Antiphase boundaries in B2 intermetallics: Proximate structures, formation energies, and chemical stability

Multiphase bcc/B2-based alloy systems have recently received considerable attention because their microstructures are often remarkably similar to the gamma /gamma' microstructure of Ni-based superalloys. The underlying plastic deformation mechanisms of bcc-based intermetallics, however, are not well understood across the composition space where they are thermodynamically stable. Within this contribution, we analyze deformation of B2 intermetallics to develop a reliable platform for efficiently predicting antiphase boundary energies and the associated fault widths as a function of elemental substitution on a particular lattice site of the intermetallic. To achieve this we extend the diffuse multilayer fault model to predict close packed structures that recreate the bonding environment within the layers adjacent to the 12 (111){110} antiphase boundary of the B2 intermetallic. Specifically, the impact of elemental substitution on both antiphase boundary energy and fault width is presented for Hf1_xTixRu and Hf1_xAlxRu and the implications of our findings are discussed. We also highlight a simple bonding model for transition metal -based B2 intermetallics that explains their chemical stability and large antiphase boundary energies. The results presented here offer insight into both the nature of plastic deformation within the B2 intermetallic and the important underlying chemical concepts that can potentially be leveraged to aid in the design of bcc-based alloy systems that rival Ni-based gamma /gamma' microstructures.