On the bcc/B2 interface structure in a refractory high entropy alloy

Abstract

A refined microstructure consisting of bcc precipitates embedded in an ordered B2 matrix has been observed in the refractory high entropy alloy (RHEA) AlMo0.5NbTa0.5TiZr, resembling an “inverted superalloy-like” microstructure. A planar {100} bcc/B2 interface exists in this state. Coarsening of the microstructure occurs after aging at 1000 °C for 6 h, resulting in a faceted interface. In this case, the primary plane of the interface is parallel to a {100} plane, while the step associated with the facet is parallel to a {110} plane. Misfit dislocations at the interface were observed on the {110} interface plane, with Burgers vector of a/2〈111〉bcc, which extend into the bcc phase, and have an average spacing of 13.7 ± 0.6 nm. No lattice invariant deformation (LID) normal to the primary {110} planes was observed, such that the transformation between the B2 and bcc phases constitutes a pure expansion.