Effect of pre-exposure to water on the acoustic emission behavior of 2091-T3 Al-Li alloy

The effect of pre-exposure to water with imposed weak ultrasonic field on the acoustic emission (AE) behavior of 2091-T3 Al-Li alloy was studied. AE characteristics were evaluated during tensile deformation utilizing a micro-computer based system and an rms voltmeter. Two types of AE were observed; initially, AE was of a continuous nature with a maximum at the yield, followed by a change to burst type AE coinciding with the onset of PLC serrations. A significant difference in AE behavior between as-received and pre-exposed material has been observed, especially in the yield region. The pre-exposed specimens gave rise to more intense AE activity manifested in higher peak amplitude AE events. Although the precise mechanism of the observed effect is not known, it is believed to stem from hydrogen charging that took place during pre-exposure, and which also caused reduction of the tensile elongation of the material.