Acoustic emission characteristics associated with microstructures and plate orientations of an Al-Li 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 Al-Li 8090 alloy, and to correlate it with the deformation mechanisms of two different microstructures (the δ′ microstructure and the S′ + δ′ micro structure), 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 K_AE values measured by AE method were well agreed with the K_IC values, implying that the K_AE could be considered as a quantitative and reliable parameter to evaluate the fracture toughness of a material.