Acoustic emission characteristics associated with macrostructures 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 delta' microstructure and the S' + delta' microstructure), and of two different orientations (L and S). For the L-oriented specimens, continuous emissions were mostly produced in the delta' microstructure due to the shearing of coherent delta' precipitates, while in the S'+delta' 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 L-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. (C) 1997 Elsevier Science S.A.