Solidification is one of the major steps in producing parts from the molten material in casting, welding or additive manufacturing. On top of process optimization and simulation to obtain good mould filling and minimized defects, the quality of the cast parts depends strongly on the microstructure developing during solidification. The microstructure, i.e. grain structure, grain morphology, dendritic structure, distribution of composition, phases and precipitations depend on the material chosen and processing conditions like cooling rates and thermal gradients. Moreover, a strong interaction between microstructure formation and gravity-dependent phenomena exists.
On a fundamental level, microgravity experiments on solidification aim at separating processing and alloy-dependent phenomena on microstructure formation from gravity dependent phenomena, i.e. buoyancy driven flow in the melt, sedimentation or floatation of particles and crystals and hydrostatic pressure. In a broader view microgravity experiments can be accompanied by hypergravity experiments using centrifugal motion to investigate the effect of a larger gravity spectrum on the aforementioned phenomena.
Several examples are given for microstructure formation (and modeling) on different microgravity platforms from parabolic flight airplanes to the international space station.
Dr. Laszlo Sturz studied Physics and obtained a PhD in Physical Chemistry in 1999 from RWTH-Aachen (Germany), studying nuclear magnetic resonance in carbohydrates. From 2000 to 2001 he worked on image analysis for positron emission tomography & magnetic resonance imaging (PET/MRT) at the University hospital of Aachen. Since 2001, he is a Senior Researcher in the solidification research group at Access e.V. in Aachen. His main research fields include: solidification in metallic and organic alloys, microgravity experiments, and multi-scale modeling.