Grain size dependence of the martensite morphology – A phase-field study

Abstract The two-dimensional elastic phase-field simulation is applied to study the grain size effect on martensite morphology with Fe–31at.%Ni alloy as the prototype material. Martensitic transformations containing one or two variants are simulated in the single-crystal and poly-crystal models, and the morphologies related to different models and their grain size dependences are displayed. The simulated results show that the accommodation ability to the martensitic shape changes plays an important role in the grain size effect of martensite morphology. Although the transformation strains in a grain can be relaxed to surrounding grains, effective self-accommodations of different variants can only proceed in the individual grain. The size of martensitic domains proportionally decreases with grain size reduction, due to harder relaxation ability induced by the grain boundaries. The decreasing of the width for multi-variant domains can be realized by decreasing the number of sub-domain variant plates without decreasing the width of the plates.