In situ measurement and modelling of the growth and length scale of twins in a-uranium

an illustration of the model and the results achieved

 Dr Edmund Tarleton, Professor Alan Cocks and Dr Grilli, with collaborators from Oak Ridge National Laboratory, constructed a simple phase field model which captured the physics of crystalline twin growth, then produced the details observed during in situ electron backscatter diffraction experiments on a-uranium.  

The interaction between residual dislocations at twin interfaces and mobile dislocations in untwinned regions increased the stress needed for twin growth.  Their paper, published in Physical Review Materials, describes the competition between slip and twinning favouring the nucleation of a new twin, rather than the growth of a pre-existing twin.  

Using the phase field model with a crystal plasticity finite element solver that included the plastic deformation due to twinning, the simulations were able to reproduce the number of twins and their thickness as a function of the strain, which was observed during in situ electron backscatter diffraction experiments.