Rules of plastic strain-induced phase transformations and nanostructure evolution under high-pressure and severe plastic flow

Rough diamond anvils (rough-DA) are introduced to intensify all occurring processes during an in-situ study of heterogeneous compression of strongly pre-deformed Zr in diamond anvil cell (DAC). Crystallite size and dislocation density of Zr are getting pressure-, plastic strain tensor- and strain-path-independent during α-ω phase transformation (PT) and depend solely on the volume fraction of ω-Zr. Rough-DA produce a steady nanostructure in α-Zr with lower crystallite size and larger dislocation density than smooth-DA, leading to a two-time reduction in a minimum pressure for α-ω PT to a record value 0.67 GPa. The kinetics of strain-induced PT unexpectedly depends on time.