Computer simulation of sequential transformations

Simultaneous and sequential transformations may take place in a diversity of materials and processes. Recently, Rios and Villa derived an exact analytical expression that describes simultaneous and/or sequential transformations. Analytical mathematical methods are able to yield mean values as a function of time. In contrast, computer simulation is able to generate the microstructure itself as a function of time. First, simultaneous and sequential transformations are simulated and the corresponding microstructures are generated. The simulations agree well with results from Rios and Villa analytical model. Furthermore, in addition to the mean volume density and mean interfacial area density between transformed and untransformed regions additional parameters are proposed to further describe the arrangement of the three phases in space. These new parameters can be measured directly from the simulation but are difficult perhaps even impossible to be obtained analytically. Moreover, a point of significant practical relevance is investigated. Namely, the situation in which one might mistakenly analyze a simultaneous transformation as if it were a sequential transformation. Consequences of this for the correct determination of the nucleation and growth velocity are fully discussed.

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