Real-time observation of AZ91 solidification by synchrotron radiography

Abstract

The equiaxed solidification of AZ91 has been studied by time-resolved synchrotron radiography of 150, µm thick samples. Primary Al8Mn5 and α-Mg dendrite growth has been observed and analysed during solidification at a cooling rate of 5, K/min. Morphological, compositional and kinetic information of AZ91 solidification has been extracted from quantitative image analysis on synchrotron radiographs combined with thermodynamic calculations. α-Mg dendrites appeared to grow largely independently of the surrounding Al8Mn5 particles. Solute partitioning mainly occurred during the dendrite coarsening stage and Zn/Al solute build-up was studied in a region that remains a liquid channel until a late stage of AZ91 solidification.