Equiaxed dendrite growth in non-refined Al-base alloys in real time

Abstract

Numerical computer simulations of microstructure evolution during dendritic solidification require reliable experimental data for comparison. In the last two decades X-ray radiography was shown to be a powerful method to in real-time monitor dendritic solidification in thin samples. Here, we present data on equiaxed dendritic growth of fcc-Al dendrites in non-grain refined Al-Ge and Al-Cu alloys. The disc-shaped samples of up to 12 mm diameter and between 200 and 350 µm thickness were processed in a near-isothermal furnace at constant cooling rates of 1 to 3 K/min. We compare dendrite tip velocities determined in horizontally aligned samples on ground with data acquired during two recent microgravity experiments using DLRs X-RISE facility aboard the sounding rocket MAPHEUS. Furthermore, the evolution of solute concentration field evolution in the interdendritic liquid is measured and discussed. The velocity data are compared with theoretical dendrite growth models.