Observations of dislocations near θ' precipitates in neutron-irradiated Al-4% Cu by WBDF

Abstract

In this paper some observations of dislocation structure in a neutron-irradiated Al—4% Cu alloy containing θ' precipitate are reported. Both weak-beam dark-field and strong-beam bright-field methods were used. During irradiation, coherency loss begins to occur, and swelling resistance decreases. The WBDF method is necessary to resolve dislocation configurations near the matrix/precipitate interfaces.The microstructure of the alloy after a neutron fluence of 2.8 x 1025 n/m2(E>0.1 MeV,T ∼ 330 K) is shown in WBDF (Fig. 1). The main features of the irradiated microstructure are the θ' precipitates, faulted and unfaulted loops with diameter ∽30 nm in the matrix, a few long dislocations lying in the precipitate/matrix interfaces, and some small (< 10 nm) contrast features in the background. The latter may be a result of the small amount of Si formed during irradiation by transmutation of the Al. Of primary present interest are dislocations in and near the interfaces.