Orientation relationship formed during irradiation induced precipitation of W in Cu

Abstract

Irradiation of dilute Cu–W alloys with 1.8MeV Kr+ between 300K and 573K is found to induce nucleation of a high density of W nano-precipitates. HRTEM and aberration-corrected STEM reveal that the ∼3nm precipitates have a preferred orientation relationship with the matrix. A variant of the Bain relationship exists with preferred alignment occurring along Cu〈220〉||W〈010〉, with small angular differences amongst the particles, which is compensated by interfacial dislocations or strain. The formation mechanism for such an orientation relationship is rationalized on the basis that small W clusters form within the local melt of an energetic displacements cascade, resulting in the partial alignment of the nanoprecipitates with the Cu lattice as the Cu solidifies.