The Precipitation and Strengthening Mechanism of Cu-Ni-Si-Co Alloy

The precipitates, mechanical properties and strengthening effect of Cu-Ni-Si,Cu-Ni-Si-Co0.8 and Cu-Ni-Si-Co1.9 alloys are investigated. It is concluded from the TEM and XRD analysis that the strengthening of Cu-Ni-Si-Co alloy is mainly attributed to precipitates of both Ni2Si and Co2Si phases, with the same structures and very close lattice parameters. The addition of 1.9 wt% Co barely affects the precipitation process of Ni2Si or Co2Si, and may not be beneficial for enhancing the strength. The strengthening of Cu-Ni-Si-Co alloy is determined by the Orowan mechanism, and a critical precipitate radii rc about 1.5 nm corresponding to the peak strength is obtained through the theoretical analysis. It can be deduced that the peak strength of aged Cu-Ni-Si-Co alloy is obtained with the microstructures containing metastable phase and Ni2Si (or Co2Si) precipitates.