EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Refractory multi-principal element alloys (MPEA) with single-phase body-centered cubic (bcc) structure, such as the NbMoCrTiAl system and TaNbHfZrTi, are promising candidates for high-temperature applications. NbMoCrTiAl, like other refractory HEAs, are typically brittle at ambient temperature and fail in a catastrophic manner during conventional mechanical testing. However, TaNbHfZrTi shows ductility up to 40% strain. There is limited research to understand the difference in these deformation behaviors and mechanisms. In this study, to understand the mechanical behavior of the two bcc refractory MPEAs in terms of dislocation nucleation nanoindentation is used.

The comparison of dislocation nucleation of the different alloys was made based on a statistical analysis of the pop-in phenomena. Considering the bcc structure of the alloys, the nucleation is expected to be heterogeneous and may be aided by atom-vacancy exchange. The reported dislocation mechanism for the aforementioned alloys is expected to influence the dislocation nucleation mechanisms. There are clear differences in the behaviors of the two alloys studied, which will be discussed with regard to our current understanding of the deformation of bcc metals and alloys.