Lawrence Berkeley National Laboratory

The recently discovered pressure-induced polymorphic transitions (PIPT) in high-entropy alloys (HEAs) have opened an avenue towards understanding the phase stability and achieving atomic structural tuning of HEAs. So far, whether there is any PIPT in the body-centered cubic (bcc) HEAs remains unclear. Here, we studied an ordered bcc-structured (B2 phase) AlCoCrFeNi HEA using in situ synchrotron radiation X-ray diffraction (XRD) up to 42 GPa and ex situ transmission electron microscopy, a PIPT to a likely-distorted phase was observed. These results highlight the effect of the lattice distortion on the stability of HEAs and extend the polymorphism into ordered bcc-structured HEAs.