采用声发射测试技术,对Al-Si和Al-Cu系合金凝固过程进行监测,证实合金在凝固过程中存在声发射现象,表现为两个声发射信号计数率峰,两个峰的总计数都随着合金中气体含量增加而增高。本文对Al-Si,Al-Cu合金系产生声发射现象的机理进行了探讨,同时,借助其它实验手段证实了声发射信号与合金凝固中气体析出有很好的对应性。第一个计数率峰与气泡在枝晶臂间形核相吻合。第二个计数率峰与凝固末期的枝晶间拉裂现象相对应,可能是氢在枝晶间析出和聚集产生高压氢导致的拉裂。
Study of the solidification process of both Al-Si and Al-Cu alloysproved the presence of acoustic emission phenomena. Two peaks of count rate hasbeen observed. The total counts of both peaks increases with the increasing hydro-gen content of the alloy. The mechanism of producing the acoustic emission hasbeen 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 causeof the first peak, while the fracture of the bridge connecting the interdendrites atthe 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 theinterdendritic region.
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