beta_1-Ni_3Si+alpha-Cu(Ni,Si).When the Cu content is about 40 percent, only the eutectic phase (beta_1-Ni_3Si+alpha-Cu(Ni,Si)) is present. DTA analysis shows there are three phase transitions during every cooling cycle of alloys with higher than 40 percent Cu content, but only one for 40 percent Cu content. Cu-Ni-Si alloy with 40 percent Cu solidifies by a eutectic reaction, but Cu-Ni-Si alloys with higher than 40 percent Cu content solidify as a hypoeutectic reaction.