Solidification microstructures of the undercooled Co-24 atSn eutectic alloy containing 0.5 atMn

摘要

Solidification samples of undercooled Co-24 atSn eutectic alloy containing a small amount of Mn (<1.0 at) were prepared by the glass fluxing technique. The surface and internal solidification microstructures of the samples were observed by a scanning electron microscope (SEM) and an optical microscope (OM), respectively. The experiment results revealed that the addition of 0.5 atMn remarkably changed the solidification behaviors of the undercooled Co-24 atSn eutectic alloy. The addition of 0.5 atMn influenced the morphological selection of eutectic growth interface by increasing the interface energy anisotropy during the solidification of the undercooled Co-24 atSn eutectic melt. As undercooling increases, the coupled eutectic growth interface morphology successively experienced dendritic pattern, factual seaweed pattern and compact seaweed pattern. Besides, the addition of 0.5 atMn decreased the critical undercooling for the formation of anomalous eutectic by introducing a new formation mechanism of anomalous eutectic, i.e. divorce eutectic mechanism. (C) 2015 Elsevier Ltd. All rights reserved.