First experimental observation of shear induced hcp to bcc transformation in pure Zr.

Shear stresses are shown to induce the alpha (hcp) to omega (simple hexagonal) plus beta (bcc) transformation in pure Zr at room temperature. The beta Zr thus fabricated is stable at 1 atm and room temperature. This phase has so far only been found to occur at high pressures (P>30 GPa) and/or at high temperatures (T>1135 K). This experimental observation provides new insights about the physical processes underlying allotropic transformations and opens the door to future investigations aiming to stabilize high temperature or pressure phases at ambient conditions.