The high-temperature rheological behavior of polycrystalline periclase, MgO, has been investigated using the deformation-DIA on a synchrotron beamline at pressures up to 10 GPa. Significant experimental scatter in stress measurement illustrates current limitations of this technique. Although temperature and stress sensitivities are not well constrained, there is a clear dependence of creep rate on pressure. Based on our results, the creep rate of MgO depends on confining pressure with an activation volume of V* ≈ 2.4 × 10-6 m3/mol. The grain-scale view of deformation processes reveals, as other D-DIA studies have, that subpopulations of grains, grouped by orientation, obey slightly different flow laws. The measurements also reveal that stress heterogeneity in the sample, whether caused by external conditions or processes internal to the sample itself, contribute a significant portion of the overall uncertainty in stress measurement.
Bibliographical noteFunding Information:
This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under contract W-7405-ENG-48 (LLNL) and grant DE-FG02-04ER15500 (UMN). Experiments were carried out at the X17B2 beamline of the National Synchrotron Light Source, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences under Contract No. DE-AC02-76CH00016 and by COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF Cooperative Agreement EAR 01-35554. We thank Drs Mike Vaughan, Donald Weidner, Li Li for their technical support and/or discussions at the X17B2 beamline.