Microfracture Behaviour of Fine Grained Alumina Studied by Indentation and Acoustic Emission in Various Environments

Abstract

Fracture micromechanisms in fully dense fine grained aluminas have been investigated by carefully controlled indentation and concurrent recording of acoustic emissions. Samples in the form of hot-pressed and polished Al₂O₃ discs, 40 mm diamater by 4 mm thickness, and of varying grain sizes were submitted to a diamond Vickers indenter in a specially designed testing rig allowing for controlled environments. Experimental testing parameters, acoustic activities and microstructural observations were correlated and are presented, allowing different types of mechanical behaviours to be documented, as functions of microstructure and environment. Attempts at rationalizing the results in the light of our present understanding of indentation fracture are discussed.