The solidification of Inconel 718 alloy (IN718) from undercooled liquid is studied. The solidification kinetics is evaluated in melted and undercooled droplets processed using the electromagnetic levitation (EML) technique by the temperature–time profiles and solid/liquid (S/L) interface movement during recalescence. The kinetics is monitored in real time by special pyrometrical measurements and high-speed digital camera. It is shown that the growth velocity of $\gamma$-phase (the primary phase in IN718), the final crystalline microstructure (dendritic and grained), and the mechanical properties (microhardness) are strongly dependent on the initial undercooling $\Delta T$ at which the samples started to solidify with the originating $\gamma$-phase. Particularly, with the increase in undercooling, the secondary dendrite arm spacing decreases from 28 μm to 5 μm. At small and intermediate ranges of undercooling, the solidified droplets have a dendritic crystalline microstructure. At higher undercooling values reached in the experiment, $\Delta T>160$ K (namely, for samples solidified with $\Delta T=170$ K and $\Delta T=263$ K), fine crystalline grains are observed instead of the dendritic structure of solidified drops. Such change in the crystalline morphology is qualitatively consistent with the behavior of crystal growth kinetics which exhibits the change from the power law to linear law at $\Delta T\approx 160$ K in the velocity–undercooling relationship (measured by the advancement of the recalescence front in solidifying droplets). Study of the local mechanical properties shows that the microhardness increases with the increase in the ${\gamma }^{″}$-phase within interdendritic spacing. The obtained data are the basis for testing the theoretical and computational of multicomponent alloy samples.

We studied bulk metallic glasses produced from gas flow-assisted laser-based powder bed fusion process, which is capable of additive manufacturing metallic parts in microgravity. A Zr-based bulk metallic glass composition Zr $$_{59.3}$$ 59.3 Cu $$_{28.8}$$ 28.8 Al $$_{10.4}$$ 10.4 Nb $$_{1.5}$$ 1.5 has been processed on ground and in microgravity in a compact sounding rocket payload MARS-M. Microstructure characterization was performed using electron microscopy and X-ray diffraction computed tomography, which cope with small amounts of sample materials, especially for those fabricated under microgravity conditions. Very similar microstructures and crystalline fractions are observed in sample manufactured on ground and in microgravity, which shows that process parameters of conventional laser powder bed fusion for manufacturing metallic glasses can be transferred to the processes in microgravity. Two different origins of crystallization have been identified in the Zr $$_{59.3}$$ 59.3 Cu $$_{28.8}$$ 28.8 Al $$_{10.4}$$ 10.4 Nb $$_{1.5}$$ 1.5 sample. The preferred occurrence of CuZr $$_2$$ 2 at the interlayer boundaries is likely a result of recrystallization from the undercooled melt and hence associated with laser scanning strategy. In contrast, the more uniformly distributed Al $$_3$$ 3 Zr $$_4$$ 4 phase is considered to be triggered by the formation of Cu $$_2$$ 2 Zr $$_4$$ 4 O. Thus, for the fabrication of fully amorphous builds both on ground and in space, our findings point to higher scanning speeds and lower oxygen contents, while the latter can also be used to tune the crystalline fractions in the sample.