The stability of the ODS alloy CMSX6-Al2O3 during melting and solidification under low gravity

Abstract By reference to experiments on the ODS alloy CMSX6-1 vol% Al 2 O 3 (∅ 2 O 3 /Cu. As a result of the Brownian motion, the oxide particles form clusters of 1–2 μm in size in a matter of seconds. Such clusters form weak points in the microstructure. Within minutes, these clusters build up chains, which interlink. During solidification, the clusters and chains are displaced by the solidification front and decorate the surface of the dendrites in the single crystal. They are concentrated in the solidified residual melt. Large, highly interlaced areas partially lose their mobility in the melt and are consequently enclosed by the dendrite arms. Both processes – the formation of clusters and the displacement of the particles by the solidification front – are the result of energetic interactions. In metallic melts, these interactions can be described by means of van der Waals forces. As long as the dielectric constants of the involved phases are not known, the concept of specific free interfacial tensions can be employed as an alternative basis for calculating the interaction.