Rice University engineers have modeled how shear affects grain boundaries in polycrystalline materials.
The researchers were not surprised by the fact that the boundaries can change so quickly.
Interfacial shear at the crystal-void boundary can drive how microstructures evolve.
Engineers can use the technique reported in Science Advances.
Common metals, ceramics, and Semiconductors look solid to the untrained eye. These materials are polycrystalline and separated by defects. Conductivity and strength are governed by the organization of the polycrystalline aggregate.
Grain boundaries can be altered under applied stress. Control of their phase transitions has been a challenge even though they've been used as model systems.
The grain boundaries in most of the studies are stationary. It's set in stone. Grain boundaries are dynamic and we can watch them.
The researchers spun colloids of paramagnetic particles to form polycrystalline structures. A previous study shows that this type of system is good for showing phase transitions of atomic systems.
Polycrystalline structures that include particle-free regions can be found here. The voids act as sinks for grain boundaries.
The new study shows how the Read-Shockley theory of hard Condensed Matter predicts the misorientation angles and energies of low angle grain boundaries.
By applying a magnetic field on the particles, Lobmeyer caused the iron oxide - embedded polystyrene particles to assemble and watch as the crystals formed grain boundaries.
She said that they started out with a lot of small crystals. The grain boundaries began to disappear, so we thought it might lead to a single, perfect crystal.
Shear at the void interface caused new grain boundaries to form. The misorientation angle and energy predictions of Read and Shockley were similar to polycrystalline materials.
Understanding how voids can be used to control Crystalline Materials offers us new ways to design them. The next step is to study the process of annealing, a process that involves multiple heating and cooling cycles.
The research was supported by the foundation. He is also a professor of chemical and biomolecular engineering.
More information: Dana M. Lobmeyer et al, Grain boundary dynamics driven by magnetically induced circulation at the void interface of 2D colloidal crystals, Science Advances (2022). DOI: 10.1126/sciadv.abn5715 Journal information: Science Advances
All Rights Reserved © 2024
