Shear driven instability in zirconium

Figure caption: Elastic moduli measured under various high pressure and high temperature conditions, displayed in contour plots of the longitudinal modulus (a), shear modulus (b), and adiabatic bulk modulus (c), all numbers in GPa. Overlaid on these plots are proposed phase boundaries.
Figure caption: Elastic moduli measured under various high pressure and high temperature conditions, displayed in contour plots of the longitudinal modulus (a), shear modulus (b), and adiabatic bulk modulus (c), all numbers in GPa. Overlaid on these plots are proposed phase boundaries.

Zirconium has a low neutron cross section and high degree of corrosion resistance. It is widely used in industry and engineering, in particular in the area of refractory applications. Knowledge of elastic and thermal properties of zirconium is important for understanding the behavior and performance of the materials at extreme conditions. By combining X-ray diffraction and X-ray imaging techniques, together with ultrasonic wave velocity measurements, in a Paris-Edinburgh press at HPCAT, a research team has determined multiple elastic and thermal properties including bulk modulus, shear modulus, Poisson’s ratio, and Debye temperature at high pressure and high temperature conditions.  The results show marked changes in the elastic moduli across the a-w phase transition.  In particular, a clear shear softening is observed in a narrow temperature range across the a-w phase transition.  Exploration of the pressure-temperature phase diagram in view of the elastic and thermal properties provides fundamental information on understanding the nature of the phase transition.   Details in Jacobsen et al., Phys. Rev. B, 95, 134101, 2017.