Acoustic emission during channel-die compression of Mg-Li and Mg-Li-Al alloys and composites reinforced by short δ Al2O3 fibres

The paper presents preliminary results of the investigations of the correlations occurring between the rate of the acoustic emission (AE) events and the plastic deformation mechanisms during channel-die compression of Mg-Li and Mg-Li-Al alloys, as well as the corresponding metallic matrix composites reinforced with short delta Al2O3 fibres. Essential qualitative and quantitative differences in the AE behaviour have been observed in the composites and in the pure alloys. The obtained results are discussed on the basis of the possible dislocation and microcracking processes and also on the basis of microstructure observations using the optical microscopy. It is suggested that the highly jumping character of AE behaviour in two-phase (alpha+beta) Mg8Li3Al alloys is related to the twinning in alpha phase and to the microcracking along the interfaces, while in Mg8Li+deltaAl(2)O(3) composites also to the fibres cracking and debonding processes, i.e. the loss of cohesion between the fibres and the matrix.