dilatant shear bands in solidifying metals | nature - what is die casting
Compacted granular materials respond to shear1 expansion and can exhibit behavior of solids, liquids, and gases that are different from their composition.
The application of granular material physics adds an understanding of the flow in avalanches 2, geological faults 3, 4, hoppers and silos5, and soil machinery 6, 7.
During the isoaxial solidification of metal alloys, a series of solid parts exist, in which the microstructure is composed of geometric crowding disorder assembly of crystals of saturated liquids.
Therefore, it is natural to ask whether this microstructure will deform into granular materials, which may be of any relevance to solidification processing.
Here, we show that partially solidified alloys can exhibit features of non-viscous granular materials, including strain localization in the expansion 1 of Renault and the expansion shear band 7-18 mean Crystal width.
We show that this behavior is important in the formation of defects in the process of high pressure die casting of Al and Mg alloys, a global industry that contributes more than $7.
For 3 billion of the US economy, it is used to make products including mobile devices.
Phone case and steering wheel.
More broadly, these findings highlight the potential of applying the principles and modeling methods developed in particle mechanics to the field of solidification processing, it also points out the possible benefits of exploring and utilizing further synergies between these areas.