Effects of yttrium addition on grain boundary character distribution and stacking fault probabilities of 90Cu10Ni alloy

In this comparative study, the grain boundary character distribution (GBCD) and stacking fault probability (P-sf) of 90Cu10Ni alloys with different amounts of the rare earth (RE) element yttrium (Y) are investigated. The results showed that the frequency of low-Sigma CSL boundaries, especially the Sigma 3 twin boundaries, was significantly enhanced with increasing the Y addition. Meanwhile, the increase in Psf implies that Y can reduce the stacking fault energy of the 90Cu10Ni alloy, and promote the formation of twining. On the other hand, the yttrium-rich oxysulfide inclusion distributed uniformly in grain boundary and the Ni2Y precipitates dispersed in the matrix hinder the movement of dislocations and thus increase the density of dislocations during deformation. After subsequently final annealing step, they would be also conducive to the formation of twins and of large grain clusters.