In-situ radial synchrotron diffraction in conjunction with the diamond anvil cell (DAC) or deformation-DIA (D-DIA) multi-anvil press can be used to study the response of materials to non-hydrostatic stresses at extreme pressures and temperatures.   In particular, radial diffraction can be used to measure lattice strain and texture (crystallographic preferred orientation) development during deformation at extreme conditions.  Lattice strains can be used to calculate the stress supported by the sample and in turn to estimate the sample’s flow strength.  Texture development can be used to understand deformation mechanisms, phase transformation mechanisms, and anisotropy development in polycrystals.  If a polycrystal is composed of anisotropic minerals, texturing can result in bulk anisotropy of physical properties such as magnetic properties, heat flow, electrical conductivity, elastic properties, and plastic properties.  During deformation, texture development results from dislocation glide and twinning and can be modified by recrystallization and phase transformation.  By using polycrystal plasticity codes to model experimental data, deformation mechanisms and activities can be determined for the conditions of the experiment.  In previous years we have used the ViscoPlastic Self-Consistent (VPSC) code to model texture development as a function of slip system activities.  However, recently we modified and applied the Elasto-Viscoplastic Self-Consistent (EVPSC) method to simultaneously model texture and lattice strain evolution during high pressure and temperature deformation experiments.  Compared to VPSC, EVPSC has the advantage that the additional constraints from lattice strains can resolve slip systems that generate ambiguous textures, can provide constraints on secondary slip systems and can quantitatively determine polycrystal critical resolved shear stress values. This talk will cover recent examples of deformation experiment as high pressures and temperature in the DAC and D-DIA, and will discuss the application of polycrystal plasticity modeling to characterize deformation mechanism at extreme conditions. <br/>

Deformation mechanisms at extreme conditions

256th National Meeting (2018)

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