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Kinetic Wulff Shape: Effect of Interface Anisotropy on Grain Boundary Migration

Thursday (27.09.2018)
12:15 - 12:30 S1/03 - 223
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As microstructures evolve, the velocity of a grain boundary is controlled by both the driving force and the mobility. Since both of these quantities can be anisotropic, investigating their effect requires carefully designed experiments and analyses, beyond simply measuring average grain growth in a polycrystal. Growth of a large single crystal grain into a polycrystalline matrix is one experimental method to study the orientation dependence of interface migration as the driving force is determined by the matrix grains and the orientation of the interface can be controlled on average by the large grain. However, the curvature of the grain boundaries between the single crystal and the matrix grains changes the grain boundary plane orientation locally. Because the interface is moving, the shape of the interface is not expected to be composed of segments of grain boundary Wulff shapes, but will be a kinetic shape. In general, the kinetic shape of an isolated single crystal under condition of uniform driving force is bounded either by the slowest growing orientations for a growing crystal or by the fastest for a shrinking crystal. However, during grain growth, a grain boundary has both a “growing” and a “shrinking” grain. As a result, a “roughening” of the interface can occur on a scale larger than the matrix grain size, while highly anisotropic interface migration is possible locally even for an isotropic migration rate. The kinetic grain boundary Wulff shape can be determined from local measurements and compared to the equilibrium surface and grain boundary Wulff shapes to observe changes in the migration with composition and temperature. We have used this analysis on SrTiO3 and are extending it to SrTiO3-BaTiO3 and MgO-NiO alloys. Both systems show changes in the surface Wulff shape with composition and temperature. We will discuss how changes in the surface Wulff shapes impact microstructural evolution in these highly anisotropic systems.

Dr. John Blendell
Purdue University
Additional Authors:
  • David Lowing
    Purdue University
  • Matthew Michie
    Purdue University
  • Prof. Wolfgang Rheinheimer
    Purdue University
  • Prof. Carol Handwerker
    Purdue University