ACOUSTIC EMISSION AND HYDROGEN EVOLUTION DURING SOLIDIFICATION OF ALUMINUM ALLOYS
铝合金凝固过程的声发射及氢气析出过程

Study of the solidification process of both Al-Si and Al-Cu alloys proved the presence of acoustic emission phenomena. Two peaks of count rate has been observed. The total counts of both peaks increases with the increasing hydro- gen content of the alloy. The mechanism of producing the acoustic emission has been discussed. At the same time, results obtained by other techniques strongly sup- port the good correlation between the acoustic emission and hydrogen releasing dur- ing solidification. The bubble nucleation between dendrite arms is the main cause of the first peak, while the fracture of the bridge connecting the interdendrites at the later stage of solidification is the main cause of the second peak. It is proba- bly due to high pressure the hydrogen evolution and accumulation created by in the interdendritic region.