The significance of the existence of a gas-filled cavity in the interdendritic liquid on the hot tearing tendency of a freezing metal casting has been examined. Such cavities arise because of the contraction accompanying freezing and lie within a thermal gradient field. Since the surface tension of an alloy liquid is a function of both local temperature and composition, a "Marangoni" force arises which can contribute to the local mass flow in the surrounding liquid. A general criterion has been derived to predict the possibility that a bubble, created by gas precipitation in a void nucleated at an inclusion, can move out of the liquid between two dendrite stems under given circumstances and so reduce hot tearing tendency. The criterion shows that if the existing solidification speed is less than a specific value, dependent of the material and solidification parameters, the bubble/cavity may move out of the liquid pocket, driven by Marangoni convective forces and so reduce the hot tearing tendency. For A201 alloy in a typical chilled situation, this critical solidification velocity is approximately 5 mm/sec.
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