Size and plasticity effects in zirconia micropillars compression

Abstract

The micropillar compression technique has shown the potential for activating the brittle-to-ductile transition in ceramic monocrystals when testing reduced volumes. In this work, the role of size is studied by comparing the mechanical response of polycrystalline tetragonal zirconia micropillars and macroscopic specimens under compression. In micropillars, the absence of the natural defect population typical of bulk zirconia increases considerably the strength, allowing the activation of plastic deformation mechanisms and their study, showing in this way that the brittle-to-ductile transition is not limited to ceramic monocrystals only. The main mechanism of plastic deformation is transformation-induced plasticity, which is shown to be size dependent. The deformation behavior is studied in detail by loading-unloading tests at constant and increasing peak stresses, while the microstructure evolution is revealed by FIB cross-sections, TEM and STEM observations performed on lamellas extracted from pillars retrieved before failure. Finally, a failure mechanism is proposed, based on the damage induced by phase transformation.

Granular shape memory ceramic packings

“…To preliminarily explore the possible distribution of transformed regions, we use finite element simulation of single-particle compression, which may be viewed as a simple unit model of the contact physics that prevail at many particle-particle contacts throughout a granular packing, without addressing the complexity of stress distribution throughout such a packing. The model is not intended to simulate details of the austenite-martensite transformation in SMCs, which is challenging because it is crystallographic, anisotropic, and dependent on the microstructure [49,53] and stress states [18][19]. Instead, we simply adopt a constitutive behavior that permits strain accumulation at a constant deviatoric-stress such as is seen during a martensitic transformation.…”

Forty years after the promise of «ceramic steel?»: Zirconia‐based composites with a metal‐like mechanical behavior

“…Some zirconia indeed exhibit pronounced R-curve behavior (high fracture toughness ≥20 MPa·√m reported in some cases 14 ) and a few studies have shown that Ce-TZP-based ceramics might be considered as "ductile," with a certain degree of transformation-induced plasticity before failure (Figure 1). [6][7][8][9][10]20,21,51,57 Recent studies on micropillars have also reported that some Y-TZP ceramics exhibit transformation-induced plasticity, 58 provided the size of the tested samples was small enough and free of processing defects. Transformation-induced plasticity is thus more limited in 3Y-TZP than in Ce-TZP and has never been reported on large-sized samples.…”

Study of deformation mechanisms in flash-sintered yttria-stabilized zirconia by in-situ micromechanical testing at elevated temperatures

“…Mechanical behavior of YSZ has been intensively investigated. There are several studies on microscale mechanical testing, which mostly highlight superior superelasticity and shape memory effect at room temperature owing to martensitic transformation [12][13][14][15][16][17][18]. However, our understanding on deformation mechanisms of microscale YSZ at elevated temperatures remains lim-ited.…”