Temperature Dependence of Static and Cyclic Fatigue Behavior of Aluminum Titanate Ceramics

Abstract

Aluminum titanate (Al₂TiO₅: AT) ceramics have been recently applied as refractories in Al alloy casting systems, because they have excellent thermal shock resistance and corrosion resistance to molten Al alloys. The AT ceramics contain many microcracks at grain boundaries as a result of the large thermal expansion anisotropy during cooling after sintering. In this study, static and cyclic fatigue of the AT ceramics was investigated at actual casting operating temperatures (RT-700^oC) and the fatigue life related to the morphological change of the microcracks. The fatigue lives at R.T. and 700^oC decreased when a cyclic stress was applied, especially shorter at R.T. During cyclic fatigue at R.T., the microcracks around the main crack tip are thought to combine and propagate according to grain bridging degradation and wedging-microcracking mechanisms. In contrast, at 700^oC microcracks underwent repeated initiation and self-healing via a glassy phase segregated at the grain boundaries.