Modelling and Simulation of Materials and Processes

A number of researchers in the Department of Materials Engineering are involved in modelling and simulation of materials and processes.  In most cases, these activities are part of larger research programs that contain substantial experimental components and all efforts are made to make the most of the synergies between experiment and modelling

A major area of activity in the department is in modelling the mechanical properties and forming or deformation processes of metals and alloys. The bulk of research conducted is on steels and copper, as well as for light alloys based on aluminium, magnesium and titanium. These studies cover a range of materials length scales. At the largest scale this includes finite elements (FE) simulations of metal forming, while homogenization techniques such as elasto-plastic and visco-plastic self-consistent methods are used to incorporate texture into simulations of polycrystalline deformation. Physically motivated models of large strain deformation are used for process optimisation in such areas as equal channel angular pressing (ECAP), microforming, and other modern technologies.  A large fraction of the modelling activities within this area are focused at the microstructural length scale. Physically based constitutive approaches are used to explicitly incorporate microstructural features in the modelling methodology.  This includes internal variable based approaches due to Kocks, Mecking and Estrin, as well as gradient plasticity models with an emphasis on incorporating microstructurally based origins for the gradient terms.  These approaches are used to model tensile deformation and creep behaviour, the microstructure evolution during severe plastic deformation  used as a means for obtaining nanocrystalline materials, localisation of plastic flow, e.g. as a result of dynamic strain ageing, the mechanical response of magnesium and titanium alloys where twinning is an important deformation mode, the evolution of texture during deformation and the deformation behaviour of micro-materials (microforming). An emerging research direction is centred around molecular dynamics simulations (MD) of the mechanical properties of nanostructured metals and alloys.

A second major modelling stream in the department is in the thermodynamics and kinetics of solid state phase transformations and recrystallisation behaviour in metals and alloys. The principal activities in phase transformations include modelling the competition in phase formation from supersaturated solid solution (including metallic glasses such as Fe-Nd-B), modelling the kinetics of precipitation processes in Al and Mg based alloys, the design of non-isothermal thermal processes for precipitation hardening systems and the kinetics of the decomposition of austenite in steels into ferrite and pearlite with a particular emphasis on solute effects on boundary migration.  An emerging area in the department is in the modelling of atomistic clustering processes during the early stages of the decomposition of metallic supersaturated solid solutions; both the kinetics of decomposition and the thermodynamic pathway are of interest as well as the resulting mechanical properties of the inhomogeneous solid solution. Kinetic Monte Carlo (KMC) and Molecular Statics (MS) approaches are being used. A number of researchers are active in the area of static and dynamic recrystallisation processes with interests in the kinetics of the processes and the effects of solute and precipitates, the texture evolution during recrystallisation and the modelling of the nucleation stages of recrystallisation. A number of approaches are being used including the hybrid Cellular Automaton (CA) technique.

An area of interest common to modelling work in both the phase transformations and recrystallization areas is interfacial mobility including questions of solute effects on mobility (solute drag).  These issues are important for understanding the stability of nanocrystalline materials and the kinetics of microstructural change during phase transformations, recrystallisation and grain growth.

A new research effort in the Department addresses modelling of corrosion processes in metals. An example is studying the kinetics of damage accumulation through the 3D simulation of the evolution of pits on metallic surfaces. These simulations aim to serve as predictive tools for assessment of component lifetimes, particularly aerospace materials (high strength Al alloys and Ni based superalloys).

There are also a number of smaller activities in the modelling of non-metallic materials.  This includes ab initio modelling of the properties of nano-ceramic particles.  Within the field of polymeric materials, research focuses on modelling the visco-elastic mechanical properties of polymers, including polymeric foams and scaffolds, as a function of temperature. Computer simulations of polymer processing, e.g. the injection molding, involve coupling problems in heat transfer, fluid dynamics and phase transformations.

Active researchers in this area include:

Professor Yuri Estrin
A/Professor Chris Davies
A/Professor Graham Edward
Dr Peter Thomson
Dr Christopher Hutchinson
Dr Rimma Lapovok
Dr Vargese Swamy
Dr Nick Birbilis