Unraveling the fundamental principles of eutectic solidification with real-time, nanoscale imaging

During eutectic solidification, a mixture of two or more solids self-assemble, forming composite microstructures ranging from ordered layers to intricate maze-like patterns that underlie properties like tensile strength or ductility. Up to this point, researchers have not understood what conditions drive eutectics to form certain patterns, which is critical for designing reproducible next-generation eutectic composites. Capturing real-time solidification of an aluminum-nickel eutectic alloy (Al-Al3Ni) in nanometer resolution revealed that increasing the solidification velocity shifts microstructure from irregular and faceted to regular and rounded, according to a study led by University of Michigan researchers recently published in Acta Materialia.

New study into solute transport and solidification mechanisms in additive manufacturing

Additive manufacturing (AM), or 3D printing, is a rapidly growing technology with the potential to revolutionize many industries. However, AM parts can be susceptible to defects, such as porosities and cracks, which can limit their performance and reliability. Researchers at Queen Mary University of London, in collaboration with Shanghai Jiao Tong University, Center of Excellence for Advanced Materials, and University of Leicester, have developed a computational model to reveal how solute trapping occurs during the rapid solidification process in additive manufacturing (AM). The study, published in Nature Communications, provides new insights into the solute transport and solidification mechanisms in AM, which could lead to the development of new materials and processes for 3D printing.

Nano droplets go skiing at high temperatures

Currently, many (nano)structures are grown in layers, one above the other, but their ordering on the atomic scale is generally far from perfect. Researchers from the University of Twente have aimed for a better understanding of these processes that can eventually lead to smaller, faster and overall better nanotechnology and have, in a worldwide first observation, discovered pre-solidification in droplet mixture. They recently published these exciting findings in the journal Physical Review Letters. The droplets are composed of a mixture of the metals platinum and germanium and move on a heated substrate in the direction of the heat source. But as soon as the temperature lowers, the droplets start their unique behavior. Like professional skiers, they suddenly change their direction and make a slalom. "Using a photo-emission electron microscope, we were able to film the skiing and show the whole process of solidifying," explains Arie van Houselt, corresponding author of the publication.

Scientists from the University of Birmingham have described how microscopic crystals grow and change shape in molten metals as they cool, in research that is breaking new ground in alloy research and paves the way for improving the tensile strength of alloys used in casting and welding.

Their research, published today in Acta Materialia, used high-speed synchrotron X-ray tomography to 'photograph' the changing crystal structures in molten alloys as they cool.

The study shows that as aluminium-copper alloy cools the solidification process starts with the formation of faceted dendrites, which are formed by a layer-by-layer stacking of basic units that are just micrometres in size. These units start out as L shaped and stack on top of each other like building blocks, but as they cool they change shape and transform into a U shape and finally a hollowed out cube, while some of them stacked together to form beautiful dendrites.

The study was led by Dr Biao Cai, from the University of Birmingham's School of Metallurgy and Materials, whose research has already demonstrated how magnetic fields influence crystal growth.