Phase transformation induces plasticity with negligible damage in ceria-stabilized zirconia-based ceramics

Abstract

Ceramics and their composites are in general brittle materials because they are predominantly made up of ionic and covalent bonds that avoid dislocation motion at room temperature. However, a remarkable ductile behavior has been observed on newly developed 11 mol.% ceria-stabilized zirconia (11Ce-TZP) composite containing fine alumina (8vol.% Al 2 O 3 ) and elongated strontium hexa-aluminate (8vol.% SrAl 12 O 19 ) grains. The assynthesized composite also has shown full resistance to Low Temperature Degradation (LTD), relatively high strength and exceptionally high Weibull modulus, allowing its use in a broader range of biomedical applications. In this study, to deepen the understanding of *Manuscript Click here to download Manuscript: TEXT-Final_revised_reveron et al.docx Click here to view linked References plastic deformation in Ce-TZP based composites that could soon be used for manufacturing dental implants, different mechanical tests were applied on the material, followed by complete microstructural characterization. Distinct from pure Ce-TZP material or other zirconia-based ceramics developed in the past, the material here studied can be permanently strained without affecting the Young modulus, indicating that the ductile response of tested samples cannot be associated to damage occurrence. This ductility is related to the stressinduced tetragonal to monoclinic (t-m) zirconia phase transformation, analogue to Transformation-Induced Plasticity (TRIP) steels, where retained austenite is transformed to martensite. The aim of this study is to corroborate if the observed plasticity can be associated exclusively to the zirconia t-m phase transformation, or also to microcraking induced by the transformation. The t-m transformed-zones produced after bending and biaxial tests were examined by X-ray refraction and SEM/TEM coupled with Raman. The results revealed that the observed elastic-plastic behavior occurs without extensive microcracking, confirming a purely elastic-plastic behavior driven by the phase transformation (absence of damage).

Tough and damage-tolerant monolithic zirconia ceramics with transformation-induced plasticity by grain-boundary segregation

“…Only few judiciously manufactured zirconia composites showed the capability of inelastic deformation in combination with biaxial bending strength (~1 GPa), toughness (~ 10 MPa•m 1/2 ) and high reliability (Weibull modulus > 20) [21,27,29]. These composites include 10Ce-TZP-30Al2O3 nanocomposites with inter-and intragranularly located alumina particles [21] and three-phase ZA8Sr8Ce11 (11Ce-TZP with 8 vol% Al2O3 and 8 vol% SrAl12O19) composites [20,26,27,34]. It has also been shown that the plastic deformation in the ZA8Sr8Ce11 composite was not associated to crack occurence or phase debonding inside the transformation bands, revealing a purely elastic-plastic behavior driven by phase transformation and not by microcracking [34].…”

“…These composites include 10Ce-TZP-30Al2O3 nanocomposites with inter-and intragranularly located alumina particles [21] and three-phase ZA8Sr8Ce11 (11Ce-TZP with 8 vol% Al2O3 and 8 vol% SrAl12O19) composites [20,26,27,34]. It has also been shown that the plastic deformation in the ZA8Sr8Ce11 composite was not associated to crack occurence or phase debonding inside the transformation bands, revealing a purely elastic-plastic behavior driven by phase transformation and not by microcracking [34]. However, all these observations were conducted after loading and a clear clarification about the t-m transformation process in correlation with crack initiation and propagation is still missing.…”

Alumina toughened zirconia reinforced with equiaxed and elongated lanthanum hexa-aluminate precipitates

“…However, only very few reported studies were available on lanthanum hexa-aluminate containing zirconia based ceramics [29][30][31][32][33]. Furthermore, different forms of elongated precipitates can be generated by different processing methodologies even with the same overall composition [14,25,34]. In-situ formed large-sized strontium or lanthanum hexa-aluminate elongated precipitates were reported to have a negative effect on both fracture toughness and strength of 12Ce-TZP based composites, as compared to alumina particle additions [25].…”

Plastic deformation in silicon nitride ceramics via bond switching at coherent interfaces

“…In alloys with metallic bonds, plastic deformation is realized by local atomic displacements that proceed through switching one or a few interatomic bonds at a time along the lattice planes, also known as dislocation motion (25,26). Stress-induced phase transformation and the consequent plasticity have been realized in metallic materials and even in ionically bonded ceramics such as ZrO 2 (27)(28)(29)(30)(31)(32) with nondirectional bonding. Although this mechanism has enabled plastic deformation in other materials, it has remained elusive in covalently bonded ceramics (33), mainly because of the directionality of covalent bonds.…”