Effect of inclusion on strength and conductivity of Cu-Ni-Si alloys with discontinuous precipitation

The effect of inclusion on the strength and conductivity of fully discontinuous precipitated Cu-Ni-Si alloys with and without inclusion was studied. No inclusions were observed in Cu-4.75Ni-1.13Si alloy, the Ni + Si content of which was close to the solubility limit, while they were formed in solution-treated Cu-6Ni-1.42Si alloy at 980 degrees C. The duration of aging for full discontinuous precipitation (DP) at 500 degrees C was found to be shorter in Cu-6Ni-1.42Si alloy than Cu-4.75Ni-1.13Si alloy. The strength/conductivity of Cu-6%Ni-1.42%Si alloy with inclusion was 1071 MPa/46% IACS, while it was 966 MPa/50% IACS for Cu-4.75Ni-1.13Si alloy without inclusion, after drawing to the strain of 4. The drawing-induced uni-directional alignment of fiber-like Ni2Si precipitates was believed to increase the conductivity of Cu-Ni-Si alloys by reducing the cross sectional area of lamellar precipitates for the passage of electrons. The increase in strength was possibly due the higher volume fraction of fiber-like Ni2Si precipitates, along with the smaller inter-distance between them, in Cu-6%Ni-1.42%Si alloy with inclusion, than Cu-4.75Ni-1.13Si alloy without inclusion. (C) 2020 Elsevier B.V. All rights reserved.