Pressure–temperature route from disordered BCC to a 2 × 2 × 2 B2 superstructure

The interplay between configurational entropy and the enthalpy of ordered structures governs phase stability in compositionally complex alloys. In the refractory alloy Re_0.6(NbTiZrHf)_0.4, this balance is particularly delicate: pressure stabilizes a disordered body-centred-cubic (bcc) solid solution over the ambient hexagonal Laves phase via a martensitic route. Using in situ laser heating with synchrotron X-ray diffraction in a diamond-anvil cell, we demonstrate that the metastable bcc phase can be controllably transformed into a large-scale 2 × 2 × 2 B2-type superstructure with primitive-cubic symmetry ([Formula: see text]). This long-period ordered phase is crystallographically distinct from conventional B2 ordering in multicomponent alloys, establishing a pathway to achieve chemical ordering from pressure-stabilized solid solutions. More broadly, these findings demonstrate that combining compression with subsequent thermal activation can unlock recoverable three-dimensional superstructures, offering new opportunities to tailor strength, transport properties, and stability in compositionally complex alloys.