Abstract
Acoustic emission (AE) accompanied by environmental embrittlement was examined for a coarse-grained Al–Mg–Si alloy tensile tested at slow strain rates in laboratory air with a relative humidity of 70%. Elongation was slightly decreased with a decrease in the initial strain rate from 1.7× 10−4s−1 to 1.7× 10−6s−1. Fracture morphology under the strain rate of 1.7× 10−4s−1 was completely transgranular, while those of 1.7× 10−5s−1 and 1.7× 10−6s−1 were a mixture of transgranular and intergranular. Occurrence of the intergranular cracks near the specimen surface due to the environmental embrittlement could be discerned by the variation in root mean square (RMS) voltage at the moment of fracture. Propagation of the intergranular cracks was also detectable by the variation of AE signals with high amplitude ranges up to 100 dB at the final stage of plastic deformation. In addition, hydrogen microprint technique (HMT) revealed a trace of hydrogen accumulation at grain boundaries in the Al–Mg–Si alloy slowly strained by 15%.
