Undercooling and solidification of metallic melts suspended in a non-nucleating matrix: Experiment NUCAL of the German Spacelab Mission D-2
During the German Spacelab Mission D-2 bulk alloy samples, surrounded by a non-nucleating liquid B 2O 3 matrix, were molten and solidified in the isothermal heating facility. In reduced gravity, sedimentation and thus heterogeneous nucleation at container walls were suppressed. By measuring the recalescence temperature with thermocouples, it was possible to determine the degree of undercooling for eutectic Ag-Ge and for iron-rich Fe-Ni samples. Deep undercoolings of around 100 K for Ag-Ge and up to 392 K for Fe-Ni have been achieved. The metallographic microstructure analysis of the Fe-Ni samples indicates the formation of a metastable δ-phase in the Fe-Ni system.