Design and processing of Al2O3–Al2TiO5 layered structures

Abstract

Al2O3-Al2TiO5 layered composites were manufactured by a colloidal route from aqueous Al2O3 and TiO2 suspensions with 50vol.% solids. The mechanical behaviours of individual monolithic composite materials were combined and taken as basis for the design of the layered structures. Residual stresses which are likely to occur due to processing and thermally introduced misfits were calculated and considered for the manufacture of the laminates. Monoliths with 10, 30 and 40 vol.% of second phase showed that increasing proportions of aluminium titanate decrease strength and increase the non-linear behaviour. In order to obtain the desired combination of mechanical behaviours of the layers, two laminate designs with external and central layers of one composition and the alternating internal layer of the other composition were chosen taking into account chemical compatibility and development of residual stresses. In the system AA10, external and central layers of monophase Al2O3 with high strength were combined with intermediate layers of Al2O3 with 10vol.% of Al2TiO5. The system A10A40 was selected to combine low strength and energy absorbing intermediate layers of Al2O3 with 40vol.% of Al2TiO5 and sufficient strength provided by external layers of Al2O3 with 10vol.% of Al2TiO5. The stress-strain behaviour of the laminates was linear up to their failure stresses, with apparent strain for zero load after fracture larger than that corresponding the monoliths of the same composition as that of the external layers. Moreover, the stress drop of the laminate samples occurred in step-like form thus suggesting the occurrence of additional energy consuming processes during fracture.