Ferroelastic and plastic behaviors in pseudo-single crystal micropillars of nontransformable tetragonal zirconia. (15th January 2021)

• Record Type: Journal Article
• Authors: Masuda, Hiroshi; Morita, Koji; Watanabe, Makoto; Hara, Toru; Yoshida, Hidehiro; Ohmura, Takahito
• Is Part Of: Acta materialia. Volume 203(2021)
• Publication Date: 2021-01-15
• Subjects: Domain switching -- Dislocation -- Slip -- Twinning -- Kink band; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.11.013
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The orientation-dependent micromechanical properties of nontransformable tetragonal ( t ') zirconia, which underwent a diffusionless transformation from the fluorite cubic phase and does not exhibit a 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 exhibited a nanodomain microstructure of three t ' variants partitioned by {1 0 1} c twin boundaries with 90° symmetry. These micropillars 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 hard 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 soft slips accompanied by strain hardening with negligible ferroelasticity, which resulted in buckling deformation with rotational kinking. In both the hard- and soft-slip orientations, ferroelastic toughening was observed with certain t ' variants awaken around the crack tips. Contrarily, cleavage fractures subsequent to yielding were observed in near-<1 0 1> c compressions. In the cubic counterpart with a domain-free microstructure (8.0 mol% YSZ), ferroelastic toughening was not observed. Hence, it is viewed as the origin of enhanced toughness in t ' zirconia. Graphical abstract: Image, graphical abstract