Tensorial stress-plastic strain fields in α - ω Zr mixture, transformation kinetics, and friction in diamond anvil cell

Various phenomena (phase transformations, chemical reactions, microstructure evolution, strength, and friction) under high pressures in diamond anvil cell are strongly affected by fields of all components of stress and plastic strain tensors. However, they could not be measured. Even measured pressure distribution contains significant error because axial strain does not contribute to x-ray patterns, and the equation of state determined under hydrostatic conditions is used for nonhydrostatic loading. We suggest coupled experimental-analytical and experimental-analytical-computational approaches utilizing synchrotron x-ray diffraction to solve an inverse problem and find fields of all components of stress and plastic strain tensors in each phase and mixture and friction rules before, during, and after α-ω phase transformation in strongly plastically predeformed Zr. The results of both approaches are in good correspondence with each other and experiments. Due to advanced characterization, the minimum pressure for the strain-induced α-ω phase transformation is changed from 1.36 to 2.7 GPa. It is independent of the plastic strain before phase transformations and compression-shear path. The theoretically predicted plastic strain-controlled kinetic equation is verified and quantified. Obtained results open opportunities for developing quantitative high-pressure/stress science, including mechanochemistry, synthesis of new nanostructured materials, geophysics, and tribology.