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Lecture

Shape Memory Effect in Zirconia-Based Ceramics via Micropillar Compression

Monday (17.06.2019)
14:30 - 14:45

Martensitic transformations, which give rise to the interesting properties of Shape Memory Alloys (SMA), has long been studied in metallic systems, yet its application to oxides has been limited. Known for their transformation toughening mechanism, the chemical composition of zirconia-based ceramics can be altered to increase the interphase compatibility between its high temperature phase (Austenite) and low temperature phase (Martensite), exhibiting a high potential for Shape Memory Effects (SME). Transmission Electron Microscopy (TEM) and Electron Backscattering Diffraction (EBSD) reveal grains of both retained Austenite and stable Martensite at room temperature, as well as finely twinned microstructure within single Martensite grains. We use uniaxial compression tests on single-crystalline nano- to micro-pillars as well as free-standing single-crystalline particles to characterize the mechanical properties of the studied samples. We recover the full circle one-way SME in samples with high compatibility and reveal a deformation mechanism of combined slip and twinning that is strongly dependent on the crystal microstructures, orientation, and sample composition. Experiments conducted on pillars of different diameters show a size effect on the critical stress for martensite rearrangement, which can give insight into the role of deformation twinning in ceramic plasticity.

Speaker:
Haolu Zhang
California Institute of Technology
Additional Authors:
  • Justin Jetter
    Kiel University
  • Hanlin Gu
    University of Minnesota
  • Richard D. James
    University of Minnesota
  • Eckhard Quandt
    Kiel University
  • Julia R. Greer
    California Institute of Technology