Separation of AE signals for detecting solidification cracking of Al-7mass%Si alloy by using acoustic emission method

Detection of solidification cracking of Al-7 mass%Si alloy was attempted by using acoustic emission method. According to our previous report, it was found that it is necessary to separate AE of solidification cracking from other estimated sources such as gas porosity, shrinkage cavity, or eutectic solidification to detect AE of solidification cracking. Then, we investigated about AE signals of gas porosity, shrinkage cavity, and eutectic solidification. As a result, AE of eutectic solidification was not generated or was too small to detect. AE of shrinkage cavity and gas porosity formation were detected at the start of eutectic solidification, and the frequency band was 150 kHz or less. The frequency band of AE accompanied with fracture of solidifying castings was also 150 kHz or less. Therefore, it was difficult to separate AE of solidification cracking from gas porosity, shrinkage cavity, or eutectic solidification by the frequency band. However, integrated AE peak volt during solidification correlated with crack ratio. When Solidification cracking occurred, Integrated AE peak volt was about more than 1000 V during solidification. In situ detection of solidification cracking will be possible by investigating integrated AE peak volt.