Intelligent materials design and processing: simulating microstructural evolution during metal processing

摘要

Simulations of microstructural evolution during metal processing must represent at an appropriate scale the variation of microstructure across and through a section sufficient to allow the metallurgical engineer to predict the behaviour of the metal both during and after forming operations. One path to this goal, employing the cellular automaton (CA) method, is demonstrated in this paper. Cellular automata are used extensively in situations where the evolution of a structure or pattern is of interest and explicit analytical solutions for that evolution are either unknown or intractable. The automation is an arrangement of deterministic finite-state cells which obey a simple set of rules and whose state depends only on the states of neighbouring cells. Thus, the CA need not be explicitly coded with the kinetics of a transfromation. It is simply given, for example, a probability of nucleation and an interface migration rate - both derived from experiment - and from these rules results a microstructure which can be analysed in the same way a physical microstructure is examined. Cellular automata can be used to simulate recrystallisation, grain growth, precipitation, and combinations of these. Alternatively, the CA can be employed as an exploratory tool to investigate fundamental aspects of microstructural evolution in an heuristic manner. Examples of both these uses are shown, and the extent of progress towards the objective is discussed.