The Coupling of Interphase Boundary Migration and Precipitation: Example of a Microalloyed Nb‐Containing Steel

The microstructural changes that occur during the processing of many important metals and alloys usually result from the competition and interactions between different ‘modes’ of microstructural change. In complex systems the variety of possible behaviours arising from simultaneous coupled modes of microstructural evolution can indeed be very rich. An interesting example comes from the thermo‐mechanical processing of microalloyed steels. In these materials, strong carbide forming elements such as Nb and/or Ti are added to form precipitates with C in solution. The goals are twofold: (a) to reduce the C content of the Fe matrix to improve the deep drawability of the resulting product and (b) to form precipitates that will hinder re‐crystallization of the austenite phase after high temperature deformation, resulting in an increased ferrite nucleation site density upon cooling and a smaller final ferrite grain size.