Effect of Cr addition on the microstructure and properties of Cu-15Ni-8Sn alloy

The Cu-15Ni-8Sn alloy has attracted considerable attention as a novel copper-based alloy material. The impact of chromium (Cr) addition on the microstructure and properties of the Cu-15Ni-8Sn alloy were investigated by using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the incorporation of Cr reduces the secondary dendrite spacing in as-cast alloys and effectively mitigates dendrite segregation. Additionally, Cr begins to precipitate during the solidification process, forming Cr-rich phases. During the aging process, these Cr phases occupy the nucleation sites of the discontinuous precipitates and impede the movement of their front interfaces, thereby effectively suppressing the formation of discontinuous precipitates. The addition of 0.7 wt% Cr exhibited the most pronounced inhibitory effect, leading to a peak hardness of 357.9 HV, tensile strength of 742.6 MPa, and conductivity of similar to 9.8 % IACS after aging at 450 degrees C for 7 hours.