Acoustic emission characteristics associated with microstructures and plate orientations of an AlLi 8090 alloy

An investigation was carried out to study the microstructural influence on the acoustic emission (AE) behavior during the tensile and fracture tests of an AlLi 8090 alloy, and to correlate it with the deformation mechanisms of two different microstructures (the δ′ microstructure and the S′ + δ′ microstructure), and of two different orientations (L and S). For the L-oriented specimens, continuous emissions were mostly produced in the δ′ microstructure due to the shearing of coherent δ′ precipitates, while in the S′ + δ′ microstructure the burst type emissions were dominant mainly due to the shearing or microcracking of large incoherent S′ precipitates as well as the intergranular failure. The S-oriented specimens of both microstructures showed more burst emissions than the L-oriented ones, which resulted from the frequent occurrence of intergranular delamination in the S-oriented specimens. The KAE values measured by AE method were well agreed with the KIC values, implying that the KAE could be considered as a quantitative and reliable parameter to evaluate the fracture toughness of a material.