IN-SITU OBSERVATION OF TRANSITION FROM COLUMNAR TO EQUIAXED GROWTH IN AL-3.5 wt NI ALLOYS BY SYNCHROTRON RADIOGRAPHY

摘要

We present results on Columnar to Equiaxed Transition (CET) induced by applying pulling rate jumps during the solidification of refined alloys. Solidifications of Al-3.5 wt% Ni alloys are performed in a Bridgman furnace at the European Synchrotron Radiation Facility (ESRF) in Grenoble. The use of synchrotron X-ray radiography allows direct observation of the solid-liquid interface for metallic alloys, in particular during the CET where most of events are dynamical. The morphology of growing columnar or equiaxed dendrites can be well resolved, in real time and with high image contrast. These experiments provide direct access to specific behaviours during CET and equiaxed growth.