Multi-Scale Simulation and Design of Magnetic Alloys

In this work, a list of multi-scale simulations have been conducted and proposed to study the change in degree of order and microstrucure of B2 to L21 ordering transformation in meta-magnetic shape memory alloys and their effect on martensitic transformation. Initially, it was thought that this was due to changes in the overall B2-L21 degree of order and their effect on the magneto-thermo-mechanical couplings. However, a first-principles investigation discovered that the observed behavior cannot be explained solely by the overall degree of order and one must invoke microstructural effects. We used a model for atomic-scale ordering and clustering with the atomic density field approximation to simulate the B2 to L21 order-disorder transformation and domain coarsening in these alloys. This model's predictions are in good agreement with previous experimental estimations via X-ray diffraction and electron microscopy, which support the hypothesis relating MT characteristics evolution to atomic order microstructure length-scale. To investigate the size effect of B2-L21 phase domain on martensitic transformation, we used a computational model with combined phase-field method and micromagnetic simulation including the B2 and L21 order-disorder phase distribution in the parent austenite phase. The simulations show that the elastic barriers produced by certain atomic order microstructural configurations can significantly hinder the martensitic transformation in both L21 and B2 domains. In addition, a data-driven approach was utilized to accelerate the design of Fe-based soft magnetic materials. Experimental validations have been applied on several predicted materials, which showed that the predicted novel material could have similar performance as the commercial FINEMET-like alloys