On the advanced microstructural characterisation of additively manufactured alumina-zirconia based eutectic ceramics: Overview and outlook

Abstract

Recently, there have been a number of reports on the fabrication of Alumina-Zirconia (Al2O3-ZrO2 (AZ))-based eutectic ceramics using laser additive manufacturing (AM) techniques owing to the exceptional creep and oxidation resistance coupled with excellent microstructural stability in these materials. Moreover, a number of interesting microstructural features (in these materials) have been reported to be formed by the variation of process parameters (especially, laser scanning speed) associated with the aforementioned AM techniques. The present review provides an overview of the present state of research in the area of laser AM AZ-based eutectic ceramics and highlights the challenges and future outlooks in this avenue of research. In addition, the requirement of employing correlative microstructural characterisation in these materials has been highlighted in the outlooks section.

On the Advanced Microstructural Characterisation of Additively Manufactured Alumina-Zirconia Based Eutectic Ceramics: Overview and Outlook

“…Moreover, as mentioned in section 1, laser AM-based techniques are based on layer-by-layer deposition of materials. This adds up to the complexity (in terms of obtaining GBE microstructures) by inducing large-scale microstructural heterogeneities (with high defect concentration) [32][33][34][35][36][37][38][39][40][41], resulting in non-equilibrium microstructures. Hence, obtaining GBE microstructures in AM-based AZ ceramics provides an immense potential towards future investigations in field of AZ ceramics.…”

New Frontiers in Characterising ZrB2-MoSi2 Ultra-High Temperature Ceramics

“…The onset of correlative microscopy [1] has completely revolutionised the field of research in structural materials. Ranging from the study of segregated atoms [4,5,10] to characterising nanoscale precipitates at different interfaces [5], the novel technique has enabled material scientists to correlate the properties of a material with its bulk and interfacial structure, simultaneously. From the fundamental viewpoint, there still remain a lot of unexplored avenues, in the context of oxidation studies in the UHTCMCs, which may be potentially addressed by this novel technique.…”

“…Unfortunately, at present, there is limited understanding of the effect of volume expansion associated with the formation of MoO3 at temperatures lower than 1200 ˚C on the stress pile-up at GBs. Hence, its the GB cohesion [10] and GB energy [5] which needs to be addressed, for a detailed understanding of the influence of the same on the stress pile-up associated with volume expansion, due to formation of MoO3, in the present context. Besides, adhesion between the oxide layer and the surface of the base material (ZrB2-MoSi2, in the present context) is also something which needs to be addressed as a function of the local chemistry at the substrate-oxide interface before subjecting these materials to service at elevated temperatures.…”

“…Although a number of theoretical studies based on the kinetics of oxidation as a function of the diffusivity of oxygen, have illustrated the properties of the oxides, formed during oxidation of ZrB2-MoSi2 at different temperatures [26][27][28][29][30], but however, there exists a huge possibility of understanding the same experimentally, through detailed study of oxygen-defect interaction, using extensive defect and orientation based microscopy techniques such as Electron Backscatter Diffraction (EBSD) [10], Electron Channeling Contrast Imaging (ECCI) [69,70] e.t.c. and correlating the structural information, obtained henceforth with the atomic-level chemistry using Atom Probe Tomography (APT) [7] technique, using Focussed Ion Beaming (FIB) [7] as a lift-out technique to prepare samples for APT.…”

Nanocrystalline Alumina-Zirconia-Based Eutectic Ceramics Fabricated with High-Energy Beams: Principle, Solidification Techniques, Microstructure and Mechanical Properties

“…In this regard, the current studies reported have been mainly restricted to thin-walled or long, cylinder-shaped, alumina-zirconia-based eutectic ceramics: for example, Al 2 O 3 -GdAlO 3 -ZrO 2 [27,82,83,92,93], Al 2 O 3 -ZrO 2 [77,80,91], Al 2 O 3 -GdAlO 3 [25], Al 2 O 3 -YAG-ZrO 2 [78], Al 2 O 3 -YAG [31], etc. Detailed descriptions of the microstructures and crystallography of alumina-zirconia-based nanoeutectic ceramics fabricated with laser AM can be found in the recently published literature [94].…”