Influence of grain boundaries on the austenitic and martensitic phase transitions in iron

Using classical molecular dynamics simulations, we study the martensitic and austenitic phase transformation in an iron crystal containing a symmetric tilt grain boundary (GB). Without a GB, the system does not transform. The presence of a GB enables the transformation. The new phase nucleates at the GB. The austenitic transition temperature decreases approximately linearly with the GB energy. Here, the GB inherits its inherent periodicity to the microstructure of the forming austenite phase. The martensitic transformation proceeds via a two-step pathway resulting in a twinned microstructure. Graphical abstract:

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