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Ferroelastic and Plastic Behaviors in Pseudo-Single Crystal Micropillars of Nontransformable Tetragonal Zirconia

48 Pages Posted: 1 Jun 2020 Publication Status: Accepted

See all articles by Hiroshi Masuda

Hiroshi Masuda

University of Tokyo - Department of Materials Science & Engineering

Koji Morita

National Institute for Materials Science

Makoto Watanabe

National Institute for Materials Science - Research Center for Structural Materials

Toru Hara

National Institute for Materials Science - Research Center for Structural Materials

Hidehiro Yoshida

University of Tokyo - Department of Materials Science & Engineering

Takahito Ohmura

National Institute for Materials Science - Innovative Structural Materials Association (ISMA)

Abstract

The orientation-dependent micromechanical properties of nontransformable tetragonal (t') zirconia, which diffusionlessly transformed from the fluorite cubic phase and does not show stress-induced phase transformation, were characterized via pseudo-single crystal micropillar compression and electron microscopy. The t' zirconia sample was obtained via atmospheric plasma spraying of 4.5 mol% yttria-stabilized zirconia (YSZ) powders into liquid nitrogen and consolidated into a bulk state via hot pressing at 1100°C. Dense and cylindrical micropillars were fabricated using a focused ion beam from pseudo-single crystalline regions, which had a nanodomain microstructure of three t' variants partitioned by {1 0 1}c twin boundaries with 90° symmetry, and were compressed using a flat-end diamond indenter. Near-<0 0 1>c compressions were attributed to ferroelastic domain switching and subsequent {1 0 1}c and/or {1 1 1}c slips. In ferroelastic deformation, a certain t' variant diminished and a binary domain microstructure developed with c axes perpendicular to the compressive direction. Near-<1 1 1>c compressions were governed by {0 0 1}c slips accompanied by strain hardening with negligible ferroelasticity, resulting in buckling deformation with rotational kinking. Crack-tolerant plasticity was ascribed to ferroelastic toughening, where t' variants with c axes across crack planes developed to relieve stress concentrations around the crack tips in both orientations. In contrast, pseudo-cleavage fractures on low-index planes were observed in near-<1 0 1>c compressions. Crack-tolerant behavior was not observed in the cubic counterpart with a domain-free microstructure (8.0 mol% YSZ), which demonstrated catastrophic fractures. Hence, ferroelastic toughening is viewed as the origin of enhanced toughness in t' zirconia.

Keywords: Domain switching, Dislocation, Slip, Twinning, Kink band

Suggested Citation

Masuda, Hiroshi and Morita, Koji and Watanabe, Makoto and Hara, Toru and Yoshida, Hidehiro and Ohmura, Takahito, Ferroelastic and Plastic Behaviors in Pseudo-Single Crystal Micropillars of Nontransformable Tetragonal Zirconia. Available at SSRN: https://ssrn.com/abstract=3604625 or http://dx.doi.org/10.2139/ssrn.3604625

Hiroshi Masuda (Contact Author)

University of Tokyo - Department of Materials Science & Engineering ( email )

Tokyo
Japan

Koji Morita

National Institute for Materials Science

Tsukuba, Ibaraki 305-0047
Japan

Makoto Watanabe

National Institute for Materials Science - Research Center for Structural Materials

Tsukuba
Japan

Toru Hara

National Institute for Materials Science - Research Center for Structural Materials

Tsukuba
Japan

Hidehiro Yoshida

University of Tokyo - Department of Materials Science & Engineering ( email )

Tokyo
Japan

Takahito Ohmura

National Institute for Materials Science - Innovative Structural Materials Association (ISMA)

Japan

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