Understanding recrystallisation: atomistic simulations of defect-driven grain structure evolution

At the cutting-edge of technological development, we are placing ever more exacting demands on the performance of metallic components and so we need an ever increasing degree of control over the properties of our metallic materials. These properties depend in large part on the grain structure of the metal, i.e. on the pattern of grain shapes and orientations within the microstructure. A key process in obtaining an optimal grain structure is that of recrystallisation, in which new grains of defect-free material nucleate and grow within the defect-laden microstructure of deformed material.

This proposal will use atomistic simulations to gain new insight into the process of recrystallisation. Previous simulations of recrystallisation have focussed on simulating the process at larger length scales, using mesoscale techniques such as cellular automata and phase-field models. However, such models require that the dynamics of nucleation and growth of new grains be specified at the outset and the structure of the grain boundaries and deformation defects is entirely absent. By using classical molecular dynamics methods you will model aspects of the recrystallisation process from the level of atoms upwards. The structure of deformation defects and grain boundaries will be represented explicitly and processes such of nucleation and grain boundary migration will emerge from within the simulations. This will allow you to study the mechanisms and kinetics of recrystallisation directly.

you will use simulations of carefully chosen model bicrystal and tricrystal systems to determine how the presence of large amounts of damage (in the form of dislocations formed during plastic deformation) affects the properties of grain boundaries. You will examine the energy and structure of grain boundaries as a function of their geometry in the presence of defects and compare with boundaries in pristine material. You will then undertake dynamical simulations of grain boundary migration in the model systems and determine the mechanisms associated with this motion and the implications for the kinetics of grain structure evolution during recrystallisation. Finally, you will study the processes by which new grains nucleate at different microstructural sites within deformed material.

Applicants should have or expect to achieve at least a 2.1 honours degree in physics, materials science or a related subject and have demonstrated an aptitude for computational and theoretical aspects of their degree.