High Pressure Phase-Transformation Induced Texture Evolution and Strengthening in Zirconium Metal: Experiment and Modeling

We studied the phase-transition induced texture changes and strengthening mechanism for zirconium metal under quasi-hydrostatic compression and uni-axial deformation under confined high pressure using the deformation-DIA (D-DIA) apparatus. It is shown that the experimentally obtained texture for omega-phase Zr can be qualitatively described by combining a subset of orientation variants previously proposed in two different models. The determined flow stress for the high-pressure alpha-phase is 0.5-1.2 GPa, more than three times higher than that of the a-phase. Using first-principles calculations, we investigated the mechanical and electronic properties of the two Zr polymorphs. We find that the observed strengthening can be attributed to the relatively strong directional bonding in the omega phase, which significantly increases its shear plastic resistance over the alpha-phase Zr. The present findings provide an alternate route for Zr metal strengthening by high-pressure phase transformation.