Orientation dependency of the alpha to omega plus beta transformation in commercially pure zirconium by high-pressure torsion

The alpha (α) to omega (ω) plus beta (β) phase transformation in pure zirconium by high-pressure torsion depends on the orientation of the polycrystalline aggregate with respect to the applied stress. The transformation can be triggered without any applied shear at 1 GPa when the pressure is perpendicular to the c-axes. Twinning plays a major role in the transformation, as it gives rise to new boundaries, which are favorable sites for dislocation pile-ups and therefore constitute potent stress-concentration points.