Acoustic Emission Generation Behavior in A7075-T651 and A6061-T6 Aluminum Alloys With and Without Cathodic Hydrogen Charging Under Cyclic Loading

Acoustic emission (AE) signals from non-charged and cathodic hydrogen charged A7075-T651 and A6061-T6 samples under tension–tension cyclic loading conditions at various stress intensity factor ranges were monitored. Although the AE event counts per cyclic load (AE count rates) were proportional to the crack growth rates in all kind of the sample, the rates were less than unity. Many cracked inclusions were observed on the crack surfaces and were identified as AE sources. Large inclusions in both Al alloys were prone to be fractured. The AE count rate in the A7075 sample was 10 times higher than that in A6061. However, no significant difference in the AE count rates and fatigue crack growth between the non-charged and charged samples were observed.